Past Events

All past events

21
JUN'17
Title: Bridging the THz Gap using Rydberg Atoms Lucy Downes 1st Year Talk
Seminar (Durham University)
This event will be held 13:00 - 14:00, in PH30 THz (or sub-mm) radiation lies on the EM spectrum between the IR and microwave regions. It has promising applications ranging from biomedicine and chemistry to defence and security. However a lack of easily available high power sources (>1mW) and convenient detection methods mean there is far less technological exploitation of radiation in this region (the so-called THz Gap) [1]. Alkali Rydberg atoms, having high sensitivity to EM radiation and atomic transitions spanning the THz gap, make promising THz detectors. Recent work in Durham [2] showed that Rydberg atoms could be used to image a single frequency THz field in real time, and relate the field strength directly to SI units. This method is now of considerable interest in academia and industry as a possible new quantum technology [3]. This talk will outline the way in which Rydberg atoms can function as THz detectors and describe recent extensions to the previous work. [1] C. Sirtori, Nature 417, 132-133 (9 May 2002) [2] C. Wade et al, Nature Photonics 11, 40–43 (2017) [3] https://www.epsrc.ac.uk/newsevents/news/qtshowcase/
Speakers: Lucy Downes
19
JUN'17
Title: Nick Spong 1st Year Talk
Seminar (Durham University)
This event will be held 10:00 - 11:00, location TBC Abstract TBC
Speakers: Nick Spong
14
JUN'17
Title: Continuous-time quantum computing
Seminar (Durham University)
This event will be held in PH8, 12:00 - 13:00 Adiabatic quantum computing, quantum annealing, and computation by quantum walk all use a continuous-time evolution to process qubits from an initial state to a final state that encodes the solution. Several types of special purpose quantum simulators also fit into this model. Treating these different types of quantum computing as variations on the same continuous-time quantum computing model, we can employ hybrid strategies to optimise algorithms. Hardware designed for one of these types should be capable of a wider range of computations than originally envisaged, making early quantum simulators and quantum annealers more useful as first generation quantum computers.
Speakers: Viv Kendon
12
JUN'17
Title: Understanding collisions in 87RbCs Towards an atom-diatom mixture Jacob Blackmore 1st Year Talk
Seminar (Durham University)
This event will be held 10:00 - 11:00, location TBC Polar hetero-nuclear molecules promise to be a power system for quantum computation [1], quantum simulation [2] and high precision measurement [3] due to their rich rovibrational and hyperfine structure, large permanent dipole moments and long ground state lifetimes. In ultracold samples of 87RbCs, which is chemically stable [4], lifetimes on the order of 100 milliseconds are observed. One proposed mechanism for the high loss rate is known as “sticky collisions” which proposes that molecular collisions produce long lived complexes due to the high number of states accessible [5]. In practice observation and description of molecule-molecule collisions is challenging, we present progress towards the simplified atom-diatom system. [1] D. DeMille, Phys. Rev. Lett. 88, 067901 (2002). [2] M. A. Baranov, M. Dalmonte, G. Pupillo, and P. Zoller, Chem. Rev. 112, 5012 (2012). [3] V. V. Flambaum and M. G. Kozlov, Phys. Rev. Lett. 99, 150801 (2007). [4] P. S. Żuchowski and J. M. Hutson, Phys. Rev. A 81, 060703 (2010). [5] J. F. E. Croft and J. L. Bohn, Physical Review A 89 (2014), 10.1103/PhysRevA.89.012714.
Speakers: Jacob Blackmore
07
JUN'17
Title: Four-wave mixing, seeded and spontaneous Renju Mathew 1st Year Talk
Seminar (Durham University)
This event will be held 12:00-13:00 in PH8 Four wave mixing (4WM) is useful for many experiments in atomic/optical physics, including for the generation of time-correlated photon pairs. Unfortunately, multi-photon interference across many energy levels can lead to sub-optimal effects. Application of a large magnetic field accesses the hyperfine Paschen-Back regime, a regime in which there is decoupling of the total electronic momentum J and the nuclear spin momentum, I. This has been shown to produce simplified, i.e. non-overlapping, energy levels and so produce cleaner signals in the case of electromagnetically induced absorption and electromagnetically induced transparency. We present experimental results to show similar benefits for four wave mixing experiments, allowing us good quantitative agreement with models. We contrast the complex FWM signals produced in the case of zero magnetic field with the simple 4WM signals produced in the case of a large magnetic field. We show the experimental setup used to create the simpler 4WM signals. We show results from the transmission of the seed laser alone, the seed plus pump lasers and the seed plus pump plus coupling lasers. We discuss the variation of the 4WM signal as a function of the detuning of the beams and of their powers.
Speakers: Renju Mathew
31
MAY'17
Title: Vortices, turbulence and rogue waves in lasers and fluids of light
Seminar (Durham University)
This event will take place at 12:00-13:00 in PH8 Rogue waves are characterized by rare peak intensities that are much higher than the long-time average height of the oscillations in a medium. These waves occur unexpectedly and are typically accompanied by wide and/or deep troughs before and after the event. In nonlinear optical cavities, experimental evidence of deterministic rogue waves was first provided in lasers with injected signals. The dynamics of these systems, however, are confined to one spatial dimension. In this talk we describe a mechanism for the generation of fully two-dimensional spatio-temporal rogue waves in the presence of turbulence of interacting optical vortices. We consider the dynamics in the transverse plane of the complex Ginzburg-Landau (CGL) and complex Swift-Hohenberg equations in the presence of an external forcing. These equations are equivalent to the hydrodynamics of a viscous, compressible and irrotational fluid. Without spatio-temporal coupling, chaos, turbulence and, consequently, rogue waves are forbidden. With spatio-temporal coupling and below the locking threshold, we demonstrate phase and amplitude instabilities leading to regimes of defect-mediated turbulence with interacting optical vortices. Depending on the density of the moving vortices, short distance interactions lead to sudden, rare, large and randomly positioned peaks of the light intensity. The small aspect ratio, the full 2D character and the quick dynamics represent major advantages of transverse optical devices for studying the generation and control of rare events with applications, by universality, in hydrodynamics and oceanography. The CGL model equations have a broad range of applications in optics, ranging from broad area lasers to optical parametric oscillators, and to polaritons in semiconductor microcavities.
10
MAY'17
Title: Ultracold atoms in optical lattices
Seminar (Durham University)
This event will take place in PH8 @ 12:00-13:00 Ultracold atoms in optical lattices have emerged as a very versatile platform to study quantum many-body physics in a clean and well-controlled environment with tunable dimensions. I will give an overview over our recent work on non-equilibrium dynamics in these systems, including the observation of Many-body Localization, interferometric probes for topology and the dynamics at quantum phase transitions.
Speakers: Ulrich Schneider
03
MAY'17
Title: Quantum Optical Routes to Quantum Supremacy
Seminar (Durham University)
This seminar will be held in PH8 @ 12:00 - 13:00 Quantum states of many particles offer the opportunity to study the rich physics of large-scale quantum correlations. Such multi-partite correlations are believed to underlie a range of physical phenomena such as structure and transport in many-body quantum systems and promises performance that dramatically exceeds any classical processor. Building machines able to achieve this so-called Quantum Supremacy has obvious motivation from a technological standpoint [1]. Systems in which all particles and their interactions can be controlled to some degree can deliver functionality for sensing, imaging, communications, simulation and computation that goes well beyond what is possible with classical systems possessing a similar set of resources. One approach is to build large quantum states of light, constructing quantum correlated light beams, with a system comprising many photons in which each input and their interactions are controllable. The rationale for using light is three-fold. First, photons are one of a very few systems that exhibit palpable quantum phenomena under ambient conditions, and therefore the engineering required to produce and control particles in identical pure quantum states is minimized. Second, the number of bosons required to enter a regime that cannot be simulated is relatively small [2]: several tens to a hundred photons in a similar number of modes. Third, a light beam becomes correlated with another at the quantum level by means of a fundamental quantum interaction – exchange – manifested as quantum interference. Indistinguishability and the exchange interaction play a central role in the emergence of entanglement and other stronger-than- classical correlations in the interference of many quantum particles. Photons are quite unique in that, having no charge, they are purely influenced by their particle statistics and provide an ideal opportunity to study the effects of purity and distinguishability on quantum interference, isolated from any contributions from external forces. One important development in this direction was the formulation of the Boson Sampling problem [3]. As originally envisioned – sampling the output distribution of identical Fock states scattered through a linear optical network [2] – Boson Sampling is unique: it implements a classically hard problem but with massively reduced resource requirement compared to more traditional quantum technologies. I will explain how simple quantum networks implement quantum walks and Boson Sampling. This was supported by the EPSRC Programme BLOQS (Building Large Quantum States out of Light), a collaboration between Oxford, Southampton and Imperial College. References [1] P Kok, Contemp Phys 1178472 (2016); arXiv:1603.05036 and references therein.
[2] S Scheel, K Nemoto, W J Munro and P L Knight, Phys Rev A68, 032310 (2003) for an early demonstration of quantum supremacy in a linear quantum optical network, showing how output distributions are described by permanents, hard to evaluate by classical means. [3] Aaronson & Arkhipov Proc. ACM sym. 333-342 (2011).
Speakers: Sir Peter Knight
19
APR'17
Title: Superfluid Flow, Solid Body Rotation and Necklace States in BECs in Annular Traps
Seminar (Durham University)
This event will take place at 12:00-13:00 in PH8 Ring traps for ultracold atoms are an example of non-trivally connected geometries and they allow to create and study stable persistent currents of irrotational flow. In this work I will discuss a two-component condensate in the phase separation regime, where simple energy considerations suggest that the phase separation is azimuthal and that the phase boundary is radial to minimise the interaction energy. Adding rotation to such a systems requires the atoms to start moving around the trap centre. However, the flow of each component is irrotational and the standard solution for a current in a ring trap consisting only of azimuthal flow alone is therefore at odds with the solid-body rotation of the density distribution. I will show that the system solves this dichotomy by creating a radial flow within the region of a healing length close to the phase boundary, without the need for having additional phase singularities. In a second step I will discuss how to create a condensate on a ring where alternating regions of different components of adjustable width in the azimuthal direction can be created via spin-orbit coupling. This effect relies on the interplay between the non-linear and spin-orbit energies and allows to study highly excited condensates in a controlled way.
Speakers: Thomas Busch
15
MAR'17
Title: BEC interferometry on ground and in space
Seminar (Durham University)
This event will be held at 12:00 - 13:00 in PH8 Interferometers employing Bose-Einstein condensates will be at the heart the next generation quantum sensors, promising to improve on both, precision and accuracy. They move forward the frontier towards large scale atom interferometers as well as novel miniaturized sources based on atom chips for transportable, long term stable and accurate devices. Beyond fundamental physics, fields of application are geodesy or generally Earth observation. The talk will give an overview on our activities in the field of atom-chip-based sensors both for ground and space operation. It will also report on the recent successful launch of the rocket mission MAIUS-1 exploring methods for BEC interferometry in space.
Speakers: Prof Ernst Rasel
14
MAR'17
Title: Negative frequency at the horizon: scattering of light at a refractive index front
Seminar (Durham University)
This event will take place in the Sir James Knott Library (PH132) @ 11:00 In 1974, against all expectations, Hawking showed that black holes actually emit radiation. According to Einstein’s Theory of General Relativity, black holes are cosmic objects so compact that nothing should escape from them. Anything, even light, that crosses the event horizon – the boundary of the black hole – is doomed to fall upon the black hole’s central singularity. Hawking investigated the fate of pairs of particles and antiparticles that are constantly coming to life and annihilating, an effect known as quantum fluctuations of the vacuum, at the horizon. He discovered that the horizon can separate them so that the antiparticle (partner) falls on the black hole and the particle (Hawking radiation, HR) escapes it: a quantum effect lets black holes radiate. However the effect of HR is so feeble that the universe’s own thermal glow, the Cosmic Microwave Background, hides it from us. Yet, it would be essential to observe Hawking radiation to better understand black holes and how a quantum effect on the scale of black holes influences the repartition of mass on the scale of the universe – a milestone towards a unified theory of everything. We will begin with some basic considerations on General Relativity, before turning to black holes and introducing the phenomenon of HR. Having gained intuition on the behaviour of waves in the vicinity of the event horizon, we will show how the motion of fluids can be made to reproduce this physics. From waterfalls to water flows from a kitchen-tap, we will review the various analogue gravity systems that have been proposed to observe HR. In particular, we will focus on optical event horizons. We will see how light can be made to interact with itself to create conditions analogous to wave propagation at the event horizon, and reveal the essential ingredient of spontaneous emission – the mixing of light-modes with positive and negative frequency at the horizon. To conclude, we will look into the current experimental investigation of scattering to a negative frequency wave at an optical horizon created by a soliton in a fibre. This will provide a broad overview of the field of horizon-analogues, and open discussions of the theoretical and experimental challenges in the field.
Speakers: Maxime Jacquet
08
MAR'17
Title: Dipolar Quantum Matter near Absolute Zero Temperature
Seminar (Durham University)
This seminar will be held in PH8 @ 12:00 - 13:00 With the tremendous advances in cooling and manipulation techniques, ultracold atomic gases have consolidated themselves as an ideal system to address fundamental questions in quantum few- and many-body physics. Recently, we have reached Bose-Einstein condensation and Fermi degeneracy with ultracold Erbium atoms. This “exotic” atomic species combines unusually rich atomic spectra and a large magnetic moment. In the quantum regime, bosonic Er atoms feature interactions of genuinely different nature. The more ordinary and magnetically-tunable contact interaction combines with the long-range and anisotropic magnetic dipolar interaction. The mere existence and competition between these two sources of interactions dictate the physics at play, disclosing a variety of intriguing quantum phases. This talk will provide an overview of some fascinating dipolar phenomena from the Innsbruck prospective.
Speakers: Francesca Ferlaino
01
MAR'17
Title: Out of equilibrium dynamics in AMO quantum simulators: addressing new fundamental questions
Seminar (Durham University)
This seminar will be held in PH8 @ 12:00 - 13:00 Over the last two decades, experiments with atomic, molecular and optical systems such as ultracold atoms and molecules or trapped ions have developed to a level where we have strongly interacting quantum gases that are controllable and measurable on a single-particle level. This now allows us to engineer a range of fundamental models - especially those that were previously used to describe electrons in solid state physics - and explore their properties cleanly on a microscopic level. Beyond textbook demonstrations of equilibrium and single-particle properties (e.g., insulating phases, magnetic superexchange, and Bloch oscillations), this now enables us to explore fundamental aspects of non-equilibrium dynamics in quantum many-particle systems. These range from from the approach of systems to equilibrium and thermalisation in statistical mechanics, to fundamentally new features that arise from unique aspects of the AMO systems - such as long-range interactions in ions or polar molecules. I will discuss some of the recent developments in this area, illustrated with our theoretical work on dynamics in systems with long-range interactions. I will also discuss the recent measurement of many-body entanglement in itinerant particles with ultracold atoms in optical lattices.
Speakers: Andrew Daley
22
FEB'17
Title: The uncertain science of physics and economics
Seminar (Durham University)
This event will be held in PH8 @ 12:00-13:00 The physicist world view is one of certainty and only later do we learn that at the microscopic level almost everything is unknown and we are only certain about averages. Physics as a methodology is about breaking a complex whole into simple parts, parts where the rules are probabilistic. As economics is so interconnected it is less clear that such a reductionist approach can work. In this talk I will review some simple physics models and compare their predictions to what we find in econometric data. As always in science it is the data that really matters.
Speakers: Charles Adams
15
FEB'17
Title: Nanoscale interfacial ionic networks at biointerfaces
Seminar (Durham University)
This event will take place in PH8 @ 12:00-13:00 When immersed into water, most solids develop a surface charge. In order to ensure electroneutrality, ions in solution accumulate near the surface of the solid, creating a so-called double layer of counterions. The density of counterions in the double layer is generally well described by continuum theories, but the lateral organisation and dynamics of ions adsorbed directly onto the solid is poorly understood and continuum theories often breakdown. This layer of counterions, called Stern layer, modulates some of the interface’s properties and plays a central in many processes, ranging from electrochemistry to crystal growth, heterogeneous catalysis, and biological function. In soft biological systems, the importance of the Stern layer is further emphasised by its ability to shape matter. Biological membranes are composed of lipids and biomolecules organised to support the function of the cell. The lipids, which form a fluid double layer –the bilayer- are often seen as a passive matrix that embeds and anchors bioactive molecules. Here I show that simple metal ions such as K+ and Na+ can develop extended networks at the surface of lipid bilayers in aqueous solutions. These networks, formed through a combination of electrostatic and hydration interactions, are composed of nanoscale ionic domains evolving on a timescale of several seconds. Using in-situ high-resolution atomic force microscopy we image the organisation and dynamics of ionic domains at the surface of bilayers with single ion resolutions. At the interface with homogenous bilayers, the presence of ionic networks is sufficient to induce local variations in the membrane’s mechanical properties. It also affects the diffusion properties of the lipids modulate the adsorption of biomolecules.
Speakers: Kislon Voitchovsky
08
FEB'17
Title: Simulating The Universe
Seminar (Durham University)
This event will be held in PH8 @ 12:00-13:00 One of the main aims of the ICC is to re-create the Universes inside a super-computer. Our world-leading simulations track the emergence of structure, starting shortly after the big-bang and following the complex web of non-linear structures until the present day. In our latest calculations, we follow the formation of star and black holes, creating realistic galaxies that closely match those seen with the worlds largest telescopes. In my talk, I'll outline how this all happens, and discuss some of the challenges that will be of deep interest across all science domains.
Speakers: Richard Bower
01
FEB'17
Title: Ultrafast spectroscopy of molecular anions
Seminar (Durham University)
This event will be held in PH8 @ 12:00-13:00
Speakers: Jan Verlet
25
JAN'17
Title: Optical forces: some fundamentals and some surprises
Seminar (Durham University)
This event will be held at 12:00 - 13:00 in PH8 The mechanical effects of light on matter have been known of for a long time, indeed Maxwell’s treatise on electricity and magnetism includes an accurate calculation of the radiation pressure exerted by sunlight on the surface of the earth. Today, optical tweezers for manipulating small objects are widely employed and the exchange of momentum between light and atoms underpins the science of laser cooling and trapping. In this talk I shall present as simply as I can, some novelties and surprises arising in the study of optical forces. These include a paradox in spontaneous emission, the dispersive force on a single atom and the optical force on a dielectric body. Things become more subtle when the object has both a magnetic and an electric response and here unexpected and potentially useful phenomena can result. Important examples include chiral molecules and novel metamaterials including those with a negative refractive index.
Speakers: Steve Barnett
12
DEC'16
Title: Open Day for Prospective PhD Students
Seminar (Durham University)
Bransden Room 14:00 - 16:00 Come and learn more about the range of exciting research opportunities in atomic and molecular research from current PhD students and supervisors within the Joint Quantum Centre (JQC). The JQC joins Durham Atomic and Molecular Physics and Newcastle Quantum Fluids and Gases (Applied Mathematics and Mechanical and Systems Engineering) with members of Durham Chemistry Theory and Dynamics. Projects are available in all these areas.
07
DEC'16
Title: A search algorithm for quantum state engineering and metrology
Seminar (Durham University)
This seminar will be held in PH8 @ 12:00 - 13:00 With the fast growing interest in quantum technologies it is becoming increasingly important to engineer quantum states for specific applications. In this talk I will present a search algorithm for this task that finds useful optical quantum states that can be created with current technology. I apply the algorithm to the field of quantum metrology with the goal of finding states that can measure a phase shift to a high precision. The algorithm efficiently produces a number of novel solutions and finds experimentally-ready schemes to produce states that show significant improvements over the state-of-the-art. These states can measure with a precision that beats the shot noise limit by over a factor of 4, and they demonstrate a robustness to moderate/high photon losses.
Speakers: Paul Knott
30
NOV'16
Title: Interacting Rydberg polaritons in an ultracold gas
Seminar (Durham University)
This seminar will be held in PH8 @ 12:00 - 13:00 Mapping the strong interaction between Rydberg excitations in ultracold atomic ensembles onto single photons enables manipulation of light on the single photon level. This novel approach opens the possibility for controlling light photon by photon. We discuss our experimental realizations of a free-space single-photon transistor, where a single gate photon controls the transmission of many source photons, and of a single-photon absorber, where exactly one photon is subtracted from an arbitrary input state.
23
NOV'16
Title: A quantum Mach clock
Seminar (Durham University)
This seminar will be held in PH8 @ 12:00 - 13:00 For many people a clock is the epitome of a predictable, reversible dynamical system. Yet we are all familiar with the irreversible clocks used in radio carbon dating. Much earlier, Mach and Eddington both proposed irreversible thermal clocks. In general relativity the Tolman relations connect the local measurements of time and temperature. Rovelli’s thermal time hypothesis uses thermal equilibrium states to define the local flow of time in general relativity. There is a duality to time and temperature: given a good clock it is possible to make local measurements of temperature and, conversely, given a good thermometer it is possible to make a local clock. I will illustrate this concept using a physical example based on quantum opto-mechanics. Quantum correlations cause significant departures from the original Mach proposal.
Speakers: Gerard Milburn
16
NOV'16
Title: Novel Directions in Relativistic Quantum Information
Seminar (Durham University)
This seminar will be held in PH8 @ 12:00 - 13:00. The past decades have witnessed the birth of the first generation of quantum technologies, with applications that range from quantum key distribution (QKD), to quantum computing (QC) and ultra-precise measurements of physical parameters (quantum parameter estimation). Quantum mechanics, the theory of the very small, has been employed successfully as the main building block to investigate and describe those systems that are at the core of these technologies. So far relativity, the theory of the very large, has been ignored, most likely due to the overwhelming experimental evidence that relativistic effects seem not to play a role. However, cutting edge experiments have reached regimes where relativistic effects cannot be ignored. It is an open question if and how relativity will play a role in developing the next generation of quantum technologies, and what will be the consequences. The new field of Relativistic Quantum Information (RQI) aims at understanding the effects of relativity on paradigmatic quantum resources, such as entanglement. Recent work has shown that localised quantum systems moving at high speeds, or subject to space-time dynamics, can in principle be used to exploit these relativistic effects to improve current technologies and to achieve ultra-precise measurements of physically interesting parameters. We will discuss recent progress in the area of relativistic and quantum information. We will propose space-based schemes for ultra-precise measurements of relevant relativistic parameters, such as distances and the Schwarzschild radius. Furthermore, we will discuss a novel proposal for the detection of gravitational waves which is based on dynamical Casimir-like resonances of phononic excitations within micrometer quantum systems, known as Bose-Einstein Condensates (BECs). This daring proposal promises to shift the current paradigm of km-size laser interferometers, such as LIGO. Finally, we will present future avenues and applications of our techniques. We believe that the results of our research can aid our understanding of the overlap of relativity and quantum mechanics and, ultimately, in the quest for a unified theory of nature.
Speakers: David Bruschi
09
NOV'16
Title: Thermodynamics and Information at the nanoscale
Seminar (Durham University)
Thermodynamic laws have been key for the design of useful everyday devices from car engines and fridges to power plants and solar cells. Technology’s continuing miniaturisation to the nanoscale is expected to soon enter regimes where standard thermodynamic laws do not apply. I will give an introduction to quantum thermodynamics - the emerging research field that aims to uncover the thermodynamic laws that govern small ensembles of systems that follow non-equilibrium dynamics and can host quantum properties [1]. I will discuss a nanoscale thermodynamic experiment with heated optically trapped nanospheres in a dilute gas [2]. By developing a new theoretical model that captures the non-equilibrium situation of the particles, we were able to measure the surface temperature of the trapped spheres and observe temperature gradients on the nanoscale. In the second part of the talk I will discuss recent theoretical advances in defining thermodynamic work in the quantum regime. By introducing a process that removes quantum coherences we were able to show that work cannot only be extracted from classical non-equilibrium systems, additional work can be extracted from quantum coherences [3]. [1] Quantum thermodynamics, S. Vinjanampathy, J. Anders, Contemporary Physics 57, 545 (2016). [2] Nanoscale temperature measurements using non-equilibrium Brownian dynamics of a levitated nanosphere, J. Millen, T. Deesuwan, P. Barker, J. Anders, Nature Nanotechnology 9, 425 (2014). [3] Coherence and measurement in quantum thermodynamics, P. Kammerlander, J. Anders, Scientific Reports 6, 22174 (2016).
Speakers: Janet Anders
02
NOV'16
Title: A Rydberg atom single photon transistor
Seminar (Durham University)
In this talk, I will discus the coherence of single photon transistors. Recent experiments have realized an all-optical photon transistor using a cold atomic gas. This approach relies on EIT in conjunction with the strong interaction among atoms excited to high-lying Rydberg states. The transistor is gated via a so- called Rydberg spinwave, in which a single Rydberg excitation is coherently shared by the whole ensemble. In its absence the incoming photon passes through the atomic ensemble by virtue of EIT while in its presence the photon is scattered rendering the atomic gas opaque. An important current challenge is to preserve the coherence of the Rydberg spinwave during the operation of the transistor, which would enable for example its coherent optical read-out and its further processing in quantum circuits. I will show how the coherence of the Rydberg spinwave is affected by photon scattering. Here coherence becomes increasingly protected with growing interatomic interaction strength.
Speakers: Weibin Li
26
OCT'16
Title: Atomic interactions via diffractive light coupling: Magnetic ordering and optomechanical density structures
Seminar (Durham University)
The possibility to tailor interactions in cold atoms attracts considerable interest for the investigation of phase transitions and many-body physics. I discuss a novel approach to generate interactions between cold atoms mediated by multi-mode light fields undergoing diffraction. After adiabatic elimination of the light fields, the theoretical description can be reduced to equations of motion involving the atomic variables, with the light field and the optical density appearing only in the coupling parameters. The experimental system is a cloud of laser-cooled 87Rb atoms driven by a laser beam in the presence of a retro-reflecting plane mirror. Above a threshold, spatial patterns (typically hexagons) form spontaneously in the atomic medium as well as in the light field, sustaining each other via positive feedback. The spatial scale of the patterns is given by diffractive phase shifts in the feedback loop between cloud and mirror and is related to the Talbot effect. Realizations of magnetization patterns via spin-dependent selection rules and of density patterns via optomechanical dipole forces are presented. Extensions to quantum degenerate matter are discussed.
Speakers: Thorsten Ackemann
19
OCT'16
Title: A search algorithm for quantum state engineering and metrology
Seminar (Durham University)
With the fast growing interest in quantum technologies it is becoming increasingly important to engineer quantum states for specific applications. In this talk I will present a search algorithm for this task that finds useful optical quantum states that can be created with current technology. I apply the algorithm to the field of quantum metrology with the goal of finding states that can measure a phase shift to a high precision. The algorithm efficiently produces a number of novel solutions and finds experimentally-ready schemes to produce states that show significant improvements over the state-of-the-art. These states can measure with a precision that beats the shot noise limit by over a factor of 4, and they demonstrate a robustness to moderate/high photon losses.
Speakers: Paul Knott
06
JUL'16
Title: CPM seminar- Advise on funding
Seminar (Durham University)
TBC
Speakers: EPSRC
04
JUL'16
Title: Seminar- Quantum Walks Gravity Simulation
Seminar (Durham University)
As we know, spacetime is not flat at the cosmological scale. In order to describe spacetime, in General Relativity theory (GR), we need a continuous and differentiable manifold and a formal way to account for the continuous distortion of the metrics. The main point is that changing coordinate systems should not affect physics laws (General Covariance). However at the Planck length, matter is not continuous and obeys Quantum Theory (QT). Although one century has passed, finding an intrinsically discrete counterpart of GR is still an open question. In fact, discretized GR does not turn out in just a mere finite difference scheme of the old formula. I recently showed that one way to describe a discrete curved spacetime is by using Quantum Walks. From a physical perspective a QW describes situations where a quantum particle is taking steps on a discrete grid conditioned on its internal state (say, spin states). The particle dynamically explores a large Hilbert space associated with the positions of the lattice and allows thus to simulate a wide range of transport phenomena. It is surprising that this unitary and local dynamics, defined on a rigid space-time lattice coincides in the continuous limit with the dynamical behaviour of a quantum spinning-particle spreading on a curved spacetime. This could really turn out to be a powerful quantum numerical method to discretize GR.
Speakers: Giuseppe Di Molfetta
30
JUN'16
Title: Finite-temperature hydrodynamics for one-dimensional Bose gases: Breathing mode oscillations as a case study
Seminar (Durham University)
Hydrodynamics has proven to be a powerful and widely applicable approach to describing the nonequilibrium behaviour of quantum fluids. For ultracold atomic gases, it has been particularly successful at describing breathing (monopole) and higher-order (multipole) collective oscillations of Bose-Einstein condensates in 3D, including at finite temperature. In contrast to 3D systems, the applicability of the hydrodynamic approach to 1D Bose gases is not well established. Firstly, in the thermodynamic limit 1D Bose gases lack the long-range order required for superfluid hydrodynamics to be a priori applicable. Secondly, the very notion of local thermalisation, required for the validity of collisional hydrodynamics of normal fluids, is questionable due to the underlying integrability of the uniform 1D Bose gas model. Despite these reservations, the hydrodynamic approach has already been applied to zero-temperature dynamics of 1D Bose gases in various scenarios, with some success. Here I will outline a finite-temperature hydrodynamic approach for a harmonically trapped one-dimensional quasi-condensate that we have recently developed, and apply it to describe the phenomenon of frequency doubling in the breathing-mode oscillations of the quasi-condensate's momentum distribution. The doubling here refers to the oscillation frequency relative to the oscillations of the real-space density distribution, invoked by a sudden confinement quench. We find that the frequency doubling is governed by the quench strength and the initial temperature, rather than by the crossover from the ideal Bose gas to the quasicondensate regime. The hydrodynamic predictions are supported by the results of numerical simulations based on a finite-temperature c-field approach, and extend the utility of the hydrodynamic theory for low-dimensional quantum gases to the description of finite-temperature systems and their dynamics in momentum space.
Speakers: Stuart Szigeti
22
JUN'16
Title: First year talk- A versatile imaging system for non-destructive Faraday imaging of solitons in 85Rb BEC
Seminar (Durham University)
Since the turn of the century, work with tunable Bose-Einstein condensates (BECs) has resulted in new avenues of experimental ultracold atomic physics being available to us, a notable example being the ability to realise BECs that exhibit soliton-like behaviour. An ultimate aim of the soliton project in Durham is to assess the suitability of using pairs of solitons as an interferometer to measure matter-wave interactions between solitons and macroscopic surfaces. Until now the project has utilised an absorption imaging scheme which, due to its destructive nature, prevents multiple probes of the same soliton. This has strongly limited the efficiency and reliability when taking data of soliton dynamics, a crucial factor in realising a soliton interferometer. We present a widely-tunable imaging system that instead uses a minimally-destructive imaging technique (Faraday imaging) and demonstrate it's capability on an ultracold atomic cloud of 85Rb.
Speakers: Oliver Wales
15
JUN'16
Title: First year transfer talk-Compact Ion-Sources based on Surface-Patterned Atom Chips
Seminar (Durham University)
Focused ion beam technology has many applications and for this reason is ubiquitous in industry. The latest developments in the field concern the use of cold atoms as ion sources due to - amongst other things - offering the potential of even smaller beam spot sizes than previously possible and thus, greater precision for industrial application. Thus far though, such systems have been limited to operating within large vacuum chambers and so my presentation will show the process of trying to solve this problem by creating a more compact ion source based on the principle of a grating MOT.
Speakers: Dominic Reed
08
JUN'16
Title: Seminar- Secure signatures - a practical quantum technology
Seminar (Durham University)
Modern cryptography encompasses much more than encryption of secret messages. Signature schemes are widely used to guarantee that messages cannot be forged or tampered with, for example in e-mail, software updates and electronic commerce. Messages are also transferrable, which distinguishes digital signatures from message authentication. Transferability means that messages can be forwarded; in other words, that a sender is unlikely to be able to make one recipient accept a message which is subsequently rejected by another recipient if the message is forwarded. Similar to public-key encryption, the security of commonly used signature schemes relies on the assumed computational difficulty of problems such as finding discrete logarithms or factoring large primes. With quantum computers, such assumptions would no longer be valid. Partly for this reason, it is desirable to develop signature schemes with unconditional or information-theoretic security. Quantum signature schemes are one possible solution. Similar to quantum key distribution (QKD), their unconditional security relies only on the laws of quantum mechanics. Quantum signatures can be realized with the same system components as QKD, but are so far less investigated. This talk aims to provide an introduction to quantum signatures and to review progress so far.
Speakers: Erika Anderson
01
JUN'16
Title: First year transfer talk
Seminar (Durham University)
TBC
Speakers: Ryan Hanley
25
MAY'16
Title: Seminar- Spectroscopic Measurements of the Casimir-Polder interaction with atoms or molecules
Seminar (Durham University)
The modification of quantum and thermal fluctuations by a surface of finite reflectivity shifts the energy levels of quantum objects, such as atoms and molecules, and changes their radiative properties. This phenomenon is referred to as the Casimir-Polder effect. In this talk I will present our measurements of the Casimir-Polder interaction (atom-surface interaction) using selective reflection spectroscopy in atomic vapour cells. Selective reflection typically probes atoms approximately ~100nm away from the cell window [1] and as such is very well adapted for measuring a near-field temperature dependence of the Casimir-Polder interaction. In the near-field regime, thermal effects are dominated by the excitation of evanescent plasmon-polariton modes and have recently become of interest in the study of coherent thermal light [2] and near field heat transfer [3]. Here, I focus on the effects of near field thermal emission on atoms. I start from our experiments on the caesium 6P1/27D3/2 line demonstrating that the atom surface interaction between Cs(7D3/2) and sapphire increases with temperature due to the thermal excitation of sapphire polariton waves at 12.35µm [4]. Additionally, I describe a new set of measurements on the second resonance of caesium, Cs(7P1/2) and Cs(7P3/2), showing that the interaction of the two atomic states with a sapphire surface has radically different temperature dependence, thus providing a way to control atom surface interaction by means of temperature. Finally I will discuss the progress of our experiments towards demonstrating a quantum near field energy transfer from thermally excited sapphire surface polaritons to atoms (7P1/26D3/2), as well as towards performing the first spectroscopic measurements of the Casimir-Polder interaction with molecules.
18
MAY'16
Title: Seminar- In Defence of Lunacy
Seminar (Durham University)
Since its inception, physicists and philosophers have argued about how (or even if) we should interpret the theory of Quantum Mechanics. The bizarre and paradoxical implications of the theory have led many people to positions that eschew any kind of physically meaningful interpretation. To insist that Quantum Mechanics can admit a realist interpretation has caused many headaches for students, produced endless material for sci-fi fiction, and ruined a number of professional careers. Ninety years on from Max Born’s introduction of probability to Quantum Mechanics and the emergence of the “Copenhagen” consensus, I will reassess what a realistic interpretation of the theory might look like, examine how such a theory confronts the well-known quantum “paradoxes”, and speculate on what Niels Bohr would think of all this if he were around today.
Speakers: James Currie
11
MAY'16
Title: Seminar- Optical atomic clocks: from laboratory experiments to international timekeeping
Seminar (Durham University)
The most advanced optical atomic clocks have now reached levels of stability and accuracy that significantly surpass the performance of the best caesium primary frequency standards. As a result, the possibility of a future redefinition of the second in terms of an optical transition frequency is being actively considered by the international metrology community. At NPL we are developing optical atomic clocks based on two different types of technology: single laser-cooled ions confined in radiofrequency ion traps, and arrays of laser-cooled atoms trapped in an optical lattice. The principles of operation of these clocks and their current state-of-the-art performance will be described, as well as the methods we use to compare clocks both locally and in different institutes. Finally, the potential of optical atomic clocks for making high resolution measurements of the earth’s gravity field will be discussed.
Speakers: Helen Margolis
04
MAY'16
Title: Journal club talk- Double Slit and Triple Slit Experiments
Seminar (Durham University)
Weak measurements allow to empirically determine a set of average trajectories for an ensemble of quantum particles. However, when two particles are entangled, the trajectories of the first particle can depend nonlocally on the position of the second particle. Bohmian mechanics, is a minimalistic extension to the quantum mechanics, which attempts to assign realistic trajectories to quantum particles. Those trajectories become "surreal” when the second particle is used to probe the position of the first particle. Triple slit experiments are considered as a direct test of quantum mechanics. Born’s rule predicts that quantum interference, as shown by a double-slit diffraction experiment, occurs from pairs of paths. An alternative of quantum mechanics might allow multipath (i.e., higher-order) interference, thus leading to a deviation from the theory. This talk will give an overview of a double slit experiment with entangled photons and a triple slit experiment.
Speakers: Teodora Ilieva
27
APR'16
Title: Seminar-Old results and new perspectives in studies of multidimensional solitons
Seminar (Durham University)
Multidimensional solitons are objects which have been studied in detail, chiefly theoretically, but in some settings experimentally too, in nonlinear optics and Bose-Einstein condensates (BECs), in the course of past twenty years. The most important problem in that context is the stability of multidimensional solitons and solitary vortices. Recently, novel perspectives for the studies in this field have been brought to the attention of researchers. These developments reveal new theoretical and experimental settings that can support stable two- and three-dimensional (2D and 3D) solitons and vortices in optics and BEC. The present talk aims to provide an overview of some well-established results and ongoing developments in this field. In particular, as concerns matter-wave solitons, it has recently been predicted that a new mechanism, based on spin-orbit coupling, can stabilize two-component solitons of a semi-vortex type in the 2D and 3D space (in 2D they represent the ground state, while in 3D they are metastable objects).
Speakers: Boris Malomed
16
MAR'16
Title: Seminar- Cold atoms, ions, molecules and Rydbergs - new opportunities for chemical physics
Seminar (Durham University)
The development of a wide range of approaches for production and trapping of cold and ultracold species in the laboratory offers new opportunities to study chemical processes in a new physical regime. In this talk I will give an overview of our work in this area including the study of reactions of laser cooled and sympathetically cooled ions with cold molecules, the development of sources of non-alkali atoms and radicals, and the interaction of hydrogen Rydberg atoms with metallic thin-film surfaces.
Speakers: Tim Softley
09
MAR'16
Title: Seminar-Electromagnetic imaging with atomic magnetometers
Seminar (Durham University)
This talk will give an overview of our research programme on the use of atomic magnetometers to detect conductive objects via electromagnetic induction. The extreme sensitivity of atomic magnetometers at low frequencies, up to seven orders of magnitude higher than a coil-based system, allows their operation at low frequency, thus permitting deep penetration through different media and barriers, and in various operating environments. This eliminates the limitations usually associated with electromagnetic detection. Potential applications in medicine are also discussed.
Speakers: Ferruccio Renzoni
02
MAR'16
Title: Seminar- Mechanisms of surface area regulation in cells studied by artificial lipid systems
Seminar (Durham University)
The cell membrane undergoes complex morphological and surface area transformations while being confined to an underlying actin cortex, the membranes of neighboring cells or other extracellular structures. To understand the role of confinement in the membrane processes we adhere synthetic lipid bilayers to artificial substrates and subject them to two perturbations, common for cells membrane - 1) surface area changes, or 2) intake of extra lipids. Our experiments demonstrate that confined lipid bilayers are able to passively regulate the arising changes in their lipid density by delaminating and forming out of-plane protrusions. These findings were recently reproduced on cells. By varying the physicochemical properties of the confining structure and its adhesion to the membrane we aim to elucidate the intricate structure- function relationship existing at the cell interface.
24
FEB'16
Title: Seminar- Developing a Toolkit for Experimental Studies of Two-Dimensional Quantum Turbulence in Bose-Einstein Condensates
Seminar (Durham University)
Bose-Einstein condensates (BECs), with their superfluid behavior, quantized vortices, and high-level of control over trap geometry and other system parameters provide a compelling environment for studies of quantum fluid dynamics. Recently there has been an influx of theoretical and numerical progress in understanding the superfluid dynamics associated with two-dimensional quantum turbulence, with expectations that complementary experiments will soon be realized. In this talk I present recent efforts at the University of Arizona to develop an experimental toolkit that will enable such experimental studies. In particular, I will discuss a range of techniques for generating vortex distributions within a BEC, with varying degrees of control over vortex placement and winding number. The ability to gather information about the vortex dynamics of such complicated systems is equally important, and the nondeterministic dynamics of quantum turbulence and other far-from-equilibrium superfluid phenomena require the development of new imaging techniques that allow one to obtain information about vortex dynamics from a single BEC.I will discuss the state-of-the-art imaging of vortices and other superfluid phenomena in the University of Arizona BEC lab, and discuss prospects for extending these imaging methods to enable measurements of superfluid dynamics.
Speakers: Kali Wilson
17
FEB'16
Title: Seminar- Synoptics
Seminar (Durham University)
In this talk I will reflect on experiments in the field of optics where understanding both the real and imaginary part of the susceptibility of the medium are crucial for explaining the observed phenomena. I will focus on optically active media, and emphasise the point that studying the interactions of lasers, atoms and magnets spans the spectrum from the applied to the fundamental.
Speakers: Ifan Hughes
10
FEB'16
Title: Seminar-Quantum vortices: phase transitions and superfluid transport phenomena
Seminar (Durham University)
Quantized vortices play a crucial role in many phenomena in ultra-cold degenerate Bose gases. In (quasi-) two-dimensional systems point-like quantum vortices are associated with the normal to superfluid (BKT) transition, the breakdown of superfluidity in flows exceeding the critical velocity, and the Kibble-Zurek mechanism of topological defect formation. In this talk I will give an overview of these many roles played by two-dimensional quantum vortices, focusing in particular on recent work on a novel, non-equilibrium phase transition of quantum vortices that has intriguing links to the BKT transition [1,2], and on the breakdown of superfluidity in the presence of a defect [3]. I will outline current research directions relating to the Kibble-Zurek mechanism and the breakdown of superfluidity in disordered systems, which may be of relevance in the growing field of atom-tronics.
Speakers: Tom Billam
03
FEB'16
Title: Seminar- QBists, newbists, many world or many words- Reflections on the interpretation of quantum mechanics
Seminar (Durham University)
Should practicing physicists really care about matters of interpretation? Is this physics or metaphysics? In this talk, I review some of current viewpoints, give some arguments as to why we might care, and conclude with my current world view which at least appears to partially address the issue of free will versus determinism, albeit in a way that for some may still be rather deficient!
Speakers: Charles Adams
27
JAN'16
Title: Journal club- Simulating Quantum Magnetism: Reaching the Antiferromagnetically Ordered Phase
Seminar (Durham University)
Ultracold atoms in optical lattices offer a near perfect realisation of various types of Hubbard models, offering a highly tunable, well controlled system for exploring condensed matter physics. In recent years, the realisation of these quantum simulators has been the subject of huge interest in AMO physics [1]. The large amount of research activity in this field has led to viable quantum simulators of quantum magnetism, a topic of fundamental importance in condensed matter physics. The realisation of an antiferromagnetic phase in an atomic system would answer many open questions on the mechanisms behind high Tc superconductivity and could lead to the observation of many novel, exotic quantum phases, such as valence bond solids, resonating valence bond states and various kinds of quantum spin liquids [3]. A two-spin-component Fermi gas of ultracold atoms in an optical lattice is a tunable simulator of the Hubbard model which allows for the systematic exploration of its phase diagram. However, realising these strongly correlated phases is hampered by the requirement to cool the atoms to temperatures as low as the magnetic exchange energy (typically 10 nK). In this talk I shall briefly review open problems in condensed matter physics and the recent progress of AMO experiments which seek to resolve them. I will then focus on recent experimental observations of antiferromagnetic spin correlations [4][5] and discuss the techniques employed to reach such low temperatures and the thermometry required to measure the temperatures accurately. I will then review new techniques for cooling and thermometry which may allow the observation of the antiferromagnetically ordered phase and other exotic quantum phases.
Speakers: Alexander Guttridge
20
JAN'16
Title: Journal club- Intracellular microlasers
Seminar (Durham University)
Whispering-gallery modes are specific resonances of a wave field inside a resonator with smooth edges. They correspond to waves circulating in the resonator as a result of being trapped duo to total internal reflection off the resonator surface. The field of whispering-gallery mode microresonators has gained a lot of interest due to their unique combination of high Q-factors and low mode volumes. Whispering-gallery microresonators are widely used in a vast array of practical applications ranging from light storage devices and nonlinear optical effects to biochemical and optomechanical sensing. Recently, M. Humar and S. H. Yun have used whispering gallery microresonators and suitable optical gain material inside living cells to generate intracellular microlaser. They explored two distinct types of intracellular microresonators that support whispering-gallery modes. First, soft droplets formed by injecting oil or using natural lipid droplets. The laser spectra from oil droplet microlasers allows to measure cell generated mechanical stresses and its dynamic fluctuations at a sensitivity of 20 pN μm–2 (20 Pa). Second, solid polystyrene microspheres offer an effective way to device a non-deformable, intracellular lasers. Using different sizes of the solid microspheres enable individual tagging of thousands of cells easily.
Speakers: Nada Al Taisan
09
DEC'15
Title: Seminar- 10 people in the room, 11 views on many-body localization
Seminar (Durham University)
The phenomenon of many-body localization received a lot of attention recently, both for its implications in condensed-matter physics of allowing systems to be an insulator even at non-zero temperature as well as - maybe most importantly - in the context of the foundations of quantum statistical mechanics, providing examples of systems showing the absence of thermalization following out-of-equilibrium dynamics. Still, it seems fair to say that many aspects of it are still unsatisfactorily understood. In this talk, following an introduction into recent progress on thermalization of closed quantum systems, I will make the attempt to bring together several aspects of the phenomenology of many-body localization, attaining new insights into the connections between seemingly unrelated features. Ideas of entanglement area laws, Lieb-Robinson bounds, filter functions, approximately local constants of motion, transport, and tensor networks will feature strongly. We will discuss experimentally accessible witnesses of many-body localization in cold atomic quantum simulators.
Speakers: Jens Eisert
04
DEC'15
Title: How are Black Holes and Superfluids connected
Seminar (Newcastle University)
Abstract TBA
Speakers: Prof. Ruth Gregory
02
DEC'15
Title: Seminar- Interlinking Atomic Vapours and Solid-State Emitters
Seminar (Durham University)
Many scientific groups world wide research on the properties of single solid-state emitters– this covers quantum dots, nano-crystals, defect centers e.g. in diamond, or single organic molecules [1]. They are commonly used as tiny labels, single quantum emitters [2] or as nanoscopic reporters to their specific nano-environment. If the physics is carefully described, it is commonly performed in the language of atomic physics, a field which developed parallel to the research on solid-state systems. Recently, some attempts were made to combine solid-state studies with atomic spectroscopy. I will introduce and explain the basics of single molecule studies under ambient and cryogenic conditions. Our attempts for combining these studies with atomic spectroscopy will be outlined. Special organic dye molecules under cryogenic conditions allow for a spectral superposition with atomic systems and these emitters can be used for an infinite time [3]. Despite the common believe, they do not blink or bleach. Their brightness outperforms many other emitters due to the high index medium, which allows for efficient light extraction [4]. Also for the microscopy and spectroscopy of single emitters under ambient conditions atomic vapors can be used as efficient filters and enhance the collection efficiencies in a confocal or wide-field microscope [5]. As an example for the spin-active defects in a solid state environment, the nitrogen-vacancy defect center in diamond is commonly used as nanoscopic magnetic field sensor [6]. I will introduce our attempts to combine a large ensemble of these with a macroscopic Mx magnetometer based on hot rubidium vapor. We achieve sensitivities on the order of fT/√Hz in the macroscopic vapor cell with special coatings and buffer gas.
Speakers: Ilja Gerhardt
25
NOV'15
Title: Seminar- Direct Laser Cooling of Simple Molecules
Seminar (Durham University)
It was long thought that it would be hopeless to apply the laser cooling techniques that are so successful in atoms to even simple diatomic molecules, as their plethora of rotational and vibrational energies makes finding a closed cycle cooling transition extremely difficult. In the last few years a few diatomic molecules which are amenable to cooling have been identified. Both laser cooling and magneto-optical traps have been demonstrated. In this talk I will discuss the specific challenges of laser cooling molecules and how they are overcome. I will review our work at Imperial College on laser slowing of CaF. I will also discuss recent progress on slowing with a new Zeeman-Sisyphus technique, and our plans for a CaF MOT. Finally, I will outline our plans to apply laser cooling to YbF, a molecule which is of interest for precision tests of time reversal violation.
Speakers: Ben Sauer
18
NOV'15
Title: Seminar- Plasma Diagnostics: from the lab to the high-redshift Universe
Seminar (Durham University)
In this talk I will present a brief overview of activities in the Centre for Advanced Instrumentation at Durham, and explore in more depth three sub-fields loosely based around the theme of plasma spectroscopy. In particular I will describe the role of CfAI in an EPSRC CDT in Fusion Science & Technology, our development of facility-class infrared instrumentation for the ESO VLT, and our ongoing H2020-funded activities in astrophotonics. I will conclude by reviewing the potential for increased synergy and collaboration between CfAI and the JQC.
Speakers: Ray Sharples
11
NOV'15
Title: Seminar- Cold Atom Interferometry towards Gravity Mapping and other Space Applications
Seminar (Durham University)
“Gravity measurements are ideally suited to look deep inside the ground and they have been used for over 100 years in fields as oil and mineral exploration, underground mapping and climate research. Current classical gravimeters are reaching their fundamental limitations, mainly given by manufacturing tolerances and macroscopic size of the test mass. During the past 20 years big efforts have been put into developing Cold Atom based inertial sensors based on atom interferometry, with the state of the art laboratory experiments surpassing by several orders of magnitude the sensitivity of their classical counter parts. In recent years there have been promising developments of transportable Cold Atom Interferometer prototypes. In this seminar recent developments in portable accelerometers at the University of Birmingham will be presented. Also, the activities at RAL Space towards a space borne atom interferometer will be discussed.”
06
NOV'15
Title: A Quantum Gas in a Box: from BEC thermodynamics to Turbulence
Seminar (Newcastle University)
I will report on recent advances on the experimental production of a uniform Bose gas in a box of light [1]. This progress has allowed to revisit fundamental "textbook" topics in Bose-Einstein condensation: the saturation of the thermal component in a partially condensed cloud [2], the quantum Joule-Thomson effect of an ideal gas [2], or Heisenberg-limited momentum distribution of the ground state, consistent with a fully coherent macroscopic BEC spanning the whole box [3]. More recently, we have turned to far-from-equilibrium studies, and addressed the critical dynamics of spontaneous symmetry breaking during a temperature quench through the BEC phase transition. Using homodyne matter-wave interferometry we have observed the homogeneous Kibble-Zurek power-law scaling of coherence length with quench time, which allowed us to extract the dynamical critical exponent of that universality class [4]. Finally, I will present ongoing studies of turbulence in a Bose gas. Using an oscillating gradient, we pump energy in the lowest lying mode of the BEC and observe the emergence of a turbulent cascade in the momentum distribution.
Speakers: Dr Nir Navon
04
NOV'15
Title: Journal club- Detecting Gravitational Waves using Laser Interferometry
Seminar (Durham University)
The Laser Interferometer Gravitational-Wave Observatory (LIGO) is an experiment which aims to directly detect gravitational waves. The detectors are essentially Michelson interferometers with Fabry-Perot cavities in the arms. Initial LIGO (2002-2010) did not reach sensitivities high enough for detecting these waves, and was followed by a shutdown in which the detectors were replaced by Advanced LIGO [1]. Advanced LIGO is designed to have a factor of 10 improvement in sensitivity, through better seismic isolation [2], the addition of a quadruple suspension for the test masses [3], higher laser power [4], and enhanced core optics [1]. Data collecting runs began in September 2015, where it is expected to be possible to observe several gravitational wave detections every year, the most promising of which are compact binary mergers [5]. Measuring gravitational waves will help to broaden our understanding of fundamental physics, while introducing a new branch of observational astronomy.
Speakers: Niamh Keegan
30
OCT'15
Title: Dark soliton like excitations in a disk shaped Bose-Einstein Condensate
Seminar (Newcastle University)
Nonlinear systems out of equilibrium give rise to vortex and soliton solutions that play an important role in high speed optical communication[1], energy transport mechanisms in molecular biology [2] and astrophysics[3]. Collective excitations play a paramount role in transport of energy and information and are of special interest. In order to gain a deeper insight in these phenomena well controlled and flexible many body quantum systems at finite temperatures can be used for the simulation of these fundamental collective excitations of the nonlinear Gross-Pitaevski equation (GPE) and their dynamics. The finite temperature regime thereby models systems closer to realistic, everyday life systems in physics and biology. Here we present the experimental observation of quasi 2D excitations of the soliton family and spontaneous vortex formation in a disk shaped Bose-Einstein condensate of 87 Rb. For quasi 2D solitons the evolution, dynamics and their premature decay confined in an ultracold atomic system will be discussed. By using a spatial light modulator (SLM) for optical imprinting, the quantum phase of the Bose-Einstein condensate can be arbitrarily engineered. This versatile method gives rise to a nonlinear particle like matterwave pulses where the dispersion of the soliton like excitation is balanced by the repulsive interatomic interaction. The flexibility of the SLM gives the opportunity for the creation of more stable Jones-Roberts solitons by varying imprint shapes. Longer lifetimes are crucial for directed and efficient transport on surfaces. In contrast to formerly performed experiments in elongated BEC traps [4] the soliton like excitation created in the disk shaped Bose-Einstein condensate is dynamically unstable along one degree of freedom leading to the so-called snaking instability. However the collective excitation decays rapidly within a few ms which stands in contrast to numerical simulations of the GPE and prevents the onset of the expected decay into vortices. Investigating the lifetime of soliton like structures in the finite temperature regime shows a prolonged lifetime at lower temperatures. The results are compared to a modified model developed for quasi-1D BECs based on the scattering of thermal excitations [5, 6] and shows reasonable agreement.
Speakers: Dr. Nadine Meyer
28
OCT'15
Title: Seminar- Cavity Cooling and Quantum Control of nanoparticles in high vacuum
Seminar (Durham University)
It is predicted that levitated nanoparticles can be cooled to their c.o.m. ground state via the interaction with an optical cavity [1]. Levitated particles exhibit very large quality factors, plus dissipation and decoherence mechanisms are greatly reduced, leading to the potential to produce long-lived mechanical quantum states. Since the particle is free, it should be possible to produce macroscopically-spread quantum superpositions, allowing tests of collapse models and any mass limit of quantum physics. Reaching the low pressures required to cavity-cool to the ground state has proved challenging [2]. One method that has overcome this barrier is to levitate nanospheres in a Paul trap [3], using an optical cavity to cool to the mK level [4]. This hybrid system is stable at all pressures, and offers access to both linear and non-linear optomechanical coupling. Another approach is not to levitate at all, but rather to cavity cool a beam of nanoparticles in high vacuum [4], utilizing novel high finesse microcavities to enhance the optomechanical cooling, preparing the particles in a coherent beam ideally suited to high mass interferometry. We also have access to degrees of freedom other than the centre of mass, such as the rotational motion of nanorods [5].
Speakers: James Millen
28
OCT'15
Title: Vortex reconnections in fluids and superfluids
Seminar (Newcastle University)
Reconnections of field lines are critical events in which the topology of a system suddenly changes. Reconnections are also important because they seem to be associated with energy losses. In this talk I shall introduce the concept of reconnection in classical, astrophysical and quantum fluids, show that their geometrical nature is particularly simple in quantum fluids, and describe recent experimental and theoretical progress in understanding this phenomenon.
21
OCT'15
Title: Seminar - Hybrid quantum information processing with atoms, photons and superconducting circuits
Seminar (Durham University)
Hybrid quantum computation exploits the unique strengths of disparate quantum technologies, enabling realization of a scalable quantum device capable of both fast gates and long coherence times. We propose a quantum interface for creating hybrid entanglement between neutral atoms, superconducting circuits and optical photons. The interface is mediated by coupling superconducting circuits to Rydberg excited single atoms using chip-based coplanar waveguide microwave cavities. We have developed a simple gate scheme to enable entanglement of an atomic qubit with a microwave photon, with fidelity calculations based on realistic parameters giving Bell-state preparation fidelity exceeding 0.999 on μs timescales. Experimental progress towards the coherent excitation of a single atom above a coplanar waveguide in a 4 K cryostat at the University of Wisconsin-Madison will be presented, along with an overview of a newly established experiment at the University of Strathclyde focused on quantum networking of hybrid systems.
Speakers: John Pritchard
16
OCT'15
Title: Quantum Bright Solitons
Seminar (Newcastle University)
In a recent experiment at Durham University with attractively interacting bosons, we observed quantum reflection off an attractive barrier. The talk will start with modelling these results numerically. Attractively interacting Bosons in quasi-one-dimensional waveguides form weakly bound molecules, bright solitons. Bright solitons were discovered more than 160 years ago in a water channel: a water wave did not change its shape for many kilo-metres. Ultracold atoms with pairwise attractive interactions allow the creation of micro-versions of these bright solitons. These quantum bright solitons provide an ideal system to study quan-tum effects in the realm between macroscopic world our physical intuition is based on and the microscopic world of single atoms. The talk will show how many-particle quantum superpositions (Schro¨dinger-cat states) generated from quantum bright solitons can be used for quantum-enhanced interferometry. While decoherence would destroy such quantum superpositions, it can also lead to new physics.
Speakers: Dr Christoph Weiss
14
OCT'15
Title: Journal club: The Eigenstate Thermalization Hypothesis
Seminar (Durham University)
The question of when and why isolated quantum systems can be described by classical statistical mechanics has been open for many years. A question of particular interest is why isolated quantum systems initially prepared in a far-from-equilibrium state can eventually reach a state which appears to be in thermal equilibrium. The Eigenstate Thermalization Hypothesis says that for an arbitrary initial state, the expectation value of the observables of an isolated system will ultimately evolve to those predicted by a microcanonical ensemble. A system in this final state is said to have undergone thermalization. It has also been predicted that such systems can relax towards intermediate non-thermal values, which is known as prethermalization and has been established to occur in several models [1], and recent experiments [2,3,4]. In situations where thermalization is inhibited, the statistics of a quantum many-body system are described by a Generalized Gibbs Ensemble, rather than the usual thermodynamical ensembles. We will discuss recent experiments with degenerate 1-d Bose gases, in which this Generalized Gibbs Ensemble has been observed. Langen et al., Experimental observation of a generalized Gibbs ensemble, Science 348, 6231 (2015)
Speakers: Ben Beswick
29
SEP'15
Title: Seminar- How to trap 1 photon with N atoms- From Anderson Localization to Dicke Subradiance
Seminar (Durham University)
The quest for Anderson localization of light is at the center of many experimental and theoretical activities. Cold atoms have emerged as interesting quantum system to study coherent transport properties of light. Initial experiments have established that dilute samples with large optical thickness allow studying weak localization of light. The goal of our research is to study coherent transport of photons in dense samples. One important aspect is the quest of Anderson localization of light with cold atoms and its relation to Dicke super- or subradiance and possibly to many body physics with long range interactions. In this talk I will give an overview on our research and present results on cooperative scattering of light by cold atoms.
Speakers: Robin Kaiser
06
JUL'15
Title: JQC Symposium 2015
Conference (Durham University)

06
JUL'15
Title: JQC Colloquium 2015 - Ultrabright Ions from Ultracold Atoms
Seminar (Durham University)
Bright sources of charged particles represent a key enabling technology for imaging and nanoscale fabrication with the best possible spatial resolution, temporal sensitivity, and coherence. Traditionally, brightness is achieved by devising ways to get as many charged particles as possible to emit from as small a source area as possible. Sources such as the liquid metal ion source or the field emission electron source are representative of this approach. We have developed a new type of source that takes a radically different approach to attaining high brightness. Utilizing the ultracold temperatures achievable with laser cooling, our source can produce ion beams that not only have very high brightness, but also provide a wide choice of ionic species and a narrow energy spread. This source allows the creation of focused ion beams (FIBs) of new species such as alkalis and alkaline earths with nanometer resolution and picoampere currents, opening new opportunities for nanoscale imaging, material modification and ion implantation. For our first realization, we have constructed a source based on photoionization of a Li magneto-optical trap and mated this source with a conventional FIB column. I will discuss applications of this focused ion beam, both as an imaging tool and as a potential enabler of nanoscale ion transport studies. I will also discuss development of a new, higher brightness cold atom source with applications in nanomachining and integrated circuit edit.
Speakers: Jabez McClelland
28
JUN'15
Title: iCoRD
Conference
A conference on Rydberg physics to be held in Durham in 2015
24
JUN'15
Title: Seminar - Quantum simulation with ultracold Ytterbium atoms
Seminar (Durham University)
In quantum simulation of condensed matter models with ultracold atoms, the choice of the atomic element strongly depends on the model that has to be realized. Alkaline-earth-like atoms have several peculiarities which make them extremely attractive for quantum simulation, including the possibility of simulating multi-component fermionic systems possessing SU(N) symmetry and having an orbital degree of freedom. I will present the main results of the activity carried out in the last year with the Florence Ytterbium machine in which Ytterbium properties are used to realize different quantum simulations. In a first experiment [1], we have exploited the properties of the nuclear spin substates of ground state 173Yb to create one-dimensional liquids of ultracold fermions interacting repulsively within SU(N) symmetry. We observe that static and dynamic properties of the system deviate from those of ideal fermions, and that in the large-N limit, the system exhibits properties of a bosonic spinless liquid. In a second experiment [2], we coherent couple the nuclear spin substates by using two-photon Raman coupling. This coupling can be interpreted as a coherent tunneling term along a "synthetic lattice" made of up to six sites along the spin dimension. We use this analogy to explore the physics of a two-dimensional lattice in the presence of a synthetic magnetic field, and we witness the presence of chiral edge currents that build up in this Hall ribbon. Finally, we exploit the Yb clock transition to study the spin-exchange dynamics that originate when two atoms in the ground and excited electronic states collide [3]. We observe coherent oscillations between different long-lived electronic orbitals. This observation allows us to retrieve important information on the inter-orbital collisional properties of 173Yb atoms, paving the way to novel quantum simulations of paradigmatic models of two-orbital quantum magnetism.

[1] G. Pagano et al. Nature Phys. 10, 198 (2014)
[2] M. Mancini et al. arXiv1502.02495 (2015)
[3] G. Cappellini et al. Phys. Rev. Lett. 113, 120402 (2014)

Speakers: Carlo Sias
22
JUN'15
Title: Seminar - First Year Talk
Seminar (Durham University)
Abstract TBC
Speakers: Teodora Ilieva
17
JUN'15
Title: Seminar - First Year Talk
Seminar (Durham University)
Abstract TBC
Speakers: Nada Al Taisan
15
JUN'15
Title: Seminar - First Year Talk
Seminar (Durham University)
Abstract TBC
Speakers: Niamh Keegan
10
JUN'15
Title: Seminar - First Year Talk
Seminar (Durham University)
Abstract TBC
Speakers: Alex Guttridge
08
JUN'15
Title: Seminar - First Year Talk
Seminar (Durham University)
Abstract TBC
Speakers: Ben Beswick
03
JUN'15
Title: Seminar - Two-dimensional Spatial Adiabatic Passage of matter waves
Seminar (Durham University)
A full control of matter-wave transport is one of the key ingredients to design new quantum devices for neutral atoms circuits. In this context, adiabatic passage processes offer robustness, i.e., if the dynamical evolution is performed adiabatically the transfer will be efficient regardless of the selected specific parameter values used to drive the system and their fluctuations. Here, we focus onto the possibilities that two dimensional (2D) SAP offers. For instance, we show how to implement a novel scheme for matter-wave interferometry in a system of three identical 2D harmonic traps in a triangular geometry [1]. Specifically, we take advantage of an energy level crossing that occurs during the dynamics to create an equal probability coherent superposition of the atomic wave-function in two of the traps. If the trapping frequency of the final trap is half the trapping frequency of the other two harmonic traps, by following a superposition of two energy eigenstates of the system, a single cold atom is completely transferred from the ground state of the initial trap to the degenerate first excited states of the final trap. Depending on the total time of the process, angular momentum is generated in the final trap, with values that oscillate between ±ħ [2]. More involved geometries including four harmonic traps will be also discussed.

[1] R. Menchon-Enrich, S. McEndoo, J. Mompart, V. Ahufinger, and Th. Busch, Phys. Rev. A. 89, 053611 (2014).
[2] R. Menchon-Enrich, S. McEndoo, Th. Busch, V. Ahufinger, and J. Mompart, Phys. Rev. A 89, 013626 (2014).

20
MAY'15
Title: Seminar - Dynamic processes observed by scanning tunneling microscopes: vibrations, diffusions and reactions
Seminar (Durham University)
Dynamic processes in scanning tunneling microscopy (STM) are increasingly the focus of cutting edge research due to their importance for energy conversion and reaction processes. It is in principle possible to study these processes by suitable adaptation of STM theory and a step-by-step analysis of the processes themselves. I shall give several examples where such a detailed understanding is indispensible for a comprehensive understanding e.g. in atomic switching and diffusion processes, in molecular growth processes, condensation reactions, and long range molecular propagation even on reactive surfaces. At the end of my talk I shall demonstrate that careful statistical analysis in combination with high-resolution STM can even lead to surprising new insights into fundamental physics.

Selected references:
1. WA Hofer, AS Foster and AL Shluger, Theories of Scanning probe Microscopes at the Atomic Scale, Reviews of Modern Physics 75, 1287-1331 (2003)
2. PG Piva et al., Field regulation of single-molecule conductivity by a charged surface atom, Nature 435, 658-661 (2005)
3. KR Harikumar et al., Dipole-directed assembly of lines of 1,5-dichloropentane on silicon substrates by displacement of surface charge, Nature Nanotechnology 3, 222-229 (2008)
4. KR Harikumar et al., Cooperative molecular dynamics in surface reactions, Nature Chemistry 1, 716-721 (2009)
5. KR Harikumar et al., Directed long-range molecular migration energized by surface reaction, Nature Chemistry 3, 400-408 (2011)
6. L Liu et al., Reversible Spin Control of Individual Magnetic Molecule by Hydrogen Atom Adsorption, Scientific Reports 3, 1210 (2013)
7. WA Hofer, Heisenberg, uncertainty, and the scanning tunnelling microscope, Frontiers of Physics 7, 218 – 222 (2012)

Speakers: Werner Hofer
18
MAY'15
Title: Seminar - Quantum Turbulence in a trapped atomic superfluid
Seminar (Newcastle University)
We present our most recent results in the investigation of quantum turbulence in a sample of trapped Quantum fluid of Rb atom. Characteristics of the generation, momentum distribution, and other aspects will be presented.
Speakers: Vanderlei Bagnato
13
MAY'15
Title: Seminar - Fault-tolerant quantum computing: a gentle introduction
Seminar (Durham University)
I will present the theory behind how we hope to make quantum computers that tolerate faults, and so perform fast computations despite experimental imperfections. Don't worry if your unfamiliar with the field, I won't be assuming any prior knowledge of quantum computing theory. I shall start with some examples of error correction in modern (classical) technologies, before sketching how these ideas extend into the quantum domain. The most exciting area in this field is topological quantum codes, and I'll describe the simplest topological code. The talk will be largely pedagogical, but I will close by sketching some of my own research directions, including my work on cellular automata decoders for topological codes.
Speakers: Earl Campbell
12
MAY'15
Title: Seminar - Weak value amplification in resonance fluorescence
Seminar (Durham University)
The definition of measured values of an observable acting on a quantum system, also includes measurement results where the final system state is post-selected. A weak interaction regime of this observable can be consistently defined within this framework, as shown in Phys.Rev.Lett. Vol.60, 1351 (1988). Within this regime, the weak value of an observable is its first order truncated value, whenever the unitary evolution associated with the observable is (Taylor) expandable on a small parameter. Between nearly orthogonal initial and final states, and upon satisfying certain inequalities, this weak value gets amplified and the observable is said to show "weak value amplification".

In this talk, the case of resonance fluorescence arising from atomic decay with closely spaced excited states will be presented, for its weak value amplification effect, as reported recently in experiments. An understanding of this effect from the Wigner-Weiskopff theory will be laid out. This will clarify the sense in which, the observed weak value amplification in this system should be interpreted. The implications of this result to systems with interference effects in their spontaneous emission pathways, will also be indicated.

Speakers: Andal Narayanan
08
MAY'15
Title: Seminar - Solitons, vortices and solitonic vortices in superfluid atomic gases
Seminar (Newcastle University)
An overview of recent results (both theory and experiment) concerning solitons, vortices and solitonic vortices in trapped atomic gases with high aspect ratios.
Speakers: Franco Dalfovo
06
MAY'15
Title: Seminar - Electronic structure calculations from first principles
Seminar (Durham University)
The simulator builds a model of a real system and explores its behaviour. The model is a mathematical one and the exploration is done on a computer, and in many ways simulation studies share the same mentality as experimental ones. However, in a simulation there is (almost) absolute control and access to detail, the ability to compute almost any observable, and given enough computer muscle, exact answers for the model. These strengths have been exploited for the last sixty years and have led to many advances in the theory of condensed matter. However, it is only in the last twenty years or so that we have been able to compute the properties of condensed matter from first principles. The first-principles approach is vastly ambitious because its goal is to model real systems using no approximations whatsoever. That one can even hope to do this is down to the accuracy of quantum mechanics. Dirac’s apocryphal quip that after the discovery of quantum mechanics ‘the rest is chemistry’ sums it up. I will discuss ways in which this is done in Condensed Matter Physics.
Speakers: Stewart Clark
29
APR'15
Title: Seminar - Optical Preparation and Manipulation of Positronium Atoms
Seminar (Durham University)
The use of a Surko-type buffer gas trap [1] has made it possible to turn ordinary neon-moderated d.c. positron beams with pA currents [2] into devices that can deliver high quality cold positrons for high resolution scattering studies [3] or pulses containing up to 107 positrons in a ns burst [4]. The latter can be used to make a “gas” of positronium having a pressure of the order of 1 Torr, which in turn can be probed with pulsed lasers in much the same way as any other atomic species. The ability to create a Ps gas makes feasible a vast array of hitherto impractical or impossible experiments, such as the production of molecular positronium [5]. In this talk I will discuss some ongoing experiments in which highly excited atomic states of Ps can be created and studied. This includes Doppler-free 2-photon state-selective production of Rydberg Ps [6] and the production of selected Stark-States in electric fields [8]. The ultimate goal of such work is the electrostatic manipulation of Rydberg Ps with inhomogeneous electric fields [7]. In this way we hope to produce Ps “atom-optics” and focus and decelerate Ps atoms, enabling many new experiments, from spectroscopy to gravity measurements.

[1] J. R. Danielson, D. H. E. Dubin, R. G. Greaves, and C. M. Surko, Plasma and trap-based techniques for science with positrons, Rev. Mod. Phys. 87, 247 (2015).
[2] Positron Beams and Their Applications, edited by P. G. Coleman (World Scientific, Singapore, 2000).
[3] S. J. Gilbert, R. G. Greaves, and C. M. Surko “Positron Scattering from Atoms and Molecules at Low Energies” Phys. Rev. Lett. 82, 5032 (1999)
[4] D. B. Cassidy, S. H. M. Deng, R. G. Greaves, and A. P. Mills Jr. “Accumulator for the production of intense positron pulses” Rev. Sci. Instrum. 77, 073106 (2006).
[5] D. B. Cassidy, T. H. Hisakado, H. W. K. Tom, and A. P. Mills, Jr. “Optical Spectroscopy of Molecular Positronium” Phys. Rev. Lett. 108, 133402 (2012).
[6] T. E. Wall, D. B. Cassidy, and S. D. Hogan Single-color two-photon spectroscopy of Rydberg states in electric fields, Phys. Rev. A 90, 053430 (2014).
[7] S. D. Hogan and F. Merkt “Demonstration of Three-Dimensional Electrostatic Trapping of State-Selected Rydberg Atoms” Phys. Rev. Lett. 100, 043001 (2008).
[8] T. E. Wall, A. M. Alonso, B. S. Cooper, A. Deller, S. D. Hogan, and D. B. Cassidy, Selective production of Rydberg-Stark states of positronium, Accepted PRL, 9 April (2015).

Speakers: David Cassidy
22
APR'15
Title: Seminar - The creation of ultracold RbCs molecules in the rovibrational ground state
Seminar (Durham University)
Ultracold and quantum degenerate mixtures of two or more atomic species open up many new research avenues, including the formation of ultracold heteronuclear ground-state molecules possessing a permanent electric dipole moment. The anisotropic, long range dipole-dipole interactions between such molecules offer many potential applications, including novel schemes for quantum simulation. The most successful technique to date for the realisation of ultracold molecules has relied on a two-step approach using magnetoassocation on a Feshbach resonance followed by optical transfer to the rovibrational ground state. I will give a tutorial-style overview of this approach, illustrated with results from our own work [1,2] on RbCs. [1] P.K. Molony, P.D. Gregory, Z. Ji, B. Lu, M.P. Köppinger, C.R. Le Sueur, C.L. Blackley, J.M. Hutson, and S.L. Cornish, Phys. Rev. Lett. 113, 255301 (2014). [2] M.P. Köppinger, D.J. McCarron, D.L. Jenkin, P.K. Molony, H.-W. Cho, C.R. Le Sueur, C.L. Blackley, J.M. Hutson and S. L. Cornish, Phys. Rev. A 89, 033604 (2014).
Speakers: Simon Cornish
17
APR'15
Title: Newcastle Applied Maths Seminar - Superfluid turbulence and vortex dynamics in the zero temperature limit
Seminar (Newcastle University)
Newcastle Applied Maths Seminar - Superfluid turbulence and vortex dynamics in the zero temperature limit.
Speakers: Paul Walmsley
13
MAR'15
Title: Newcastle Applied Maths Seminar: Fluctuating fields - with three variations
Seminar (Newcastle University)
Fluctuating fields are very common concept that we are virtually forced to use in a variety of contexts, be it traffic dynamics, the acoustics of hearing, or plasma physics. The approaches also differ widely: mathematicians think of probability functionals, while physicists ask for "what" is fluctuating and how "its" fluctuations can be measured and characterized. In this talk, I introduce three examples and explain recent work in progress: (a) vacuum fluctuations of the electromagnetic field; (b) density and phase fluctuations in dilute Bose gases; and (c) thermal current and magnetic field noise near conducting surfaces and its impact on precision measurements of dispersion forces (van der Waals, Casimir).
Speakers: Carsten Henkel
11
MAR'15
Title: Seminar - Dynamical Condensation Routes in Single and Binary Condensates
Seminar (Durham University)
The issue of condensate formation is a long-standing milestone problem for different physical systems. Diverse techniques used in experiment include (direct) evaporative cooling, surface evaporative cooling, quenches and, in the context of multiple species, sympathetic cooling. Different theoretical models have been developed and applied to such distinct dynamical processes. Starting from a general overview for single and binary condensate formation, I will discuss recent progress in our group in those areas.

More specifically, I will discuss our contributions to the study of condensation dynamics during (i) surface evaporative cooling on an atom chip [1], (ii) the splitting of a single-component condensate [2], and competing condensation dynamics (iii) when quenching an equilibrated binary immiscible mixture [3], (iv) during the sympathetic cooling of a two-species system [4], and (v) during the turbulent phase following from random non-equilibrium initial conditions.

[1] Maerkle et al., Evaporative cooling of cold atoms at surfaces, PRA 90, 023614 (2014)
[2] Pattinson et al., Equilibration of a finite-temperature binary Bose gas formed by population transfer, PRA 90, 033625 (2014)
[3] Liu et al., Spontaneously-Generated Defects and Dark-Bright Solitary Waves in the Growth of Trapped Immiscible Binary Condensates, arXiv:1408.0891 (2014)
[4] Edmonds et al., Kinetic model of trapped finite-temperature binary condensates, PRA 91, 011602 (R) (2014)

Speakers: Nikolaos Proukakis
04
MAR'15
Title: Seminar - Photon interactions in a laser-driven Rydberg gas
Seminar (Durham University)
Electromagnetically induced transparency (EIT) in a system of interacting Rydberg atoms provi-des a unique platform to explore strong and nonlocal optical nonlinearities, both in the classical and quantum regime. We present our recent progress in understanding the nature of effective photon interactions in such a medium. In the limit of large photon numbers and moderate nonlinearities we discuss the applicability of a mean-field approach for the light field, which is shown to permit an analytical treatment of its propagation dynamics. In the opposite limit, strong correlation effects start to play a dominant role and are explored within few-body quantum calculations. Experimental signatures for the found interaction effects will also be discussed.
Speakers: Dario Jukić
27
FEB'15
Title: Newcastle Applied Maths Seminar: Title TBA
Seminar (Newcastle University)
Newcastle Applied Maths Seminar: Viv Kendon, Durham
Speakers: Viv Kendon
25
FEB'15
Title: Seminar - Journal Club: Possibilities of Direct Laser Cooling of Molecules with the Bichromatic Force
Seminar (Durham University)
The force atoms experience while scattering photons from a monochromatic light field is extensively used in experiments to cool and trap atoms. The peak magnitude of this force is limited by the maximum scattering rate. Another limiting factor is that over the course of many cycles of absorption and spontaneous emission only the former contributes to the net momentum exchange. This in turn sets a lower limit on the distance and time required for atoms to be decelerated.

It has recently been shown that laser cooling can be achieved without spontaneous emission [1]. This was possible using bichromatic light to generate a force consisting of cycles of absorption and stimulated emission which greatly exceeds the peak magnitude of the radiative force and works on much shorter time scales. This concept has been put to use in a few applications including the deceleration of atomic beams [2]. The main example presented here will be the application of direct laser cooling of molecules. This will be illustrated by driving multiple transitions in metastable Helium [3].

References:
[1] J. Söding et al. Phys. Rev. Lett. 78, 1420 (1997).
[2] C. Corder, B. Arnold & H. Metcalf. Phys. Rev. Lett. 114, 043002 (2015).
[3] M. A. Chieda & E. E. Eyler, Phys. Rev. A. 84, 063401 (2011).

Speakers: Lewis McArd
20
FEB'15
Title: Newcastle Applied Maths Seminar: Finite helicity change and energy dissipation in Navier-Stokes reconnection
Seminar (Newcastle University)
Newcastle Applied Maths Seminar: Bob Kerr, Warwick
Speakers: Bob Kerr
18
FEB'15
Title: Seminar - Probing light-matter entangled states through environmental transitions
Seminar (Durham University)
In this talk I shall show that emitter-cavity dressed states may be probed through interactions with a thermal environment in solid-state cavity QED systems. This is true even in regimes that can be described semiclassically in the absence of such an environment, for example when the emitter-cavity coupling strength is dominated by cavity losses. For this experimentally relevant case, I shall outline how bath-induced dressed state transitions lead to asymmetries in the cavity emission properties, which are absent otherwise. This behaviour is attributed to the quantum nature of the environment and its resulting sensitivity to the joint eigenstructure of the cavity and emitter. This heralds a failure of the semiclassical approach, and challenges the notion that coupling to a thermal bath supports a more classical description of the system. Bath-induced asymmetries also persist over wider regions of parameter space, including the Fano and quantum strong coupling regimes.
Speakers: Ahsan Nazir
11
FEB'15
Title: Ultracold Atoms - A new playground for quantum physics
Seminar (Newcastle University)
Ultracold Atoms: A new playground for quantum physics?
11
FEB'15
Title: Defects in silicon carbide - limitation or exploitation
Seminar (Newcastle University)
The density of defects in state of the art silicon carbide wafers is often expressed in terms of 1,000's per cm2, which is significantly higher than mature technologies such as silicon or gallium arsenide. Conventional thinking has concentrated on correlating these defects with low breakdown voltage behaviour and poor carrier mobility, with significant effort concentrating on the removal of micropipes and minimising the concentration of Z1/2 and ON1 and ON2 defects through crystal growth and process optimisation. However, the long spin coherence times of these deep defect levels have shown behaviour similar to the well known NV defect in diamond. Initial results indicate that carbon-silicon defects are extremely sensitive to the local environment within the crystal and may well act as high spatial resolution sensors for magnetic field and temperature. The talk will outline the scale of the challenge and opportunities possible with this new paradigm.
Speakers: Dr. Alton Horsfall
11
FEB'15
Title: Seminar - Journal Club: Photons that travel in free space slower than the speed of light
Seminar (Durham University)
Controlling the speed of light pulses is an important aspect of most modern communication networks. Generally speaking experiments involving fast and slow light are based on dispersion in atomic media. However, modification of the spatial structure of light also results in a change of group velocity. Recently this has been demonstrated for single photons in both Bessel and focused Gaussian beams [1]. I present the results for discussion. [1] Daniel Giovannini, et. al., Spatially structured photons that travel in free space slower than the speed of light, Sciencexpress, DOI: 10.1126/science.aaa3035
Speakers: Dan Whiting
04
FEB'15
Title: Seminar - Capabilities in nano and micro fabrication in Durham and applications to spintronics and nanomagnetism
Seminar (Durham University)
This talk will begin with an overview of the methodologies and facilities for nano-scale and micro-scale fabrication of thin-films and micro/nanoscale structures created using lithographic methods and vapour phase thin-film deposition. The talk will show examples of the applications of these techniques to create samples and structures used to study and understand magnetic and magneto-electronic behaviour.
Speakers: Del Atkinson
30
JAN'15
Title: Leggett-Garg Inequalities
Seminar (Newcastle University)
Newcastle Applied Maths Seminar: Clive Emary, Hull Leggett-Garg inequalities
Speakers: Dr. Clive Emary
28
JAN'15
Title: Seminar - Semiconductor Devices for Quantum Security Technologies
Seminar (Durham University)
In the present day there is only one commercial application of quantum information processing (QIP), quantum key distribution, and the market embracing it is small. The development of further applications requires the realisation of a suite of practical devices that are able to create, buffer, process and repeat quantum information. Semiconductor structures have dominated digital information’s history, as their ease of use and scalability are both ideal in meeting market demands. In the Quantum Technology Centre at Lancaster University we are developing semiconductor devices for practical applications of QIP, and in this talk I will discuss our progress.
Speakers: Robert Young
28
JAN'15
Title: How real are electrons
Seminar (Newcastle University)
Given the experimental precision in condensed matter physics — positions are measured with errors of less than 0.1pm, energies with about 0.1meV, and temperature levels are below 20mK — it can be inferred that standard quantum mechanics, with its inherent uncertainties, is a model at the end of its natural lifetime. In this talk I want to explore a future physical framework beyond this model. Extended electrons, which lend themselves to a spacetime description of wave properties, will be the key to such a framework. After all, even Einstein considered the question, what electrons actually are, as the main question in all physical theory. The model introduced combines wave mechanics and density functional theory at the level of single electrons and in a non-statistical manner...
21
JAN'15
Title: Seminar - Journal Club: Topologically Protected States in AMO Physics
Seminar (Durham University)
Sometimes measurable properties of the system depend directly on the global shape of the state space, as measured by topological invariants. These properties are then well reproducible and produce countable values. Their global character protects them against changes due to local perturbations. This concepts are already exploited in secondary voltage and resistance standards, that are consistent between each other to several parts in 10^17 and 10^10 respectively, in spite in microscopic variations between the produced standards. In recent years, interest in this concepts has been renewed due to discovery of novel states of mater (topological insulators [1]) and theoretically predicted possibility for particle statistics in 2-dimensional systems that is between bosonic and fermionic statistics, raising hopes for possible quantum computation approaches insensitive to local perturbations [2].

In this talk I will cover the history of basic topological ideas in physics, before giving examples from atomic, optical and molecular physics. We will see details of topologically protected transport phenomena [3] and possible avenues for preparation of the states with non-trivial topology [4].

[1] M.Z.Hassan, C.L.Kane, Reviews of Modern Physics 82:3045 (2010)
[2] C. Nayek et al, Reviews of Modern Physics 90:1083 (2008); P. Zanardi, S. Lloyd, PRL 90:067902 (2003); L. Jiang et al, Nature Physics 4:482 (2008)
[3] M.Hafezi et. al, Nature Physics 7:907 (2011); M.Hafezi et.al, Nature Photonics 7:1001 (2013); Kitagawa T. et al, PRA 82, 033429 (2010); Kitagawa, T. et al, Nat. Commun. 3:882 (2012)
[4] N.Yao et al, PRL 110:185302 (2013); N. Cooper, J. Dalibard, PRL 110:185301 (2013); D.Peter et al, arXiv:1410.5667 (2014); M. Maghrebi et al. arXiv:1411.6624 (2014)

Speakers: Nikola Sibalic
14
JAN'15
Title: Seminar - Strong Interactions in Alkaline-Earth Rydberg Ensembles
Seminar (Durham University)
Ultra-cold atoms in optical lattices provide a versatile and robust platform to study fundamental condensed-matter physics problems and have applications in quantum optics as well as quantum information processing. For many of these applications, Rydberg atoms (atoms excited to large principal quantum numbers) are ideal due to its long coherence times and strong interactions. However, one of the pre-requisite for such applications is identical confinement of ground state atoms with Rydberg atoms. This is challenging for conventionally used alkali atoms. In this talk, I would like to discuss the potential of using alkaline-earth Rydberg atoms for many-body physics by implementing simultaneous trapping for the relevant internal states. In particular, I will discuss a scheme for generating multi-particle entanglement and explore charge transport in a one dimensional atomic lattice.
Speakers: Rick Mukherjee
12
DEC'14
Title: Emergent phenomena in two-dimensional quantum vortex dynamics
Seminar (Newcastle University)
Tom Billam (Durham)
Speakers: Tom Billam