A story of deception
At the age of 11 or 12, during a hot summer, I started throwing stones into the air and timing them as they hit the ground to try and find out if I could somehow describe their motion. Obviously, I failed: I did not understand the importance of repeatability in experiments.
...thus I decided that I would become a Physicist.
Later, when I was studying Theoretical Physics in the Universidad Complutense de Madrid (Spain), I really loved Differential Geometry and Relativity, but had to take some modules on Quantum Physics, and Atomic and Molecular Physics... and failed them (once): I did not understand the non-intuitive ways in which matter and light interact at the fundamental level.
That's why I decided to do research on Quantum and Atomic Optics.
And after spending a summer at the Catalonian Institute of Photonic Sciences (ICFO), I landed in Durham.
Here, under the supervision of Charles Adams we study the (highly) nonlinear properties of cold Rydberg gases and their interactions with light.
Can we make two photons interact?
We want to make photons interact (for several reasons), but that can only happen if we provide a very nonlinear medium that can provide interactions even between single photons.
In our experiment  we store quanta of light in a tightly-confined ensemble of atoms that are excited to a high principal quantum number state (also called Rydberg atoms). To do that, we use electromagnetically induced transparency , which "converts" these photons into excitations in the medium. These atoms interact very strongly with each other, and we can map that interaction to an effective interaction between the photons that have been stored (called polaritons). Then, when we retrieve the photons, we check the effect of the interactions in the photons.
For some details, you can take a look at our Research page.
We are building a new experiment to study these interactions in new systems. We are working on schemes to implement a photonic phase-gate, which might be useful for Quantum Computation, and to try to observe excitation transfer between Rydberg atoms, with some applications related to the study of photosynthesis in Biology.
Food for thought (just a couple of links)
 D. Maxwell et al. Phys. Rev. Lett. 110, 103001 (2013)[free version here]
 M. Fleischhauer, A. Imamoglu, and J. P. Marangos (2005), "Electromagnetically induced transparency: Optics in Coherent Media", Reviews Modern Physics, 77, 633 [free version here]