tahan.com/charlie: Quantum phase transitions of light
As physics and engineering extend their reach to the control of single excitations of nature, we gain the ability to explore and even design the interaction of matter and energy in fundamentally new ways. One of the most interesting opportunities this presents is controllable interactions between many quantum particles — such as electrons — which is traditionally the realm of condensed matter physics. The questions we asked ourselves were these: Can we also do this with light? Can it be useful? We show that the answer is YES!
Cover Letter
Condensed matter and quantum optics are two branches of physics that attempt to understand the complexities of interacting quantum systems. Traditionally, condensed matter has adopted a ‘top down’ approach, by considering large systems of interacting particles, whilst quantum optics has taken a ‘bottom up’ approach by concentrating on individual quantum systems. Such approaches have been warranted because condensed matter systems usually are typified by many interacting particles, but little ability to readout individual constituents, whereas quantum optical systems are relatively easy to interrogate, but it is difficult to create strongly interacting many-body systems.
We unite these two fields by theoretically demonstrating that a quantum optical system comprised of a 2D lattice of cavities, each containing a single two-level atom, can be viewed as being analogous to a Hubbard system, a standard model for the understanding of condensed matter. Such a connection opens up the rich field of condensed matter physics to exploration by the quantum optics community, and because of the superb outcoupling potential of optical cavities, it is likely that new devices may be developed based on these approaches. One example device which could be built would be a 2D lattice of single (or multiple) photon sources, which would self-organise, and could be simultaneously out-coupled, with obvious applications to linear optics quantum computing and quantum communication. [More]