Theory of Bose condensation of light via laser cooling of atoms

Abstract

A Bose-Einstein condensate (BEC) is a quantum phase of matter achieved at low temperatures. Photons, one of the most prominent species of bosons, do not typically condense due to the lack of a particle number-conservation. We recently described a photon thermalization mechanism which gives rise to a grand canonical ensemble of light with effective photon number conservation between a subsystem and a particle reservoir. This mechanism occurs during Doppler laser cooling of atoms where the atoms serve as a temperature reservoir while the cooling laser photons serve as a particle reservoir. Here we address the question of the possibility of a BEC of photons in this laser cooling photon thermalization scenario and theoretically demonstrate that a Bose condensation of photons can be realized by cooling an ensemble of two-level atoms (realizable with alkaline earth atoms) inside a Fabry-Perot cavity. arXiv:1809.07777v1 [physics.atom-ph]

Photon Pair Condensation by Engineered Dissipation

“…With the rapid development of quantum optical technology and quantum information platforms such as cavity/circuit quantum electrodynamics (QED) [1][2][3] and Rydberg polaritons [4], it is now possible to investigate strongly-correlated many-body physics of photons [3,[5][6][7][8]. While photons can have strong interactions in these platforms, they do not naturally thermalize, and one has to synthesize thermalization and a chemical potential to obtain many-body ground states [9][10][11][12][13][14]. Remarkably, dissipation induced by the environment, which is usually regarded as a noise source leading to decoherence of the states, can actually become a useful resource.…”