Session M4: Invited Session: Quantum Simulation with Photons

High Orbital Exciton-Polariton Condensates in Two-Dimensional Lattices

Microcavity exciton-polaritons are hybrid quantum quasi-particles as admixtures of cavity photons and quantum-well excitons. The inherent light-matter duality provides experimental advantages to undergo a phase change to condensation at high temperatures (e.g. 4-10 K in GaAs and room temperatures in GaN materials) due to the extremely light effective mass and stimulated scattering processes, and the dynamical nature in the open-dissipative condition allows us to control orbital symmetries of condensates. We have engineered two-dimensional polariton-lattice systems for the investigation of exotic quantum phase order arising from high orbital bands. Via photoluminescence signals in both real and momentum coordinates, we have observed $d$-orbital meta-stable condensation, vortex-antivortex phase order, linear Dirac dispersion, and flattened band structures in square, honeycomb, triangular and kagome lattices respectively. We envision that the polariton-lattice systems will be promising solid-state quantum emulators in the quest for understanding strongly correlated materials and in the development of novel optoelectronic devices.   

Quantum Hall physics with light

Quantum Hall physics provides a variety of novel phenomena in both the integer and fractional domain, with applications in metrology, technology, and quantum computation. I will discuss implementing quantum Hall physics with optical systems by means of synthetic gauge fields and photon-photon interactions. First, in the integer quantum Hall regime, I consider our theoretical and experimental efforts using established photonics technology to see expected phenomena, such as edge states of light. I will then consider the nonlinear regime, where photon-photon interactions via optical or microwave nonlinearities enable the potential realization of fractional quantum Hall states, and indicate challenges and solutions for examining pumped, non-equilibrium systems that do not admit a mean-field description. Finally, potential applications of these ideas in passive and active photonics will be examined.   

Many body physics with light

Systems of strongly interacting atoms and photons, which can be realized wiring up individual Cavity QED (CQED) systems into lattices, are perceived as a new platform for quantum simulation [1-3]. While sharing important properties with other systems of interacting quantum particles, the nature of light-matter interaction gives rise to unique features with no analogs in condensed matter or atomic physics setups. Such Lattice CQED systems operate on polaritonic quasi-particles that are hybrids of light and matter in a controllable proportion, combining long-range coherence of photons and strong interactions typically displayed by massive particles. In this talk, I will discuss our recent efforts [4-6] on the possibility of observing quantum many body physics and quantum phase transitions in Lattice CQED systems. Unavoidable photon loss coupled with the ease of feeding in additional photons through continuous external driving renders such lattices open quantum systems [5]. Another key aspect of many body physics with light that I will focus on is the particle number non-conserving nature of the fundamental light-matter interaction [6] and the question of what quantity, if not the chemical potential, can stabilize finite density quantum phases of correlated photons.\\[4pt] [1] M. J. Hartmann, F. G. Brandao, and M. B. Plenio, Laser and Photonics Reviews {\bf 2}, 527 (2008).\\[0pt] [2] A. Tomadin and R. Fazio, JOSA B {\bf 27}, A130 (2010).\\[0pt] [3] A. Houck, H. E. Tureci, and J. Koch, Nature Phys. {\bf 8}, 292 (2012).\\[0pt] [4] S. Schmidt, D. Gerace, A. A. Houck, G. Blatter, and H. E. Tureci, Physical Review B {\bf 82}, 100507 (2010).\\[0pt] [5] F. Nissen, S. Schmidt, M. Biondi, G. Blatter, H. E. Tureci, J. Keeling, Phys. Rev. Lett. {\bf 108}, 233603 (2012).\\[0pt] [6] M. Schiro, M. Bordyuh, B. Oztop, H. E. Tureci, Phys. Rev. Lett. {\bf 109}, 053601 (2012).   

Bose-Einstein condensation of photons

In recent work, we have observed Bose-Einstein condensation (BEC) of a two-dimensional photon gas in an optical microcavity [1]. Here, the transversal motional degrees of freedom of the photons are thermally coupled to the cavity environment by multiple absorption-fluorescence cycles in a dye medium, with the latter serving both as a heat bath and a particle reservoir. The photon energies in this system are found to follow a Bose-Einstein distribution at room temperature. Upon reaching a critical total photon number, a condensation into the transversal ground state of the resonator sets in, while the population of the transversally excited modes roughly saturates. The critical photon number is experimentally verified to agree well with theoretical predictions. Owing to particle exchange between the photon gas and the dye molecules, grandcanonical experimental conditions can approximately be realized in this system. Under these conditions, two markedly different condensate regimes are theoretically expected [2]. On the one hand, this includes a condensate with Poissonian photon number statistics, being the analog to present atomic Bose condensates. Additionally, we predict a second regime with anomalously large condensate fluctuations accompanied by a Bose-Einstein-like photon number distribution that is not observed in present atomic BEC experiments. The crossover between these two regimes, corresponding to the emergence of second-order coherence, depends on the size of the molecular reservoir (e.g. the dye concentration) and is expected to occur at a temperature below the BEC phase transition. In my talk, I will give an update on our experimental work.\\[4pt] [1] J. Klaers, J. Schmitt, F. Vewinger, and M. Weitz, \textit{Nature} \textbf{468}, 545 (2010)\\[0pt] [2] J. Klaers, J. Schmitt, T. Damm, F. Vewinger, and M. Weitz, \textit{Phys. Rev. Lett.} \textbf{108}, 160403 (2012)   

From Mott transitions to interacting relativistic theories with light: A brief history of photonic quantum simulators

I will start by reviewing our early works for observing photon-blockade induced Mott transitions in coupled cavity QED systems [1]. After briefly touching on the idea of simulating spin-models and the Fractional Hall effect [2], I will analyze more recent developments in realizing continuous 1D models in nonlinear optical fibers exhibiting electromagnetically induced transparency nonlinearities. Here the concept of the ``photonic Luttinger liquid'' will be introduced, along with a proposal to observe spin-charge separation with polarized photons in a nonlinear slow light set up [3]. I will continue by presenting our recent efforts in simulating 1D lattice models in the non-relativistic regime, such as the sine-Gordon and Bose-Hubbard [4], and the efforts for simulations of out of equilibrium phenomena using driven systems [5,6]. I will conclude by presenting ongoing work on interacting relativistic models (Thirring)[7]. Possible experimental implementations in quantum optical systems such as photonic crystals, optical fibers coupled to cold atoms, and Circuit QED will be discussed.\\[4pt] [1] D.G. Angelakis, M.F. Santos and S. Bose, Phys. Rev. A \textbf{76}, 031805(R) (2007); D.G. Angelakis, Reports in Progress in Phys., IOP (2012) to appear.\\[0pt] [2] J. Cho, D.G. Angelakis, Phys. Rev. Lett \textbf{101}, 246809 (2008).\\[0pt] [3] D.G. Angelakis, M.-X. Huo, E. Kyoseva and L.C.Kwek, Phys. Rev. Lett. \textbf{106}, 153601 (2011).\\[0pt] [4] M.-X. Huo, D.G. Angelakis, Phys. Rev. A \textbf{85} 023821 (2012)\\[0pt] [5] T. Gruzic, S. R. Clark, D. G. Angelakis. Dieter Jacksh, New Jour,. of Phys. \textbf{14}, 103025 (2012). [6] P. Das, C. Noh, D.G. Angelakis, arXiv:1208.0313.\\[0pt] [7] D.G. Angelakis, M.-X. Huo, D. Chang, L.C. Kwek, V. Korepin arXiv:1207.7272.