Floquet engineering or coherent time periodic driving of quantum systems has been successfully used to synthesize Hamiltonians with novel properties. In ultracold atomic systems, this has led to experimental realizations of artificial gauge fields, topological band structures, and observation of dynamical localization, to name just a few. Here we present a Floquet-based framework to stroboscopically engineer Hamiltonians with spatial features and periodicity below the diffraction limit of light used to create them by time-averaging over various configurations of a 1D optical Kronig-Penney (KP) lattice. The KP potential is a lattice of narrow subwavelength barriers spaced by half the optical wavelength (λ/2) and arises from the non-linear optical response of the atomic dark state. Stroboscopic control over the strength and position of this lattice requires time-dependent adiabatic manipulation of the dark state spin composition. We investigate adiabaticity requirements and shape our time-dependent light fields to respect the requirements. We apply this framework to show that a λ/4-spaced lattice can be synthesized using realistic experimental parameters as an example, discuss mechanisms that limit lifetimes in these lattices, explore candidate systems and their limitations, and treat adiabatic loading into the ground band of these lattices.

%8 06/18/2019 %G eng %U https://arxiv.org/abs/1906.07646 %0 Journal Article %D 2018 %T Bose Condensation of Photons Thermalized via Laser Cooling of Atoms %A Chiao-Hsuan Wang %A M. J. Gullans %A J. V. Porto %A William D. Phillips %A Jacob M. Taylor %XA 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.

%G eng %U https://arxiv.org/abs/1809.07777 %0 Journal Article %D 2018 %T Coherent optical nano-tweezers for ultra-cold atoms %A P. Bienias %A S. Subhankar %A Y. Wang %A T-C Tsui %A F. Jendrzejewski %A T. Tiecke %A G. Juzeliūnas %A L. Jiang %A S. L. Rolston %A J. V. Porto %A Alexey V. Gorshkov %XThere has been a recent surge of interest and progress in creating subwavelength free-space optical potentials for ultra-cold atoms. A key open question is whether geometric potentials, which are repulsive and ubiquitous in the creation of subwavelength free-space potentials, forbid the creation of narrow traps with long lifetimes. Here, we show that it is possible to create such traps. We propose two schemes for realizing subwavelength traps and demonstrate their superiority over existing proposals. We analyze the lifetime of atoms in such traps and show that long-lived bound states are possible. This work opens a new frontier for the subwavelength control and manipulation of ultracold matter, with applications in quantum chemistry and quantum simulation.

%G eng %U https://arxiv.org/abs/1808.02487 %0 Journal Article %J New Journal of Physics %D 2018 %T Optimization of photon storage fidelity in ordered atomic arrays %A M. T. Manzoni %A M. Moreno-Cardoner %A A. Asenjo-Garcia %A J. V. Porto %A Alexey V. Gorshkov %A D. E. Chang %XA major application for atomic ensembles consists of a quantum memory for light, in which an optical state can be reversibly converted to a collective atomic excitation on demand. There exists a well-known fundamental bound on the storage error, when the ensemble is describable by a continuous medium governed by the Maxwell-Bloch equations. The validity of this model can break down, however, in systems such as dense, ordered atomic arrays, where strong interference in emission can give rise to phenomena such as subradiance and "selective" radiance. Here, we develop a general formalism that finds the maximum storage efficiency for a collection of atoms with discrete, known positions, and a given spatial mode in which an optical field is sent. As an example, we apply this technique to study a finite two-dimensional square array of atoms. We show that such a system enables a storage error that scales with atom number Na like ∼(logNa)2/N2a, and that, remarkably, an array of just 4×4 atoms in principle allows for an efficiency comparable to a disordered ensemble with optical depth of around 600.

%B New Journal of Physics %V 20 %8 2018/08/31 %G eng %U https://arxiv.org/abs/1710.06312 %N 083048 %R https://doi.org/10.1088/1367-2630/aadb74 %0 Journal Article %J Phys. Rev. A 98, 013834 %D 2018 %T Photon thermalization via laser cooling of atoms %A Chiao-Hsuan Wang %A M. J. Gullans %A J. V. Porto %A William D. Phillips %A Jacob M. Taylor %XLaser cooling of atomic motion enables a wide variety of technological and scientific explorations using cold atoms. Here we focus on the effect of laser cooling on the photons instead of on the atoms. Specifically, we show that non-interacting photons can thermalize with the atoms to a grand canonical ensemble with a non-zero chemical potential. This thermalization is accomplished via scattering of light between different optical modes, mediated by the laser cooling process. While optically thin modes lead to traditional laser cooling of the atoms, the dynamics of multiple scattering in optically thick modes has been more challenging to describe. We find that in an appropriate set of limits, multiple scattering leads to thermalization of the light with the atomic motion in a manner that approximately conserves total photon number between the laser beams and optically thick modes. In this regime, the subsystem corresponding to the thermalized modes is describable by a grand canonical ensemble with a chemical potential set by the energy of a single laser photon. We consider realization of this regime using two-level atoms in Doppler cooling, and find physically realistic conditions for rare earth atoms. With the addition of photon-photon interactions, this system could provide a new platform for exploring many-body physics.

%B Phys. Rev. A 98, 013834 %8 2018 %G eng %U https://arxiv.org/abs/1712.08643 %R https://doi.org/10.1103/PhysRevA.98.013834 %0 Journal Article %D 2018 %T Single-photon bound states in atomic ensembles %A Yidan Wang %A Michael J. Gullans %A Antoine Browaeys %A J. V. Porto %A Darrick E. Chang %A Alexey V. Gorshkov %XWe illustrate the existence of single-excitation bound states for propagating photons interacting with N two-level atoms. These bound states can be calculated from an effective spin model, and their existence relies on dissipation in the system. The appearance of these bound states is in a one-to-one correspondence with zeros in the single-photon transmission and with divergent bunching in the second-order photon-photon correlation function. We also formulate a dissipative version of Levinson's theorem for this system by looking at the relation between the number of bound states and the winding number of the transmission phases. This theorem allows a direct experimental measurement of the number of bound states using the measured transmission phases.

%G eng %U https://arxiv.org/abs/1809.01147 %0 Journal Article %J Physical Review Letters %D 2016 %T Anomalous broadening in driven dissipative Rydberg systems %A E. A. Goldschmidt %A T. Boulier %A R. C. Brown %A S. B. Koller %A J. T. Young %A Alexey V. Gorshkov %A S. L. Rolston %A J. V. Porto %X We observe interaction-induced broadening of the two-photon 5s-18s transition in 87Rb atoms trapped in a 3D optical lattice. The measured linewidth increases by nearly two orders of magnitude with increasing atomic density and excitation strength, with corresponding suppression of resonant scattering and enhancement of off-resonant scattering. We attribute the increased linewidth to resonant dipole-dipole interactions of 18s atoms with spontaneously created populations of nearby np states. Over a range of initial atomic densities and excitation strengths, the transition width is described by a single function of the steady-state density of Rydberg atoms, and the observed resonant excitation rate corresponds to that of a two-level system with the measured, rather than natural, linewidth. The broadening mechanism observed here is likely to have negative implications for many proposals with coherently interacting Rydberg atoms. %B Physical Review Letters %V 116 %P 113001 %8 2016/03/16 %G eng %U http://arxiv.org/abs/1510.08710 %N 11 %R 10.1103/PhysRevLett.116.113001 %0 Journal Article %J Science %D 2015 %T 2D Superexchange mediated magnetization dynamics in an optical lattice %A R. C. Brown %A R. Wyllie %A S. B. Koller %A E. A. Goldschmidt %A Michael Foss-Feig %A J. V. Porto %X The competition of magnetic exchange interactions and tunneling underlies many complex quantum phenomena observed in real materials. We study non-equilibrium magnetization dynamics in an extended 2D system by loading effective spin-1/2 bosons into a spin-dependent optical lattice, and we use the lattice to separately control the resonance conditions for tunneling and superexchange. After preparing a non-equilibrium anti-ferromagnetically ordered state, we observe relaxation dynamics governed by two well-separated rates, which scale with the underlying Hamiltonian parameters associated with superexchange and tunneling. Remarkably, with tunneling off-resonantly suppressed, we are able to observe superexchange dominated dynamics over two orders of magnitude in magnetic coupling strength, despite the presence of vacancies. In this regime, the measured timescales are in agreement with simple theoretical estimates, but the detailed dynamics of this 2D, strongly correlated, and far-from-equilibrium quantum system remain out of reach of current computational techniques. %B Science %V 348 %P 540 - 544 %8 2015/04/30 %G eng %U http://arxiv.org/abs/1411.7036v1 %N 6234 %! Science %R 10.1126/science.aaa1385 %0 Journal Article %J Physical Review A %D 2010 %T Adiabatic preparation of many-body states in optical lattices %A Anders S. Sorensen %A Ehud Altman %A Michael Gullans %A J. V. Porto %A Mikhail D. Lukin %A Eugene Demler %X We analyze a technique for the preparation of low entropy many body states of atoms in optical lattices based on adiabatic passage. In particular, we show that this method allows preparation of strongly correlated states as stable highest energy states of Hamiltonians that have trivial ground states. As an example, we analyze the generation of antiferromagnetically ordered states by adiabatic change of a staggered field acting on the spins of bosonic atoms with ferromagnetic interactions. %B Physical Review A %V 81 %8 2010/6/22 %G eng %U http://arxiv.org/abs/0906.2567v3 %N 6 %! Phys. Rev. A %R 10.1103/PhysRevA.81.061603