Highly tunable platforms for realizing topological phases of matter are emerging from atomic and photonic systems, and offer the prospect of designing interactions between particles. The shape of the potential, besides playing an important role in the competition between different fractional quantum Hall phases, can also trigger the transition to symmetry-broken phases, or even to phases where topological and symmetry-breaking order coexist. Here, we explore the phase diagram of an interacting bosonic model in the lowest Landau level at half-filling as two-body interactions are tuned. Apart from the well-known Laughlin liquid, Wigner crystal phase, stripe, and bubble phases, we also find evidence of a phase that exhibits crystalline order at fractional filling per crystal site. The Laughlin liquid transits into this phase when pairs of bosons strongly repel each other at relative angular momentum 4ℏ. We show that such interactions can be achieved by dressing ground-state cold atoms with multiple different-parity Rydberg states.

UR - https://arxiv.org/abs/1809.04493 ER - TY - JOUR T1 - Observation of three-photon bound states in a quantum nonlinear medium JF - Science Y1 - 2018 A1 - Qi-Yu Liang A1 - Aditya V. Venkatramani A1 - Sergio H. Cantu A1 - Travis L. Nicholson A1 - Michael J. Gullans A1 - Alexey V. Gorshkov A1 - Jeff D. Thompson A1 - Cheng Chin A1 - Mikhail D. Lukin A1 - Vladan Vuletic AB -Bound states of massive particles, such as nuclei, atoms or molecules, are ubiquitous in nature and constitute the bulk of the visible world around us. In contrast, photons typically only weakly influence each other due to their very weak interactions and vanishing mass. We report the observation of traveling three-photon bound states in a quantum nonlinear medium where the interactions between photons are mediated by atomic Rydberg states. In particular, photon correlation and conditional phase measurements reveal the distinct features associated with three-photon and two-photon bound states. Such photonic trimers and dimers can be viewed as quantum solitons with shape-preserving wavefunctions that depend on the constituent photon number. The observed bunching and strongly nonlinear optical phase are quantitatively described by an effective field theory (EFT) of Rydberg-induced photon-photon interactions, which demonstrates the presence of a substantial effective three-body force between the photons. These observations pave the way towards the realization, studies, and control of strongly interacting quantum many-body states of light.

VL - 359 U4 - 783-786 UR - http://science.sciencemag.org/content/359/6377/783 CP - 6377 U5 - 10.1126/science.aao7293 ER - TY - JOUR T1 - Photon propagation through dissipative Rydberg media at large input rates Y1 - 2018 A1 - Przemyslaw Bienias A1 - James Douglas A1 - Asaf Paris-Mandoki A1 - Paraj Titum A1 - Ivan Mirgorodskiy A1 - Christoph Tresp A1 - Emil Zeuthen A1 - Michael J. Gullans A1 - Marco Manzoni A1 - Sebastian Hofferberth A1 - Darrick Chang A1 - Alexey V. Gorshkov AB -We study the dissipative propagation of quantized light in interacting Rydberg media under the conditions of electromagnetically induced transparency (EIT). Rydberg blockade physics in optically dense atomic media leads to strong dissipative interactions between single photons. The regime of high incoming photon flux constitutes a challenging many-body dissipative problem. We experimentally study in detail for the first time the pulse shapes and the second-order correlation function of the outgoing field and compare our data with simulations based on two novel theoretical approaches well-suited to treat this many-photon limit. At low incoming flux, we report good agreement between both theories and the experiment. For higher input flux, the intensity of the outgoing light is lower than that obtained from theoretical predictions. We explain this discrepancy using a simple phenomenological model taking into account pollutants, which are nearly-stationary Rydberg excitations coming from the reabsorption of scattered probe photons. At high incoming photon rates, the blockade physics results in unconventional shapes of measured correlation functions.

UR - https://arxiv.org/abs/1807.07586 ER - TY - JOUR T1 - Single-photon bound states in atomic ensembles Y1 - 2018 A1 - Yidan Wang A1 - Michael J. Gullans A1 - Antoine Browaeys A1 - J. V. Porto A1 - Darrick E. Chang A1 - Alexey V. Gorshkov AB -We 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.

UR - https://arxiv.org/abs/1809.01147 ER - TY - JOUR T1 - Light-induced fractional quantum Hall phases in graphene JF - Physical Review Letters Y1 - 2017 A1 - Areg Ghazaryan A1 - Tobias Graß A1 - Michael J. Gullans A1 - Pouyan Ghaemi A1 - Mohammad Hafezi AB -We show how to realize two-component fractional quantum Hall phases in monolayer graphene by optically driving the system. A laser is tuned into resonance between two Landau levels, giving rise to an effective tunneling between these two synthetic layers. Remarkably, because of this coupling, the interlayer interaction at non-zero relative angular momentum can become dominant, resembling a hollow-core pseudo-potential. In the weak tunneling regime, this interaction favors the formation of singlet states, as we explicitly show by numerical diagonalization, at fillings ν = 1/2 and ν = 2/3. We discuss possible candidate phases, including the Haldane-Rezayi phase, the interlayer Pfaffian phase, and a Fibonacci phase. This demonstrates that our method may pave the way towards the realization of non-Abelian phases, as well as the control of topological phase transitions, in graphene quantum Hall systems using optical fields and integrated photonic structures.

VL - 119 U4 - 247403 UR - https://arxiv.org/abs/1612.08748 CP - 24 U5 - 10.1103/PhysRevLett.119.247403 ER -