We present an experimental and theoretical investigation of the scattering-induced decoherence of multiple photons stored in a strongly interacting atomic ensemble. We derive an exact solution to this many-body problem, allowing for a rigorous understanding of the underlying dissipative quantum dynamics. Combined with our experiments, this analysis demonstrates a correlated coherence-protection process, in which the induced decoherence of one photon can preserve the spatial coherence of all others. We discuss how this effect can be used to manipulate light at the quantum level, providing a robust mechanism for single-photon subtraction, and experimentally demonstrate this capability.

%8 2018/03/13 %G eng %U https://arxiv.org/abs/1710.10047 %R https://doi.org/10.1103/PhysRevLett.120.113601 %0 Journal Article %J New Journal of Physics %D 2016 %T Many-body decoherence dynamics and optimised operation of a single-photon switch %A Callum R. Murray %A Alexey V. Gorshkov %A Thomas Pohl %XWe develop a theoretical framework to characterize the decoherence dynamics due to multi-photon scattering in an all-optical switch based on Rydberg atom induced nonlinearities. By incorporating the knowledge of this decoherence process into optimal photon storage and retrieval strategies, we establish optimised switching protocols for experimentally relevant conditions, and evaluate the corresponding limits in the achievable fidelities. Based on these results we work out a simplified description that reproduces recent experiments [arXiv:1511.09445] and provides a new interpretation in terms of many-body decoherence involving multiple incident photons and multiple gate excitations forming the switch. Aside from offering insights into the operational capacity of realistic photon switching capabilities, our work provides a complete description of spin wave decoherence in a Rydberg quantum optics setting, and has immediate relevance to a number of further applications employing photon storage in Rydberg media.

%B New Journal of Physics %V 18 %P 092001 %8 2016/09/13 %G eng %U http://iopscience.iop.org/article/10.1088/1367-2630/18/9/092001 %R 10.1088/1367-2630/18/9/092001 %0 Journal Article %J Physical Review A %D 2015 %T Fractional Quantum Hall States of Rydberg Polaritons %A Mohammad F. Maghrebi %A Norman Y. Yao %A Mohammad Hafezi %A Thomas Pohl %A Ofer Firstenberg %A Alexey V. Gorshkov %X We propose a scheme for realizing fractional quantum Hall states of light. In our scheme, photons of two polarizations are coupled to different atomic Rydberg states to form two flavors of Rydberg polaritons that behave as an effective spin. An array of optical cavity modes overlapping with the atomic cloud enables the realization of an effective spin-1/2 lattice. We show that the dipolar interaction between such polaritons, inherited from the Rydberg states, can be exploited to create a flat, topological band for a single spin-flip excitation. At half filling, this gives rise to a photonic (or polaritonic) fractional Chern insulator -- a lattice-based, fractional quantum Hall state of light. %B Physical Review A %V 91 %P 033838 %8 2015/03/31 %G eng %U http://arxiv.org/abs/1411.6624v1 %N 3 %! Phys. Rev. A %R 10.1103/PhysRevA.91.033838 %0 Journal Article %J Physical Review Letters %D 2013 %T Dissipative Many-body Quantum Optics in Rydberg Media %A Alexey V. Gorshkov %A Rejish Nath %A Thomas Pohl %X We develop a theoretical framework for the dissipative propagation of quantized light in interacting optical media under conditions of electromagnetically induced transparency (EIT). The theory allows us to determine the peculiar spatiotemporal structure of the output of two complementary Rydberg-EIT-based light-processing modules: the recently demonstrated single-photon filter and the recently proposed single-photon subtractor, which, respectively, let through and absorb a single photon. In addition to being crucial for applications of these and other optical quantum devices, the theory opens the door to the study of exotic dissipative many-body dynamics of strongly interacting photons in nonlinear nonlocal media. %B Physical Review Letters %V 110 %8 2013/4/9 %G eng %U http://arxiv.org/abs/1211.7060v1 %N 15 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.110.153601 %0 Journal Article %J Physical Review Letters %D 2011 %T Photon-Photon Interactions via Rydberg Blockade %A Alexey V. Gorshkov %A Johannes Otterbach %A Michael Fleischhauer %A Thomas Pohl %A Mikhail D. Lukin %X We develop the theory of light propagation under the conditions of electromagnetically induced transparency (EIT) in systems involving strongly interacting Rydberg states. Taking into account the quantum nature and the spatial propagation of light, we analyze interactions involving few-photon pulses. We demonstrate that this system can be used for the generation of nonclassical states of light including trains of single photons with an avoided volume between them, for implementing photon-photon quantum gates, as well as for studying many-body phenomena with strongly correlated photons. %B Physical Review Letters %V 107 %8 2011/9/22 %G eng %U http://arxiv.org/abs/1103.3700v1 %N 13 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.107.133602