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SYDD: Symposium Driven-dissipative Quantum Systems

SYDD 1: Driven-Dissipative Quantum Systems

SYDD 1.2: Hauptvortrag

Montag, 6. März 2017, 15:00–15:30, P 1

Many-body physics of driven, open quantum systems: optically driven Rydberg gases — •Michael Fleischhauer — Dept. of Physics & Research Center OPTIMAS, Univ. Kaiserslautern

Quantum optical realizations of many-body systems must often be considered as open systems, and ususally much effort is put into isolating quantum systems from the environment. However, with the tools available to manipulate reservoirs or the coupling to them, a new approach emerged in recent years. Reservoir couplings and external drive can be used deliberately to prepare and stabilize quantum states, to generate novel phases and drive phase transitions between non-equilibrium steady states. After giving an introduction into some of the tools to theoretically describe open many-body systems, the above questions will be addressed for the experimentally relevant example of optically driven Rydberg gases. Here there are two different regimes of the many-body dynamics depending on the resonance conditions of the optical excitation. Under conditions of resonant excitation the van-der Waals repulsion results in an effect called Rydberg blockade. The interaction drives the system towards a state with crystalline order but competes with fluctuations inherent to the open system. For off-resonant excitation, where the driving field is tuned out of resonance, an anti-blockaded situation is established. Here the presence of a single excitation shifts other atoms at a certain distance into resonance causing a fast excitation cascade. Mean field approximations to the many-body dynamics predict a bi-stable steady state, which will be critically reexamined.