Driven-Dissipative Ensembles of Ultracold Atoms in Optical Lattices

Many key existing and emerging technologies, ranging from switches in current computing and data networks to quantum devices for high-precision sensing, derive their functionality from out-of-equilibrium physics. As electronic devices become smaller, better understanding and control of this physics at the quantum level will become crucial to developing future technologies, and to address major challenges, such as developing energy-efficient switching and communications links. How to exploit the advantages of increasingly complex devices in the quantum regime and in the presence of noise and decoherence is intrinsically an issue of out-of-equilibrium many-body quantum physics. It is therefore crucial to put methods in place now that will underpin the design of out-of-equilibrium quantum systems, and lead to novel quantum devices.

This theoretical DPhil project is attached to the EPSRC programme grant entitled 'Designing Out-of-Equilibrium Many-Body Quantum Systems' which aims to explore, understand, and design out-of-equilibrium quantum dynamics that are relevant for future technologies, using quantum simulators with atomic gases in optical potentials. These simulators offer a unique level of controllability on a microscopic level, where interactions and trapping potentials are quantitatively understood from first principles. Their size and time scales make it possible to directly image and manipulate the system on the level of a single atom, as well as to track and control dynamics in real time. The DPhil project will consider steady-states of driven, dissipative ultracold atomic systems with the aim of reaching otherwise inaccessible quantum phases [1,2] in out-of-equilibrium scenarios. Specifically, it will consider the periodically driven Hubbard model as investigated in [1] and extend the model to include coupling to a dissipate thermal bath. The project will start by studying a minimal two-site model utilizing standard quantum optics techniques for describing its dynamics towards a driven steady state. This will be followed by a mean-field study of larger lattice systems and the development of numerical methods based on tensor network theory (TNT) for investigating regular lattices of driven atoms. A specific aim of the project will be to optimize driving-induced pairing of fermions in the presence of dissipation to the thermal bath.

This DPhil project falls into the EPSRC area of quantum technologies and the grand challenge of non-equilibrium physics. It aims at bringing these two fields together and gaining insights into how quantum phases of matter that are not reachable in thermal equilibrium could be attained through driving a system far out of thermal equilibrium. In addition to providing insights into the fundamentals of many-body quantum dynamics this research has potential applications in future quantum technologies. No companies are involved in this DPhil research project. Close collaboration with projects partners in EPSRC programme grant entitled 'Designing Out-of-Equilibrium Many-Body Quantum Systems' (EPSRC reference: EP/P009565/1) is expected.

[1] J. R. Coulthard, S. R. Clark, S. Al-Assam, A. Cavalleri, and D. Jaksch, Phys. Rev. B 96, 085104 (2017).
[2] F. Görg, M. Messer, K. Sandholzer, G. Jotzu, R. Desbuquois, T. Esslinger, arXiv:1708.06751 (2017).