Architectures and control techniques for neutral atom quantum computing and simulation

Research context and potential impact: Control over individual quantum particles was originally pioneered from the point of view of quantum optics (resulting in the Nobel prize for Serge Haroche and Dave Wineland in 2012). There has been a long tradition since then of exploring both how control techniques can be generalised to many-particle quantum systems, and also how quantum optics methods can be used to microscopically model decoherence in such systems.

This is becoming rapidly more important, as we look for new ways to implement and optimise quantum computing architectures, and to control analogue quantum simulators for the realisation of many-body states and also resource states for quantum computing and quantum metrology. In particular in the analogue case, there is a lot of excitement about near-term possibilities, but these will rely on an understanding of new ways to harness the properties becoming available in the laboratory (e.g., generation of long-range coupling through moving atoms in optical tweezers or interactions mediated by optical cavities), and our ability to develop new techniques to engineer states and models of interest, also in the presence of noise and decoherence.

Aims and objectives: In this project, we will explore near-term architectures on analogue quantum simulators, beginning with systems with long-range interactions (including the potential to realise coupling graphs with tree-like geometry). We will explore corresponding microscopic models, also understanding the behaviour under time-dependent control. We will also look to expand this in two potential directions:

(1) We will investigate the optimisation of control processes and implementations for neutral atom quantum computing and simulation, including exploration of new architectures and the application and generalisation of Counterdiabatic Optimised Local Driving [PRX Quantum 4, 010312 (2023)], which was recently developed within our group. We will take examples both from quantum simulation and quantum annealing processes, as well as the optimisation of multi-qubit gates such as those recently developed within our group [Quantum Sci.

Technol. 7 045020 (2022)], and identify where these techniques can be used to make a qualitative step-change in the fidelities with which many-body states can be realised.

(2) We will explore how these techniques operate in the presence of realistic decoherence. In addition to usual markovian processes in quantum optical systems for neutral, we recently developed new methods that allow us to compute the state of many-particle quantum systems undergoing non-markovian dissipative processes, as arises, e.g., with atomic ensembles in an optical cavity. We expect this to allow also the study of decoherence in solid-state qubits.

Alignment to EPSRC's strategies and research areas: This work will connect to the national quantum technologies programme, including work in the upcoming QCI3 hub. It will also align with analogue quantum simulation experiments in the QQQS Programme grant. This project falls within the EPSRC quantum technologies research area.