Unless otherwise specified, all talks are held starting at 1.15pm in the Theory Library on the 4th floor of Physics East.

Everyone is encouraged to ask questions during the talk. You are welcome to leave when you need to, otherwise the talk will usually wrap up by 2.30pm, at which point there will be biscuits.

Thursday 9th October 2025: Nigel Cooper (Cambridge)

Ideal Optical Flux Lattices

We present a new approach for engineering fractional quantum Hall (FQH) states in cold atoms, overcoming the limitations of current methods. By introducing a simple scalar potential to a two-state optical flux lattice, we show how one can create Chern bands that are both exceptionally flat and “ideal” for hosting strongly correlated phases. Drawing inspiration from “magic-angle” physics in moiré materials, our method allows for precise tuning of the band geometry, and stabilizing robust abelian and non-abelian FQH states. The scheme is compatible with existing experimental techniques, providing a practical path toward exploring topological quantum matter with ultracold atoms.

Thursday 23rd October 2025: Thomas Siday (Birmingham)

TBA

TBA

Thursday 6th November 2025: Alessandro Romito (Lancaster)

TBA

TBA

Thursday 13th November 2025: Lucas Sá (Cambridge)

TBA

TBA

Thursday 27th November 2025: Zlatko Papić (Leeds)

TBA

TBA

Thursday 2nd October 2025: Jonathan Keeling (St Andrews)

Modelling realistic open quantum systems with process tensors

When an open quantum system is strongly coupled to a structured environment, describing the dynamics of that system becomes a challenging problem. Moreover, traditional approaches, based on time evolution of the reduced density matrix are generally harder to use when calculating higher-order or multi-time correlations.

I will review recent progress that addresses both these issues, by showing how the time evolution of the system can be efficiently simulated using tensor network methods [1]. Such a tensor network naturally leads one to consider the process tensor (PT), an object which encodes all multi-time correlations of the reservoir [2,3]. A key insight is that one can construct efficient MPO representations of the PT [4]. This idea makes possible many otherwise challenging tasks, including optimisation of non-Markovian systems [5,6], and modelling the non-Markovian dynamics of many-body open quantum systems [7], and calculation of two dimensional spectroscopy[8].

The algorithm underpinning this work is publicly available [9], and we are keen to help support other researchers in using this approach.

[1] A. Strathearn, P. Kirton, D. Kilda, J. Keeling, B. W. Lovett., Efficient non-Markovian quantum dynamics using time-evolving matrix product operators, Nature Commun. 9, 3322 (2018).

[2] M. R. Jørgensen and F. A. Pollock, Exploiting the causal tensor network structure of quantum processes to efficiently simulate non-Markovian path integrals, Phys. Rev. Lett. 123, 240602 (2019).

[3] M. Cygorek, M. Cosacchi, A. Vagov, V. M. Axt, B. W. Lovett, J. Keeling, E. M. Gauger, Simulation of open quantum systems by automated compression of arbitrary environments, Nat. Phys. 18, 662 (2022).

[4] J. Keeling, E. M. Stoudenmire, M.-C. Bañuls, D. R Reichman, Process Tensor Approaches to Non-Markovian Quantum Dynamics, arXiv:2509.07661 (2025).

[5] G. E. Fux, E. P. Butler, P. R. Eastham, B. W. Lovett, J. Keeling, Efficient exploration of Hamiltonian parameter space for optimal control of non-Markovian open quantum systems, Phys. Rev. Lett. 126, 200401 (2021).

[6] E. P. Butler, G. E. Fux, C. Ortega-Taberner, B. W. Lovett, J. Keeling, and P. R. Eastham, Optimizing performance of quantum operations with non-Markovian decoherence: The tortoise or the hare?, Phys. Rev. Lett. 132 060401 (2024).

[7] P. Fowler-Wright, B. W. Lovett, J. Keeling, Efficient many-body non-Markovian dynamics of organic polaritons, Phys. Rev. Lett. 129 173001 (2022).

[8] R. de Wit, J. Keeling, B. W. Lovett, A. W. Chin, Process tensor approaches to modeling two-dimensional spectroscopy, Phys. Rev. Research 7, 013209 (2025).

[9] The OQuPy package, https://github.com/tempoCollaboration/OQuPy