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Condensed Matter and Quantum Theory Group

Condensed Matter and Quantum Theory Group

The field of quantum information science has advanced significantly over the last two decades. Indeed the last few years have seen the arrival of viable devices in both the research and commercial sectors, leading to claims that we are undergoing a ‘second quantum revolution’. In this revolution the laws of quantum mechanics are not only used to understand physical systems better, but are now directly applied to build powerful new technologies. Despite the impressive progress, the milestone of quantum supremacy (i.e. quantum processors outperforming their classical counterparts in a practical way) is still some years away. The key barriers in the way of viable quantum processors are decoherence (the degradation of information due to the environment), and the compounded imperfections of the quantum-logic-gates.

Image from upcoming paper on Quantum Modification to the TASEP
Figure from arXiv:2101:00022

The central theme of our research is complex condensed-matter systems and their potential use in the next generation of quantum technologies. There are two main aspects to this. The first is exploring exotic materials and how to use them to encode quantum information in topological degrees of freedom. The general idea here is that, by spreading the information out, it is less susceptible to noise processes that tend to act locally.

The second part of this is on the Eigenstate Thermalisation Hypothesis (ETH) and how to use violations of it to further enhance the stability of quantum devices. This began as a study into what is called Many-Body Localisation (MBL) and its interplay with topological order, but has now branched out to include other ETH violations such as Quantum Many-Body Scars and Pre-thermalisation.

Some recent publications

Quantum Sensing and Many-body Scars
S. Dooley, arXiv:2101.04670

On Dynamical Phase Error in Interacting Topological Memories
L. Coopmans, K. Kavanagh, I. Jubb, S. Dooley and G. Kells, arXiv:2101:00022

Protocol Discovery for the Quantum Control of Majoranas by Differential Programming and Natural Evolution Strategies
L. Coopmans, D. Luo, G. Kells, B. Clark, and J. Carrasquilla, arXiv:2008.09128

Enhancing the effect of quantum many-body scars on dynamics by minimising the effective dimension
S Dooley and G. Kells, Phys. Rev. B 102, 195114 (2020)

Constrained thermalization and topological superconductivity
S. Nulty, J. Vala, D. Meidan, and G. Kells, Phys. Rev. B 102, 054508 (2020)

Constructing edge zero modes through domain wall angle conservation
D. Pellegrino, G. Kells, N. Moran and J. K Slingerland.
Journal of Physics A: Mathematical and Theoretical 53, 095006 (2020)

Impossible measurements revisited
L. Borsten, I. Jubb, and G. Kells, arXiv:1912.06141

Simulating quantum circuits by adiabatic computation: improved spectral gap bounds
S. Dooley, G. Kells, H. Katsura and T. C. Dorlas. Physical Review A 101, 042302 (2019)

Error generation and propagation in Majorana based topological qubits
A. Conlon, D. Pellegrino, S. Dooley, J.K. Slingerland & G. Kells, Phys. Rev. B 100, 134307 (2019)

Collapse and revival of entanglement between qubits coupled to a spin coherent state
I. Bahari, T. P. Spiller, S. Dooley, A. Hayes, F. McCrossan
International Journal of Quantum Information 16 (02), 1850017

Localization enhanced and degraded topological order in interacting p-wave wires
G. Kells, N. Moran, and D. Meidan, Phys. Rev. B 97, 085425 (2018)

Robust quantum sensing with strongly interacting probe systems
S Dooley, M Hanks, S Nakayama, WJ Munro, K Nemoto NJP Quantum Information 4 1 (2018)

Making the most of time in quantum metrology: concurrent state preparation and sensing
A. J. Hayes, S. Dooley, W. J. Munro, K. Nemoto, J. Dunningham Quantum Sci. Technol. 3 035007 (2018)

Parafermionic clock models and quantum resonance
N. Moran, D. Pellegrino, J.K. Slingerland and G. Kells, Phys. Rev. B 95, 235127 (2017)