Entanglement dynamics and exotic phases of matter: NISQ era simulations

Thesis

Quantum many-body physics is often outside the scope of what we can model using classical computers. Using variational algorithms, one can sometimes sidestep this issue; however, the choice of the variational space always presumes certain phenomenology, e.g. matrix product states cannot efficiently model certain long-range correlations, etc. This is the reason why, in our search towards new physics, we should consider programmable quantum devices in the study of complex quantum systems. Coupled with the promised real-world application of quantum computers, this has led to a series of rapid technological developments in this field in recent years. In this thesis, I explore the capabilities of (current) noisy intermediate-scale quantum (NISQ) simulators applied to problems in many-body quantum physics. To that end, I provide three studies: one that deals with scrambling and transport of quantum information in dynamical quantum systems, providing a method for time-evolution channel tomography; one that presents a practical experimental proposal to probe non-Abelian anyon physics, with concrete circuits compiled and optimised; and, lastly, one that explores a phase diagram of steady states of a certain monitored circuit based on the toric code and its resilience to errors. In order to demonstrate the practicality of our proposals, in the first two studies, we have run our proposed experiments either on actual quantum devices or on noisy classical simulators, achieving acceptable signal-to-noise ratios. I comment on the connecting thread between the three studies, establishing non-local correlations and engagement in NISQ devices; and offer near term extensions to all three avenues of research.

Authors: Jovanović, JD

• DOI: 10.5287/ora-aqbky8zkv
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: quantum simulations; quantum information; topological phases of matter; many-body physics; transport in quantum many-body systems; quantum error correction
• Subjects: Quantum computing; Quantum entanglement; Condensed matter