Quantum Many-Body Scars

Supervisor(s)

Contact Dr Zlatko Papic to discuss this project further informally.

Project description

In recent years, investigations of out-of-equilibrium phenomena in quantum many-particle systems have become one of the most active research areas in physics. A recent state-of-the-art experiment at Harvard/MIT [1] has succeeded in assembling large chains of strongly-interacting Rydberg atoms, which allowed them to build an impressive 51-atom quantum simulator.

This experiment might not only pave the way to important quantum technology applications, but it has already discovered a new physical phenomenon: when the simulator was driven away from its equilibrium configuration, the experiment observed enigmatic quantum oscillations that remained coherent for unusually long times. In our recent work [2] (which was also featured in Press, see [3, 4, 5]) we provided an explanation of this intriguing phenomenon by introducing a new concept of quantum many-body scar. In typical systems, as explained by Boltzmann and Gibbs in the 19th century, dynamics is usually chaotic, which allows such systems to reach thermal equilibrium after long times. Our work shows that there are surprising exceptions to this behaviour when a “scar” forms: the quantum system can retain some memory of its initial condition even though its dynamics is chaotic, similar to what happens to a particle scattering in a chaotic billiard [6].

Our work thus introduced a new mechanism to “protect” coherent oscillations in a chaotic system, such as the one engineered by Harvard/MIT. The goal of this PhD project is to develop a deeper understanding of quantum many-body scars as a new class of systems where ergodicity is weakly broken. One of the pressing questions is what kind of systems support scars. Currently, it is believed that kinetic constraints (such as strong nearest-neighbour interactions between the atoms) are essential to the formation of scars, thus one of the goals of the project would be to investigate more systematically other types of models with similar constraints. On the other hand, the project will aim to answer a fundamental question: what is the meaning of a periodic orbit in a quantum many-body system? Such orbits play a fundamental role in the theory of single-particle chaotic billiards [6], but their meaning for a quantum many-body system is currently an open problem. Finally, the project will also investigate possible practical applications of quantum scars. Since the scars effectively “shield” the system from thermal relaxation, this might allow for new mechanisms of storing and manipulating quantum information.

References
[1] Probing many-body dynamics on a 51-atom quantum simulator, H. Bernien et al., Nature 551, 579-584 (2017).
[2] Quantum many-body scars, C. J. Turner, A. A. Michailidis, D. A. Abanin, M. Serbyn, and Z. Papic, Nature Physics 14, 745 (2018).
[3] https://www.leeds.ac.uk/news/article/4231/insight_into_quantum_chaos_may_be_the_key_to_quantum_computers [4] https://ist.ac.at/nc/news-media/news/news-detail/article/explanation-for-puzzling-quantum-oscillations-has-been-found/6/ [5] https://www.nature.com/articles/s41567-018-0157-1
[6] Bound-State Eigenfunctions of Classically Chaotic Hamiltonian Systems: Scars of Periodic Orbits, Eric J. Heller, Phys. Rev. Lett. 53, 1515 (1984).

Entry requirements

Applications are invited from candidates with or expecting a minimum of a UK upper second class honours degree (2:1), and/or a Master's degree in physics, or a relevant degree (e.g., mathematics). The candidate should be highly motivated, with strong analytical and problem solving skills. Background in theoretical physics, condensed matter physics, and numerical simulations would be beneficial.

If English is not your first language, you must provide evidence that you meet the University's minimum English Language requirements.

How to apply

Formal applications for research degree study should be made online through the university's website. Please state clearly in the research information section that the PhD you wish to be considered for is 'Quantum Many-Body Scars' as well as Dr Zlatko Papic as your proposed supervisor.

We welcome scholarship applications from all suitably-qualified candidates, but UK black and minority ethnic (BME) researchers are currently under-represented in our Postgraduate Research community, and we would therefore particularly encourage applications from UK BME candidates. All scholarships will be awarded on the basis of merit.

If you require any further information please contact the Graduate School Office, e: maps.pgr.admissions@leeds.ac.uk