PIRSA:18040128

Video URL

https://pirsa.org/18040128

Driven Quantum Dynamics: Will It Blend?

Banchi, L. (2018). Driven Quantum Dynamics: Will It Blend?. Perimeter Institute for Theoretical Physics. https://pirsa.org/18040128

Banchi, Leonardo. Driven Quantum Dynamics: Will It Blend?. Perimeter Institute for Theoretical Physics, Apr. 25, 2018, https://pirsa.org/18040128 

          @misc{ scivideos_PIRSA:18040128,
            doi = {10.48660/18040128},
            url = {https://pirsa.org/18040128},
            author = {Banchi, Leonardo},
            keywords = {Quantum Information},
            language = {en},
            title = {Driven Quantum Dynamics: Will It Blend?},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2018},
            month = {apr},
            note = {PIRSA:18040128 see, \url{https://scivideos.org/index.php/pirsa/18040128}}
          }

Leonardo Banchi Imperial College London

Talk numberPIRSA:18040128
DOI10.48660/18040128
Source RepositoryPIRSA
Collection
Talk Type Scientific Series
Subject

Abstract

Randomness is an essential tool in many disciplines of modern sciences, such as cryptography, black hole physics, random matrix theory, and Monte Carlo sampling. In quantum systems, random operations can be obtained via random circuits thanks to so-called q-designs and play a central role in condensed-matter physics and in the fast scrambling conjecture for black holes. Here, we consider a more physically motivated way of generating random evolutions by exploiting the many-body dynamics of a quantum system driven with stochastic external pulses. We combine techniques from quantum control, open quantum systems, and exactly solvable models (via the Bethe ansatz) to generate Haar-uniform random operations in driven many-body systems. We show that any fully controllable system converges to a unitary q-design in the long-time limit. Moreover, we study the convergence time of a driven spin chain by mapping its random evolution into a semigroup with an integrable Liouvillian and finding its gap. Remarkably, we find via Bethe-ansatz techniques that the gap is independent of q. We use mean-field techniques to argue that this property may be typical for other controllable systems, although we explicitly construct counterexamples via symmetry-breaking arguments to show that this is not always the case. Our findings open up new physical methods to transform classical randomness into quantum randomness, via a combination of quantum many-body dynamics and random driving.

Reference: L. Banchi, D. Burgarth, M. J. Kastoryano, Phys. Rev. X 7, 041015 (2017)