Quantum Interactive Dynamics

Workshop Report

Quantum many-body systems out of equilibrium represent a challenging frontier and have been shown to exhibit extremely rich phenomena. Recent experimental advances in building Noisy Intermediate-Scale Quantum (NISQ) devices have opened up a completely new territory in this context. The natural evolution implemented by NISQ devices is a quantum interactive dynamics gen- erated by a combination of unitary gates and measurements. These platforms provide an opportunity to explore vastly larger parts of the Hilbert space and go beyond what can be realized in purely unitary systems.

In pioneering works, an entanglement phase transition was identified in the dynamics of circuits of random unitary gates interleaved with local projective measurements. This phase transition separates a disentangling phase, obeying an area law, and an entangling phase obeying a volume law. Successively, it has been shown that additional phase transitions between different area phases can occur and new kinds of quantum phase transitions have been discovered.

The international workshop on Quantum Interactive Dynamics focussed on recent developments in this new field and brought together a small group of experts from academia and industry. The workshop was held in-person with one remote talk. The format included 18 invited talks spread across a two and a half day program and particularly focussed on the following topics:

  • Noisy Intermediate-Scale Quantum (NISQ) devices [talks by HannesBernien (US), Xiao Mi (US), Hongzheng Zhao (CN)]

  • Measurement based transitions [Tianci Zhou (US)]

  • Open quantum systems [Vir Bulchandani (US)]

  • Error correction [Sagar Vijay (US)]

  • Computational complexity

  • Classical shadows [Andreas Elben (US)]

Beyond those topics, additional themes emerged:

  • Active phases of matter [Tibor Rakovszky (US)]

  • Classically-assisted quantum state preparation [Barbara Kraus (DE), Henrik Dreyer (DE), Ruben Verresen (US), Kevin Smith (US), Marin Bukov (DE)]

  • Tests of ergodicity [Samuel Garratt (US), Mari Carmen Bañuls (DE), Federica Maria Surace (US)]

  • Constrained quantum dynamics [Katja Klobas (UK), Tomaž Prosen (SLO)]


The workshop brought together leading experts from the USA, China, UK, and Europe, and the invited talks of all sessions led to stimulating discussions. Given the high-quality contributions, which addressed all of the topics that were set out and beyond, we believe the goal of the workshop was clearly achieved.