Ergodic dynamics and thermalization in an isolated quantum system

By C. Neill, P. Roushan, Michael T. Fang, Yu Chen, M. Kolodrubetz, Zijun Chen, A. Megrant, R. Barends, B. Campbell, B. Chiaro and 12 more. Nature Physics, 2016

301 citations recorded by the source corpus.

The realization of a quantum kicked top provides evidence for ergodic dynamics and thermalization in a small quantum system consisting of three superconducting qubits. Statistical mechanics is founded on the assumption that all accessible configurations of a system are equally likely. This requires dynamics that explore all states over time, known as ergodic dynamics. In isolated quantum systems, however, the occurrence of ergodic behaviour has remained an outstanding question1,2,3,4. Here, we demonstrate ergodic dynamics in a small quantum system consisting of only three superconducting qubits. The qubits undergo a sequence of rotations and interactions and we measure the evolution of the density matrix. Maps of the entanglement entropy show that the full system can act like a reservoir for individual qubits, increasing their entropy through entanglement. Surprisingly, these maps bear a strong resemblance to the phase space dynamics in the classical limit; classically, chaotic motion coincides with higher entanglement entropy. We further show that in regions of high entropy the full multi-qubit system undergoes ergodic dynamics. Our work illustrates how controllable quantum systems can investigate fundamental questions in non-equilibrium thermodynamics.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/3b8b3605b0ea112ce9ab39767a762d22bd074790

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In Artificial Intelligence

1. V. Khemani
2. A. Kaufman
3. A. Lukin
4. M. Rispoli
5. P. Preiss
6. M. Greiner
7. M. Tai
8. A. Nahum

In Atomic and Molecular Physics, and Optics

1. V. Khemani
2. A. Kaufman
3. Anushya Chandran
4. A. Lukin
5. M. Rispoli
6. C. Laumann
7. P. Preiss
8. M. Greiner

In Statistical and Nonlinear Physics

1. Anushya Chandran
2. V. Khemani
3. A. Nahum

Citations in the corpus

• Quantum thermalization through entanglement in an isolated many-body system (2016, background): “Recent experiments have demonstrated analogies between classical chaotic dynamics and the role of entanglement in fewqubit spin systems [14], as well as the dynamics of thermalization within an ion system [15].”
• Signatures of integrability in the dynamics of Rydberg-blockaded chains (2018, background): “initial state memory when spatial inhomogeneities are strong, and long-lived prethermal states near special integrable points [4–14].”