Coherent Many-Body Oscillations Induced by a Superposition of Broken Symmetry States in the Wake of a Quantum Phase Transition

TL;DR

This paper explores how superpositions of broken-symmetry states after a quantum phase transition lead to observable coherent oscillations, revealing new dynamical behavior and potential applications in quantum simulation verification.

Contribution

It uncovers the existence of quantum coherent oscillations caused by superpositions of broken-symmetry states post-quench, linking them to Kibble-Zurek scaling laws.

Findings

Coherent oscillations are induced by superpositions of broken-symmetry states.

Oscillation frequencies are primarily determined by the system's energy gap.

Oscillations follow Kibble-Zurek dynamical scaling laws.

Abstract

It is now widely accepted that quenches through the critical region of quantum phase transitions result in post-transition states populated with topological defects -- analogs of the classical topological defects. However, consequences of the very non-classical fact that the state after a quench is a {\it superposition} of distinct, broken-symmetry vacua with different numbers and locations of defects have remained largely unexplored. We identify coherent quantum oscillations induced by such superpositions in observables complementary to the one involved in symmetry breaking. These oscillations satisfy Kibble-Zurek dynamical scaling laws with the quench rate, with an instantaneous oscillation frequency set primarily by the gap of the system. In addition to the obvious fundamental significance of a superposition of different broken symmetry states, quantum coherent oscillations can be used to verify unitarity and test for imperfections of the experimental implementations of quantum simulators.