Probing quantum many-body correlations by universal ramping dynamics

TL;DR

This paper introduces a universal ramping-based method to probe quantum many-body correlations, demonstrated experimentally with ultracold atoms in optical lattices, revealing insights into quasi-particle properties near quantum critical points.

Contribution

The authors propose a novel non-adiabatic linear response technique using ramping dynamics to probe quantum correlations, which is experimentally validated in the Bose-Hubbard model.

Findings

Universal first-order correction reveals many-body correlations.

Method distinguishes between phases with and without well-defined quasi-particles.

Significant response observed in the quantum critical regime.

Abstract

Ramping a physical parameter is one of the most common experimental protocols in studying a quantum system, and ramping dynamics has been widely used in preparing a quantum state and probing physical properties. Here, we present a novel method of probing quantum many-body correlation by ramping dynamics. We ramp a Hamiltonian parameter to the same target value from different initial values and with different velocities, and we show that the first-order correction on the finite ramping velocity is universal and path-independent, revealing a novel quantum many-body correlation function of the equilibrium phases at the target values. We term this method as the non-adiabatic linear response since this is the leading order correction beyond the adiabatic limit. We demonstrate this method experimentally by studying the Bose-Hubbard model with ultracold atoms in three-dimensional optical lattices. Unlike the conventional linear response that reveals whether the quasi-particle dispersion of a quantum phase is gapped or gapless, this probe is more sensitive to whether the quasi-particle lifetime is long enough such that the quantum phase possesses a well-defined quasi-particle description. In the Bose-Hubbard model, this non-adiabatic linear response is significant in the quantum critical regime where well-defined quasi-particles are absent. And in contrast, this response is vanishingly small in both superfluid and Mott insulators which possess well-defined quasi-particles. Because our proposal uses the most common experimental protocol, we envision that our method can find broad applications in probing various quantum systems.