Direct measurement of non-local interactions in the many-body localized phase

TL;DR

This paper experimentally investigates the many-body localized phase in superconducting qubits, revealing non-local interactions through phase-sensitive measurements, entanglement growth, and local integrals of motion, advancing understanding of MBL properties.

Contribution

It introduces phase-sensitive techniques to directly measure non-local interactions and entanglement in the MBL phase using superconducting qubits, providing new insights into MBL structure.

Findings

Mapping of local integrals of motion in MBL phase

Observation of logarithmic entanglement growth

Confirmation of preserved entanglement in MBL

Abstract

The interplay of interactions and strong disorder can lead to an exotic quantum many-body localized (MBL) phase. Beyond the absence of transport, the MBL phase has distinctive signatures, such as slow dephasing and logarithmic entanglement growth; they commonly result in slow and subtle modification of the dynamics, making their measurement challenging. Here, we experimentally characterize these properties of the MBL phase in a system of coupled superconducting qubits. By implementing phase sensitive techniques, we map out the structure of local integrals of motion in the MBL phase. Tomographic reconstruction of single and two qubit density matrices allowed us to determine the spatial and temporal entanglement growth between the localized sites. In addition, we study the preservation of entanglement in the MBL phase. The interferometric protocols implemented here measure affirmative correlations and allow us to exclude artifacts due to the imperfect isolation of the system. By measuring elusive MBL quantities, our work highlights the advantages of phase sensitive measurements in studying novel phases of matter.