Tunneling Spectroscopy in Superconducting Circuit Lattices

TL;DR

This paper introduces a method for tunneling spectroscopy in superconducting circuit lattices, enabling detailed analysis of many-body quantum states and phase transitions in synthetic quantum matter.

Contribution

It presents a novel site-resolved spectroscopy technique using engineered baths to probe excitations in superconducting circuit lattices, including strongly interacting Bose-Hubbard models.

Findings

Observation of energy gap changes across superfluid to Mott-insulator transition

Detection of effects of three-body interactions on spectra

Reconstruction of spatial structure of collective excitations

Abstract

We demonstrate tunneling spectroscopy of synthetic quantum matter in superconducting circuit lattices. We measure site-resolved excitation spectra by coupling the lattice to engineered driven-dissipative particle baths that serve as local tunneling probes. Using incoherent particle source and drain, we independently extract quasi-particle and quasi-hole spectra and reconstruct the spatial structure of collective excitations. We perform spectroscopy of a strongly interacting Bose-Hubbard lattice at different densities, observing changes in energy gaps across the superfluid to Mott-insulator transition and the effects of three-body interactions. Our results provide a new toolset for characterizing many-body states in analog quantum simulators.