A scanning transmon qubit for strong coupling circuit quantum electrodynamics

TL;DR

This paper introduces a scanning transmon qubit as a novel local probe for photon number detection in superconducting resonator lattices, demonstrating strong coupling over a wide area to advance quantum simulation capabilities.

Contribution

It presents the first demonstration of a scanning transmon qubit for local probing in circuit QED, enabling detailed studies of photon interactions in superconducting lattices.

Findings

Achieved strong coupling between the qubit and resonator.

Mapped coupling strength across a wide scanning area.

Proposed use of the system as a local photon number probe.

Abstract

Like a quantum computer designed for a particular class of problems, a quantum simulator enables quantitative modeling of quantum systems that is computationally intractable with a classical computer. Quantum simulations of quantum many-body systems have been performed using ultracold atoms and trapped ions among other systems. Superconducting circuits have recently been investigated as an alternative system in which microwave photons confined to a lattice of coupled resonators act as the particles under study with qubits coupled to the resonators producing effective photon-photon interactions. Such a system promises insight into the nonequilibrium physics of interacting bosons but new tools are needed to understand this complex behavior. Here we demonstrate the operation of a scanning transmon qubit and propose its use as a local probe of photon number within a superconducting resonator lattice. We map the coupling strength of the qubit to a resonator on a separate chip and show that the system reaches the strong coupling regime over a wide scanning area.