Mach-Zehnder Interferometry in a Strongly Driven Superconducting Qubit

TL;DR

This paper demonstrates a Mach-Zehnder interferometer using a superconducting flux qubit, exploiting Landau-Zener transitions as beam splitters to observe quantum interference in a strongly driven regime.

Contribution

It introduces a novel implementation of Mach-Zehnder interferometry in a superconducting qubit, utilizing Landau-Zener transitions as coherent beam splitters in phase space.

Findings

Observation of quantum interference fringes for multiple photon transitions

Demonstration of phase manipulation in a strongly driven superconducting qubit

Alternative qubit characterization method in the strongly-driven regime

Abstract

We demonstrate Mach-Zehnder-type interferometry in a superconducting flux qubit. The qubit is a tunable artificial atom, whose ground and excited states exhibit an avoided crossing. Strongly driving the qubit with harmonic excitation sweeps it through the avoided crossing two times per period. As the induced Landau-Zener transitions act as coherent beamsplitters, the accumulated phase between transitions, which varies with microwave amplitude, results in quantum interference fringes for n=1...20 photon transitions. The generalization of optical Mach-Zehnder interferometry, performed in qubit phase space, provides an alternative means to manipulate and characterize the qubit in the strongly-driven regime.