Direct Wigner tomography of a superconducting anharmonic oscillator

TL;DR

This paper demonstrates a straightforward method for directly measuring the Wigner distribution of complex photon states in a superconducting anharmonic oscillator, simplifying phase-space analysis of wave-packet dynamics.

Contribution

It introduces a simple calibration-based technique for direct Wigner tomography applicable to superconducting anharmonic oscillators up to the fifth energy level.

Findings

Successfully measured Wigner distributions of non-classical states

Demonstrated phase-locked wavepacket dynamics

Method is simple and broadly applicable

Abstract

The analysis of wave-packet dynamics may be greatly simplified when viewed in phase-space. While harmonic oscillators are often used as a convenient platform to study wave-packets, arbitrary state preparation in these systems is more challenging. Here, we demonstrate a direct measurement of the Wigner distribution of complex photon states in an anharmonic oscillator - a superconducting phase circuit, biased in the small anharmonicity regime. We test our method on both non-classical states composed of two energy eigenstates and on the dynamics of a phase-locked wavepacket. This method requires a simple calibration, and is easily applicable in our system out to the fifth level.