Qubit-State Purity Oscillations from Anisotropic Transverse Noise

TL;DR

This study investigates how anisotropic transverse noise affects qubit purity oscillations, revealing their dependence on noise characteristics and offering insights into decoherence mechanisms in superconducting qubits.

Contribution

It demonstrates the observation of purity oscillations caused by anisotropic transverse noise and analyzes their dependence on noise parameters in fluxonium qubits.

Findings

Purity oscillations occur at twice the qubit frequency due to intrinsic precession.

Oscillation amplitude depends on noise anisotropy, orientation, and spectral density.

Results help distinguish charge and flux noise effects in superconducting circuits.

Abstract

We explore the dynamics of qubit-state purity in the presence of transverse noise that is anisotropically distributed in the Bloch-sphere XY plane. We perform Ramsey experiments with noise injected along a fixed laboratory-frame axis and observe oscillations in the purity at twice the qubit frequency arising from the intrinsic qubit Larmor precession. We probe the oscillation dependence on the noise anisotropy, orientation, and power spectral density, using a low-frequency fluxonium qubit. Our results elucidate the impact of transverse noise anisotropy on qubit decoherence and may be useful to disentangle charge and flux noise in superconducting quantum circuits.