Quasiparticle-induced decoherence of a driven superconducting qubit

TL;DR

This paper develops a theory describing how quasiparticles cause decoherence in driven superconducting qubits, revealing fundamental limits on qubit operation fidelity due to quasiparticle interactions.

Contribution

It introduces two novel quasiparticle-induced decoherence mechanisms specific to driven superconducting qubits, expanding understanding beyond previous QP-insensitive models.

Findings

Quasiparticle tunneling can absorb qubit excitations and photons, causing decoherence.

Qubit transitions can occur during non-linear absorption, generating new quasiparticles.

These mechanisms set fundamental limits on microwave qubit operation fidelity.

Abstract

We develop a theory for two quasiparticle-induced decoherence mechanisms of a driven superconducting qubit. In the first mechanism, an existing quasiparticle (QP) tunnels across the qubit's Josephson junction while simultaneously absorbing a qubit excitation and one (or several) photons from the drive. In the second mechanism, a qubit transition occurs during the non-linear absorption process converting multiple drive quanta into a pair of new QPs. Both mechanisms can remain significant in gap engineered qubits whose coherence is insensitive to QPs without the drive. Our theory establishes a fundamental limitation on fidelity of the microwave qubit operations, such as readout and gates, stemming from QPs.