Stabilization of Kerr-cat qubits with quantum circuit refrigerator

TL;DR

This paper proposes on-chip quantum circuit refrigerator technology to stabilize Kerr-cat qubits, significantly reducing dephasing and bit-flip errors, thereby enhancing qubit lifetime for quantum computing.

Contribution

It introduces a tunable QCR that suppresses unwanted excitations and stabilizes Kerr-cat qubits, improving their coherence properties.

Findings

QCR rates can be tuned over four orders of magnitude.

Quantum interference suppresses QCR-induced bit flips.

QCR stabilizes Kerr-cat qubits, extending their lifetime.

Abstract

A periodically-driven superconducting nonlinear resonator can implement a Kerr-cat qubit, which provides a promising route to a quantum computer with a long lifetime. However, the system is vulnerable to pure dephasing, which causes unwanted excitations outside the qubit subspace. Therefore, we require a refrigeration technology which confines the system in the qubit subspace. We theoretically study on-chip refrigeration for Kerr-cat qubits based on photon-assisted electron tunneling at tunneling junctions, called quantum circuit refrigerator (QCR). Rates of QCR-induced deexcitations of the system can be changed by more than four orders of magnitude by tuning a bias voltage across the tunneling junctions. Unwanted QCR-induced bit flips are greatly suppressed due to quantum interference in the tunneling process, and thus the long lifetime is preserved. The QCR can serve as a tunable dissipation source which stabilizes Kerr-cat qubits.