Improved autonomous error correction using variable dissipation in small logical qubit architectures

TL;DR

This paper explores optimizing dissipation parameters in small logical qubit architectures to enhance coherence times, demonstrating the effectiveness of pulse-reset cycles over fixed parameters across multiple quantum error correction schemes.

Contribution

It introduces a numerical optimization method for dissipation parameters, including a pulse-reset cycle, improving logical qubit lifetimes in various small logical qubit architectures.

Findings

Pulse-reset cycle outperforms fixed parameter optimization.

Enhanced coherence times in small logical qubits.

Effective parameter tuning improves error correction performance.

Abstract

Coherence times for superconducting qubits have greatly improved over time. Moreover, small logical qubit architectures using engineered dissipation have shown great promise for further improvements in the coherence of a logical qubit manifold comprised of few physical qubits. Nevertheless, optimal working parameters for small logical qubits are generally not well understood. This work presents several approaches to finding preferential parameter configurations by looking at three different cases of increasing complexity. We begin by looking at state stabilization of a single qubit using dissipation via coupling to a lossy object. We look at the limiting factors in this approach to error correction, and how we address those by numerically optimizing the parametric coupling strength with the lossy object having an effective time-varying dissipation rate---we call this a pulse-reset cycle. We then translate this approach to more efficient state stabilization to an abstracted three-qubit flip code, and end by looking at the Very Small Logical Qubit (VSLQ). By using these techniques, we can further increase logical state lifetimes for different architectures. We show significant advantages in using a pulse-reset cycle over numerically optimized, fixed parameter spaces.