Error-detected coherence metrology of a dual-rail encoded fixed-frequency multimode superconducting qubit

TL;DR

This paper demonstrates a dual-rail encoding method within a fixed-frequency superconducting qubit that significantly reduces logical error rates and offers a new approach for studying noise and decoherence in quantum processors.

Contribution

It introduces a novel dual-rail encoding in a single fixed-frequency superconducting transmon, achieving lower logical error rates and enabling fundamental noise investigations.

Findings

Logical error rates are over ten times lower than physical error rates.

The architecture shows high stability and repeatability across multiple devices.

The method provides a pathway for studying noise and decoherence in superconducting qubits.

Abstract

Amplitude damping is a dominant source of error in high performance quantum processors. A promising approach in quantum error correction is erasure error conversion, where errors are converted into detectable leakage states. Dual-rail encoding has been shown as a candidate for the conversion of amplitude-damping errors; with unique sensitivities to noise and decoherence sources. Here we present a dual-rail encoding within a single fixed-frequency superconducting multimode transmon qubit. The three island, two junction device comprises two transmonlike modes with a detuning of 0.75-1 GHz, in a coaxial circuit QED architecture. We show the logical bit-flip and phase-flip error rates are more than one order of magnitude lower than the physical error rates, and demonstrate stability and repeatability of the architecture through an extended measurement of three such devices. Finally, we discuss how the error-detected subspace can be used for investigations into the fundamentals of noise and decoherence in fixed-frequency transmon qubits.