Fault-Tolerant Computing With Biased-Noise Superconducting Qubits

TL;DR

This paper proposes a fault-tolerant quantum computing scheme using biased-noise superconducting qubits, leveraging noise characteristics to optimize logical gate implementation and error correction.

Contribution

It introduces a universal pulsed operation scheme for IBM flux qubits and a specialized encoding exploiting noise bias to improve logical gate fidelity.

Findings

Error rates for operations can be as low as 0.5%.

Noise is highly biased with phase errors dominant.

A logical CNOT gate with balanced error rates around 0.4% is achievable.

Abstract

We present a universal scheme of pulsed operations for the IBM oscillator-stabilized flux qubit comprising the CPHASE gate, single-qubit preparations and measurements. Based on numerical simulations, we argue that the error rates for these operations can be as low as about .5% and that noise is highly biased, with phase errors being stronger than all other types of errors by a factor of nearly 10^3. In contrast, the design of a CNOT gate for this system with an error rate of less than about 1.2% seems extremely challenging. We propose a special encoding which exploits the noise bias allowing us to implement a logical CNOT gate where phase errors and all other types of errors have nearly balanced rates of about .4%. Our results illustrate how the design of an encoding scheme can be adjusted and optimized according to the available physical operations and the particular noise characteristics of experimental devices.