Experimental demonstration of continuous quantum error correction

TL;DR

This paper demonstrates a resource-efficient continuous quantum error correction method that improves qubit lifetime by actively correcting errors without entangling gates or ancilla qubits, advancing fault-tolerant quantum computing.

Contribution

It introduces a continuous quantum error correction protocol using direct parity measurements, eliminating the need for entangling gates and ancilla qubits, and demonstrates its effectiveness in extending qubit coherence.

Findings

Achieved up to 91% bit-flip detection efficiency.

Increased logical qubit relaxation time by a factor of 2.7.

Showcased resource-efficient stabilizer measurements in a multi-qubit system.

Abstract

The storage and processing of quantum information are susceptible to external noise, resulting in computational errors that are inherently continuous A powerful method to suppress these effects is to use quantum error correction. Typically, quantum error correction is executed in discrete rounds where errors are digitized and detected by projective multi-qubit parity measurements. These stabilizer measurements are traditionally realized with entangling gates and projective measurement on ancillary qubits to complete a round of error correction. However, their gate structure makes them vulnerable to errors occurring at specific times in the code and errors on the ancilla qubits. Here we use direct parity measurements to implement a continuous quantum bit-flip correction code in a resource-efficient manner, eliminating entangling gates, ancilla qubits, and their associated errors. The continuous measurements are monitored by an FPGA controller that actively corrects errors as they are detected. Using this method, we achieve an average bit-flip detection efficiency of up to 91%. Furthermore, we use the protocol to increase the relaxation time of the protected logical qubit by a factor of 2.7 over the relaxation times of the bare comprising qubits. Our results showcase resource-efficient stabilizer measurements in a multi-qubit architecture and demonstrate how continuous error correction codes can address challenges in realizing a fault-tolerant system.