Journal Article

Fault-tolerant control of an error-corrected qubit

Noel, Crystal, Risinger, Andrew, Brown, Kenneth R., Monroe, Christopher, Debroy, Dripto M., Biswas, Debopriyo, Cetina, Marko, Egan, Laird, Zhu, Daiwei, Li, Muyuan, Newman, Michael

2021

Overview

Quantum error correction protects fragile quantum information by encoding it into a larger quantum system 1 , 2 . These extra degrees of freedom enable the detection and correction of errors, but also increase the control complexity of the encoded logical qubit. Fault-tolerant circuits contain the spread of errors while controlling the logical qubit, and are essential for realizing error suppression in practice 3 – 6 . Although fault-tolerant design works in principle, it has not previously been demonstrated in an error-corrected physical system with native noise characteristics. Here we experimentally demonstrate fault-tolerant circuits for the preparation, measurement, rotation and stabilizer measurement of a Bacon–Shor logical qubit using 13 trapped ion qubits. When we compare these fault-tolerant protocols to non-fault-tolerant protocols, we see significant reductions in the error rates of the logical primitives in the presence of noise. The result of fault-tolerant design is an average state preparation and measurement error of 0.6 per cent and a Clifford gate error of 0.3 per cent after offline error correction. In addition, we prepare magic states with fidelities that exceed the distillation threshold 7 , demonstrating all of the key single-qubit ingredients required for universal fault-tolerant control. These results demonstrate that fault-tolerant circuits enable highly accurate logical primitives in current quantum systems. With improved two-qubit gates and the use of intermediate measurements, a stabilized logical qubit can be achieved. Fault-tolerant circuits for the control of a logical qubit encoded in 13 trapped ion qubits through a Bacon–Shor quantum error correction code are demonstrated.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/766/483/2802 / 639/766/483/481 / Circuits / Distillation / Engineering research / Error correction / Error correction & detection / Error-correcting codes / Fault tolerance / Fault tolerance (Computers) / Humanities and Social Sciences / multidisciplinary / Quantum computing / Quantum phenomena / Qubits (quantum computing) / Science / Science (multidisciplinary)