Enhancing quantum control by bootstrapping a quantum processor of 12 qubits

TL;DR

This paper demonstrates control of a 12-qubit quantum system using measurement-based feedback, improving control accuracy and showcasing the potential of quantum processors as lab instruments for complex tasks.

Contribution

It introduces a method for controlling a 12-qubit system with feedback, surpassing classical techniques in accuracy, and extends to optimizing quantum gates with combined protocols.

Findings

Control of a 12-qubit system achieved

Control sequence 10% more accurate than classical methods

Quantum processor effectively used as a lab instrument

Abstract

Accurate and efficient control of quantum systems is one of the central challenges for quantum information processing. Current state-of-the-art experiments rarely go beyond 10 qubits and in most cases demonstrate only limited control. Here we demonstrate control of a 12-qubit system, and show that the system can be employed as a quantum processor to optimize its own control sequence by using measurement-based feedback control (MQFC). The final product is a control sequence for a complex 12-qubit task: preparation of a 12-coherent state. The control sequence is about 10% more accurate than the one generated by the standard (classical) technique, showing that MQFC can correct for unknown imperfections. Apart from demonstrating a high level of control over a relatively large system, our results show that even at the 12-qubit level, a quantum processor can be a useful lab instrument. As an extension of our work, we propose a method for combining the MQFC technique with a twirling protocol, to optimize the control sequence that produces a desired Clifford gate.