Experimental time-optimal universal control of spin qubits in solids

TL;DR

This paper reports the first experimental implementation of time-optimal universal control of spin qubits in diamond, achieving high-fidelity quantum gates within minimal time using generalized quantum brachistochrone solutions.

Contribution

It demonstrates a practical method for realizing time-optimal quantum control in solid-state qubits, extending theoretical approaches to experimental settings.

Findings

Achieved 99% fidelity for single- and two-qubit gates.

Implemented time-optimal control protocols based on quantum brachistochrone equations.

Provided a scalable approach for high-fidelity, time-efficient quantum operations.

Abstract

Quantum control of systems plays important roles in modern science and technology. The ultimate goal of quantum control is to achieve high fidelity universal control in the time-optimal way. Although high fidelity universal control has been reported in various quantum systems, experimental implementation of time-optimal universal control remains elusive. Here we report the experimental realization of time-optimal universal control of spin qubits in diamond. By generalizing a recent method for solving quantum brachistochrone equations [X. Wang, et al., Phys. Rev. Lett. 114, 170501 (2015)], we obtained accurate minimum time protocols for multiple qubits with fixed qubits' interactions and constrained control field. Single- and two-qubit time-optimal gates are experimentally implemented with fidelities of 99% obtained via quantum process tomography. Our work provides a time-optimal route to achieve accurate quantum control, and unlocks new capabilities for emerging field of time-optimal control in general quantum systems.