Improving quantum gate performance through neighboring optimal control

Abstract

Successful implementation of a fault-tolerant quantum computation on a system of qubits places severe demands on the hardware used to control the many-qubit state. It is known that an accuracy threshold $P_a$ exists for any quantum gate that is to be used in such a computation. Specifically, the error probability $P_e$ for such a gate must fall below the accuracy threshold: $P_e<P_a$. Estimates of $P_a$ vary widely, though $P_a\sim 10^{-4}$ has emerged as a challenging target for hardware designers. In this paper we present a theoretical framework based on neighboring optimal control that takes as input a good quantum gate and returns a new gate with better performance. We illustrate this approach by applying it to all gates in a universal set of quantum gates produced using non-adiabatic rapid passage that has appeared in the literature. Performance improvements are substantial, both for ideal and non-ideal controls. Under suitable conditions detailed below, all gate error probabilities fall well below the target threshold of $10^{-4}$.

arXiv comment27 pages; 11 figures; 13 tables; to appear in Phys. Rev. A

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Cited by in corpus (1)

• High-fidelity quantum state preparation using neighboring optimal control