Robust two-qubit gates for donors in silicon controlled by hyperfine interactions

TL;DR

This paper introduces two robust methods for implementing high-fidelity two-qubit gates in silicon-based donor systems by leveraging hyperfine interactions and nuclear spin control, eliminating the need for dynamic exchange tuning.

Contribution

It proposes novel strategies for two-qubit gates in silicon donors that utilize hyperfine interactions and nuclear spin states, enhancing robustness and experimental feasibility.

Findings

High-fidelity conditional rotation gates achieved without dynamic exchange tuning

Hyperfine detuning enables switching of SWAP operations with modest exchange tuning

Methods are compatible with realistic experimental conditions

Abstract

We present two strategies for performing two-qubit operations on the electron spins of an exchange-coupled pair of phosphorus donors in silicon, using the ability to set the donor nuclear spins in arbitrary states. The effective magnetic detuning of the two electron qubits is provided by the hyperfine interaction when the $^{31}$P nuclei are prepared in opposite spin states. This can be exploited to switch on and off SWAP operations with modest tuning of the electron exchange interaction. Furthermore, the hyperfine detuning enables high-fidelity conditional rotation gates based on selective resonant excitation. The latter requires no dynamic tuning of the exchange interaction at all, and offers a very attractive scheme to implement two-qubit logic gates under realistic experimental conditions.