Fast high-fidelity single-qubit gates for flip-flop qubits in silicon

TL;DR

This paper proposes an optimal control scheme for flip-flop qubits in silicon that enables fast, high-fidelity single-qubit gates while enhancing relaxation times and qubit quality factors, addressing challenges of electron spin control near interfaces.

Contribution

It introduces a theoretical framework and control method for fast, robust single-qubit gates in flip-flop qubits, improving qubit coherence and control without relying on sweet spots.

Findings

The control scheme achieves faster gate operations.

It significantly increases qubit relaxation times.

The method enhances overall qubit quality factors.

Abstract

The flip-flop qubit, encoded in the states with antiparallel donor-bound electron and donor nuclear spins in silicon, showcases long coherence times, good controllability, and, in contrast to other donor-spin-based schemes, long-distance coupling. Electron spin control near the interface, however, is likely to shorten the relaxation time by many orders of magnitude, reducing the overall qubit quality factor. Here, we theoretically study the multilevel system that is formed by the interacting electron and nuclear spins and derive analytical effective two-level Hamiltonians with and without periodic driving. We then propose an optimal control scheme that produces fast and robust single-qubit gates in the presence of low-frequency noise without relying on parametrically restrictive sweet spots. This scheme increases considerably both the relaxation time and the qubit quality factor.