Fast high-fidelity geometric gates for singlet-triplet qubits

TL;DR

This paper demonstrates a method to implement fast, high-fidelity geometric quantum gates for singlet-triplet qubits by modulating exchange interactions, avoiding microwave control and reducing decoherence effects.

Contribution

The authors introduce a scheme for fast geometric gates using only exchange interaction modulation, achieving gate times of a few nanoseconds with fidelity over 99%.

Findings

Gate time reduced to several nanoseconds.

Fidelity surpassing 99%.

Applicable to systems without microwave drive.

Abstract

Geometric gates that use the global property of the geometric phase is believed to be a powerful tool to realize fault-tolerant quantum computation. However, for singlet-triplet qubits in semiconductor quantum dot, the low Rabi frequency of the microwave control leads to overly long gating time, and thus the constructing geometric gate suffers more from the decoherence effect. Here we investigate the key issue of whether the fast geometric gate can be realized for singlet-triplet qubits without introducing an extra microwave-driven pulse, while maintaining the high-fidelity gate operation at the same time. We surprisingly find that both the single- and two-qubit geometric gates can be implemented via only modulating the time-dependent exchange interaction of the Hamiltonian, which can typically be on the order of $\sim$GHz, and thus the corresponding gate time is of several nanoseconds. Furthermore, the obtained geometric gates are superior to their counterparts, i.e., the conventional dynamical gates for singlet-triplet qubits, with a relatively high fidelity surpassing $99\%$. Therefore our scheme is particularly applied to singlet-triplet qubits to obtain fast and high-fidelity geometric gates. Our scheme can also be extended to other systems without a microwave drive.