A diverse set of two-qubit gates for spin qubits in semiconductor quantum dots

TL;DR

This paper introduces a versatile composite two-qubit gate scheme for spin qubits in semiconductor quantum dots, enabling multiple gate types with simplified control parameters, verified experimentally, and advancing scalable quantum computing.

Contribution

It proposes a unified, fast composite gate scheme that extends available two-qubit operations and simplifies device requirements for spin qubits, with experimental validation.

Findings

The scheme enables CPhase, SWAP, iSWAP-family, and fSim gates.

All gates share a common parameter region J~ΔE_Z.

Experimental results show excellent agreement with theoretical predictions.

Abstract

To realize large-scale quantum information processes, an ideal scheme for two-qubit operations should enable diverse operations with given hardware and physical interaction. However, for spin qubits in semiconductor quantum dots, the common two-qubit operations, including CPhase gates, SWAP gates, and CROT gates, are realized with distinct parameter regions and control waveforms, posing challenges for their simultaneous implementation. Here, taking advantage of the inherent Heisenberg interaction between spin qubits, we propose and verify a fast composite two-qubit gate scheme to extend the available two-qubit gate types as well as reduce the requirements for device properties. Apart from the formerly proposed CPhase (controlled-phase) gates and SWAP gates, theoretical results indicate that the iSWAP-family gate and Fermionic simulation (fSim) gate set are additionally available for spin qubits. Meanwhile, our gate scheme limits the parameter requirements of all essential two-qubit gates to a common J~{\Delta}E_Z region, facilitate the simultaneous realization of them. Furthermore, we present the preliminary experimental demonstration of the composite gate scheme, observing excellent match between the measured and simulated results. With this versatile composite gate scheme, broad-spectrum two-qubit operations allow us to efficiently utilize the hardware and the underlying physics resources, helping accelerate and broaden the scope of the upcoming noise intermediate-scale quantum (NISQ) computing.