Limits to Quantum Gate Fidelity from Near-Field Thermal and Vacuum Fluctuations

TL;DR

This paper develops a quantum electrodynamics framework and numerical methods to quantify and mitigate near-field thermal and vacuum fluctuations, which limit the fidelity of spin-qubit quantum gates in nanofabricated devices.

Contribution

It introduces a novel theory and computational approach to assess EWJN effects and proposes Lindbladian engineering to improve quantum gate fidelity against these fluctuations.

Findings

Quantified EWJN effects near metallic gates using volume integral equations.

Demonstrated limits to spin-qubit gate fidelity imposed by thermal and vacuum fluctuations.

Showed that control pulse optimization can mitigate EWJN impacts effectively.

Abstract

High-fidelity quantum gate operations are essential for achieving scalable quantum circuits. In spin qubit quantum computing systems, metallic gates and antennas which are necessary for qubit operation, initialization, and readout, also cause detriments by enhancing fluctuations of electromagnetic fields. Therefore evanescent wave Johnson noise (EWJN) caused by thermal and vacuum fluctuations becomes an important unmitigated noise, which induces the decay of spin qubits and limits the quantum gate operation fidelity. Here, we first develop a quantum electrodynamics theory of EWJN. Then we propose a numerical technique based on volume integral equations to quantify EWJN strength in the vicinity of nanofabricated metallic gates with arbitrary geometry. We study the limits to two spin-qubit gate fidelity from EWJN-induced relaxation processes in two experimentally relevant quantum computing platforms: (a) silicon quantum dot system and (b) NV centers in diamond. Finally, we introduce the Lindbladian engineering method to optimize the control pulse sequence design and show its enhanced performance over Hamiltonian engineering in mitigating the influence of thermal and vacuum fluctuations. Our work leverages advances in computational electromagnetics, fluctuational electrodynamics and open quantum systems to suppress the effects of thermal and vacuum fluctuations and reach the limits of two-spin-qubit gate fidelity.