High-fidelity quantum gates in Si/SiGe double quantum dots

TL;DR

This paper presents a theoretical framework for implementing high-fidelity two-qubit gates in Si/SiGe quantum dots by optimizing pulse sequences and phase control, addressing challenges like spin flips and phase mismatches.

Contribution

It introduces a novel synchronization method and detailed analysis of phase mismatches to enhance gate fidelity in silicon quantum dot systems.

Findings

Optimal pulse sequences improve gate fidelity

Synchronization reduces spin flip errors

Phase compensation enhances gate performance

Abstract

Motivated by recent experiments of Zajac et al. [arXiv:1708.03530], we theoretically describe high-fidelity two-qubit gates using the exchange interaction between the spins in neighboring quantum dots subject to a magnetic field gradient. We use a combination of analytical calculations and numerical simulations to provide the optimal pulse sequences and parameter settings for the gate operation. We present a novel synchronization method which avoids detrimental spin flips during the gate operation and provide details about phase mismatches accumulated during the two-qubit gates which occur due to residual exchange interaction, non-adiabatic pulses, and off-resonant driving. By adjusting the gate times, synchronizing the resonant and off-resonant transitions, and compensating these phase mismatches by phase control, the overall gate fidelity can be increased significantly.