Remote Entangling Gates for Spin Qubits in Quantum Dots using a Charge-Sensitive Superconducting Coupler

TL;DR

This paper introduces a method for implementing high-fidelity microwave-activated CZ gates between remote spin qubits in quantum dots using a charge-sensitive superconducting coupler, with noise mitigation strategies.

Contribution

It proposes a novel coupling scheme utilizing a charge-sensitive superconducting device and analyzes pulse schemes with dynamical decoupling for improved gate fidelity.

Findings

Achieves over 90% CZ gate fidelity in simulations

Demonstrates robustness against charge noise with pulse engineering

Provides a detailed charge-based coupling model for quantum dots

Abstract

We propose a method to realize microwave-activated CZ gates between two remote spin qubits in quantum dots using a charge-sensitive superconducting coupler. The qubits are longitudinally coupled to the coupler, so that the transition frequency of the coupler depends on the logical qubit states; a capacitive network model using first-quantized charge operators is developed to illustrate this. Driving the coupler transition then implements a conditional phase shift on the qubits. Two pulsing schemes are investigated: a rapid, off-resonant pulse with constant amplitude, and a pulse with envelope engineering that incorporates dynamical decoupling to mitigate charge noise. We develop non-Markovian time-domain simulations to accurately model gate performance in the presence of $1/f^\beta$ charge noise. Simulation results indicate that a CZ gate fidelity exceeding 90% is possible with realistic parameters and noise models.