Input-output theory for spin-photon coupling in Si double quantum dots

TL;DR

This paper presents a theoretical approach to enable strong spin-photon coupling in silicon double quantum dots by using spin-charge hybridization and input-output theory, facilitating long-range quantum entanglement and readout.

Contribution

It introduces a method to achieve sizable spin-photon coupling in silicon quantum dots using magnetic field gradients and predicts observable signatures for experimental detection.

Findings

Optimal working points for coherent spin-photon coupling identified.

Predicted observable signatures in cavity output field.

Provides guidance for experimental realization of strong coupling.

Abstract

The interaction of qubits via microwave frequency photons enables long-distance qubit-qubit coupling and facilitates the realization of a large-scale quantum processor. However, qubits based on electron spins in semiconductor quantum dots have proven challenging to couple to microwave photons. In this theoretical work we show that a sizable coupling for a single electron spin is possible via spin-charge hybridization using a magnetic field gradient in a silicon double quantum dot. Based on parameters already shown in recent experiments, we predict optimal working points to achieve a coherent spin-photon coupling, an essential ingredient for the generation of long-range entanglement. Furthermore, we employ input-output theory to identify observable signatures of spin-photon coupling in the cavity output field, which may provide guidance to the experimental search for strong coupling in such spin-photon systems and opens the way to cavity-based readout of the spin qubit.