Amplified and tunable transverse and longitudinal spin-photon coupling in hybrid circuit-QED

TL;DR

This paper presents a method to dynamically tune between transverse and longitudinal spin-photon coupling in a hybrid circuit-QED system, enabling enhanced control and measurement capabilities in quantum information processing.

Contribution

It introduces a novel in-situ modulation technique to switch and amplify light-matter coupling types, including a longitudinal readout scheme applicable when intrinsic Hamiltonians are transverse.

Findings

Effective simulation of ultra-strong coupling regime

Implementation of longitudinal readout without changing intrinsic frequencies

Potential for improved quantum measurement fidelity

Abstract

We describe a method to tune, in-situ, between transverse and longitudinal light-matter coupling in a hybrid circuit-QED device composed of an electron spin degree of freedom coupled to a microwave transmission line cavity. Our approach relies on periodic modulation of the coupling itself, such that in a certain frame the interaction is both amplified and either transverse, or, by modulating at two frequencies, longitudinal. The former realizes an effective simulation of certain aspects of the ultra-strong coupling regime, while the latter allows one to implement a longitudinal readout scheme even when the intrinsic Hamiltonian is transverse, and the individual spin or cavity frequencies cannot be changed. We analyze the fidelity of using such a scheme to measure the state of the electron spin degree of freedom, and argue that the longitudinal readout scheme can operate in regimes where the traditional dispersive approach fails.