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.
@article{arxiv.1712.02077,
title = {Amplified and tunable transverse and longitudinal spin-photon coupling in hybrid circuit-QED},
author = {Neill Lambert and Mauro Cirio and Matthieu Delbecq and Giles Allison and Marian Marx and Seigo Tarucha and Franco Nori},
journal= {arXiv preprint arXiv:1712.02077},
year = {2018}
}