We investigate coupling an encoded spin qubit to a microwave resonator via qubit energy level curvature versus gate voltage. This approach enables quantum non-demolition readout with strength of tens to hundred MHz all while the qubit stays at its full sweet-spot to charge noise, with zero dipole moment. A "dispersive-like" spin readout approach similar to circuit-QED but avoiding the Purcell effect is proposed. With the addition of gate voltage modulation, selective longitudinal readout and n-qubit entanglement-by-measurement are possible.
@article{arxiv.1704.05876,
title = {Quantum-limited measurement of spin qubits via curvature coupling to a cavity},
author = {Rusko Ruskov and Charles Tahan},
journal= {arXiv preprint arXiv:1704.05876},
year = {2019}
}