Coupling a single electron spin to a microwave resonator: Controlling transverse and longitudinal couplings

Félix Beaudoin, Dany Lachance-Quirion, W. A. Coish, Michel Pioro-Ladrière

Published 2016-06-15Version 1

Microwave resonators have been used to realize qubit readout, two-qubit gates, and state shuttling between distant quantum systems. Strong coupling between a spin qubit and a resonator may be achieved using an inhomogeneous magnetic field generated with a nanomagnet. We consider a spin qubit in a double quantum dot exposed to a stray magnetic field with transverse and longitudinal components with respect to an applied external field. We show that this geometry leads to transverse and longitudinal couplings of ~1 MHz between the spin qubit and the resonator. Using realistic simulations of a GaAs device, we show how precise placement of the nanomagnet allows to select between transverse and longitudinal coupling. We also explain how to mitigate new dephasing and relaxation channels that are inherent to this coupling scheme. This analysis gives a clear route towards realization of coherent state transfer between a microwave resonator and a single spin in quantum dots with a fidelity above 90%. Improved dynamical decoupling sequences, low-noise environments, and longer-lived microwave cavities may lead to substantially higher fidelities in the near future.