Dephasing mechanisms and fidelity of entangled spin qubits preparation under joint continuous measurement via longitudinal couplings to a superconducting resonator

We consider the preparation dynamics of spin qubits entanglement via joint continuous measurement with longitudinal couplings to a superconducting resonator (see [1]). Enhancement of the measurement rate via the dynamical longitudinal coupling allows to effectively overcome the typical dephasing mechanisms, such as charge dephasing and qubit relaxation. Another dephasing mechanism originates from the unitary back action arising in a homodyne measurement. We show how it can be cancelled for a system of N qubits in an appropriate limit when the resonator dynamics is much faster than the qubits rates. We study these mechanisms on the realistic example of a charge-spin qubit with magnetic field gradient, and discuss possible experimental signatures of the spin-qubit entanglement.



[1] R. Ruskov and C. Tahan, Phys. Rev. B 99, 245306 (2019); arXiv: 1704.05876