Stroboscopically Robust Operating Points on Ising-Coupled Qubits*

Recent work on Ising-coupled double-quantum-dot spin qubits in GaAs with voltage-controlled exchange interaction had shown improved two-qubit gate fidelities from the application of a.c. exchange gates along with a strong magnetic field gradient between adjacent dots [1]. By examining how noise propagates in the time evolution operator of the system, we find an optimal set of parameters that provides passive stroboscopic circumvention of errors in two-qubit gates to first order, provided that the fluctutations in the total qubit energy splitting is no greater than the inter-qubit coupling strength. We predict over 99% two-qubit gate fidelities for the case of quasi-static noise, which is an order of magnitude improvement over the typical unoptimzed implementation. The effects of 1/f noise are also taken into consideration.

[1] J. M. Nichol et al., High-fidelity entangling gates for double-quantum-dot spin qubit. NPJ Quantum Inform. 3, 3 (2017).