Robust entangling shaped pulses for cavity-coupled silicon quantum dot spin qubits with always-on coupling*

The fidelity of cavity-mediated long-range entanglement between singly-loaded double quantum dot spin qubits in silicon is ultimately limited by charge noise. Leading order effects of quasistatic charge noise can be suppressed by using a composite pulse sequence provided that the coupling can be switched on and off rapidly by pulsing on the tunnel barrier voltage [1]. However, a different approach is needed when bandwidth limitations [2] preclude rapid pulsing of the tunnel barrier. Here, we report a robust iSWAP gate for such a system, with both qubits driven slightly off-resonantly using a shaped pulse obtained using a physics informed neural network [3], in the presence of an always-on exchange coupling. The resulting gate is robust against quasistatic charge noise as well as driving amplitude errors, and the control requirements are within experimental limitations.

[1] A. Warren, U. Güngördü, J. P. Kestner, E. Barnes, S. E. Economou, Phys. Rev. B 104, 115308 (2021)

[2] W. Huang et al Nature (London) 569, 532 (2019)

[3] U. Güngördü, J. P. Kestner, arXiv:2011.02512 (2020)