Crosstalk resistant CZ gate robust against charge noise in silicon two qubit devices*

Although silicon is a promising and scalable platform for quantum computing the fidelity of two qubit gates in silicon is limited by charge noise and potential crosstalk. Schemes to deal with either individually have been proposed, but this work presents a method of dealing with both at the same time. The presence of crosstalk and charge noise results in a unitary error propagator that involves all 15 generators of SU(4), making it very difficult to create a robust pulse analytically. Therefore a robust pulse shape is determined by numerically optimizing a neural network. The effects of crosstalk are taken into account exactly through the hamiltonian while also being computationally efficient. Neural networks are computationally efficient to optimize because of the rapid evaluation of the high-dimensional gradient of the cost function through back propagation. This approach was then also applied to create robust sections of the composite pulse sequence of Ref [1] that suppresses exchange noise and Zeeman energy fluctuations. The resulting pulse sequence has an infidelity of 10^-3 for quasi static noise fluctuations in exchange J of 10% or fluctuations in Zeeman energy of 10kHz.

 

[1] U. Güngördü and J. P. Kestner, Phys. Rev. B98, 165301(2018).