Southwest Quantum Information and Technology

Operation and intrinsic error budget of a two-qubit cross-resonance gate

Presenting Author: Vinay Tripathi, University of Southern California; University of California Riverside
Contributing Author(s): Mostafa Khezri, Alexander N. Korotkov

We analyze analytically, semianalytically, and numerically the operation of a cross-resonance (CR) gate for superconducting qubits (transmons). We find that a relatively simple semianalytical method gives accurate results for the controlled-not (cnot) - equivalent gate duration and compensating single-qubit rotations. It also allows us to minimize the cnot gate duration over the amplitude of the applied microwave drive and find the dependence on the detuning between the qubits. However, full numerical simulations are needed to calculate the intrinsic fidelity of the CR gate. We decompose numerical infidelity into contributions from various physical mechanisms, thus finding the intrinsic error budget. In particular, at small drive amplitudes, the CR gate fidelity is limited by imperfections of the target-qubit rotations, while at large amplitudes it is limited by leakage. The gate duration and fidelity are analyzed numerically as functions of the detuning between qubits, their coupling, drive frequency, relative duration of pulse ramps, and microwave crosstalk. The effect of the echo sequence is also analyzed numerically. Our results show that the CR gate can provide intrinsic infidelity of less than $10^-3$ when a simple pulse shape is used.

Read this article online: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.012301

(Session : from 5:00pm - 7:00pm)