Southwest Quantum Information and Technology

Bipartite Control of Noisy Qubits Using the Quantum Approximate Optimization Algorithm

Presenting Author: Zhibo Yang, University of California Berkeley
Contributing Author(s): Robert Kosut, K. Birgitta Whaley

We employ bipartite control with a Quantum Approximate Optimization Algorithm (QAOA) control ansatz to mitigate noise on qubits. We illustrate the approach with application to the protection of quantum gates performed on a central spin qubit coupling to bath spins through isotropic Heisenberg interactions, on superconducting transmon qubits coupling to environmental two-level-systems (TLS) through dipole-dipole interactions, and on qubits coupled to both TLS and a Lindblad bath. The control field is classical and only acts on the system qubits. We use policy gradient (PG) and sequential convex programming (SCP) as classical optimization methods to optimize the QAOA control protocols with a fidelity objective defined with respect to specific target quantum gates. We demonstrate effective suppression of coherent noise, with numerical studies achieving target gate fidelities over 0.9999 in the majority of test cases for this. We analyze how specific implementations determine the fidelity achieved by the optimal protocols and reveal some critical behaviors of bipartite QAOA control of quantum gates.

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