Systematic Magnus-Based Approach for Suppressing Leakage and Nonadiabatic Errors in Quantum Dynamics

Abstract

We present a systematic, perturbative method for correcting quantum gates to suppress errors that take the target system out of a chosen subspace. Our method addresses the generic problem of nonadiabatic errors in adiabatic evolution and state preparation, as well as general leakage errors due to spurious couplings to undesirable states. The method is based on the Magnus expansion: By correcting control pulses, we modify the Magnus expansion of an initially given, imperfect unitary in such a way that the desired evolution is obtained. Applications to adiabatic quantum state transfer, superconducting qubits, and generalized Landau-Zener problems are discussed.