Local control theory for superconducting qubits

TL;DR

This paper introduces a local control theory-based method for designing control pulses in fixed-frequency superconducting qubits, enabling efficient and reversible population transfer with potential for further optimization.

Contribution

It develops a novel control pulse design approach using local control theory tailored for superconducting qubits, which was not previously applied in this context.

Findings

The method allows monotonic population transfer between states.

It requires only a single forward wavefunction propagation.

The approach can be refined for improved pulse properties.

Abstract

In this work, we develop a method to design control pulses for fixed-frequency superconducting qubits coupled via tunable couplers based on local control theory, an approach commonly employed to steer chemical reactions. Local control theory provides an algorithm for the monotonic population transfer from a selected initial state to a desired final state of a quantum system through the on-the-fly shaping of an external pulse. The method, which only requires a unique forward time-propagation of the system wavefunction, can serve as starting point for additional refinements that lead to new pulses with improved properties. Among others, we propose an algorithm for the design of pulses that can transfer population in a reversible manner between given initial and final states of coupled fixed-frequency superconducting qubits.