Efficient Quantum Gate Discovery with Optimal Control

TL;DR

This paper introduces a new framework for designing objective functions in optimal control theory, enabling the discovery of more effective quantum gates like echo pulses with higher fidelity and fewer optimization steps.

Contribution

The paper proposes novel objective functions for quantum control that allow for the design of advanced gate types, improving efficiency and performance in quantum gate synthesis.

Findings

Higher fidelity quantum gates achieved with new objective functions

Fewer optimization iterations needed for gate design

Effective microwave-only pulses for superconducting transmon qubits

Abstract

Optimal control theory provides a framework for numerical discovery of device controls that implement quantum logic gates, but common objective functions used for optimization often assign arbitrarily high costs to otherwise useful controls. We propose a framework for designing objective functions that permit novel gate designs such as echo pulses or locally-equivalent gates. We use numerical simulations to demonstrate the efficacy of the new objective functions by designing microwave-only pulses that act as entangling gates for superconducting transmon architectures. We observe that the proposed objective functions lead to higher fidelity controls in fewer optimization iterations than obtainable by traditional objective functions.