Frequency- and Amplitude-Modulated Gates for Universal Quantum Control

TL;DR

This paper introduces a theoretical framework for high-fidelity quantum gates using combined frequency and amplitude modulation of microwave drives, enabling universal control of fixed-frequency qubits with broad applicability.

Contribution

It extends conventional amplitude modulation by incorporating frequency modulation, allowing fixed-frequency qubits to achieve universal quantum gates with high fidelity.

Findings

Achieved gate errors below 0.1% in simulations.

Demonstrated universal gate set including X, Hadamard, phase, and CZ gates.

Gate times are within 25-135 ns depending on the operation.

Abstract

Achieving high-fidelity single- and two-qubit gates is essential for executing arbitrary digital quantum algorithms and for building error-corrected quantum computers. We propose a theoretical framework for implementing quantum gates using frequency- and amplitude-modulated microwave control, which extends conventional amplitude modulation by introducing frequency modulation as an additional degree of control. Our approach operates on fixed-frequency qubits, converting the need for qubit frequency tunability into drive frequency modulation. Using Floquet theory, we analyze and design these drives for optimal fidelity within specified criteria. Our framework spans adiabatic to nonadiabatic gates within the Floquet framework, ensuring broad applicability across gate types and control schemes. Using typical transmon qubit parameters in numerical simulations, we demonstrate a universal gate set-including the X, Hadamard, phase, and CZ gates-with control error well below 0.1% and gate times of 25-40 ns for single-qubit operations and 125-135 ns for two-qubit operations. Furthermore, we show an always-on CZ gate tailored for driven qubits, which has gate times of 80-90 ns.