Digital-Analog Quantum Simulations Using The Cross-Resonance Effect

TL;DR

This paper proposes a method for digital-analog quantum simulation using the cross-resonance effect in superconducting qubits, enabling efficient simulation of spin models with reduced Trotter errors and practical calibration strategies.

Contribution

It extends the cross-resonance effect to generate analog Hamiltonians on 1D and 2D qubit lattices, enabling Trotter error-free simulation of certain spin models.

Findings

Trotter error-free simulation for 1D Ising and XY models.

Reduced Trotter errors for 2D XY and 1D Heisenberg models.

Practical strategies for Hamiltonian calibration and extension to complex models.

Abstract

Digital-analog quantum computation aims to reduce the currently infeasible resource requirements needed for near-term quantum information processing by replacing sequences of one- and two-qubit gates with a unitary transformation generated by the systems' underlying Hamiltonian. Inspired by this paradigm, we consider superconducting architectures and extend the cross-resonance effect, up to first order in perturbation theory, from a two-qubit interaction to an analog Hamiltonian acting on 1D chains and 2D square lattices which, in an appropriate reference frame, results in a purely two-local Hamiltonian. By augmenting the analog Hamiltonian dynamics with single-qubit gates we show how one may generate a larger variety of distinct analog Hamiltonians. We then synthesize unitary sequences, in which we toggle between the various analog Hamiltonians as needed, simulating the dynamics of Ising, $XY$, and Heisenberg spin models. Our dynamics simulations are Trotter error-free for the Ising and $XY$ models in 1D. We also show that the Trotter errors for 2D $XY$ and 1D Heisenberg chains are reduced, with respect to a digital decomposition, by a constant factor. In order to realize these important near-term speedups, we discuss the practical considerations needed to accurately characterize and calibrate our analog Hamiltonians for use in quantum simulations. We conclude with a discussion of how the Hamiltonian toggling techniques could be extended to derive new analog Hamiltonians which may be of use in more complex digital-analog quantum simulations for various models of interacting spins.