Analog Quantum Phase Estimation with Single-Mode Readout

TL;DR

This paper introduces an analog quantum phase estimation protocol that uses continuous evolution and cavity measurement to efficiently estimate eigenvalues, reducing circuit complexity and enabling near-term quantum applications.

Contribution

The authors develop an analog quantum phase estimation method that leverages cavity measurements, avoiding deep circuits and entangling gates, suitable for current quantum hardware.

Findings

Demonstrated feasibility with XY model Hamiltonian

Achieved resource-efficient eigenvalue estimation

Compatible with existing circuit QED technology

Abstract

Eigenvalue estimation is a central problem for demonstrating quantum advantage, yet its implementation on digital quantum computers remains limited by circuit depth and operational overhead. We present an analog quantum phase estimation (aQPE) protocol that extracts the eigenenergies of a target Hamiltonian via continuous time evolution and single-mode cavity measurement. By encoding eigenvalue information as conditional cavity phase-space rotations, the scheme avoids deep quantum circuits and entangling gates, while enabling readout through established cavity tomography techniques. We further illustrate the feasibility of this approach by engineering a Hamiltonian that implements aQPE of the XY model, whose ground-state energy problem is QMA-complete, within a physical architecture compatible with existing circuit quantum electrodynamics technology. Our results provide a resource-efficient and scalable framework for implementing quantum phase estimation in near-term quantum platforms.