Quantum phase measurement and Gauss sum factorization of large integers in a superconducting circuit

TL;DR

This paper demonstrates a quantum phase measurement technique in superconducting circuits that enables Gauss sum factorization of large integers and precise parameter estimation, with performance limited mainly by coherence times.

Contribution

It introduces a novel phase measurement method in superconducting circuits for large integer factorization and parameter measurement, leveraging Kerr nonlinearity to enhance visibility.

Findings

Phase measurement can be used for factorization of numbers ≥10^4.

Enhanced visibility achieved through Kerr nonlinearity.

Largest factorizable number scales with resonator coherence time.

Abstract

We study the implementation of quantum phase measurement in a superconducting circuit, where two Josephson phase qubits are coupled to the photon field inside a resonator. We show that the relative phase of the superposition of two Fock states can be imprinted in one of the qubits. The qubit can thus be used to probe and store the quantum coherence of two distinguishable Fock states of the single-mode photon field inside the resonator. The effects of dissipation of the photon field on the phase detection are investigated. We find that the visibilities can be greatly enhanced if the Kerr nonlinearity is exploited. We also show that the phase measurement method can be used to perform the Gauss sum factorization of numbers (${\geq} 10^4$) into a product of prime integers, as well as to precisely measure both the resonator's frequency and the nonlinear interaction strength. The largest factorizable number is mainly limited by the coherence time. If the relaxation time of the resonator were to be ${\sim} 10$ $\mu$s (${\sim} 1$ ms), then the largest factorizable number can be ${\geq} 10^4N$ (${\geq} 10^{7}N$), where $N$ is the number of photons in the resonator.