Noise-spectroscopy of multiqubit systems: Determining all their parameters by applying an external classical noise

TL;DR

This paper proposes a method to determine all parameters of two coupled qubits by applying external classical noise and analyzing the Fourier spectrum of the density matrix, offering an alternative to traditional spectroscopy.

Contribution

The authors introduce a noise-spectroscopy technique for extracting all Hamiltonian parameters of coupled qubits through numerical modeling and spectral analysis.

Findings

All system parameters can be identified using external classical noise.

Interlevel spacings and qubit-qubit coupling can be accurately determined.

The method provides a new approach to qubit characterization without traditional spectroscopy.

Abstract

Imagine that you have several sets of two coupled qubits, but you do not know the parameters of their Hamitonians. How to determine these without resorting to the usual spectroscopy approach to the problem? Based on numerical modeling, we show that all the parameters of a system of two coupled qubits can be determined by applying to it an external classical noise and analysing the Fourier spectrum of the elements of the system's density matrix. In particular, the interlevel spacings as well as the strength and sign of qubit-qubit coupling can be determined this way.