Measurement of energy eigenstates by a slow detector

TL;DR

This paper introduces a method for weakly measuring the energy states of a fast quantum system using a slow detector, enabling detection of quantum jumps with minimal back-action beyond decoherence.

Contribution

It presents a novel measurement scheme that allows energy eigenstate detection with limited back-action, applicable to quantum jump detection in harmonic oscillators.

Findings

Effective weak measurement of energy eigenstates demonstrated

Quantum jumps between energy levels can be detected with minimal disturbance

Back-action limited to decoherence of superpositions

Abstract

We propose a method for a weak continuous measurement of the energy eigenstates of a fast quantum system by means of a "slow" detector. Such a detector is only sensitive to slowly-changing variables, e. g. energy, while its back-action can be limited solely to decoherence of the eigenstate superpositions. We apply this scheme to the problem of detection of quantum jumps between energy eigenstates in a harmonic oscillator.