Quantum state preparation and readout with modulated electrons

TL;DR

This paper explores how modulated electron wavefunctions can be used for quantum state preparation, readout, and tomography of quantum emitters, highlighting their potential in quantum technologies.

Contribution

It demonstrates that modulated electrons can prepare, read out, and perform tomography on quantum emitters without entanglement, extending to realistic wavepackets and practical conditions.

Findings

Perfectly periodic electron combs induce Rabi-like dynamics in emitters.

Realistic modulated wavepackets preserve key phenomenology.

Small electron combs enable quantum state tomography of emitters.

Abstract

We provide a comprehensive study of the capabilities of modulated electron wavefunctions for the preparation and readout of the quantum state of the quantum emitters (QEs) they interact with. First, we consider perfectly periodic electron combs, which do not produce QE-electron entanglement, preserving the purity of the QE while inducing Rabi-like dynamics in it. We extend our findings to realistic, non-ideally modulated electron wavepackets, showing that the phenomenology persists, and exploring their use to prepare the emitter in a desired quantum state. Thus, we establish the balance that electron comb size, emitter radiative decay, and electron-emitter coupling strength must fulfil in order to implement our ideas in experimentally feasible platforms. Finally, moving into the limit of small electron combs, we reveal that these wavefunctions allow for quantum state tomography of their target, providing access not only to the populations, but also the coherences of the QE density matrix. We believe that our theoretical results showcase modulated free-electrons as very promising tools for quantum technologies based on light-matter coupling.