Heralded Free-Electron Writing of the Most Subradiant State in an Atomic Array

Abstract:The most subradiant eigenstate of a finite subwavelength atomic chain in free space, protected by strongly suppressed radiative decay, offers a powerful resource for photon storage, quantum sensing, and many-body quantum optics. Yet its optical preparation is hindered by the simultaneous need to match a wave vector outside the light cone and a nonuniform envelope. Here, we show that a free electron can overcome these constraints: its velocity sets the imprinted wave vector, while the trajectory of the diffracting wave packet shapes the excitation envelope. This simultaneous momentum and envelope matching enables heralded preparation with near-unity conditional fidelity ($F>99.5\%$) even in a deeply subwavelength regime that is difficult to access with propagating free-space photons. We further show that a path-superposed free electron can excite an antisymmetric state in two closely spaced parallel chains, whose interchain destructive interference yields stronger subradiance than a single chain with the same total number of atoms. These results establish free electrons as quantum writers for collective excitations that are difficult to access with propagating optical fields.

Quantum Physics (quant-ph); Optics (physics.optics)

arXiv:2608.03056 [quant-ph]

(or arXiv:2608.03056v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2608.03056 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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