Abstract
Entanglement engineering plays a central role in quantum-enhanced technologies, with potential physical platforms that outperform their classical counterparts. However, free electrons remain largely unexplored despite their great capacity to encode and manipulate quantum information, due in part to the lack of a suitable theoretical framework. Here we link theoretical concepts from quantum information to available free-electron sources. Specifically, we consider the interactions among electrons propagating near the surface of a polariton-supporting medium and study the entanglement induced by pair-wise coupling. These correlations depend on the controlled interaction interval and the initial electron bandwidth. We show that long interaction times of broadband electrons extend their temporal coherence. This in turn is revealed through a widened Hong–Ou–Mandel peak and is associated with an increased entanglement entropy. We then introduce a discrete basis of electronic temporal modes and discriminate between them via coincidence detection with a shaped probe. This paves the way for ultrafast quantum information transfer by means of free electrons, rendering the large alphabet that they span in the time domain accessible.
Highlights
Quantum degrees of freedom occupy a large parameter space compared with their classical counterparts
Near fields evolving at the surface of polariton-supporting materials provide a novel approach to generate and shape quantum correlations in charged particles, and in particular in free electrons
While such pairing mechanisms are suppressed in matter due to ambient noise, electrons structured in a beam undergo significantly less scattering events, enabling coherent interactions to persist over longer space–time intervals
Summary
Quantum degrees of freedom occupy a large parameter space compared with their classical counterparts. A key concept in the generation of such useful states is initiation of well-monitored interactions between continuous variables The latter exhibit rich entanglement spectra and large state space on which information can be recorded and accessed[15,16,17,18,19]. Extraordinary electron-beam-shaping capabilities have been recently demonstrated in electron microscopes combining ultrafast optics elements[21,22,23] Revolutionary concepts such as free-electron qubits[24] and cavity-induced quantum control[25,26,27] are becoming available, pointing toward the emergence of next-generation quantum light–electron technologies. This effect is closely related to Amperean pairing of electrons discussed in refs. 28–30, shown here to induce an entangled Einstein–Podolsky–Rosen state in the long interaction time limit
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
