Entanglement of single-photons and chiral phonons in atomically thin WSe2

Abstract

Quantum entanglement is a fundamental phenomenon that, on the one hand, reveals deep connections between quantum mechanics, gravity and spacetime 1,2 , and on the other hand, has practical applications as a key resource in quantum information processing 3 . Although it is routinely achieved in photon–atom ensembles 4 , entanglement involving solid-state 5–7 or macroscopic objects 8 remains challenging albeit promising for both fundamental physics and technological applications. Here, we report entanglement between collective, chiral vibrations in a two-dimensional WSe 2 host—chiral phonons (CPs)—and single-photons emitted from quantum dots 9–13 (QDs) present in it. CPs that carry angular momentum were recently observed in WSe 2 and are a distinguishing feature of the underlying honeycomb lattice 14,15 . The entanglement results from a ‘which-way’ scattering process, involving an optical excitation in a QD and doubly-degenerate CPs, which takes place via two indistinguishable paths. Our unveiling of entanglement involving a macroscopic, collective excitation together with strong interactions between CPs and QDs in two-dimensional materials opens up ways for phonon-driven entanglement of QDs and engineering chiral or non-reciprocal interactions at the single-photon level.