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

Abstract

Quantum entanglement is a fundamental phenomenon which, on the one hand, reveals deep connections between quantum mechanics, gravity and the space-time [1, 2]; on the other hand, has practical applications as a key resource in quantum information processing [3]. While it is routinely achieved in photon-atom ensembles [4], entanglement involving the 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 two-dimensional (2D) WSe 2 host -chiral phonons (CPs) -and single-photons emitted from quantum dots [9-13] (QDs) present in it. CPs which 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 interaction between CPs and QDs in 2D materials opens up ways for phonon-driven entanglement of QDs and engineering chiral or non-reciprocal interactions at the single-photon level.Two dimensional (2D) materials with a honeycomb lattice, such as graphene and WSe 2 , have degenerate, low energy electronic states which exhibit handedness. In the momentum space, this arXiv:1808.09984v1 [cond-mat.mes-hall]

Valley-selective chiral phonon replicas of dark excitons and trions in monolayer WSe2

“…We have observed a set of three replica luminescent peaks at ~21.4 meV below the dark exciton and exciton-polarons (or trions) in the negatively and positively charged Fermi sea. The redshift energy (21.4 meV) matches the energy of the zone-center E" chiral phonons in monolayer WSe2 [37][38][39]. The replica emission exhibits parallel gating dependence and the same g-factors as the dark excitonic states, but follows distinct optical selection rules.…”

“…Furthermore, recent research shows that coherent dark exciton can be formed between two valleys [27]. A valley-coherent dark exciton can decay into a pair of photon and phonon with entangled chirality, as reported for quantum-dot excitons in monolayer WSe2 [37] (see Supplementary Materials [40]). Such entanglement functionality, together with the long and detectable valley polarization of the dark excitonic states and replicas, shall open a new venue for fundamental exciton research and novel valleytronic applications.…”

Identifying defect-related quantum emitters in monolayer WSe2

“…In addition, the single photon emission has been realized with several approaches, such as heterostructures driven electrically [13], nanoscale strain engineering [14][15][16][17] and sub-nm focused helium ion irradiation [18], which are mostly defect related. Meanwhile, the properties of such a 2D host of quantum emitters have been intensely investigated, including 3D localized trions in heterostuctures [19], manipulation of fine structure splitting (FSS) [20] and photon-phonon interaction [21]. Furthermore, the optical initialization of a single spin-valley in charged WSe 2 quantum dots [22] and the ability to deterministically load either a single electron or single hole into a Van der Waals heterostructure quantum device via a Coulomb blockade [23] have been demonstrated, which enable a new class of quantum-confined spin system to store and process information.…”

Thermal Transport in 2D Semiconductors—Considerations for Device Applications

“…This gives rise to potential applications in valleytronics and phonon‐chirality‐based phononics . In quantum dots of WSe 2 , the entanglement between chiral phonons and optical excitation have also been reported very recently …”