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

Nature Physics volume 15, pages 221–227 (2019)Cite this article

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Abstract

Quantum entanglement is a fundamental phenomenon that, on the one hand, reveals deep connections between quantum mechanics, gravity and spacetime1,2, and on the other hand, has practical applications as a key resource in quantum information processing3. Although it is routinely achieved in photon–atom ensembles4, entanglement involving solid-state5,6,7 or macroscopic objects8 remains challenging albeit promising for both fundamental physics and technological applications. Here, we report entanglement between collective, chiral vibrations in a two-dimensional WSe2 host—chiral phonons (CPs)—and single-photons emitted from quantum dots9,10,11,12,13 (QDs) present in it. CPs that carry angular momentum were recently observed in WSe2 and are a distinguishing feature of the underlying honeycomb lattice14,15. 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.

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Fig. 1: Chiral phonons and phonon–photon entanglement.
Fig. 2: QDs and their phonon replicas in monolayer WSe2.
Fig. 3: Polarization dependence of QDs and their phonon replicas in monolayer WSe2.
Fig. 4: Recovery of polarization of phonon replicas in a magnetic field.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We acknowledge many enlightening discussions with A. Imamoğlu, W. Gao and M. Kroner. We also acknowledge technical help from T. Neal and E. Liu. A.S. acknowledges support from Emory University startup funds and the National Science Foundation through the EFRI Program grant number EFMA-1741691. L.Z. thanks M. Gao for helpful calculations and discussions, and acknowledges support from the National Natural Science Foundation of China (grant No. 11574154). Q.X. gratefully acknowledges strong support from the Singapore National Research Foundation via an NRF-ANR joint grant (NRF2017-NRF-ANR002 2D-Chiral) and the Singapore Ministry of Education via an AcRF Tier2 grant (MOE2017-T2-1-040) and Tier1 grants (RG 113/16 and RG 194/17)

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Author notes

  1. These authors contributed equally. Xiaotong Chen, Xin Lu, Sudipta Dubey.

Authors and Affiliations

  1. Department of Physics, Emory University, Atlanta, GA, USA

    Xiaotong Chen, Xin Lu, Sudipta Dubey, Qiang Yao & Ajit Srivastava

  2. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore

    Sheng Liu, Xingzhi Wang & Qihua Xiong

  3. NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, Singapore

    Qihua Xiong

  4. Center for Quantum Transport and Thermal Energy Science, School of Physics and Technology, Nanjing Normal University, Nanjing, China

    Lifa Zhang

Authors
  1. Xiaotong Chen
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Contributions

X.C., X.L., S.D. and Q.Y. carried out the quantum dot measurements and S.L. measured the Raman data. X.L. and X.W. prepared the samples. A.S., L.Z. and Q.X. supervised the project. All authors were involved in analysis of the experimental data and contributed extensively to this work.

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Correspondence to Ajit Srivastava.

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Supplementary information

Supplementary Text, Figure 1–13 and Supplementary References

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Chen, X., Lu, X., Dubey, S. et al. Entanglement of single-photons and chiral phonons in atomically thin WSe2. Nat. Phys. 15, 221–227 (2019). https://doi.org/10.1038/s41567-018-0366-7

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