Towards optimal single-photon sources from polarized microcavities


An optimal single-photon source should deterministically deliver one, and only one, photon at a time, with no trade-off between the source’s efficiency and the photon indistinguishability. However, all reported solid-state sources of indistinguishable single photons had to rely on polarization filtering, which reduced the efficiency by 50%, fundamentally limiting the scaling of photonic quantum technologies. Here, we overcome this long-standing challenge by coherently driving quantum dots deterministically coupled to polarization-selective Purcell microcavities. We present two examples: narrowband, elliptical micropillars and broadband, elliptical Bragg gratings. A polarization-orthogonal excitation–collection scheme is designed to minimize the polarization filtering loss under resonant excitation. We demonstrate a polarized single-photon efficiency of 0.60 ± 0.02 (0.56 ± 0.02), a single-photon purity of 0.975 ± 0.005 (0.991 ± 0.003) and an indistinguishability of 0.975 ± 0.006 (0.951 ± 0.005) for the micropillar (Bragg grating) device. Our work provides promising solutions for truly optimal single-photon sources combining near-unity indistinguishability and near-unity system efficiency simultaneously.

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Fig. 1: Theoretical scheme of a polarized single-photon source by resonantly pumping a quantum emitter in a birefringent microcavity.
Fig. 2: Characterization of the elliptical micropillar and elliptical Bragg grating.
Fig. 3: Deterministic generation of polarized single photons under resonant excitation.
Fig. 4: Single-photon purity and indistinguishability.

Data availability

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


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This work is supported by the National Natural Science Foundation of China (grant no. 11525419, 91836303, 11674308), the Chinese Academy of Science, the Anhui Initiative in Quantum Information Technologies, the Science and Technology Commission of Shanghai Municipality, the National Fundamental Research Program (grant no. 2018YFA0306104) and the State of Bavaria.

Author information

C.-Y.L. and J.-W.P. conceived the research, and M.-C.C., C.-Y.L. and J.-W.P. designed the protocol. S.G., K.W., J.J. and S.H. grew the quantum dot samples. X.D. performed the optical imaging for positioning the quantum dots. H.W., Y.-M.H. and C.-Y.L. designed the parameters of the microcavities. Y.Y., S.C., L.-J.W. and S.Y. etched the micropillars. T.H.C., H.H., X.Y., Y.-H.H. and Q.D. etched the bullseyes. H.W., Y.-M.H., J.Q., R.-Z.L., Z.-C.D., J.-P.L. and C.-Y.L. performed the resonant optical excitation and quantum optics measurements. H.W. and N.G. performed theoretical simulations and numerical analyses. All authors discussed the results and prepared the manuscript. C.-Y.L. and J.-W.P. supervised the project.

Correspondence to Chao-Yang Lu or Jian-Wei Pan.

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