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Near-optimal single-photon sources in the solid state


The scaling of optical quantum technologies requires efficient, on-demand sources of highly indistinguishable single photons. Semiconductor quantum dots inserted into photonic structures are ultrabright single-photon sources, yet the indistinguishability is limited by charge noise. Parametric downconversion sources provide highly indistinguishable photons but are operated at very low brightness to maintain high single-photon purity. To date, no technology has provided a bright source generating near-unity indistinguishability and pure single photons. Here, we report such devices made of quantum dots in electrically controlled cavities. Application of an electrical bias on the deterministically fabricated structures is shown to strongly reduce charge noise. Under resonant excitation, an indistinguishability of 0.9956 ± 0.0045 is demonstrated with g(2)(0) = 0.0028 ± 0.0012. The photon extraction of 65% and measured brightness of 0.154 ± 0.015 make this source 20 times brighter than any source of equal quality. This new generation of sources opens the way to new levels of complexity and scalability in optical quantum technologies.

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Figure 1: Electrically controlled single-photon sources.
Figure 2: Characteristics of single-photon source QD1 under non-resonant excitation.
Figure 3: Characteristics of single-photon source QD3 under resonant excitation.
Figure 4: Comparison with other QD and SPDC single-photon sources.


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This work was partially supported by European Research Council starting grant no. 277885 QD-CQED, the French Agence Nationale pour la Recherche (grant ANR QDOM), the French RENATECH network, the Labex NanoSaclay, EU FP7 grant no. 618072 (WASPS), the Centre for Engineered Quantum Systems (grant no. CE110001013), the Centre for Quantum Computation and Communication Technology (grant no. CE110001027), and the Asian Office of Aerospace Research and Development (grant FA2386-13-1-4070). J.C.L., M.P.A. and A.G.W. thank M. Ringbauer and M. Goggin for insightful discussions, and thank the team from the Austrian Institute of Technology for providing the time-tagging modules for the SPDC measurements. The LPN–CNRS authors are very thankful to A. Nowak for her help with the technology. N.D.L.K. was supported by the FP7 Marie Curie Fellowship OMSiQuD. M.P.A. acknowledges support from the Australian Research Council Discovery Early Career Awards (no. DE120101899). A.G.W. was supported by the University of Queensland Vice-Chancellor's Research and Teaching Fellowship.

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Optical measurements on the QD devices were conducted primarily by V.G., N.S. and L.d.S., with help from L.L., S.L.P. and P.S. The electrically controlled samples were fabricated by N.S. with help from C.A. The sample was grown by C.G. and A.L., and the etching was performed by I.S. The measurements on the SPDC sources and analysis of that data were conducted by J.C.L. and M.P.A, with help from A.G.W. Theoretical support for the experiment was provided by G.H., T.G. and A.A. The project was conducted by P.S. with help from L.L. All authors discussed the results and participated in manuscript preparation.

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Correspondence to P. Senellart.

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The authors declare no competing financial interests.

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Somaschi, N., Giesz, V., De Santis, L. et al. Near-optimal single-photon sources in the solid state. Nature Photon 10, 340–345 (2016).

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