Purcell-enhanced two-photon emission from a quantum dot via dark-state biexciton loading

Nature Materials (2026)Cite this article Generating light in well-defined photon-number states is central to photonic quantum technologies. While deterministic single-photon sources are well established, producing efficient two-photon states from individual emitters remains challenging. Here we demonstrate a high-efficiency two-photon emitter using the degenerate biexciton–exciton cascade in a Purcell-enhanced quantum dot–micropillar system. Leveraging polarization-selective p-shell excitation, we achieve effective biexciton loading and identify stimulated emission as a key mechanism enhancing two-photon temporal correlation. The emitter exhibits a two-photon correlation of g(2)(0) = 3,966(324), with a two-photon fraction of 0.983(1), and operates in a hybrid, predominantly cascade-dominated regime where cavity-stimulated two-photon emission coexists with the conventional biexciton–exciton cascade. These findings represent progress towards developing practical, on-demand, solid-state two-photon sources.This is a preview of subscription content, access via your institution Access Nature and 54 other Nature Portfolio journals Get Nature+, our best-value online-access subscription $32.99 / 30 days cancel any timeSubscribe to this journal Receive 12 print issues and online access $259.00 per yearonly $21.58 per issueBuy this articleUSD 39.95Prices may be subject to local taxes which are calculated during checkoutThe data that support the plots in this Article and other findings of this study are available via Figshare at https://doi.org/10.6084/m9.figshare.31160614 (ref. 49). All other data used in this study are available from the corresponding author upon request. Source data are provided with this paper.All codes produced during this research are available from the corresponding author upon request.Slusher, R. E., Hollberg, L. W., Yurke, B., Mertz, J. C. & Valley, J. F. 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This work was supported by the National Natural Science Foundation of China (grant nos. 12494604, 12494600, 12504410, 12504409 and 12204049), Beijing Natural Science Foundation (grant no. 1254065), China Postdoctoral Science Foundation (grant no. 2024M760215) and The Innovation Program for Quantum Science and Technology (grant no. 2021ZD0300801).Beijing Academy of Quantum Information Sciences, Beijing, ChinaBang Wu, Li Liu, Xinrui Mao, Xu-Jie Wang & Zhiliang YuanState Key Laboratory of Optoelectronic Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, ChinaHanqing Liu, Haiqiao Ni & Zhichuan NiuCenter of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, ChinaHanqing Liu, Haiqiao Ni & Zhichuan NiuSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarB.W. and Z.Y. conceived the project and prepared the manuscript. B.W. carried out the experiments with assistance from X.M. and X.-J.W. L.L. fabricated the device. H.L., H.N. and Z.N. grew the semiconductor wafer. Z.Y. supervised the project.Correspondence to Zhiliang Yuan.The authors declare no competing interests.Nature Materials thanks Fei Ding and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.a, Distribution of biexciton binding energies and fine-structure splitting values across multiple cool-down cycles. b, Time-resolved PL of the QD emission under cavity resonance (cool-down cycle #5) and far-detuned (cool-down cycle #3) conditions with p-shell excitation. The detuning magnitude corresponds to a 672.7 μeV (0.44 nm) blue-shift relative to cavity resonance—equivalent to 5.6 cavity linewidths. The on-resonance and degenerate XX lifetime (τon) of 52.7(5) ps, while the far-detuned and non-degenerate XX lifetime (τoff) of 483(8) ps. Their ratio yields a Purcell factor of Fp = τoff/τon − 1 = 8.2(1). Purple line: instrument response function (IRF).a, Energy-level diagram of the XX-X radiative cascade under an applied Faraday magnetic field. b, Photoluminescence map under varying magnetic fields at 10 μW p-shell continuous-wave excitation. c, Second-order auto-correlation function g(2)(τ) measured under pulsed p-shell excitation (10 μW) on the spectrally isolated left-circularly polarized exciton transition at a 4 T Zeeman splitting (marked by the square in b). The application of the magnetic field spectrally separates the degenerate XX and X transitions. The measured g(2)(0) of 0.055(1) for the isolated exciton transition confirms that the single, unsplit emission line at zero field originates from the target quantum dot, with negligible contribution from off-resonant emitters.a, Temperature-dependent photoluminescence (PL) intensity map of the degenerate QD under 888 nm CW excitation with a low pump power of 50 μW. The white dashed line indicates the cavity resonance. b, PL spectra at resonant (19 K, red line) and detuned (30 K, blue line) conditions, showing a 150-fold intensity enhancement at resonance. c, Temperature dependence of degenerated X/XX lifetimes. d, Time-resolved PL at resonant (19 K, red line) and far detuned (55 K, green line) conditions, showing a Purcell factor of 11.2(2) and confirming cavity-enhanced dynamics within a single thermal cycle.a, b, PL spectra, and the biexciton/exciton intensity ratio under above GaAs bandgap pumping. c, d, Comparison data for p-shell dark-state pumping.a, Excitation-power dependence of the second-order auto-correlation function g(2)(0). b, Second-order correlation histogram measured at a pump power of 15 μW. c, Corresponding three-fold correlation data measured under the same conditions as b, using a pump power of 15 μW and a time bin of 1.25 ns. For the three-fold correlations shown in Fig. 4b of the main text, we integrate the coincidence counts over a 6 × 6 ns2 temporal window and normalize them to the average value of pixels corresponding to uncorrelated delays. This procedure yields the normalized three-fold coincidence values reported in the main text.a, b, Measured time-resolved correlation maps for two photons detected (a) from adjacent excitation cycles or (b) within the same excitation cycle. c, Extracted degree of Tc versus excitation power for the two data sets.Supplementary Figs. 1–6, Notes 1–5 and Tables 1 and 2.Source data.Source data.Source data.Source data.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.Reprints and permissionsWu, B., Liu, L., Liu, H. et al. Purcell-enhanced two-photon emission from a quantum dot via dark-state biexciton loading. Nat. Mater. (2026). https://doi.org/10.1038/s41563-026-02522-9Download citationReceived: 30 May 2025Accepted: 28 January 2026Published: 02 March 2026Version of record: 02 March 2026DOI: https://doi.org/10.1038/s41563-026-02522-9Anyone you share the following link with will be able to read this content:Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative