- Physical Review Journals
All JournalsPhysics Magazine

Physical Review Letters

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

Export citation

Export citation

Choose format for download:

Download Citation
  • Open Access

Indistinguishable Photons from a Two-Photon Cascade

Timon L. Baltisberger1,*,†, Francesco Salusti2,3,*, Mark R. Hogg1, Malwina A. Marczak1, Nils Heinisch2,3, Sascha R. Valentin4, Stefan Schumacher2,3,5, Arne Ludwig4, Klaus D. Jöns2,3 et al.

Richard J. Warburton1

  • 1Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
  • 2Department of Physics and Center for Optoelectronics and Photonics Paderborn (CeOPP), Paderborn University, Warburger Strasse 100, 33098 Paderborn, Germany
  • 3Institute for Photonic Quantum Systems (PhoQS), Paderborn University, 33098 Paderborn, Germany
  • 4Faculty of Physics and Astronomy, Experimental Physics VI, Ruhr University Bochum, Universitätsstrasse 150, 44801 Bochum, Germany
  • 5Wyant College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA

  • *These authors contributed equally to this work.
  • †Contact author: timon.baltisberger@unibas.ch
PDF

Phys. Rev. Lett. 137, 073603 – Published 12 August, 2026

DOI: https://doi.org/10.1103/t8sk-b2w4

Abstract

Decay of a four-level diamond scheme via a cascade is a potential source of entangled photon pairs. A solid-state implementation is the biexciton cascade in a semiconductor quantum dot. While high entanglement fidelities have been demonstrated, the two photons, XX and X, are temporally correlated, typically resulting in poor photon coherence. Here, we demonstrate a high two-photon interference visibility (a measure of the photon coherence) for both XX (90±2%) and X (80±6%) photons. This is achieved by Purcell enhancing the biexciton transition in a low-noise device. We find that the interference visibility follows the well-known quantum optics result upon tuning the XX:X lifetime ratio over 2 orders of magnitude. In addition, we show that the XX purity, 98%, is limited not by quantum optics but by the phonons in the semiconductor matrix via cavity feeding.

View figure in article

Physics Subject Headings (PhySH)

Article Text

Supplemental Material

References (45)

  1. N. Gisin and R. Thew, Quantum communication, Nat. Photonics 1, 165 (2007).
  2. A. K. Ekert, Quantum cryptography based on Bell’s theorem, Phys. Rev. Lett. 67, 661 (1991).
  3. J.-W. Pan, D. Bouwmeester, H. Weinfurter, and A. Zeilinger, Experimental entanglement swapping: Entangling photons that never interacted, Phys. Rev. Lett. 80, 3891 (1998).
  4. P. G. Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. Shih, New high-intensity source of polarization-entangled photon pairs, Phys. Rev. Lett. 75, 4337 (1995).
  5. H.-S. Zhong, Y. Li, W. Li, L.-C. Peng, Z.-E. Su, Y. Hu, Y.-M. He, X. Ding, W. Zhang, H. Li, L. Zhang, Z. Wang, L. You, X.-L. Wang, X. Jiang, L. Li, Y.-A. Chen, N.-L. Liu, C.-Y. Lu, and J.-W. Pan, 12-photon entanglement and scalable scattershot boson sampling with optimal entangled-photon pairs from parametric down-conversion, Phys. Rev. Lett. 121, 250505 (2018).
  6. L. Rickert, K. Żołnacz, D. A. Vajner, M. von Helversen, S. Rodt, S. Reitzenstein, H. Liu, S. Li, H. Ni, P. Wyborski, G. Sȩk, A. Musiał, Z. Niu, and T. Heindel, A fiber-pigtailed quantum dot device generating indistinguishable photons at GHz clock-rates, Nanophotonics 14, 1795 (2025).
  7. A. V. Kuhlmann, J. Houel, A. Ludwig, L. Greuter, D. Reuter, A. D. Wieck, M. Poggio, and R. J. Warburton, Charge noise and spin noise in a semiconductor quantum device, Nat. Phys. 9, 570 (2013).
  8. N. Somaschi, V. Giesz, L. De Santis, J. Loredo, M. P. Almeida, G. Hornecker, S. L. Portalupi, T. Grange, C. Anton, J. Demory, C. Gómez, I. Sagnes, N. D. Lanzillotti-Kimura, A. Lemaítre, A. Auffeves, A. G. White, L. Lanco, and P. Senellart, Near-optimal single-photon sources in the solid state, Nat. Photonics 10, 340 (2016).
  9. H. Wang, Z.-C. Duan, Y.-H. Li, S. Chen, J.-P. Li, Y.-M. He, M.-C. Chen, Y. He, X. Ding, C.-Z. Peng, C. Schneider, M. Kamp, S. Höfling, C.-Y. Lu, and J.-W. Pan, Near-transform-limited single photons from an efficient solid-state quantum emitter, Phys. Rev. Lett. 116, 213601 (2016).
  10. R. Uppu, F. T. Pedersen, Y. Wang, C. T. Olesen, C. Papon, X. Zhou, L. Midolo, S. Scholz, A. D. Wieck, A. Ludwig, and P. Lodahl, Scalable integrated single-photon source, Sci. Adv. 6, eabc8268 (2020).
  11. N. Tomm, A. Javadi, N. O. Antoniadis, D. Najer, M. C. Löbl, A. R. Korsch, R. Schott, S. R. Valentin, A. D. Wieck, A. Ludwig, and R. J. Warburton, A bright and fast source of coherent single photons, Nat. Nanotechnol. 16, 399 (2021).
  12. X. Ding, Y.-P. Guo, M.-C. Xu, R.-Z. Liu, G.-Y. Zou, J.-Y. Zhao, Z.-X. Ge, Q.-H. Zhang, H.-L. Liu, L.-J. Wang, M.-C. Chen, H. Wang, Y.-M. He, Y.-H. Huo, C.-Y. Lu, and J.-W. Pan, High-efficiency single-photon source above the loss-tolerant threshold for efficient linear optical quantum computing, Nat. Photonics 19, 387 (2025).
  13. S. Liu, Y. Wang, Y. Saleem, X. Li, H. Liu, C.-A. Yang, J. Yang, H. Ni, Z. Niu, Y. Meng, X. Hu, Y. Y. Xuehua Wang, M. Cygorek, and J. Liu, Quantum correlations of spontaneous two-photon emission from a quantum dot, Nature (London) 643, 1234 (2025).
  14. O. Benson, C. Santori, M. Pelton, and Y. Yamamoto, Regulated and entangled photons from a single quantum dot, Phys. Rev. Lett. 84, 2513 (2000).
  15. N. Akopian, N. H. Lindner, E. Poem, Y. Berlatzky, J. Avron, D. Gershoni, B. D. Gerardot, and P. M. Petroff, Entangled photon pairs from semiconductor quantum dots, Phys. Rev. Lett. 96, 130501 (2006).
  16. R. Trotta, E. Zallo, C. Ortix, P. Atkinson, J. D. Plumhof, J. van den Brink, A. Rastelli, and O. G. Schmidt, Universal recovery of the energy-level degeneracy of bright excitons in InGaAs quantum dots without a structure symmetry, Phys. Rev. Lett. 109, 147401 (2012).
  17. D. Huber, M. Reindl, S. F. Covre da Silva, C. Schimpf, J. Martín-Sánchez, H. Huang, G. Piredda, J. Edlinger, A. Rastelli, and R. Trotta, Strain-tunable GaAs quantum dot: A nearly dephasing-free source of entangled photon pairs on demand, Phys. Rev. Lett. 121, 033902 (2018).
  18. C. Schimpf, M. Reindl, D. Huber, B. Lehner, S. F. C. D. Silva, S. Manna, M. Vyvlecka, P. Walther, and A. Rastelli, Quantum cryptography with highly entangled photons from semiconductor quantum dots, Sci. Adv. 7, eabe8905 (2021).
  19. M. Pennacchietti, B. Cunard, S. Nahar, M. Zeeshan, S. Gangopadhyay, P. J. Poole, D. Dalacu, A. Fognini, K. D. Jöns, V. Zwiller, T. Jennewein, N. Lütkenhaus, and M. E. Reimer, Oscillating photonic Bell state from a semiconductor quantum dot for quantum key distribution, Commun. Phys. 7, 62 (2024).
  20. C. Simon and J.-P. Poizat, Creating single time-bin-entangled photon pairs, Phys. Rev. Lett. 94, 030502 (2005).
  21. F. Kappe, R. Schwarz, Y. Karli, T. Bracht, V. M. Axt, S. F. Covre da Silva, A. Rastelli, V. Remesh, D. E. Reiter, and G. Weihs, Keeping the photon in the dark: Enabling quantum dot dark state control by chirped pulses and magnetic fields, Sci. Adv. 11, eadu4261 (2025).
  22. P. Aumann, M. Prilmüller, F. Kappe, L. Ostermann, D. Dalacu, P. J. Poole, H. Ritsch, W. Lechner, and G. Weihs, Demonstration and modeling of time-bin entangled photons from a quantum dot in a nanowire, AIP Adv. 12, 055115 (2022).
  23. E. Schöll, L. Schweickert, L. Hanschke, K. D. Zeuner, F. Sbresny, T. Lettner, R. Trivedi, M. Reindl, S. F. Covre da Silva, R. Trotta, J. J. Finley, J. Vučković, K. Müller, A. Rastelli, V. Zwiller, and K. D. Jöns, Crux of using the cascaded emission of a three-level quantum ladder system to generate indistinguishable photons, Phys. Rev. Lett. 125, 233605 (2020).
  24. H. Huang and J. Eberly, Correlations and one-quantum pulse shapes in photon pair generation, J. Mod. Opt. 40, 915 (1993).
  25. P. A. Dalgarno, J. M. Smith, J. McFarlane, B. D. Gerardot, K. Karrai, A. Badolato, P. M. Petroff, and R. J. Warburton, Coulomb interactions in single charged self-assembled quantum dots: Radiative lifetime and recombination energy, Phys. Rev. B 77, 245311 (2008).
  26. J.-M. Gérard, B. Sermage, B. Gayral, B. Legrand, E. Costard, and V. Thierry-Mieg, Enhanced spontaneous emission by quantum boxes in a monolithic optical microcavity, Phys. Rev. Lett. 81, 1110 (1998).
  27. F. Liu, A. J. Brash, J. O’Hara, L. M. Martins, C. L. Phillips, R. J. Coles, B. Royall, E. Clarke, C. Bentham, N. Prtljaga, I. E. Itskevich, L. R. Wilson, M. S. Skolnick, and M. A. Fox, High Purcell factor generation of indistinguishable on-chip single photons, Nat. Nanotechnol. 13, 835 (2018).
  28. G. Undeutsch, M. Aigner, A. J. Garcia Jr, J. Reindl, M. Peter, S. Mader, C. Weidinger, S. F. Covre da Silva, S. Manna, E. Schöll, and A. Rastelli, Electric-field control of photon indistinguishability in cascaded decays in quantum dots, Nano Lett. 25, 7121 (2025).
  29. R. J. Barbour, P. A. Dalgarno, A. Curran, K. M. Nowak, H. J. Baker, D. R. Hall, N. G. Stoltz, P. M. Petroff, and R. J. Warburton, A tunable microcavity, J. Appl. Phys. 110, 053107 (2011).
  30. See Supplemental Material at http://link.aps.org/supplemental/10.1103/t8sk-b2w4 for experimental methods, theoretical details, and additional data, which includes Refs. [31–36].
  31. S. Schumacher, J. Förstner, A. Zrenner, M. Florian, C. Gies, P. Gartner, and F. Jahnke, Cavity-assisted emission of polarization-entangled photons from biexcitons in quantum dots with fine-structure splitting, Opt. Express 20, 5335 (2012).
  32. D. Heinze, A. Zrenner, and S. Schumacher, Polarization entangled twin photons from two-photon quantum-dot emission, Phys. Rev. B 95, 245306 (2017).
  33. C. Santori, D. Fattal, J. Vuckovic, G. S. Solomon, and Y. Yamamoto, Indistinguishable photons from a single-photon device, Nature (London) 419, 594 (2002).
  34. C. Gardiner and P. Zoller, Quantum Noise: A Handbook of Markovian and Non-Markovian Quantum Stochastic Methods With Applications to Quantum Optics (Springer Science & Business Media, 2004).
  35. P. Michler, Quantum Dots for Quantum Information Technologies (Springer, 2017), Vol. 237.
  36. C. Gustin and S. Hughes, Pulsed excitation dynamics in quantum-dot–cavity systems: Limits to optimizing the fidelity of on-demand single-photon sources, Phys. Rev. B 98, 045309 (2018).
  37. N. Tomm, A. R. Korsch, A. Javadi, D. Najer, R. Schott, S. R. Valentin, A. D. Wieck, A. Ludwig, and R. J. Warburton, Tuning the mode splitting of a semiconductor microcavity with uniaxial stress, Phys. Rev. Appl. 15, 054061 (2021).
  38. L. Greuter, S. Starosielec, D. Najer, A. Ludwig, L. Duempelmann, D. Rohner, and R. J. Warburton, A small mode volume tunable microcavity: Development and characterization, Appl. Phys. Lett. 105, 121105 (2014).
  39. M. R. Hogg, N. O. Antoniadis, M. A. Marczak, G. N. Nguyen, T. L. Baltisberger, A. Javadi, R. Schott, S. R. Valentin, A. D. Wieck, A. Ludwig, and R. J. Warburton, Fast optical control of a coherent hole spin in a microcavity, Nat. Phys. 21, 1475 (2025).
  40. C. Santori, D. Fattal, M. Pelton, G. S. Solomon, and Y. Yamamoto, Polarization-correlated photon pairs from a single quantum dot, Phys. Rev. B 66, 045308 (2002).
  41. N. Heinisch, F. Salusti, M. R. Hogg, T. L. Baltisberger, M. A. Marczak, S. R. Valentin, A. Ludwig, K. D. Jöns, R. J. Warburton, and S. Schumacher, High-quality single photons from cavity-enhanced biexciton-to-exciton transition, arXiv:2602.18153.
  42. X. Zhou, I. Kulkova, T. Lund-Hansen, S. L. Hansen, P. Lodahl, and L. Midolo, High-efficiency shallow-etched grating on GaAs membranes for quantum photonic applications, Appl. Phys. Lett. 113, 251103 (2018).
  43. J. Liu, R. Su, Y. Wei, B. Yao, S. F. C. d. Silva, Y. Yu, J. Iles-Smith, K. Srinivasan, A. Rastelli, J. Li, and X. Wang, A solid-state source of strongly entangled photon pairs with high brightness and indistinguishability, Nat. Nanotechnol. 14, 586 (2019).
  44. D. Bauch, D. Siebert, K. D. Jöns, J. Förstner, and S. Schumacher, On-demand indistinguishable and entangled photons using tailored cavity designs, Adv. Quantum Technol. 7, 2300142 (2024).
  45. T. L. Baltisberger et al., Research data for Indistinguishable photons from a two-photon cascade, Zenodo, 10.5281/zenodo.21164931 (2026).

Outline

Information

Phys. Rev. Lett. 137, 073603– Published 12 August, 2026
  • Received 19 December 2025
  • Revised 4 May 2026
  • Accepted 29 June 2026
Crossmark - Check for updates button
Creative Commons Logo

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation