- Physical Review Journals
All JournalsPhysics Magazine

Physical Review Applied

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
  • Editors' Suggestion
  • Open Access

Optimal filtering and generation of entangled photons for quantum applications in the presence of noise

Jordan M. Thomas1,*,†,‡, Andrew R. Cameron2,‡, Akil Pathiranage2, Si Xie2,3, Raju Valivarthi3,4, Panagiotis Spentzouris2, Maria Spiropulu3,4, Cristián Peña2, and Prem Kumar1,5

  • *Contact author: jmthomas@fnal.gov
  • †Present address: Fermi National Accelerator Laboratory, Batavia, IL 60510, USA.
  • ‡These authors contributed equally to this work.
PDF

Phys. Rev. Applied 25, 064064 – Published 22 June, 2026

DOI: https://doi.org/10.1103/qd6n-548v

Abstract

Filtering is commonly used in quantum optics to reject noise photons, and also to enable interference between independent photons. However, filtering the joint spectrum of photon pairs can reduce the inherent coincidence probability or loss-independent heralding efficiency. Here we investigate filtering for multiphoton applications based on entanglement and interference (e.g., quantum teleportation). We multiplex C-band entangled photons and C-band classical communications into the same long-distance fibers, which enables scalable low-loss quantum networking but requires filtering of spontaneous Raman scattering noise from classical light. Using tunable-bandwidth filters, low-jitter detectors, and polarization filters, we distribute wavelength-degenerate time-bin entangled photons in the C band (1536.5 nm) over 25 km/25 km standard fibers (50 km) each carrying 10 Gbit/s C-band classical data signals. Narrow filtering enables milliwatt-level C-band power, which exceeds the power achieved by comparable studies by roughly an order of magnitude and could feasibly support terabit per second classical rates. We evaluate how performance depends on pump and filter bandwidths, multipair emission, filter shapes, loss, phase matching, and how quantum information is measured. We find a trade-off between reducing noise impact and increasing single-mode purity, and discuss mitigation methods toward optimal multiphoton applications. Importantly, these results apply to noise in free space and in quantum devices (sources, frequency converters, switches, detectors, etc.) and provide insight into filter-induced degradation of single-photon purity and rates even in noise-free environments.

View figure in article

Physics Subject Headings (PhySH)

Article Text

References (92)

  1. H. J. Kimble, The quantum internet, Nature 453, 1023 (2008).
  2. S. Wehner, D. Elkouss, and R. Hanson, Quantum internet: A vision for the road ahead, Science 362, eaam2018 (2018).
  3. S.-H. Wei, B. Jing, X.-Y. Zhang, J.-Y. Liao, C.-Z. Yuan, B.-Y. Fan, C. Lyu, D.-L. Zhou, Y. Wang, G.-W. Deng, H.-Z. Song, D. Oblak, G.-C. Guo, and Q. Zhou, Towards real-world quantum networks: A review, Laser Photon. Rev. 16, 2100219 (2022).
  4. P. D. Townsend, Simultaneous quantum cryptographic key distribution and conventional data transmission over installed fibre using wavelength-division multiplexing, Electron. Lett. 33, 188 (1997).
  5. C. Liang, K. F. Lee, J. Chen, and P. Kumar, in 2006 Optical Fiber Communication Conference and the National Fiber Optic Engineers Conference (IEEE, Anaheim, CA, 2006), pp. 1–3.
  6. N. I. Nweke, P. Toliver, R. J. Runser, S. R. McNown, J. B. Khurgin, T. E. Chapuran, M. S. Goodman, R. J. Hughes, C. G. Peterson, K. McCabe, J. E. Nordholt, K. Tyagi, P. Hiskett, and N. Dallmann, Experimental characterization of the separation between wavelength-multiplexed quantum and classical communication channels, Appl. Phys. Lett. 87, 174103 (2005).
  7. T. E. Chapuran, P. Toliver, N. A. Peters, J. Jackel, M. S. Goodman, R. J. Runser, S. R. McNown, N. Dallmann, R. J. Hughes, K. P. McCabe, J. E. Nordholt, C. G. Peterson, K. T. Tyagi, L. Mercer, and H. Dardy, Optical networking for quantum key distribution and quantum communications, New J. Phys. 11, 105001 (2009).
  8. P. Eraerds, N. Walenta, M. Legré, N. Gisin, and H. Zbinden, Quantum key distribution and 1 Gbps data encryption over a single fibre, New J. Phys. 12, 063027 (2010).
  9. J. F. Dynes, W. W.-S. Tam, A. Plews, B. Fröhlich, A. W. Sharpe, M. Lucamarini, Z. Yuan, C. Radig, A. Straw, T. Edwards, and A. J. Shields, Ultra-high bandwidth quantum secured data transmission, Sci. Rep. 6, 35149 (2016).
  10. Y. Mao, B.-X. Wang, C. Zhao, G. Wang, R. Wang, H. Wang, F. Zhou, J. Nie, Q. Chen, Y. Zhao, Q. Zhang, J. Zhang, T.-Y. Chen, and J.-W. Pan, Integrating quantum key distribution with classical communications in backbone fiber network, Opt. Express 26, 6010 (2018).
  11. R. Valivarthi, P. Umesh, C. John, K. A. Owen, V. B. Verma, S. W. Nam, D. Oblak, Q. Zhou, and W. Tittel, Measurement-device-independent quantum key distribution coexisting with classical communication, Quantum Sci. Technol. 4, 045002 (2019).
  12. J. M. Thomas, G. S. Kanter, and P. Kumar, Designing noise-robust quantum networks coexisting in the classical fiber infrastructure, Opt. Express 31, 43035 (2023).
  13. Y.-R. Fan, Y. Luo, Z.-C. Zhang, Y.-B. Li, S. Liu, D. Wang, D.-C. Zhang, G.-W. Deng, Y. Wang, H.-Z. Song, Z. Wang, L.-X. You, C.-Z. Yuan, G.-C. Guo, and Q. Zhou, Energy-time entanglement coexisting with fiber-optical communication in the telecom C band, Phys. Rev. A 108, L020601 (2023).
  14. J. M. Thomas, G. S. Kanter, S. Xie, J. Chung, R. Valivarthi, C. Peña, R. Kettimuthu, P. Spentzouris, M. Spiropulu, and P. Kumar, in Optical Fiber Communication Conference (OFC) 2023 (Optica Publishing Group, San Diego, California, United States, 2023), p. Tu3I.3.
  15. I. A. Burenkov, A. Semionov, Hala, T. Gerrits, A. Rahmouni, D. Anand, Y.-S. Li-Baboud, O. Slattery, A. Battou, and S. V. Polyakov, Synchronization and coexistence in quantum networks, Opt. Express 31, 11431 (2023).
  16. R. Wang, R. Yang, M. J. Clark, R. D. Oliveira, S. Bahrani, M. Peranić, M. Lončarić, M. Stipčević, J. Rarity, S. K. Joshi, S. K. Joshi, R. Nejabati, and D. Simeonidou, in 49th European Conference on Optical Communications (ECOC 2023) (Institution of Engineering and Technology, Glasgow, Scottland, 2023). pp. 1682–1685.
  17. A. Rahmouni, P. S. Kuo, Y. S. Li-Baboud, I. A. Burenkov, Y. Shi, M. V. Jabir, N. Lal, D. Reddy, M. Merzouki, L. Ma, A. Battou, S. V. Polyakov, O. Slattery, and T. Gerrits, 100 km entanglement distribution with coexisting quantum and classical signals in a single fiber, J. Opt. Commun. Netw. 16, 781 (2024).
  18. X. Jing, C. Qian, X. Zheng, H. Nian, C. Wang, J. Tang, X. Gu, Y. Kong, T. Chen, Y. Liu, C. Sheng, D. Jiang, B. Niu, and L. Lu, Coexistence of multiuser entanglement distribution and classical light in optical fiber network with a semiconductor chip, Chip 3, 100083 (2024).
  19. Z.-Q. Zhong, X.-H. Zhan, J.-L. Chen, S. Wang, Z.-Q. Yin, J.-Q. Geng, D.-Y. He, W. Chen, G.-C. Guo, and Z.-F. Han, Hyperentanglement quantum communication over a 50 km noisy fiber channel, Optica 11, 1056 (2024).
  20. J. M. Thomas, F. I. Yeh, J. H. Chen, J. J. Mambretti, S. J. Kohlert, G. S. Kanter, and P. Kumar, Quantum teleportation coexisting with classical communications in optical fiber, Optica 11, 1700 (2024).
  21. T. Dou, R. Liu, S. Liao, J. Tang, J. Tong, R. Ma, Y. Wan, R. Wang, J. Wu, X. Zhang, Z. Pan, Y. Li, C. Zhang, and S. Tang, Coexistence of 11 Tbps (110×100 Gbps) classical optical communication and quantum key distribution based on single-mode fiber, Opt. Express 32, 28356 (2024).
  22. J. M. Thomas, G. S. Kanter, and P. Kumar, in Quantum Communications and Quantum Imaging XXIII, Proceedings of SPIE (SPIE, San Francisco, California, United States, 2024), Vol. 13391, p. 13391.
  23. A. Sanz, A. Atutxa, D. Franco, J. Astorga, and E. Jacob, in 2025 International Conference on Quantum Communications, Networking, and Computing (QCNC) (IEEE, Nara, Japan, 2025), pp. 110–116.
  24. G. Gül, G. S. Kanter, S. G. Tan, M. B. On, R. Proietti, S. J. B. Yoo, and P. Kumar, Noise impact of classical headers on the quantum payload in quantum wrapper networking, Optica Quantum 3, 303 (2025).
  25. M. Sena, M. Flament, S. Andrewski, I. Caltzidis, N. Bigagli, T. Rieser, G. B. Portmann, R. Sekelsky, R.-P. Braun, A. N. Craddock, et al., Robust high-fidelity quantum entanglement distribution over large-scale metropolitan fiber networks with co-propagating classical signals, J. Opt. Commun. Netw. 17, 1072 (2025).
  26. Y. Zhang, R. Broberg, A. Zhu, G. Li, L. Ge, J. M. Smith, and L. Feng, Classical-decisive quantum internet by integrated photonics, Science 389, 940 (2025).
  27. J. M. Thomas, G. M. Talcott, G. S. Kanter, and P. Kumar, in CLEO: Fundamental Science (Optica Publishing Group, Long Beach, California, United States, 2025), p. FF116_3.
  28. C.-Z. Peng, T. Yang, X.-H. Bao, J. Zhang, X.-M. Jin, F.-Y. Feng, B. Yang, J. Yang, J. Yin, Q. Zhang, N. Li, B.-L. Tian, and J.-W. Pan, Experimental free-space distribution of entangled photon pairs over 13 km: Towards satellite-based global quantum communication, Phys. Rev. Lett. 94, 150501 (2005).
  29. R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, Entanglement-based quantum communication over 144 km, Nat. Phys. 3, 481 (2007).
  30. H. Ko, K. Kim, J. Choe, B. Choi, J. Kim, Y. Baek, and C. J. Youn, Experimental filtering effect on the daylight operation of a free-space quantum key distribution, Sci. Rep. 8, 15315 (2018).
  31. F. Bouchard, D. England, P. J. Bustard, K. L. Fenwick, E. Karimi, K. Heshami, and B. Sussman, Achieving ultimate noise tolerance in quantum communication, Phys. Rev. Appl. 15, 024027 (2021).
  32. F. B. Basset, M. B. Rota, G. Beccaceci, T. M. Krieger, Q. Buchinger, J. Neuwirth, H. Huet, S. Stroj, S. F. C. da Silva, G. Ronco, C. Schimpf, S. Höfling, T. Huber-Loyol, A. Rastelli, and R. Trotta, Daylight entanglement-based quantum key distribution with a quantum dot source, Quantum Sci. Technol. 8, 025002 (2023).
  33. W.-Q. Cai et al., Free-space quantum key distribution during daylight and at night, Optica 11, 647 (2024).
  34. X. Li, P. L. Voss, J. E. Sharping, and P. Kumar, Optical-fiber source of polarization-entangled photons in the 1550 nm telecom band, Phys. Rev. Lett. 94, 053601 (2005).
  35. Q. Lin, F. Yaman, and G. P. Agrawal, Photon-pair generation in optical fibers through four-wave mixing: Role of Raman scattering and pump polarization, Phys. Rev. A 75, 023803 (2007).
  36. P. S. Kuo, J. S. Pelc, C. Langrock, and M. M. Fejer, Using temperature to reduce noise in quantum frequency conversion, Opt. Lett. 43, 2034 (2018).
  37. M. L. H. Korsgaard, J. G. Koefoed, and K. Rottwitt, Raman effects in quantum frequency conversion using Bragg scattering, Phys. Rev. A 110, 033508 (2024).
  38. M. A. Hall, J. B. Altepeter, and P. Kumar, Ultrafast switching of photonic entanglement, Phys. Rev. Lett. 106, 053901 (2011).
  39. A. R. Cameron, K. L. Fenwick, S. W. L. Cheng, S. Schwarz, B. MacLellan, P. J. Bustard, D. England, B. Sussman, and K. J. Resch, Ultrafast measurement of energy-time entanglement with an optical Kerr shutter, Phys. Rev. A 108, L041503 (2023).
  40. C. Kupchak, J. Erskine, D. England, and B. Sussman, Terahertz-bandwidth switching of heralded single photons, Opt. Lett. 44, 1427 (2019).
  41. A. Shahverdi, Y. M. Sua, L. Tumeh, and Y.-P. Huang, Quantum parametric mode sorting: Beating the time-frequency filtering, Sci. Rep. 7, 6495 (2017).
  42. S. Gao, O. Lazo-Arjona, B. Brecht, K. T. Kaczmarek, S. E. Thomas, J. Nunn, P. M. Ledingham, D. J. Saunders, and I. A. Walmsley, Optimal coherent filtering for single noisy photons, Phys. Rev. Lett. 123, 213604 (2019).
  43. M. G. Raymer and K. Banaszek, Time-frequency optical filtering: efficiency vs. temporal-mode discrimination in incoherent and coherent implementations, Opt. Express 28, 32819 (2020).
  44. C. K. Hong, Z. Y. Ou, and L. Mandel, Measurement of subpicosecond time intervals between two photons by interference, Phys. Rev. Lett. 59, 2044 (1987).
  45. J. G. Rarity, Interference of single photons from separate sources, Ann. N. Y. Acad. Sci. 755, 624 (1995).
  46. S. L. Braunstein and A. Mann, Measurement of the Bell operator and quantum teleportation, Phys. Rev. A 51, R1727 (1995).
  47. M. Żukowski, A. Zeilinger, M. A. Horne, and A. K. Ekert, “Event-ready-detectors” Bell experiment via entanglement swapping, Phys. Rev. Lett. 71, 4287 (1993).
  48. A. Zeilinger, M. A. Horne, H. Weinfurter, and M. Żukowski, Three-particle entanglements from two entangled pairs, Phys. Rev. Lett. 78, 3031 (1997).
  49. E. Knill, R. Laflamme, and G. J. Milburn, A scheme for efficient quantum computation with linear optics, Nature 409, 46 (2001).
  50. PsiQuantum Team, A manufacturable platform for photonic quantum computing, Nature 641, 876 (2025).
  51. J.-W. Pan, Z.-B. Chen, C.-Y. Lu, H. Weinfurter, A. Zeilinger, and M. Żukowski, Multiphoton entanglement and interferometry, Rev. Mod. Phys. 84, 777 (2012).
  52. F. Bouchard, A. Sit, Y. Zhang, R. Fickler, F. M. Miatto, Y. Yao, F. Sciarrino, and E. Karimi, Two-photon interference: the Hong-Ou-Mandel effect, Rep. Prog. Phys. 84, 012402 (2021).
  53. W. P. Grice and I. A. Walmsley, Spectral information and distinguishability in type-II down-conversion with a broadband pump, Phys. Rev. A 56, 1627 (1997).
  54. P. J. Mosley, J. S. Lundeen, B. J. Smith, P. Wasylczyk, A. B. U’Ren, C. Silberhorn, and I. A. Walmsley, Heralded generation of ultrafast single photons in pure quantum states, Phys. Rev. Lett. 100, 133601 (2008).
  55. L. Yang, X. Ma, X. Guo, L. Cui, and X. Li, Characterization of a fiber-based source of heralded single photons, Phys. Rev. A 83, 053843 (2011).
  56. J. Jin, M. Grimau Puigibert, L. Giner, J. A. Slater, M. R. E. Lamont, V. B. Verma, M. D. Shaw, F. Marsili, S. W. Nam, D. Oblak, and W. Tittel, Entanglement swapping with quantum-memory-compatible photons, Phys. Rev. A 92, 012329 (2015).
  57. E. Meyer-Scott, N. Montaut, J. Tiedau, L. Sansoni, H. Herrmann, T. J. Bartley, and C. Silberhorn, Limits on the heralding efficiencies and spectral purities of spectrally filtered single photons from photon-pair sources, Phys. Rev. A 95, 061803(R) (2017).
  58. L. Cui, J. Su, J. Li, Y. Liu, X. Li, and Z. Y. Ou, Quantum state engineering by nonlinear quantum interference, Phys. Rev. A 102, 033718 (2020).
  59. X.-H. Zhan et al., Measurement-device-independent quantum key distribution with practical spontaneous parametric down-conversion sources, Phys. Rev. Appl. 20, 034069 (2023).
  60. A. Mueller, S. I. Davis, B. Korzh, R. Valivarthi, A. D. Beyer, R. Youssef, N. Sinclair, C. Peña, M. D. Shaw, and M. Spiropulu, High-rate multiplexed entanglement source based on time-bin qubits for advanced quantum networks, Optica Quantum 2, 64 (2024).
  61. W. Grice, A. B. U’Ren, and I. A. Walmsley, Eliminating frequency and space-time correlations in multiphoton states, Phys. Rev. A 64, 063815 (2001).
  62. K. Garay-Palmett, H. McGuinness, O. Cohen, J. Lundeen, R. Rangel-Rojo, A. U’ren, M. Raymer, C. McKinstrie, S. Radic, and I. Walmsley, Photon pair-state preparation with tailored spectral properties by spontaneous four-wave mixing in photonic-crystal fiber, Opt. Express 15, 14870 (2007).
  63. M. Halder, J. Fulconis, B. Cemlyn, A. Clark, C. Xiong, W. J. Wadsworth, and J. G. Rarity, Nonclassical 2-photon interference with separate intrinsically narrowband fibre sources, Opt. Express 17, 4670 (2009).
  64. Y. Jeronimo-Moreno, S. Rodriguez-Benavides, and A. B. U’Ren, Theory of cavity-enhanced spontaneous parametric downconversion, Laser Phys. 20, 1221 (2010).
  65. A. Eckstein, A. Christ, P. J. Mosley, and C. Silberhorn, Highly efficient single-pass source of pulsed single-mode twin beams of light, Phys. Rev. Lett. 106, 013603 (2011).
  66. B. Fang, O. Cohen, J. B. Moreno, and V. O. Lorenz, State engineering of photon pairs produced through dual-pump spontaneous four-wave mixing, Opt. Express 21, 2707 (2013).
  67. D. Rieländer, A. Lenhard, M. Mazzera, and H. de Riedmatten, Cavity enhanced telecom heralded single photons for spin-wave solid state quantum memories, New J. Phys. 18, 123013 (2016).
  68. S. Paesani, M. Borghi, S. Signorini, A. Maïnos, L. Pavesi, and A. Laing, Near-ideal spontaneous photon sources in silicon quantum photonics, Nat. Commun. 11, 2505 (2020).
  69. Y. Liu, C. Wu, X. Gu, Y. Kong, X. Yu, R. Ge, X. Cai, X. Qiang, J. Wu, X. Yang, and P. Xu, High-spectral-purity photon generation from a dual-interferometer-coupled silicon microring, Opt. Lett. 45, 73 (2020).
  70. C. Xin, J. Mishra, C. Chen, D. Zhu, A. Shams-Ansari, C. Langrock, N. Sinclair, F. N. Wong, M. Fejer, and M. Lončar, Spectrally separable photon-pair generation in dispersion engineered thin-film lithium niobate, Opt. Lett. 47, 2830 (2022).
  71. H. Takesue, H. Fukuda, T. Tsuchizawa, T. Watanabe, K. Yamada, and S. Itabashi, Implementation of quantum state tomography for time-bin entangled photon pairs, Opt. Express 16, 5721 (2008).
  72. B. Lauritzen, J. C. V. Minář, H. de Riedmatten, M. Afzelius, N. Sangouard, C. Simon, and N. Gisin, Telecommunication-wavelength solid-state memory at the single photon level, Phys. Rev. Lett. 104, 080502 (2010).
  73. Y.-Y. An, Q. He, W. Xue, M.-H. Jiang, C. Yang, Y.-Q. Lu, S. Zhu, and X.-S. Ma, Quantum teleportation from telecom photons to erbium-ion ensembles, Phys. Rev. Lett. 135, 010804 (2025).
  74. R. Stolen, in Technical Digest: Symposium on Optical Fiber Measurements (IEEE, Boulder, CO, United States, 2001), pp. 139–140.
  75. J. C. Chapman, J. M. Lukens, M. Alshowkan, N. Rao, B. T. Kirby, and N. A. Peters, Coexistent quantum channel characterization using spectrally resolved Bayesian quantum process tomography, Phys. Rev. Appl. 19, 044026 (2023).
  76. Y. H. Shih and C. O. Alley, New type of Einstein-Podolsky-Rosen-Bohm experiment using pairs of light quanta produced by optical parametric down conversion, Phys. Rev. Lett. 61, 2921 (1988).
  77. L. Stefanazzi et al., The QICK (Quantum Instrumentation Control Kit): Readout and control for qubits and detectors, Rev. Sci. Instrum. 93, 044709 (2022).
  78. H. Takesue and K. Shimizu, Effects of multiple pairs on visibility measurements of entangled photons generated by spontaneous parametric processes, Opt. Commun. 283, 276 (2010).
  79. M. Takeoka, R.-B. Jin, and M. Sasaki, Full analysis of multi-photon pair effects in spontaneous parametric down conversion based photonic quantum information processing, New J. Phys. 17, 043030 (2015).
  80. H. Takesue, Long-distance distribution of time-bin entanglement generated in a cooled fiber, Opt. Express 14, 3453 (2006).
  81. H. Yu, A. O. Govorov, H.-Z. Song, and Z. Wang, Time-encoded photonic quantum states: Generation, processing, and applications, Appl. Phys. Rev. 11, 041318 (2024).
  82. A. Singh, A. Sethia, L. Esmaeilifar, R. Valivarthi, N. Sinclair, M. Spiropulu, and D. Oblak, Photonic quantum information with time-bins: Principles and applications, npj Quantum Inf. 11, 129 (2025).
  83. G. B. Xavier, J.-Å. Larsson, P. Villoresi, G. Vallone, and A. Cabello, Energy-time and time-bin entanglement: Past, present and future, npj Quantum Inf. 11, 129 (2025).
  84. J. Brendel, N. Gisin, W. Tittel, and H. Zbinden, Pulsed energy-time entangled twin-photon source for quantum communication, Phys. Rev. Lett. 82, 2594 (1999).
  85. J. Jin, J.-P. Bourgoin, R. Tannous, S. Agne, C. J. Pugh, K. B. Kuntz, B. L. Higgins, and T. Jennewein, Genuine time-bin-encoded quantum key distribution over a turbulent depolarizing free-space channel, Opt. Express 27, 37214 (2019).
  86. J. F. Clauser, M. A. Horne, A. Shimony, and R. A. Holt, Proposed experiment to test local hidden-variable theories, Phys. Rev. Lett. 23, 880 (1969).
  87. J.-H. Kim, J.-W. Chae, Y.-C. Jeong, and Y.-H. Kim, Quantum communication with time-bin entanglement over a wavelength-multiplexed fiber network, APL Photonics 7, 016106 (2022).
  88. C. I. Osorio, N. Sangouard, and R. T. Thew, On the purity and indistinguishability of down-converted photons, J. Phys. B: At. Mol. Opt. Phys. 46, 055501 (2013).
  89. A. Eckstein, B. Brecht, and C. Silberhorn, A quantum pulse gate based on spectrally engineered sum frequency generation, Opt. Express 19, 13770 (2011).
  90. R. Kumar, H. Qin, and R. Alléaume, Coexistence of continuous variable QKD with intense DWDM classical channels, New J. Phys. 17, 043027 (2015).
  91. M. Halder, A. Beveratos, R. Thew, C. Jorel, H. Zbinden, and N. Gisin, Entangling independent photons by time measurement, Nat. Phys. 3, 692 (2007).
  92. C. K. Hong and L. Mandel, Theory of parametric frequency down conversion of light, Phys. Rev. A 31, 2409 (1985).

Outline

Information

Phys. Rev. Applied 25, 064064– Published 22 June, 2026
  • Received 23 October 2025
  • Revised 23 March 2026
  • Accepted 15 April 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