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Λ-Enhanced Gray-Molasses Loading and EIT Cooling of Neutral Atoms in Nanophotonic Traps

Lucas Pache*, Antoine Glicenstein†, Philipp Schneeweiss, Jürgen Volz, Arno Rauschenbeutel‡, and Riccardo Pennetta

  • *Contact author: pachluca@hu-berlin.de
  • †Present address: LP2N, Laboratoire Photonique, Numérique et Nanosciences, Université de Bordeaux-IOGS-CNRS: UMR 5298, F-33400 Talence, France.
  • ‡Contact author: arno.rauschenbeutel@hu-berlin.de
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PRX Quantum 7, 043010 – Published 15 October, 2026

DOI: https://doi.org/10.1103/5l6x-4377

Abstract

Nanophotonic traps for cold atoms typically have trap volumes that are orders of magnitude smaller than, e.g., free-space optical tweezers. This makes efficient loading of these traps challenging, thereby limiting the total number of atoms coupled to the nanophotonic waveguide. Here, we demonstrate that Λ-enhanced gray-molasses (ΛGM) can substantially increase the number of trapped atoms in a nanofiber-based cold-atom setup. Specifically, we observe a sixfold increase in the number of loaded atoms compared to conventional red-detuned polarization-gradient cooling. Despite the unusually small depth of our optical trap of only 24  μK, we load about 4000 individual cesium atoms, achieving optical depths exceeding 140 and reaching the collisional blockade regime over a length of approximately 1 mm. After loading, we perform efficient electromagnetically induced transparency (EIT)-assisted cooling that is found to increase the trap storage time to 400(9) ms. This is a fivefold improvement over the passive storage time. Remarkably, we observe that EIT-cooling also works with two co-propagating nanofiber-guided light fields and requires only a few hundred picowatts of optical power. Our results provide an efficient method to boost both the number of loaded atoms and the storage time of nanophotonic atom traps.

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Popular Summary

Laser-cooled atoms close to nanophotonic waveguides enable efficient coupling between quantum light and quantum bits made from single atoms, an important ingredient for many emerging quantum technologies. A major challenge, however, is that the optical traps formed by light guided in nanophotonic structures are very small. This makes it difficult to cool atoms to sufficiently low temperatures and efficiently load them into the traps. In this work, we implement a method known as Λ-enhanced gray molasses cooling, allowing us to reach very low atomic temperatures and efficiently load atoms into traps located only about 200 nm away from the surface of a nanofiber. We trap more than 4000 atoms, a sixfold increase compared with conventional techniques, and we can hold them for about half a second. We further demonstrate that the trapped atoms can also be cooled using only light fields guided through the nanofiber, employing a technique known as electromagnetically induced transparency cooling. Our results will, for example, be beneficial for building efficient, fiber-integrated memories for optical quantum information and represent an important step toward establishing atom-nanofiber systems as a platform for quantum technologies.

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References (57)

  1. D. Chang, J. Douglas, A. González-Tudela, C.-L. Hung, and H. Kimble, Colloquium: Quantum matter built from nanoscopic lattices of atoms and photons, Rev. Mod. Phys. 90, 031002 (2018).
  2. A. S. Sheremet, M. I. Petrov, I. V. Iorsh, A. V. Poshakinskiy, and A. N. Poddubny, Waveguide quantum electrodynamics: Collective radiance and photon-photon correlations, Rev. Mod. Phys. 95, 015002 (2023).
  3. A. González-Tudela, A. Reiserer, J. J. García-Ripoll, and F. J. García-Vidal, Light–matter interactions in quantum nanophotonic devices, Nat. Rev. Phys. 6, 166 (2024).
  4. W. Li, D. Brown, A. Vylegzhanin, Z. Shahrabifarahani, A. Raj, J. Du, and S. N. Chormaic, Atom-light interactions using optical nanofibres—a perspective, J. Phys. Photonics 6, 021002 (2024).
  5. H. L. Sørensen, J.-B. Béguin, K. W. Kluge, I. Iakoupov, A.  S. Sørensen, J.  H. Müller, E. S.  Polzik, and J. Appel, Coherent backscattering of light off one-dimensional atomic strings, Phys. Rev. Lett. 117, 133604 (2016).
  6. N. V. Corzo, B. Gouraud, A. Chandra, A. Goban, A. S. Sheremet, D. V. Kupriyanov, and J. Laurat, Large Bragg reflection from one-dimensional chains of trapped atoms near a nanoscale waveguide, Phys. Rev. Lett. 117, 133603 (2016).
  7. P. Lodahl, S. Mahmoodian, S. Stobbe, A. Rauschenbeutel, P. Schneeweiss, J. Volz, H. Pichler, and P. Zoller, Chiral quantum optics, Nature (London) 541, 473 (2017).
  8. K. P. Nayak, J. Wang, and J. Keloth, Real-time observation of single atoms trapped and interfaced to a nanofiber cavity, Phys. Rev. Lett. 123 213602 (2019).
  9. A. S. Prasad, J. Hinney, S. Mahmoodian, K. Hammerer, S. Rind, P. Schneeweiss, A. S. Sørensen, J. Volz, and A. Rauschenbeutel, Correlating photons using the collective nonlinear response of atoms weakly coupled to an optical mode, Nat. Photonics 14, 719 (2020).
  10. S. Pucher, C. Liedl, S. Jin, A. Rauschenbeutel, and P. Schneeweiss, Atomic spin-controlled non-reciprocal Raman amplification of fibre-guided light, Nat. Photonics 16, 380 (2022).
  11. A. Vylegzhanin, D. J. Brown, A. Raj, D. F. Kornovan, J. L. Everett, E. Brion, J. Robert, and S. Nic Chormaic, Excitation of Rb87 Rydberg atoms to nS and nD states (n≤68) via an optical nanofiber, Opt. Quantum 1, 6 (2023).
  12. C. Sayrin, C. Clausen, B. Albrecht, P. Schneeweiss, and A. Rauschenbeutel, Storage of fiber-guided light in a nanofiber-trapped ensemble of cold atoms, Optica 2, 353 (2015).
  13. B. Gouraud, D. Maxein, A. Nicolas, O. Morin, and J. Laurat, Demonstration of a memory for tightly guided light in an optical nanofiber, Phys. Rev. Lett. 114 180503 (2015).
  14. N. V. Corzo, J. Raskop, A. Chandra, A. S. Sheremet, B. Gouraud, and J. Laurat, Waveguide-coupled single collective excitation of atomic arrays, Nature (London) 566, 359 (2019).
  15. M. Scheucher, A. Hilico, E. Will, J. Volz, and A. Rauschenbeutel, Quantum optical circulator controlled by a single chirally coupled atom, Science 354, 1577 (2016).
  16. T. G. Tiecke, J. D. Thompson, N. P. de Leon, L. R. Liu, V. Vuletić, and M. D. Lukin, Nanophotonic quantum phase switch with a single atom, Nature (London) 508, 241 (2014).
  17. T. Djordjevic, P. Samutpraphoot, P. L. Ocola, H. Bernien, B. Grinkemeyer, I. Dimitrova, V. Vuletić, and M. D. Lukin, Entanglement transport and a nanophotonic interface for atoms in optical tweezers, Science 373, 1511 (2021).
  18. I. Shomroni, S. Rosenblum, Y. Lovsky, O. Bechler, G. Guendelman, and B. Dayan, All-optical routing of single photons by a one-atom switch controlled by a single photon, Science 345, 903 (2014).
  19. S. Rosenblum, O. Bechler, I. Shomroni, Y. Lovsky, G. Guendelman, and B. Dayan, Extraction of a single photon from an optical pulse, Nat. Photonics 10, 19 (2015).
  20. A. Goban, C.-L. Hung, J. D. Hood, S.-P. Yu, J. A. Muniz, O. Painter, and H. J. Kimble, Superradiance for atoms trapped along a photonic crystal waveguide, Phys. Rev. Lett. 115, 063601 (2015).
  21. S. K. Ruddell, K. E. Webb, I. Herrera, A. S. Parkins, and M. D. Hoogerland, Collective strong coupling of cold atoms to an all-fiber ring cavity, Optica 4, 576 (2017).
  22. S. Kato, N. Német, K. Senga, S. Mizukami, X. Huang, S. Parkins, and T. Aoki, Observation of dressed states of distant atoms with delocalized photons in coupled-cavities quantum electrodynamics, Nat. Commun. 10, 1160 (2019).
  23. C. Liedl, F. Tebbenjohanns, C. Bach, S. Pucher, A. Rauschenbeutel, and P. Schneeweiss, Observation of superradiant bursts in a cascaded quantum system, Phys. Rev. X 14, 011020 (2024).
  24. E. Vetsch, D. Reitz, G. Sagué, R. Schmidt, S. T. Dawkins, and A. Rauschenbeutel, Optical interface created by laser-cooled atoms trapped in the evanescent field surrounding an optical nanofiber, Phys. Rev. Lett. 104, 203603 (2010).
  25. A. Goban, K. S. Choi, D. J. Alton, D. Ding, C. Lacroûte, M. Pototschnig, T. Thiele, N. P. Stern, and H. J. Kimble, Demonstration of a state-insensitive, compensated nanofiber trap, Phys. Rev. Lett. 109, 033603 (2012).
  26. A. Goban, C.-L. Hung, S.-P. Yu, J. D. Hood, J. A. Muniz, J. H. Lee, M. J. Martin, A. C. McClung, K. S. Choi, D. E. Chang, O. Painter, and H. J. Kimble, Atom–light interactions in photonic crystals, Nat. Commun. 5, 3808 (2014).
  27. D. J. Alton, N. P. Stern, T. Aoki, H. Lee, E. Ostby, K. J. Vahala, and H. J. Kimble, Strong interactions of single atoms and photons near a dielectric boundary, Nat. Phys. 7, 159 (2010).
  28. X. Zhou, H. Tamura, T.-H. Chang, and C.-L. Hung, Trapped atoms and superradiance on an integrated nanophotonic microring circuit, Phys. Rev. X 14, 031004 (2024).
  29. J. D. Thompson, T. G. Tiecke, N. P. de Leon, J. Feist, A. V. Akimov, M. Gullans, A. S. Zibrov, and V. V. M. D. Lukin, Coupling a single trapped atom to a nanoscale optical cavity, Science 340, 1202 (2013).
  30. S. G. Menon, N. Glachman, M. Pompili, A. Dibos, and H. Bernien, An integrated atom array-nanophotonic chip platform with background-free imaging, Nat. Commun. 15, 6156 (2024).
  31. D. Boiron, C. Triché, D. R. Meacher, P. Verkerk, and G. Grynberg, Three-dimensional cooling of cesium atoms in four-beam gray optical molasses, Phys. Rev. A 52, R3425 (1995).
  32. Y.-F. Hsiao, Y.-J. Lin, and Y.-C. Chen, Λ-enhanced gray-molasses cooling of cesium atoms on the D2 line, Phys. Rev. A 98, 033419 (2018).
  33. A. T. Grier, I. Ferrier-Barbut, B. S. Rem, M. Delehaye, L. Khaykovich, Fédéric Chevy, and C. Salomon, Λ-enhanced sub-Doppler cooling of lithium atoms in D1 gray molasses, Phys. Rev. A 87, 063411 (2013).
  34. T. Grünzweig, A. Hilliard, M. McGovern, and M. F. Andersen, Near-deterministic preparation of a single atom in an optical microtrap, Nat. Phys. 6, 951 (2010).
  35. Y. Wang, S. Chai, T. Billotte, Z. Chen, M. Xin, W. S. Leong, F. Amrani, B. Debord, F. Benabid, and S.-Y. Lan, Enhancing fiber atom interferometer by in-fiber laser cooling, Phys. Rev. Res. 4, l022058 (2022).
  36. B. J. Lester, N. Luick, A. M. Kaufman, C. M. Reynolds, and C. A. Regal, Rapid production of uniformly filled arrays of neutral atoms, Phys. Rev. Lett. 115, 073003 (2015).
  37. M. Brown, T. Thiele, C. Kiehl, T.-W. Hsu, and C. Regal, Gray-molasses optical-tweezer loading: Controlling collisions for scaling atom-array assemblyPhys. Rev. X 9, 011057 (2019).
  38. A. Glicenstein, G. Ferioli, L. Brossard, Y. R. P. Sortais, D. Barredo, F. Nogrette, I. Ferrier-Barbut, and A. Browaeys, Preparation of one-dimensional chains and dense cold atomic clouds with a high numerical aperture four-lens system, Phys. Rev. A 103, 043301 (2021).
  39. G. Morigi, J. Eschner, and C. H. Keitel, Ground state laser cooling using electromagnetically induced transparency, Phys. Rev. Lett. 85, 4458 (2000).
  40. C. F. Roos, D. Leibfried, A. Mundt, F. Schmidt-Kaler, J. Eschner, and R. Blatt, Experimental demonstration of ground state laser cooling with electromagnetically induced transparency, Phys. Rev. Lett. 85, 5547 (2000).
  41. T. Kampschulte, W. Alt, S. Manz, M. Martinez-Dorantes, Ré Reimann, S. Yoon, D. Meschede, M. Bienert, and G. Morigi, Electromagnetically-induced-transparency control of single-atom motion in an optical cavity, Phys. Rev. A 89, 033404 (2014).
  42. E. Haller, J. Hudson, A. Kelly, D. A. Cotta, B. Peaudecerf, G. D. Bruce, and S. Kuhr, Single-atom imaging of fermions in a quantum-gas microscope, Nat. Phys. 11, 738 (2015).
  43. C. H. Chow, B. L. Ng, V. Prakash, and C. Kurtsiefer, Fano resonance in excitation spectroscopy and cooling of an optically trapped single atom, Phys. Rev. Res. 6, 023154 (2024).
  44. N. Schlosser, G. Reymond, and P. Grangier, Collisional blockade in microscopic optical dipole traps, Phys. Rev. Lett. 89, 023005 (2002).
  45. F. Le Kien, P. Schneeweiss, and A. Rauschenbeutel, Dynamical polarizability of atoms in arbitrary light fields: general theory and application to cesium, Eur. Phys. J. D 67, 92 (2013).
  46. R. Pennetta, A. Glicenstein, L. Pache, P. Schneeweiss, J. Volz, and A. Rauschenbeutel, Hybrid nanophotonic trap for cold atoms using surface forces and a blue-detuned evanescent field, Nat. Photonics 20, 1153 (2026).
  47. See the Supplemental Material at http://link.aps.org/supplemental/10.1103/5l6x-4377 for additional details on the experimental sequence, the temperature of the individual molasses, and the characterization of the atom loading and loss rates when loading from it. Furthermore, we present details on the determination of the optical depth and atom number, as well as on the fluorescence imaging of the nanofiber-trapped atoms. Please note that the Supplemental Material includes Refs. [56,57].
  48. J.-B. Béguin, E. Bookjans, S. Christensen, H. Sørensen, J. Müller, E. Polzik, and J. Appel, Generation and detection of a sub-Poissonian atom number distribution in a one-dimensional optical lattice, Phys. Rev. Lett. 113, 263603 (2014).
  49. L. Pache, M. Cordier, H. Letellier, M. Schemmer, P. Schneeweiss, J. Volz, and A. Rauschenbeutel, Magic-wavelength nanofiber-based two-color dipole trap with sub-λ/2 spacing, Phys. Rev. A 112, L011701 (2025).
  50. E. Vetsch, S. T. Dawkins, R. Mitsch, D. Reitz, P. Schneeweiss, and A. Rauschenbeutel, Nanofiber-based optical trapping of cold neutral atoms, IEEE J. Sel. Top. Quantum Electron 18, 1763 (2012).
  51. S. S. Phatak, K. N. Blodgett, D. Peana, M. R. Chen, and J. D. Hood, Generalized theory for optical cooling of a trapped atom with spin, Phys. Rev. A 110, 043116 (2024).
  52. J. Piotrowski, C. Bach, N. Vera Paz, P. Schneeweiss, and A. Rauschenbeutel, Limits of stable near-field probing in nanophotonic traps, ACS Photonics 13, 4420 (2026).
  53. C. Østfeldt, J.-B. S. Béguin, F. T. Pedersen, E. S. Polzik, J. H. Müller, and J. Appel, Dipole force free optical control and cooling of nanofiber trapped atoms, Opt. Lett. 42, 4315 (2017).
  54. G. Morigi, Cooling atomic motion with quantum interference, Phys. Rev. A 67, 033402 (2003).
  55. A. Asenjo-Garcia, M. Moreno-Cardoner, A. Albrecht, H. Kimble, and D. E. Chang, Exponential improvement in photon storage fidelities using subradiance and selective radiance in atomic arrays, Phys. Rev. X 7, 031024 (2017).
  56. B. Ueberholz, S. Kuhr, D. Frese, D. Meschede, and V. Gomer, Counting cold collisions, J. Phys. B 33, L135 (2000).
  57. S. J. M. Kuppens, K. L. Corwin, K. W. Miller, T. E. Chupp, and C. E. Wieman, Loading an optical dipole trap, Phys. Rev. A 62, 013406 (2000).

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PRX Quantum 7, 043010– Published 15 October, 2026
  • Received 13 May 2026
  • Accepted 8 September 2026
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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.

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