Progress in Continuous-Wave Superradiance and Gap Protection Against Doppler Dephasing in a High-Finesse Optical Ring Cavity

POSTER

Abstract

Superradiant lasers offer narrow linewidth, high precision, and broad bandwidth by shifting phase memory from the optical cavity to an ultra-narrow atomic transition of cold trapped atoms. Our pulsed superradiance demonstration on the mHz transition in 87Sr achieved a fractional Allan deviation of 6.7×10−16 at 1s averaging. To enable continuous-wave superradiance with vastly improved short-term stability, we continuously load 2.1(3)×107 88Sr atoms/s into a high-finesse ring cavity and transport them via a moving lattice to a low-decoherence region [1]. This high-flux system provides a foundation for continuous superradiant lasers, dead-time-free interferometry, and high-precision atomic clocks. Additionally, we observe continuous lasing from laser-cooled 88Sr atoms in the ring cavity, driven by a collective recoil-induced resonance [2]. This lasing process, related to but distinct from self-organization phase transitions, exhibits 120 times less sensitive to cavity frequency fluctuations due to a lasing-induced atomic loss mechanism, providing a novel approach to suppressing low-frequency cavity noise. These results open new possibilities for continuous cavity QED quantum simulations and the realization of continuous superradiant lasers. Additionally, we observe extended coherence of collective dipole moments by suppressing Doppler decoherence through cavity-mediated spin-exchange interactions on the 7.5 kHz 1S0–3P1 transition without magic wavelength trapping [3]. This offers an alternative to Lamb-Dicke confinement for quantum sensing and many-body physics.

[1] J. R. K. Cline, V. M. Schäfer, et al. Physical Review Letters 134 (2025): 013403.

[2] V. M. Schäfer, Z. Niu, et al. Nature Physics in press, arXiv:2405.20952 (2024).

[3] Z. Niu, V. M. Schäfer, et al. arXiv:2409.16265 (2024).

**This material is based upon work supported by the US Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Systems Accelerator. We acknowledge additional funding support from the National Science Foundation under Grant Nos. 2317149 (Physics Frontier Center) and OMA-2016244 (Quantum Leap Challenge Institutes), and the National Institute of Standards and Technology.

Publication: 1. Cline, Julia RK, Vera M. Schäfer, Zhijing Niu, Dylan J. Young, Tai Hyun Yoon, and James K. Thompson. "Continuous Collective Strong Coupling of Strontium Atoms to a High Finesse Ring Cavity." Physical Review Letters 134, no. 1 (2025): 013403.
2. Schäfer, V. M., Z. Niu, J. R. K. Cline, D. J. Young, E. Y. Song, H. Ritsch, and J. K. Thompson. "Continuous momentum state lasing and cavity frequency-pinning with laser-cooled strontium atoms." arXiv:2405.20952 (2024).
3. Niu, Zhijing, Vera M. Schäfer, Haoqing Zhang, Cameron Wagner, Nathan R. Taylor, Dylan J. Young, Eric Yilun Song, Anjun Chu, Ana Maria Rey, and James K. Thompson. "Many-body gap protection of motional dephasing of an optical clock transition." arXiv:2409.16265 (2024).

Presenters

  • Zhijing Niu

    • JILA

Authors

  • Zhijing Niu

    • JILA

  • Cameron Wagner

    • JILA

  • Vera M Schäfer

    • JILA, University of Colorado

  • Julia R Cline

    • JILA

  • Dylan J Young

    • JILA

  • Eric Y Song

    • JILA

  • Seth H Chew

    • JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
    • JILA

  • Nathan R Taylor

    • JILA

  • Haoqing Zhang

    • University of Colorado, Boulder
    • JILA, CU Boulder

  • Anjun Chu

    • JILA
    • University of Chicago

  • Helmut Ritsch

    • University of Innsbruck

  • Ana Maria Rey

    • JILA, University of Colorado, Boulder
    • University of Colorado, Boulder
    • JILA, University of Colorado Boulder
    • JILA, CU Boulder

  • James K Thompson

    • JILA, NIST and Dept. of Physics, Univ. of Colorado, Boulder
    • JILA & Univ. of Colorado
    • JILA, CU Boulder