More Like this

1. Site-dependent selection of atoms for homogeneous atom-cavity coupling

   https://doi.org/10.48550/arXiv.2104.01201  

   Wu, B.; Greve, G. P.; Luo, C.; Thompson, J.K. (October 2022, ArXivorg)

   We demonstrate a method to obtain homogeneous atom-cavity coupling by selecting and keeping 87Rb atoms that are near maximally coupled to the cavity's standing-wave mode. We select atoms by imposing an AC Stark shift on the ground state hyperfine microwave transition frequency with light injected into the cavity. We then induce a spin flip with microwaves that are resonant for atoms that are near maximally coupled to the cavity mode of interest, after which, we use radiation pressure forces to remove from the cavity all the atoms in the initial spin state. Achieving greater homogeneity in the atom-cavity coupling will potentially enhance entanglement generation, intracavity driving of atomic transitions, cavity-optomechanics, and quantum simulations. This approach can easily be extended to other atomic species with microwave or optical transitions. 

   more » « less
2. Laser cooling of antihydrogen atoms

   https://doi.org/10.1038/s41586-021-03289-6  

   Baker, C. J.; Bertsche, W.; Capra, A.; Carruth, C.; Cesar, C. L.; Charlton, M.; Christensen, A.; Collister, R.; Mathad, A. Cridland; Eriksson, S.; et al (April 2021, Nature)

   null (Ed.)

   Abstract The photon—the quantum excitation of the electromagnetic field—is massless but carries momentum. A photon can therefore exert a force on an object upon collision 1 . Slowing the translational motion of atoms and ions by application of such a force 2,3 , known as laser cooling, was first demonstrated 40 years ago 4,5 . It revolutionized atomic physics over the following decades 6–8 , and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen 9 , the antimatter atom consisting of an antiproton and a positron. By exciting the 1S–2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-α laser radiation 10,11 , we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude—with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S–2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic 11–13 and gravitational 14 studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules. 

   more » « less
3. Searching for axion forces with spin precession in atoms and molecules

   https://doi.org/10.1007/JHEP07(2024)133  

   Agrawal, Prateek; Hutzler, Nicholas R; Kaplan, David E; Rajendran, Surjeet; Reig, Mario (July 2024, Journal of High Energy Physics)

   We propose to use atoms and molecules as quantum sensors of axion-mediated monopole-dipole forces. We show that electron spin precession experiments using atomic and molecular beams are well-suited for axion searches thanks to the presence of co-magnetometer states and single-shot temporal resolution. Experimental strategies to detect axion gradients from localised sources and the earth are presented, taking ACME III as a prototype example. Other possibilities including atomic beams, and laser-cooled atoms and molecules are discussed. 

   more » « less
4. Continuous recoil-driven lasing and cavity frequency pinning with laser-cooled atoms

   https://doi.org/10.1038/s41567-025-02854-4  

   Schäfer, Vera_M; Niu, Zhijing; Cline, Julia_R_K; Young, Dylan_J; Song, Eric_Yilun; Ritsch, Helmut; Thompson, James_K (April 2025, Nature Physics)

   Abstract Laser-cooled gases of atoms interacting with the field of an optical cavity are a versatile tool for quantum sensing and the simulation of quantum systems. These systems can exhibit phenomena such as self-organization phase transitions, lasing mechanisms, squeezed states and protection of quantum coherence. However, investigations of these phenomena typically occur in a discontinuous manner due to the need to reload atomic ensembles. Here we demonstrate hours-long continuous lasing from laser-cooled⁸⁸Sr atoms loaded into a ring cavity. The required inversion to produce lasing arises from inversion in the atomic-momentum degrees of freedom, which is linked to the self-organization phase transitions and collective atomic recoil lasing observed previously only in a cyclic fashion. We find that over a broad parameter range, the sensitivity of the lasing frequency to changes in cavity frequency is significantly reduced due to an atomic loss mechanism, suggesting a potential approach for mitigating low-frequency cavity noise. Our findings open opportunities for continuous cavity quantum electrodynamics experiments and robust and continuous super-radiant lasers. 

   more » « less
5. Increased atom-cavity coupling through cooling-induced atomic reorganization

   https://doi.org/10.1103/PhysRevResearch.6.L032049  

   Shu, Chi; Colombo, Simone; Li, Zeyang; Adiyatullin, Albert; Mendez, Enrique; Pedrozo-Peñafiel, Edwin; Vuletić, Vladan (September 2024, Physical Review Research)

   The strong coupling of atoms to optical cavities can improve optical lattice clocks as the cavity enables metrologically useful collective atomic entanglement and high-fidelity measurement. To this end, it is necessary to cool the ensemble to suppress motional broadening, and advantageous to maximize and homogenize the atom-cavity coupling. We demonstrate resolved Raman sideband cooling via the cavity as a method that can simultaneously achieve both goals. In 200 ms of Raman sideband cooling, we cool ${}^{171}\mathrm{Yb}$atoms to an average vibration number $\langle n_x\rangle =0.23\left(7\right)$in the tightly binding direction, resulting in $93\%$optical $\pi$-pulse fidelity on the clock transition ${}^{1}S_0\to {}^{3}P_0$. During cooling, the atoms self-organize into locations with maximal atom-cavity coupling, which will improve quantum metrology applications. Published by the American Physical Society2024 

   more » « less