Half-minute-scale atomic coherence and high relative stability in a tweezer clock

• Published in: Nature (London) 2020-12, Vol.588 (7838), p.408-413
• Main Authors: Young, Aaron W., Eckner, William J., Milner, William R., Kedar, Dhruv, Norcia, Matthew A., Oelker, Eric, Schine, Nathan, Ye, Jun, Kaufman, Adam M.
• Format: Article
• Language: English
• Subjects: 140/125; 639/766/36/1125; 639/766/483/1255; Arrays; Clocks & watches; Coherence; Coherent states; Condensed matter physics; Cooling; Entanglement; Entropy; Frequency stability; Humanities and Social Sciences; Lasers; Lifetime; multidisciplinary; Optical lattices; Properties; Q factors; Quantum theory; Questioning; Science; Science (multidisciplinary); Strontium
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-020-3009-y

The preparation of large, low-entropy, highly coherent ensembles of identical quantum systems is fundamental for many studies in quantum metrology 1 , simulation 2 and information 3 . However, the simultaneous realization of these properties remains a central challenge in quantum science across atomic and condensed-matter systems 2 , 4 – 7 . Here we leverage the favourable properties of tweezer-trapped alkaline-earth (strontium-88) atoms 8 – 10 , and introduce a hybrid approach to tailoring optical potentials that balances scalability, high-fidelity state preparation, site-resolved readout and preservation of atomic coherence. With this approach, we achieve trapping and optical-clock excited-state lifetimes exceeding 40 seconds in ensembles of approximately 150 atoms. This leads to half-minute-scale atomic coherence on an optical-clock transition, corresponding to quality factors well in excess of 10 16 . These coherence times and atom numbers reduce the effect of quantum projection noise to a level that is comparable with that of leading atomic systems, which use optical lattices to interrogate many thousands of atoms in parallel 11 , 12 . The result is a relative fractional frequency stability of 5.2(3) × 10 −17 τ −1/2 (where τ is the averaging time in seconds) for synchronous clock comparisons between sub-ensembles within the tweezer array. When further combined with the microscopic control and readout that are available in this system, these results pave the way towards long-lived engineered entanglement on an optical-clock transition 13 in tailored atom arrays. A tweezer clock containing about 150 88 Sr atoms achieves trapping and optical excited-state lifetimes exceeding 40 seconds, and shows relative fractional frequency stability similar to that of leading atomic clocks.