Jul 17 – 22, 2022
Royal Conservatory of Music, Toronto
America/Toronto timezone

Dynamic cryogenic radiation shield for sub-$10^{-19}$ blackbody radiation shift uncertainty in optical lattice clocks

Jul 18, 2022, 5:00 PM
1h 30m
Hart House (Hart House)

Hart House

Hart House

7 Hart House Cir, Toronto, ON M5S 3H3
Poster presentation Precision measurement and tests of fundamental physics Poster session


The blackbody radiation (BBR) Stark shift currently limits the performance of many atomic frequency standards. It constitutes the largest uncancelled shift and the leading uncertainty in the most accurate optical lattice clocks [1,2]. One attempt to tackle this limitation has been to create a well-characterized BBR environment at room temperature [3]. However, the uncertainty on the atomic polarizability manifested as a dynamic correction to the BBR shift limits this strategy at the $10^{-18}$ fractional frequency level. An alternative approach utilizes a cryogenic radiation shield to reduce the total BBR shift and more importantly the above-mentioned BBR dynamic correction uncertainty [4,5]. However, a lingering challenge is to achieve adequate isolation from the external environment. In these attempts, the leaking room temperature BBR limits the shift evaluation uncertainty at the same $10^{-18}$ fractional frequency level.

Here we report on the design of a mechanically dynamic cryogenic in-vacuum radiation shield that enables controlling the BBR shift uncertainty below the $10^{-19}$ level in optical lattice clocks. While the shield accommodates ample physical and optical access during atomic state preparation, mechanical actuation of its internal structure closes all physical and nearly all optical apertures during spectroscopy. The mechanical actuation encloses the atomic sample from virtually all the 4π steradians of solid angle with highly emissive cryogenic surfaces and blocks the atoms’ direct line of sight to the external environment. Consequently, shifts due to leaking room temperature BBR are suppressed below the $10^{-18}$ level. To verify the homogeneity of the cryogenic environment, the shield accommodates temperature measurement and control of all the cryogenic surfaces with direct-line-of-sight to the atoms to be within $100\ \textrm{mK}$ from a mean temperature of $75\ \textrm{K}$ or lower. The shield also acts as a Faraday shield and employs three mutually orthogonal electrode pairs for evaluation of stray electric fields inducing a DC Stark shift. The highly uniform BBR environment delivered by the shield at cryogenic temperatures and up to room temperature provides a controlled platform for many AMO experiments that investigate and seek to eliminate the perturbative BBR environment on their quantum systems.

[1] McGrew, W. F., et al. "Atomic clock performance enabling geodesy below the centimetre level." Nature 564.7734 (2018): 87-90.
[2] Bothwell, T, et al. "JILA SrI optical lattice clock with uncertainty of 2×10-18." Metrologia 56.6 (2019): 065004.
[3] Beloy, K. et al. “Atomic clock with 1×10-18 room-temperature blackbody Stark uncertainty.” Physical Review Letters 113, (2014).
[4] Ushijima, I., et al. “Cryogenic optical lattice clocks.” Nature Photonics 9, 185–189 (2015).
[5] Schwarz, R. “A cryogenic Strontium lattice clock.” Hannover: Gottfried Wilhelm Leibniz Universität, Diss., 2022, x, 166 S.

Presenter name Youssef S. Hassan
online poster URL https://docs.google.com/document/d/1BcHmcZ-LWaRM01KeVIPqJpNyhDGErEvDvwhtR02xW8s/edit?usp=sharing
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Primary authors

Youssef S. Hassan (National Institute of Standards and Technology; University of Colorado, Boulder) Kyle Beloy (National Institute of Standards and Technology) Chun-Chia Chen (National Institute of Standards and Technology; University of Colorado, Boulder) Jacob Seigel (National Institute of Standards and Technology; University of Colorado, Boulder) Tanner Grogan (National Institute of Standards and Technology; University of Colorado, Boulder) Xiaogang Zhang (National Institute of Standards and Technology; University of Colorado, Boulder) Andrew D. Ludlow (National Institute of Standards and Technology; University of Colorado, Boulder)

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