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Session B8: Quantum PNT 3

Optical Clocks in 30L, 5L, and 1L form Factors
Micah Ledbetter, Parth Patel, Abijith Kowligy, Guthrie Partridge, Sean Moore, Dan Sheredy, Elton Pashollari, Junichiro Fujitha, Kai Nambu, Tatum Wilson, Mary Kate Pasha,Clarence Mayot, Gunnar Skulason, Dorjee Tenzing, Evan Achtison, Paul Carney, Akash Rakholia, Andrew Dowd, Jamil Abo-Shaeer, Jonathan Roslund, Arman Cingoz, Martin Boyd, Vector Atomic Pleasanton
Location: Ballroom E
Date/Time: Tuesday, Jun. 2, 4:05 p.m.

Iodine optical clocks feature high stability, low phase noise, low environmental sensitivity and low power consumption in compact form factors [1]. The Evergreen-30 (EG-30) rackmount optical clock delivers performance of 3 x 10-14/sqrt(tau) in a 3U, 85 W package and is now commercially available. Performance surpassing hydrogen masers has been demonstrated at radio observatories as well as on mobile platforms including surface ships, sport utility vehicles, and light aircraft [2]. A new 5.5 L prototype (EG-5) has been developed with reduced power consumption < 40 W and extended temperature operating range. Preliminary evaluation of this unit shows short term stability within a factor of the two of the EG-30, while phase noise and long-term stability perform similarly to the rack sized unit. Parallel development of a 1.2 L version of the clock (EG-1) is also in progress showing 10^-13/sqrt(tau) short term stability and 10^-15 level long term stability.
A new environmental test campaign for the EG-30 clock has been performed to study operation under temperature, humidity, magnetic fields, and orientations. Orientation shifts, typically in the low 10^-14/g range for these clocks, were explored on a dynamic motion platform for the first time. This study strengthens the results of prior field demonstrations where clocks experienced similar environments. The EG-5 clock performance, SWaP, and operating environment will be presented in detail, including phase noise and long term stability. For the EG-1 we present new environmental testing and SWaP metrics for physics package modules; including a ~100 mL frequency comb with total power consumption of ~2 W. The Iodine cells and spectrometer have been miniaturized to sub 100 mL footprint and evaluated while operating on vibration platforms. The spectrometer frequency temp-co and operation was evaluated over 0-70 C.
Combined, we present current hardware and near term prospects for performance, environmental robustness, and SWaP trades for iodine optical clock technology.
[1] Jonathan Roslund et al., “Optical Clocks at Sea,” Nature 628, 736-740 (2024)
[2] Micah Ledbetter et al., “Iodine Optical Clock use at the Event Horizon Telescope for VLBI,” PTTI Conference, Session P2a, (2025).

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