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Session P3b: Timekeeping for Quantum Networking and Other Science Applications

Commercialization Updates of a Field-Deployable Compact Optical Atomic Clock
Judith Olson, Robert Fasano, Andrew Kortyna, Mark Yeo, Infleqtion; Gabriel Ycas, SciTech; Calvin Cahall, Infleqtion
Location: Beacon B
Date/Time: Wednesday, Jan. 24, 4:23 p.m.

Optical atomic clocks have long been promised as the future of timekeeping but have struggled to be manufactured and commercialized at scale. Most advanced optical clocks today are based on atomic lattices, single or arrayed ions, or molecules, which typically require extensive laser systems and hardware characterization to reach performance specification at or below 1e-15. Simpler clocks based on thermal atomic ensembles offer a bridge between existing commercial system availability and future development of these highly advanced optical clocks. Near-term, commercially available optical clocks are largely based on a single clock laser and/or frequency comb. These clocks use simple interrogation geometries, which enable a comparatively affordable, robust, and miniaturized optical atomic clock to be commercially available and produced at scale. The specialized laser and comb systems built to address these simple optical clocks will act as a jumping off point for later advanced clocks, both for laser pre-stabilization and photonics developments.
Infleqtion’s optical atomic clock product line is based on the monochromatic two-photon optical transition in 87Rb. This clock transition lies at 778.1 nm. An optical frequency comb is leveraged to down-convert the optical stability at 385 THz to standard industry outputs at 1 PPS and 5, 10, and 100 MHz, with customization potential for higher frequency outputs. Optical outputs are additionally provided to reference internal laser signals at 1556 nm telecom C-band and 778 nm. The 778 nm laser is used for Doppler-free interrogation of a warm vapor of 87Rb atoms, with the clock transition natural linewidth of ~330 kHz. The realized linewidth for the vapor cells lies between 0.6 and 1.2 MHz, owing to collisional broadening and background gas collisions. The cell is mounted within a passively athermal and ovenized optical housing, which prepares, samples, and delivers the clock laser to the atoms while also efficiently collecting the atom’s fluorescence response at 420 nm.
The first product in this line of optical atomic clocks is called Tiqker Prime. Tiqker Prime represents a specific design-for-manufacture system with intent to be produced at scale. Tiqker Prime has fractional frequency instability far surpassing most conventional microwave clocks based on cesium or rubidium and is competitive with existing hydrogen maser technologies. Short-term (1s) ADEV performance on all tested units falls <1e-13 with ability to average to 5e-15. Initial build and cold-start autotune of clock system parameters enables automated startup in changing environmental conditions. Unit upgrades within the same form-factor are being explored to offer 1s ADEV values at 5e-14 and flicker floors of 1e-15 in addition to user-programmable stability profiles to fit a broader range of use-cases.
Tiqker Prime has a package size of 30 L and weighs 30 kg, fitting in a standard 3U rack mount chassis. A number of Tiqker Prime pre-production units have been produced, tested, and demonstrated throughout 2022-2024, and pilot line production is now underway. Tiqker Prime pre-production units have survived a wide variety of environmental conditions, including large temperature swings, spurious accelerations, vibration, and altitude changes. Though a minimal level of performance degradation is seen for mounted applications in difficult terrain, i.e. off-road, pathways to a further ruggedized version of Tiqker in a lower SWaP package are ongoing. These efforts are expected to lead to a ruggedized version of the Tiqker optical atomic clock with 2-5x reduced size, weight, and power (SWaP) with comparable performance. This version is also being explored for potential space-based applications. A further SWaP-reduced iteration of a Tiqker prototype is feasible in the next five years, which has potential to reach sub-liter, board-mountable form factors.
The existing Tiqker Prime unit performance and testing will be discussed. A brief product line overview will also be provided and feedback from attendees solicited to better define capabilities and use cases to improve the utility of future offerings.

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