Fabrication techniques usually applied to microelectromechanical systems (MEMS) are used to reduce the size and operating power of the core physics assembly of an atomic clock. With a volume of 9.5 mm 3 , a fractional frequency instability of 2.5ϫ 10 −10 at 1 s of integration, and dissipating less than 75 mW of power, the device has the potential to bring atomically precise timing to hand-held, battery-operated devices. In addition, the design and fabrication process allows for wafer-level assembly of the structures, enabling low-cost mass-production of thousands of identical units with the same process sequence, and easy integration with other electronics.

We propose an experiment using optically trapped and cooled dielectric microspheres for the detection of short-range forces. The center-of-mass motion of a microsphere trapped in vacuum can experience extremely low dissipation and quality factors of 10 12 , leading to yoctonewton force sensitivity. Trapping the sphere in an optical field enables positioning at less than 1 µm from a surface, a regime where exotic new forces may exist. We expect that the proposed system could advance the search for non-Newtonian gravity forces via an enhanced sensitivity of 10 5 − 10 7 over current experiments at the 1 µm length scale. Moreover, our system may be useful for characterizing other short-range physics such as Casimir forces.PACS numbers: 04.80. Cc,07.10.Pz,42.50.Pq Since the pioneering work of Ashkin and coworkers in the 1970s [1], optical trapping of dielectric objects has become an extraordinarily rich area of research. Optical tweezers are used extensively in biophysics to study and manipulate the dynamics of single molecules, and in soft condensed-matter physics to study macromolecular interactions [2,3]. Much recent work has focused on trapping in solution where strong viscous damping dominates particle motion. There has also been interest in extending the regime that Ashkin and coworkers opened, namely, trapping sub-wavelength particles in vacuum where particle motion is strongly decoupled from a room-temperature environment [1,4].Recent theoretical studies have suggested that nanoscale dielectric objects trapped in ultrahigh vacuum might be cooled to their ground state of (center-of-mass) motion via radiation pressure forces of an optical cavity [5,6]. This remarkable result is made possible by isolation from the thermal bath, robust decoupling from internal vibrations, and lack of a clamping mechanism. In fact, a trapped dielectric nanosphere has been predicted to attain an ultrahigh mechanical quality factor Q exceeding 10 12 for the center-of-mass mode, limited by background gas collisions. Such large Q factors enable cavity cooling, for which the lowest possible phonon occupation of the mechanical oscillator is n T /Q, where n T is the number of room-temperature thermal phonons. Although such Q factors have yet to be observed in experiment, optically levitated microspheres have been trapped in vacuum for lifetimes exceeding 1000 s [1] and electrically levitated microspheres have exhibited pressurelimited damping that is consistent with theoretical predictions down to ∼ 10 −6 Torr [7].In addition to being beneficial for ground-state cooling and studies of quantum coherence in mesoscopic systems, mechanical oscillators with high quality factors also enable sensitive resonant force detection [8,9]. Optically levitated microspheres in vacuum have been studied theoretically in the context of reaching and exceeding the standard quantum limit of position measurement [10]. In this paper, we discuss the force sensing capability of a microsphere trapped inside a medium-finesse optical cavity at ultra-high vacuum, ...

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Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities to explore fundamental physics and enable new measurements. However, their size and use of bulk components prevent them from being more widely adopted in applications that require precision timing. By leveraging silicon-chip photonics for integration and to reduce component size and complexity, we demonstrate a compact optical-clock architecture. Here a semiconductor laser is stabilized to an optical transition in a microfabricated rubidium vapor cell, and a pair of interlocked Kerr-microresonator frequency combs provide fully coherent optical division of the clock laser to generate an electronic 22 GHz clock signal with a fractional frequency instability of one part in 10 13 . These results demonstrate key concepts of how to use silicon-chip devices in future portable and ultraprecise optical clocks. Main Text:Optical atomic clocks, which rely on high-frequency, narrow-linewidth optical transitions to stabilize a clock laser, outperform their microwave counterparts by several orders of magnitude due to their inherently large quality factors (1). Optical clocks based on laser-cooled and latticetrapped atoms have demonstrated fractional instabilities at the 10 -18 level (2), setting stringent new limits on tests of fundamental physics (3, 4) and may eventually replace microwave clocks in global timekeeping, navigation and the definition of the SI second (5). Despite their excellent performance, optical clocks are almost exclusively operated by metrological institutions and universities due to their large size and complexity.Although significant progress has been made in reducing the size of laser-cooled atomic clocks to fit inside a mobile trailer (6), applications of these clocks are still limited to metrological clock comparisons and precision geodesy (7). In contrast, optical oscillators referenced to thermal atomic or molecular vapors can be realized in small form factors and still reach instabilities below 10 -14 (8,9). A fully integrated optical clock would benefit many of the applications (10) that currently utilize compact or chip-scale (11) microwave atomic clocks but, until recently, techniques for on-chip laser stabilization to atoms (12) and optical frequency division (13) were not available. Here, we propose and demonstrate an architecture for an integrated optical clock, based on an atomic vapor cell implemented on a silicon chip and a

Using the techniques of microelectromechanical systems, we have constructed a small low-power magnetic sensor based on alkali atoms. We use a coherent population trapping resonance to probe the interaction of the atoms’ magnetic moment with a magnetic field, and we detect changes in the magnetic flux density with a sensitivity of 50pTHz−1∕2 at 10Hz. The magnetic sensor has a size of 12mm3 and dissipates 195mW of power. Further improvements in size, power dissipation, and magnetic field sensitivity are immediately foreseeable, and such a device could provide a hand-held battery-operated magnetometer with an atom shot-noise limited sensitivity of 0.05pTHz−1∕2.