Optically trapped nanospheres in high-vaccum experience little friction and hence are promising for ultra-sensitive force detection. Here we demonstrate measurement times exceeding $10^5$ seconds and zeptonewton force sensitivity with laser-cooled silica nanospheres trapped in an optical lattice. The sensitivity achieved exceeds that of conventional room-temperature solid-state force sensors, and enables a variety of applications including electric field sensing, inertial sensing, and gravimetry. The optical potential allows the particle to be confined in a number of possible trapping sites, with precise localization at the anti-nodes of the optical standing wave. By studying the motion of a particle which has been moved to an adjacent trapping site, the known spacing of the lattice anti-nodes can be used to calibrate the displacement spectrum of the particle. Finally, we study the dependence of the trap stability and lifetime on the laser intensity and gas pressure, and examine the heating rate of the particle in high vacuum in the absence of optical feedback cooling.Comment: 5 pages, 4 figures, minor changes, typos corrected, references adde

We describe the implementation of laser-cooled silica microspheres as force sensors in a dualbeam optical dipole trap in high vacuum.Using this system we have demonstrated trap lifetimes exceeding several days, attonewton force detection capability, and wide tunability in trapping and cooling parameters. Measurements have been performed with charged and neutral beads to calibrate the sensitivity of the detector. This work establishes the suitability of dual beam optical dipole traps for precision force measurement in high vacuum with long averaging times, and enables future applications including the study of gravitational inverse square law violations at short range, Casimir forces, acceleration sensing, and quantum opto-mechanics.

We have completed a new measurement of the Stark shift in 115 In within the 410 nm 5P 1/2 → 6S 1/2 transition. We measure the Stark shift constant to be kS = −122.92(33) kHz/(kV/cm) 2 , corresponding to a difference in the 6S 1/2 and 5P 1/2 state polarizabilities, ∆α0, of 1000.2 ± 2.7 a 3 0 (in atomic units). This result is a factor of 30 more precise than previous measurements and is in excellent agreement with a new theoretical value based on an ab initio calculation of the wave functions in this three-valence-electron system. The measurement was performed in an indium atomic beam apparatus, used a GaN laser diode system, and exploited an FM spectroscopy technique to extract laser transmission spectra under conditions where our interaction region optical depth was typically less than 10 −3 .I.

Optically trapped dielectric objects are well suited for reaching the quantum regime of their center of mass motion in an ultra-high vacuum environment. We show that ground state cooling of an optically trapped nanosphere is achievable when starting at room temperature, by sympathetic cooling of a cold atomic gas optically coupled to the nanoparticle. Unlike cavity cooling in the resolved sideband limit, this system requires only a modest cavity finesse and it allows the cooling to be turned off, permitting subsequent observation of strongly-coupled dynamics between the atoms and sphere. Nanospheres cooled to their quantum ground state could have applications in quantum information science or in precision sensing.Comment: 6 pages, 2 figure

A recent neutron interferometry experiment claims to demonstrate a paradoxical phenomenon dubbed the "quantum Cheshire cat" [Nat. Commun.5, 4492 (2014)]. We have reproduced and extended these results with an equivalent optical interferometer. The results suggest that the photon travels through one arm of the interferometer, while its polarization travels through the other. However, we show that these experimental results belong to the domain where quantum and classical wave theories coincide; there is nothing uniquely quantum about the illusion of this Cheshire cat.