We propose an alternative method to laser cooling. Our approach utilizes the extreme brightness of a supersonic atomic beam, and the adiabatic atomic coilgun to slow atoms in the beam or to bring them to rest. We show how internal-state optical pumpi
ng and stimulated optical transitions, combined with magnetic forces can be used to cool the translational motion of atoms. This approach does not rely on momentum transfer from photons to atoms, as in laser cooling. We predict that our method can surpass laser cooling in terms of flux of ultra-cold atoms and phase-space density, with lower required laser power and reduced complexity.
Brownian motion has played important roles in many different fields of science since its origin was first explained by Albert Einstein in 1905. Einsteins theory of Brownian motion, however, is only applicable at long time scales. At short time scales
, Brownian motion of a suspended particle is not completely random, due to the inertia of the particle and the surrounding fluid. Moreover, the thermal force exerted on a particle suspended in a liquid is not a white noise, but is colored. Recent experimental developments in optical trapping and detection have made this new regime of Brownian motion accessible. This review summarizes related theories and recent experiments on Brownian motion at short time scales, with a focus on the measurement of the instantaneous velocity of a Brownian particle in a gas and the observation of the transition from ballistic to diffusive Brownian motion in a liquid.
The apparent conflict between general relativity and quantum mechanics remains one of the unresolved mysteries of the physical world. According to recent theories, this conflict results in gravity-induced quantum state reduction of Schrodinger cats,
quantum superpositions of macroscopic observables. In recent years, great progress has been made in cooling micromechanical resonators towards their quantum mechanical ground state. This work is an important step towards the creation of Schrodinger cats in the laboratory, and the study of their destruction by decoherence. A direct test of the gravity-induced state reduction scenario may therefore be within reach. However, a recent analysis shows that for all systems reported to date, quantum superpositions are destroyed by environmental decoherence long before gravitational state reduction takes effect. Here we report optical trapping of glass microspheres in vacuum with high oscillation frequencies, and cooling of the center-of-mass motion from room temperature to a minimum temperature of 1.5 mK. This new system eliminates the physical contact inherent to clamped cantilevers, and can allow ground-state cooling from room temperature. After cooling, the optical trap can be switched off, allowing a microsphere to undergo free-fall in vacuum. During free-fall, light scattering and other sources of environmental decoherence are absent, so this system is ideal for studying gravitational state reduction. A cooled optically trapped object in vacuum can also be used to search for non-Newtonian gravity forces at small scales, measure the impact of a single air molecule, and even produce Schrodinger cats of living organisms.
We analyze the conditions for producing atomic number states in a one-dimensional optical box using the Bethe ansatz method. This approach provides a general framework, enabling the study of number state production over a wide range of realistic experimental parameters.
We analyze a system of fermionic $^{6}$Li atoms in an optical trap, and show that an atom on demand can be prepared with ultra-high fidelity, exceeding 0.99998. This process can be scaled to many sites in parallel, providing a realistic method to ini
tialize N qubits at ultra-high fidelity for quantum computing. We also show how efficient quantum gate operation can be implemented in this system, and how spatially resolved single-atom detection can be performed.
We propose a general method to cool the translational motion of molecules. Our method is an extension of single photon atomic cooling which was successfully implemented in our laboratory. Requiring a single event of absorption followed by a spontaneo
us emission, this method circumvents the need for a cycling transition and can be applied to any paramagnetic or polar molecule. In our approach, trapped molecules would be captured near their classical turning points in an optical dipole or RF-trap following an irreversible transition process.
We first devise a scheme to perform a universal entangling gate via controlled collisions between pairs of atomic qubits trapped with optical tweezers. Second, we present a modification to this scheme to allow the preparation of atomic Bell pairs via
selective excitation, suitable for quantum information processing applications that do not require universality. Both these schemes are enabled by the inherent symmetries of identical composite particles, as originally proposed by Hayes et al. Our scheme provides a technique for producing weighted graph states, entangled resources for quantum communication, and a promising approach to performing a loophole free Bell test in a single laboratory.
