Algorithmic cooling in a momentum state quantum computer

Published versio

Mirror-mediated cooling: a paradigm for particle cooling via the retarded dipole force

Cooling forces result from the retarded dipole interaction between an illuminated particle and its reflection. For a one-dimensional example, we find cooling times of milliseconds and limiting temperatures in the millikelvin range. The force, which may be considered the prototype for cavity-mediated cooling, may be enhanced by plasmon and geometric resonances at the mirror.Comment: 25 pages, 8 figure

Actively stabilized wavelength-insensitive carrier elimination from an electro-optically modulated laser beam

We demonstrate a simple and robust technique for removal of the carrier wave from a phase-modulated laser beam, using a non-interferometric method that is insensitive to the modulation frequency and instead exploits the polarization-dependence of electro-optic modulation. An actively stabilized system using feedback via a liquid crystal cell yields long-term carrier suppression in excess of 28 dB at the expense of a 6.5 dB reduction in sideband power.Comment: 9 pages, 5 figure

Optimal control of Raman pulse sequences for atom interferometry

We present the theoretical design and experimental implementation of mirror and beamsplitter pulses that improve the fidelity of atom interferometry and increase its tolerance of systematic inhomogeneities. These pulses are designed using the GRAPE optimal control algorithm and demonstrated experimentally with a cold thermal sample of 85Rb atoms. We first show a stimulated Raman inversion pulse design that achieves a ground hyperfine state transfer efficiency of 99.8(3)%, compared with a conventional π pulse efficiency of 75(3)%. This inversion pulse is robust to variations in laser intensity and detuning, maintaining a transfer efficiency of 90% at detunings for which the π pulse fidelity is below 20%, and is thus suitable for large momentum transfer interferometers using thermal atoms or operating in non-ideal environments. We then extend our optimization to all components of a Mach-Zehnder atom interferometer sequence and show that with a highly inhomogeneous atomic sample the fringe visibility is increased threefold over that using conventional π and π/2 pulses

Cooling atoms particles and polarisable objects using dissipative dipole forces

Optical cooling methods are generally applicable to a very restricted range of species. As a means of overcoming this problem, we explore the effect of the retarded interaction of any polarisable particle (an atom, a molecule or even a micromirror) with itself, similarly to cavity-mediated cooling. We use the transfermatrix method, extended to allow us to handle moving scatterers, to explore the most general configuration of a mobile particle interacting with any 1D combination of fixed optical elements. Remarkably, this model allows a solution in closed form for the force acting on the particle, without any a priori restriction on the nature of the particle