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

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

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

Efficient optomechanical cooling in one-dimensional interferometers

We present a scattering model which enables us to describe the mechanical force, including the velocity dependent component, exerted by light on polarizable massive objects in a general one-dimensional optical system. We show that the light field in an interferometer can be very sensitive to the velocity of a moving scatterer. We construct a new efficient cooling scheme, ‘external cavity cooling’, in which the scatterer, that can be an atom or a moving micromirror, is spatially separated from the cavity.This work was supported by the UK EPSRC (EP/E039839/1 and EP/E058949/1), by the CMMC collaboration within the EuroQUAM programme of the ESF, and by the National Office for Research and Technology (ERC HU 09 OPTOMECH) of Hungary.peer-reviewe