15. IMPLEMENTATIONS: QUANTUM OPTICS

The quantum Zeno effect and quantum feedback in cavity QED

Date: 
2010-09-30
Author(s): 

I. Dotsenko, J. Bernu, S. Deléglise, C. Sayrin, M. Brune, J.M. Raimond, S. Haroche, M. Mirrahimi, P. Rouchon

Reference: 

Physica Scripta T140, 014004 (2010)
doi: 10.1088/0031-8949/2010/T140/014004

We explore experimentally the fundamental projective properties of a quantum measurement and their application in the control of a system’s evolution. We perform quantum non-demolition (QND) photon counting on a microwave field trapped in a very-high-Q superconducting cavity, employing circular Rydberg atoms as non-absorbing probes of light. By repeated measurement of the cavity field we demonstrated the freeze of its initially coherent evolution, illustrating the back action of the photon number measurement on the field’s phase.

The quantum speed limit of optimal controlled phasegates for trapped neutral atoms

Date: 
2011-07-25
Author(s): 

M. H. Goerz, T. Calarco, C. P. Koch

Reference: 

J. Phys. B: At. Mol. Opt. Phys. 44, 154011 (2011)

We study controlled phasegates for ultracold atoms in an optical potential. A shaped laser pulse drives transitions between the ground and electronically excited states where the atoms are subject to a long-range 1/R3 interaction. We fully account for this interaction and use optimal control theory to calculate the pulse shapes. This allows us to determine the minimum pulse duration, respectively, gate time T that is required to obtain high fidelity.

Cavity-enhanced atom detection with cooperative noise

Date: 
2010-09-16
Reference: 

J. Goldwin, M. Trupke, J. Kenner, A. Ratnapala, E. A. Hinds
http://arxiv.org/abs/1009.2916

An optical microcavity with small mode radius is used to measure the local density of a cold atom cloud. Atom densities below 1 per cavity mode volume are measured with signals near the photon shot-noise limit. Atom detection is fast and efficient, reaching fidelities in excess of 97% after 10 us and 99.9% after 30 us. Notably, the fluctuations of the detected photon counts are smaller than expected for Poissonian distributions of atoms probed with Poissonian light fields.

Ion-assisted ground-state cooling of a trapped polar molecule

Date: 
2011-05-13
Author(s): 

Z. Idziaszek, T. Calarco, P. Zoller

Reference: 

Phys. Rev. A 83, 053413 (2011)

We propose and analyze a scheme for sympathetic cooling of the translational motion of polar molecules in an optical lattice, interacting one by one with laser-cooled ions in a radio-frequency trap. The energy gap between the excitation spectra of the particles in their respective trapping potentials is bridged by means of a parametric resonance, provided by the additional modulation of the RF field. We analyze two scenarios: simultaneous laser cooling and energy exchange between the ion and the molecule, and a scheme when these two processes take place separately.

Single-atom-resolved fluorescence imaging of an atomic Mott insulator

Date: 
2010-08-18
Author(s): 

J.F. Sherson, C. Weitemberg, M. Endres, M. Cheneau, I. Bloch and S. Kuhr

Reference: 

Nature 467, 68 (2010)

The reliable detection of single quantum particles has revolutionized the field of quantum optics and quantum information processing. For several years, researchers have aspired to extend such detection possibilities to larger scale strongly correlated quantum systems, in order to record in-situ images of a quantum fluid in which each underlying quantum particle is detected. Here we report on fluorescence imaging of strongly interacting bosonic Mott insulators in an optical lattice with single-atom and single-site resolution.

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