Matt Mcdonnell's Blog

Decoherence of motional states

Mon Jul 17 14:06:11 BST 2006

I am working on a paper at the moment describing the Schroedinger cat experiments that we performed with a single ion coupled to its motional state. In the referee comments there were a number of questions about the theoretical derivations. The majority I could answer as they related to the details of our particular experiment and analysis, however for the more fundamental ones I needed to ask one of my coauthors and he referred to the paper [Phys. Rev. A. 62 053807] by Turchette et al. This seems to be a useful for a lot of the theoretical results in the area of coupling between an ion and a bath of harmonic oscillators, as well as describing some very nice experiments.

Coupling of a charged harmonic oscillator with the surrounding electric field, E from the environment is of the form

V = -q x.E

where q is the charge on the particle and x is the position. (...)

[cooling] [physics] [qo]

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Entangled light from a single cold atom

Tue May 30 09:02:02 BST 2006

[quant-ph/0605231] [abs, ps, pdf, other] :

Title: A single cold atom as efficient stationary source of EPR-entangled light
Authors: David Vitali, Giovanna Morigi, Jürgen Eschner
Abstract: The Stokes and anti-Stokes components of the spectrum of resonance fluorescence of a single trapped atom, which originate from the mechanical coupling between the scattered photons and the quantized motion of the atomic center of mass, exhibit quantum correlations which are of two-mode-squeezing type. We study and demonstrate the build-up of such correlations in a specific setup, which is experimentally accessible, and where the atom acts as efficient and continuous source of EPR-entangled, two-mode squeezed light.

[physics] [qo]

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Two-level systems and modelocked lasers

Fri May 26 09:25:21 BST 2006

Read up on papers about driving two level systems with strong phase modulated fields eg PM CW laser or modelocked pulsed laser

Phys. Rev. A 31, 3175-3182 (1985)
- Title: Absorption and fluorescence in frequency-modulated fields under conditions of strong modulation and saturation
- Authors: N. Nayak and G. S. Agarwal
Phys. Rev. A 50, R4465-R4467 (1994)
- Title: Realization of trapping in a two-level system with frequency-modulated fields
- Authors: Girish S. Agarwal and W. Harshawardhan

[physics] [qo]

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Quantum optics with ultrafast lasers

Thu May 4 08:49:28 BST 2006

[physics/0605034]
- Title: Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb
- Authors: T. M. Fortier, Y. Le Coq, J. E. Stalnaker, D. Ortega, S. A. Diddams, C. W. Oates, L. Hollberg
- Abstract: We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is predominantly amplified. The output of the laser in both regimes was used to perform kilohertz-level spectroscopy. This experiment demonstrates the potential for high-resolution absolute-frequency spectroscopy over the entire spectrum of the frequency comb output using a single high-finesse optical reference cavity.

[physics] [qo]

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Feedback and quantum systems

Wed May 3 08:57:19 BST 2006

[quant-ph/0605015]
- Title: Applications of Feedback Control in Quantum Systems
- Authors: Kurt Jacobs
- Abstract: We give an introduction to feedback control in quantum systems, as well as an overview of the variety of applications which have been explored to date. This introductory review is aimed primarily at control theorists unfamiliar with quantum mechanics, but should also be useful to quantum physicists interested in applications of feedback control. We explain how feedback in quantum systems differs from that in traditional classical systems, and how in certain cases the results from modern optimal control theory can be applied directly to quantum systems. In addition to noise reduction and stabilization, an important application of feedback in quantum systems is adaptive measurement, and we discuss the various applications of adaptive measurements. (...)

[physics] [qo]

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Spectroscopy with frequency comb

Fri Apr 28 09:36:00 BST 2006

Phys. Rev. Lett. 96, 153001 (2006)
- Title: High Resolution Atomic Coherent Control via Spectral Phase Manipulation of an Optical Frequency Comb Authors: Matthew C. Stowe, Flavio C. Cruz, Adela Marian, and Jun Ye
- Abstract: We demonstrate high resolution coherent control of cold atomic rubidium utilizing spectral phase manipulation of a femtosecond optical frequency comb. Transient coherent accumulation is directly manifested by the enhancement of signal amplitude and spectral resolution via the pulse number. The combination of frequency comb technology and spectral phase manipulation enables coherent control techniques to enter a new regime with natural linewidth resolution.
- Comments: Uses phase stabilized optical frequency comb to perform coherent manipulation of Rb atoms. (...)

[physics] [qo]

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