238 research outputs found
Raman spectroscopy of a single ion coupled to a high-finesse cavity
We describe an ion-based cavity-QED system in which the internal dynamics of
an atom is coupled to the modes of an optical cavity by vacuum-stimulated Raman
transitions. We observe Raman spectra for different excitation polarizations
and find quantitative agreement with theoretical simulations. Residual motion
of the ion introduces motional sidebands in the Raman spectrum and leads to ion
delocalization. The system offers prospects for cavity-assisted
resolved-sideband ground-state cooling and coherent manipulation of ions and
photons.Comment: 8 pages, 6 figure
Quantum Transduction of Telecommunications-band Single Photons from a Quantum Dot by Frequency Upconversion
The ability to transduce non-classical states of light from one wavelength to
another is a requirement for integrating disparate quantum systems that take
advantage of telecommunications-band photons for optical fiber transmission of
quantum information and near-visible, stationary systems for manipulation and
storage. In addition, transducing a single-photon source at 1.3 {\mu}m to
visible wavelengths for detection would be integral to linear optical quantum
computation due to the challenges of detection in the near-infrared. Recently,
transduction at single-photon power levels has been accomplished through
frequency upconversion, but it has yet to be demonstrated for a true
single-photon source. Here, we transduce the triggered single-photon emission
of a semiconductor quantum dot at 1.3 {\mu}m to 710 nm with a total detection
(internal conversion) efficiency of 21% (75%). We demonstrate that the 710 nm
signal maintains the quantum character of the 1.3 {\mu}m signal, yielding a
photon anti-bunched second-order intensity correlation, g^(2)(t), that shows
the optical field is composed of single photons with g^(2)(0) = 0.165 < 0.5.Comment: 7 pages, 4 figure
A solid state light-matter interface at the single photon level
Coherent and reversible mapping of quantum information between light and
matter is an important experimental challenge in quantum information science.
In particular, it is a decisive milestone for the implementation of quantum
networks and quantum repeaters. So far, quantum interfaces between light and
atoms have been demonstrated with atomic gases, and with single trapped atoms
in cavities. Here we demonstrate the coherent and reversible mapping of a light
field with less than one photon per pulse onto an ensemble of 10 millions atoms
naturally trapped in a solid. This is achieved by coherently absorbing the
light field in a suitably prepared solid state atomic medium. The state of the
light is mapped onto collective atomic excitations on an optical transition and
stored for a pre-programmed time up of to 1 mu s before being released in a
well defined spatio-temporal mode as a result of a collective interference. The
coherence of the process is verified by performing an interference experiment
with two stored weak pulses with a variable phase relation. Visibilities of
more than 95% are obtained, which demonstrates the high coherence of the
mapping process at the single photon level. In addition, we show experimentally
that our interface allows one to store and retrieve light fields in multiple
temporal modes. Our results represent the first observation of collective
enhancement at the single photon level in a solid and open the way to multimode
solid state quantum memories as a promising alternative to atomic gases.Comment: 5 pages, 5 figures, version submitted on June 27 200
State Transfer Between a Mechanical Oscillator and Microwave Fields in the Quantum Regime
Recently, macroscopic mechanical oscillators have been coaxed into a regime
of quantum behavior, by direct refrigeration [1] or a combination of
refrigeration and laser-like cooling [2, 3]. This exciting result has
encouraged notions that mechanical oscillators may perform useful functions in
the processing of quantum information with superconducting circuits [1, 4-7],
either by serving as a quantum memory for the ephemeral state of a microwave
field or by providing a quantum interface between otherwise incompatible
systems [8, 9]. As yet, the transfer of an itinerant state or propagating mode
of a microwave field to and from a mechanical oscillator has not been
demonstrated owing to the inability to agilely turn on and off the interaction
between microwave electricity and mechanical motion. Here we demonstrate that
the state of an itinerant microwave field can be coherently transferred into,
stored in, and retrieved from a mechanical oscillator with amplitudes at the
single quanta level. Crucially, the time to capture and to retrieve the
microwave state is shorter than the quantum state lifetime of the mechanical
oscillator. In this quantum regime, the mechanical oscillator can both store
and transduce quantum information
Cavity-QED tests of representations of canonical commutation relations employed in field quantization
Various aspects of dissipative and nondissipative decoherence of Rabi
oscillations are discussed in the context of field quantization in alternative
representations of CCR. Theory is confronted with experiment, and a possibility
of more conclusive tests is analyzed.Comment: Discussion of dissipative and nondissipative decoherence is included.
Theory is now consistent with the existing data and predictions for new
experiments are more reliabl
Exact results on decoherence and entanglement in a system of N driven atoms and a dissipative cavity mode
We solve the dynamics of an open quantum system where N strongly driven
two-level atoms are equally coupled on resonance to a dissipative cavity mode.
Analytical results are derived on decoherence, entanglement, purity, atomic
correlations and cavity field mean photon number. We predict decoherence-free
subspaces for the whole system and the N-qubit subsystem, the monitoring of
quantum coherence and purity decay by atomic populations measurements, the
conditional generation of atomic multi-partite entangled states and of cavity
cat-like states. We show that the dynamics of atoms prepared in states
invariant under permutation of any two components remains restricted within the
subspace spanned by the completely symmetric Dicke states. We discuss examples
and applications in the cases N=3,4.Comment: 7 pages, 4 figures, accepted in EPJ
Cavity Induced Interfacing of Atoms and Light
This chapter introduces cavity-based light-matter quantum interfaces, with a
single atom or ion in strong coupling to a high-finesse optical cavity. We
discuss the deterministic generation of indistinguishable single photons from
these systems; the atom-photon entanglement intractably linked to this process;
and the information encoding using spatio-temporal modes within these photons.
Furthermore, we show how to establish a time-reversal of the aforementioned
emission process to use a coupled atom-cavity system as a quantum memory. Along
the line, we also discuss the performance and characterisation of cavity
photons in elementary linear-optics arrangements with single beam splitters for
quantum-homodyne measurements.Comment: to appear as a book chapter in a compilation "Engineering the
Atom-Photon Interaction" published by Springer in 2015, edited by A.
Predojevic and M. W. Mitchel
Theory and Applications of Non-Relativistic and Relativistic Turbulent Reconnection
Realistic astrophysical environments are turbulent due to the extremely high
Reynolds numbers. Therefore, the theories of reconnection intended for
describing astrophysical reconnection should not ignore the effects of
turbulence on magnetic reconnection. Turbulence is known to change the nature
of many physical processes dramatically and in this review we claim that
magnetic reconnection is not an exception. We stress that not only
astrophysical turbulence is ubiquitous, but also magnetic reconnection itself
induces turbulence. Thus turbulence must be accounted for in any realistic
astrophysical reconnection setup. We argue that due to the similarities of MHD
turbulence in relativistic and non-relativistic cases the theory of magnetic
reconnection developed for the non-relativistic case can be extended to the
relativistic case and we provide numerical simulations that support this
conjecture. We also provide quantitative comparisons of the theoretical
predictions and results of numerical experiments, including the situations when
turbulent reconnection is self-driven, i.e. the turbulence in the system is
generated by the reconnection process itself. We show how turbulent
reconnection entails the violation of magnetic flux freezing, the conclusion
that has really far reaching consequences for many realistically turbulent
astrophysical environments. In addition, we consider observational testing of
turbulent reconnection as well as numerous implications of the theory. The
former includes the Sun and solar wind reconnection, while the latter include
the process of reconnection diffusion induced by turbulent reconnection, the
acceleration of energetic particles, bursts of turbulent reconnection related
to black hole sources as well as gamma ray bursts. Finally, we explain why
turbulent reconnection cannot be explained by turbulent resistivity or derived
through the mean field approach.Comment: 66 pages, 24 figures, a chapter of the book "Magnetic Reconnection -
Concepts and Applications", editors W. Gonzalez, E. N. Parke
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