1,960 research outputs found
Experimental generation of four-mode continuous-variable cluster states
Continuous-variable Gaussian cluster states are a potential resource for
universal quantum computation. They can be efficiently and unconditionally
built from sources of squeezed light using beam splitters. Here we report on
the generation of three different kinds of continuous-variable four-mode
cluster states. In our realization, the resulting cluster-type correlations are
such that no corrections other than simple phase-space displacements would be
needed when quantum information propagates through these states. At the same
time, the inevitable imperfections from the finitely squeezed resource states
and from additional thermal noise are minimized, as no antisqueezing components
are left in the cluster states.Comment: 5 pages, 4 figure
Dissipation-induced pure Gaussian state
This paper provides some necessary and sufficient conditions for a
generalMarkovian Gaussian master equation to have a unique pure steady state.
The conditions are described by simple matrix equations; thus the so-called
environment engineering problem for pure-Gaussian-state preparation can be
straightforwardly dealt with in the linear algebraic framework. In fact, based
on one of those conditions, for an arbitrary given pure Gaussian state,we
obtain a complete parametrization of the Gaussian master equation having that
state as a unique steady state; this leads to a systematic procedure for
engineering a desired dissipative system.We demonstrate some examples including
Gaussian cluster states.Comment: 8 page
Time domain Einstein-Podolsky-Rosen correlation
We experimentally demonstrate creation and characterization of
Einstein-Podolsky-Rosen (EPR) correlation between optical beams in the time
domain. The correlated beams are created with two independent continuous-wave
optical parametric oscillators and a half beam splitter. We define temporal
modes using a square temporal filter with duration and make time-resolved
measurement on the generated state. We observe the correlations between the
relevant conjugate variables in time domain which correspond to the EPR
correlation. Our scheme is extendable to continuous variable quantum
teleportation of a non-Gaussian state defined in the time domain such as a
Schr\"odinger cat-like state.Comment: 4 pages, 4 figure
Teleportation of Nonclassical Wave Packets of light
We report on the experimental quantum teleportation of strongly nonclassical
wave packets of light. To perform this full quantum operation while preserving
and retrieving the fragile non-classicality of the input state, we have
developed a broadband, zero-dispersion teleportation apparatus that works in
conjunction with time-resolved state preparation equipment. Our approach brings
within experimental reach a whole new set of hybrid protocols involving
discrete- and continuous-variable techniques in quantum information processing
for optical sciences
Cavity QED with high-Q whispering gallery modes
We report measurements of cavity-QED effects for the radiative coupling of atoms in a dilute vapor to the external evanescent field of a whispering-gallery mode (WGM) in a fused silica microsphere. The high Q (5 x 10^(7)), small mode volume (10^(-8) cm^(3)), and unusual symmetry of the microcavity evanescent field enable velocity-selective interactions between fields with photon number of order unity in the WGM and (N) over bar(T) similar to 1 atoms in the surrounding vapor
Sequential Quantum Teleportation of Optical Coherent States
We demonstrate a sequence of two quantum teleportations of optical coherent
states, combining two high-fidelity teleporters for continuous variables. In
our experiment, the individual teleportation fidelities are evaluated as F_1 =
0.70 \pm 0.02 and F_2 = 0.75 \pm 0.02, while the fidelity between the input and
the sequentially teleported states is determined as F^{(2)} = 0.57 \pm 0.02.
This still exceeds the optimal fidelity of one half for classical teleportation
of arbitrary coherent states and almost attains the value of the first
(unsequential) quantum teleportation experiment with optical coherent states.Comment: 5page, 4figure
The Quantum State of an Ideal Propagating Laser Field
We give a quantum information-theoretic description of an ideal propagating
CW laser field and reinterpret typical quantum-optical experiments in light of
this. In particular we show that contrary to recent claims [T. Rudolph and B.
C. Sanders, Phys. Rev. Lett. 87, 077903 (2001)], a conventional laser can be
used for quantum teleportation with continuous variables and for generating
continuous-variable entanglement. Optical coherence is not required, but phase
coherence is. We also show that coherent states play a priveleged role in the
description of laser light.Comment: 4 pages RevTeX, to appear in PRL. For an extended version see
quant-ph/011115
The Subaru/XMM-Newton Deep Survey (SXDS) -VII. Clustering Segregation with Ultraviolet and Optical Luminosities of Lyman-Break Galaxies at z~3
We investigate clustering properties of Lyman-break galaxies (LBGs) at z~3
based on deep multi-waveband imaging data from optical to near-infrared
wavelengths in the Subaru/XMM-Newton Deep Field. The LBGs are selected by U-V
and V-z' colors in one contiguous area of 561 arcmin^2 down to z'=25.5. We
study the dependence of the clustering strength on rest-frame UV and optical
magnitudes, which can be indicators of star formation rate and stellar mass,
respectively. The correlation length is found to be a strong function of both
UV and optical magnitudes with brighter galaxies being more clustered than
faint ones in both cases. Furthermore, the correlation length is dependent on a
combination of UV and optical magnitudes in the sense that galaxies bright in
optical magnitude have large correlation lengths irrespective of UV magnitude,
while galaxies faint in optical magnitude have correlation lengths decreasing
with decreasing UV brightness. These results suggest that galaxies with large
stellar masses always belong to massive halos in which they can have various
star formation rates, while galaxies with small stellar masses reside in less
massive halos only if they have low star formation rates. There appears to be
an upper limit to the stellar mass and the star formation rate which is
determined by the mass of hosting dark halos.Comment: 16 pages, 15 figures, accepted for publication in Ap
Discrete formulation of teleportation of continuous variables
Teleportation of continuous variables can be described in two different ways,
one in terms of Wigner functions, the other in terms of discrete basis states.
The latter formulation provides the connection between the theory of
teleportation of continuous degrees of freedom of a light field and the
standard description of teleportation of discrete variables.Comment: Important reference included: L. Vaidman, Phys Rev A 49, 1473 (1994
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