2,931 research outputs found
Spin correlated interferometry for polarized and unpolarized photons on a beam splitter
Spin interferometry of the 4th order for independent polarized as well as
unpolarized photons arriving simultaneously at a beam splitter and exhibiting
spin correlation while leaving it, is formulated and discussed in the quantum
approach. Beam splitter is recognized as a source of genuine singlet photon
states. Also, typical nonclassical beating between photons taking part in the
interference of the 4th order is given a polarization dependent explanation.Comment: RevTeX, 19 pages, 1 ps figure, author web page at
http://m3k.grad.hr/pavici
Enhanced conversion efficiency for harmonic generation with double resonance
Conversion efficiency for cw harmonic generation is calculated for the situation in which both fundamental and harmonic waves are resonant. Compared with the situation of a singly resonant cavity at the fundamental, the doubly resonant geometry can lead to an increase of the effective nonlinear coefficient. High conversion efficiency can thus be achieved with nonlinear crystals of relatively low nonlinear coefficient. and with modest pump power for the fundamental input
Retraction of "Near-Deterministic Discrimination of All Bell States with Linear Optics," Phys. Rev. Lett. 107, 080403 (2011) and Erratum Phys. Rev. Lett. 107, 219901 (2011)
The original versions (1 and 2) of this paper paper contain a fatal error.
All my attempts to patch the error have failed. As a service to the community I
explain the error in some detail.Comment: The original paper (v. 1 and 2) was retracted from Phys. Rev. Lett.
107, 080403 (2011) and its Erratum Phys. Rev. Lett. 107. 219901 (2011
Mode-Locked Two-Photon States
The concept of mode locking in laser is applied to a two-photon state with
frequency entanglement. Cavity enhanced parametric down-conversion is found to
produce exactly such a state. The mode-locked two-photon state exhibits a
comb-like correlation function. An unbalanced Hong-Ou-Mandel type
interferometer is used to measure the correlation function. A revival of the
typical interference dip is observed. We will discuss schemes for engineering
of quantum states in time domain.Comment: 4 pages, 5 figure
85% efficiency for cw frequency doubling from 1.08 to 0.54 Ī¼m
Conversion efficiency of 85% has been achieved in cw second-harmonic generation from 1.08 to 0.54 Ī¼m with a potassium titanyl phosphate crystal inside an external ring cavity. An absolute comparison between the experimental data and a simple theory is made and shows good agreement
Entanglement and Superdense Coding with Linear Optics
We discuss a scheme for a full superdense coding of entangled photon states
employing only linear-optics elements. By using the mixed basis consisting of
four states that are unambiguously distinguishable by a standard and polarizing
beam splitters we can deterministically transfer four messages by manipulating
just one of the two entangled photons. The sender achieves the determinism of
the transfer either by giving up the control over 50% of sent messages
(although known to her) or by discarding 33% of incoming photons.Comment: 8 pages, 1 figur
Security improvement of using modified coherent state for quantum cryptography
Weak coherent states as a photon source for quantum cryptography have limit
in secure data rate and transmission distance because of the presence of
multi-photon events and loss in transmission line. Two-photon events in a
coherent state can be taken out by a two-photon interference scheme. We
investigate the security issue of utilizing this modified coherent state in
quantum cryptography. A 4 dB improvement in secure data rate or a nearly
two-fold increase in transmission distance over the coherent state are found.
With a recently proposed and improved encoding strategy, further improvement is
possible.Comment: 5 pages, 2 figures, to appear in Physical Review
Retrieval of phase memory in two independent atomic ensembles by Raman process
In spontaneous Raman process in atomic cell at high gain, both the Stokes
field and the accompanying collective atomic excitation (atomic spin wave) are
coherent. We find that, due to the spontaneous nature of the process, the
phases of the Stokes field and the atomic spin wave change randomly from one
realization to another but are anti-correlated. The phases of the atomic
ensembles are read out via another Raman process at a later time, thus
realizing phase memory in atoms. The observation of phase correlation between
the Stokes field and the collective atomic excitations is an important step
towards macroscopic EPR-type entanglement of continuous variables between light
and atoms
Data Descriptor: China CO2 emission accounts 1997-2015
China is the worldās top energy consumer and CO2 emitter, accounting for 30% of global emissions. Compiling an accurate accounting of Chinaās CO2 emissions is the first step in implementing reduction policies. However, no annual, officially published emissions data exist for China. The current emissions estimated by academic institutes and scholars exhibit great discrepancies. The gap between the different emissions estimates is approximately equal to the total emissions of the Russian Federation (the 4th highest emitter globally) in 2011. In this study, we constructed the time-series of CO2 emission inventories for China and its 30 provinces. We followed the Intergovernmental Panel on Climate Change (IPCC) emissions accounting method with a territorial administrative scope. The inventories include energy-related emissions (17 fossil fuels in 47 sectors) and process-related emissions (cement production). The first version of our dataset presents emission inventories from 1997 to 2015. We will update the dataset annually. The uniformly formatted emission inventories provide data support for further emission-related research as well as emissions reduction policy-making in China
Quantum amplification and quantum optical tapping with squeezed states and correlated quantum states
Quantum fluctuations in a nondegenerate optical parametric amplifier (NOPA) are investigated experimentally with a squeezed state coupled into the internal idler mode of the NOPA. Reductions of the inherent quantum noise of the amplifier are observed with a minimum noise level 0.7 dB below the usual noise level of the amplifier with its idler mode in a vacuum state. With two correlated quantum fields as the amplifier's inputs and proper adjustment of the gain of the amplifier, it is shown that the amplifier's intrinsic quantum noise can be completely suppressed so that noise-free amplification is achieved. It is also shown that the NOPA, when coupled to either a squeezed state or a nonclassically correlated state, can realize quantum tapping of optical information
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