共查询到20条相似文献,搜索用时 765 毫秒
1.
L. Vernac M. Pinard V. Josse E. Giacobino 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):129-135
Using a quantum theory for an ensemble of two- or three-level atoms driven by electromagnetic fields in an optical cavity,
we show that the various spins associated with the atomic ensemble can be squeezed. Two kinds of squeezing are obtained: on
the one hand self-spin squeezing when the input fields are coherent ones and the atomic ensemble exhibits a large non-linearity;
on the other hand squeezing transfer when one of the incoming fields is squeezed.
Received 14 August 2001 and Received in final form 7 November 2001 相似文献
2.
T. Aichele A.I. Lvovsky S. Schiller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):237-245
A detailed theoretical analysis of the spatiotemporal mode of a single photon prepared via conditional measurements on a photon pair generated in the process of parametric down-conversion is presented. The maximum
efficiency of coupling the photon into a transform-limited classical optical mode is calculated and ways for its optimization
are determined. An experimentally feasible technique of generating the optimally matching classical mode is proposed. The
theory is applied to a recent experiment on pulsed homodyne tomography of the single-photon Fock state [A.I. Lvovsky et al., Phys. Rev. Lett. 87, 050402 (2001)].
Received 16 July 2001 相似文献
3.
A. Andreoni M. Bondani G.M. D'Ariano M.G.A. Paris 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(3):415-421
We propose a novel scheme for the joint generation of two squeezed beams at arbitrary frequencies ω
1 and ω
2. The scheme consists of two successive steps, both involving nonlinear interactions in χ(2) crystals. The dynamics of the setup is analyzed both quantum mechanically and classically within the parametric approximation.
An experimental implementation involving the fundamental and the harmonics of a Nd:YAG laser pulse, and β-BaB
2
O
4 nonlinear crystals is suggested.
Received 17 May 2000 and Received in final form 9 October 2000 相似文献
4.
L. Vernac M. Pinard E. Giacobino 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):125-136
We show the equivalence between an ensemble of two-level atoms driven by a squeezed vacuum field, and a harmonic oscillator
coupled to a squeezed field. We give the conditions for optimal squeezing transfer from the field to the atomic ensemble.
We show that EPR-type correlations are created between the atomic ensemble and the incoming field.
Received 23 January 2001 相似文献
5.
A. Messina 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):379-383
A new conditional scheme for generating Bell states of two spatially separated high-Q cavities is reported. Our method is based on the passage of one atom only through the two cavities. A distinctive feature
of our treatment is that it incorporates from the very beginning the unavoidable presence of fluctuations in the atom-cavity
interaction times. The possibility of successfully implementing our proposal against cavity losses and atomic spontaneous
decay is carefully discussed.
Received 31 July 2001 and Received in final form 9 October 2001 相似文献
6.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):423-431
Several examples of photon entanglement are studied in the Q representation of quantum optics. In particular, the entangled states produced in parametric downconversion are studied in
detail, and we determine the conditions for the violation of Bell's inequality. Our approach shows that photon entanglement
is related to the existence of correlations between the quantum fluctuations of the electromagnetic field associated to different
modes.
Received 10 August 2002 / Received in final form 7 November 2002 Published online 4 February 2003 相似文献
7.
E. Brambilla A. Gatti L.A. Lugiato M.I. Kolobov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(1):127-135
We analyze theoretically spatial structures appearing in the far diffraction zone of the electromagnetic field emitted in
the cavityless parametric down-conversion. We investigate in detail the spatial correlation functions of intensity and demonstrate
the existence of strong quantum correlations between the regions of the far field symmetrical with respect to the optical
axis. Our simplified model allows us to obtain analytical results for some limiting cases. We demonstrate that in the limit
of small diffraction and ideal quantum efficiency of photodetection the noise reduction in the photocurrent difference between
symmetrical regions in the far diffraction field becomes complete at zero frequency of photocurrent fluctuations.
Received 5 February 2001 and Received in final form 11 April 2001 相似文献
8.
X.-M. Hu J.-S. Peng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):291-299
On the basis of the nondegenerate quantum-beat laser model, we introduce a coherent field which drives the transition between the upper lasing level and an
auxiliary level. We demonstrate that such a four-level system can produce squeezed two-mode laser without and with inversion.
When the laser is operated well above threshold, the intensity fluctuation in the average mode is reduced below the shot noise
with an optimum Mandel parameter Q=- 1/2. At the same time, the noises in the relative amplitude and the relative phase drop to their vaccum noise levels. Furthermore,
regardless of inversion, noninversion, and transition between inversion and noninversion, the optimum Mandel Q parameter of Q=- 1/2 is retained when the system operates well above threshold. A simple physical explanation of the squeezing mechanism
for two-mode squeezing is given.
Received: 22 December 1997 / Revised: 25 March 1998 / Accepted: 9 September 1998 相似文献
9.
M. Sebawe Abdalla F.A.A. El-Orany J. Peřina 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(3):423-438
In the present paper we introduce a new squeeze operator, which is related to the time-dependent evolution operator for Hamiltonian
representing mutual interaction between three different modes. Squeezing phenomenon as well as the variances of the photon-number
sum and difference are considered. Moreover, Glauber second-order correlation function is discussed, besides the quasiprobability
distribution function and phase distribution for different states. The joint photon-number distribution is also reported.
Received 29 March 2000 and Received in final form 20 September 2000 相似文献
10.
S.M. Barnett C. Fabre A. Maıtre 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):513-519
We compare two high sensitivity techniques which are used to measure very small displacements of physical objects by optical
techniques: the interferometric devices, measuring longitudinal phase shifts, and the devices used to monitor transverse displacement
of light beams. We detail the differences and the similarities for the quantum limits on the resolution of both systems. In
both cases squeezed light can be used to resolve beyond the standard quantum limit and number correlated states allow us to
reach the “Heisenberg” limit.
Received 12 September 2002 Published online 21 January 2003 相似文献
11.
S. Mancini D. Vitali V. Giovannetti P. Tombesi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):417-422
We show that the optomechanical coupling between an optical cavity mode and two movable cavity mirrors is able to entangle
two different macroscopic oscillation modes of the mirrors. This continuous variable entanglement is maintained by the light
bouncing between the mirrors and is robust against thermal noise. In fact, it could be experimentally demonstrated using present
technology.
Received 2 September 2002 / Received in final form 10 October 2002 Published online 7 January 2003 相似文献
12.
R. Zambrini S.M. Barnett P. Colet M. San Miguel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):461-471
We employ the Q-representation to study the non-classical correlations that are present from below to above-threshold in the degenerate optical
parametric oscillator. Our study shows that such correlations are present just above threshold, in the regime in which stripe
patterns are formed, but that they also persist further above threshold in the presence of spatially disordered structures.
Received: 13 September 2002 / Received in final form: 11 November 2002 Published online 28 January 2003 相似文献
13.
X. Luo S. Zhu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):111-117
A two-dimensional decoupling theory is developed when colored noise is included in a nonlinear dynamical system. By a functional
analysis, the colored noise is transformed to an effective noise that includes the noise correlation time, the mean dynamical
variable, and the original noise strength. When the two-dimensional decoupling theory is applied to single-mode and two-mode
dye laser systems, the mean, variance, and effective eigenvalue of laser intensity are calculated. Excellent agreement between
theoretical analysis, numerical simulations, and experimental measurements are obtained. It is seen that the increase of noise
correlation time can reduce the fluctuations in the laser system. It is also shown that there is relatively large fluctuation
in the phase when the laser undergoes from thermal light to coherent light when the theory is applied to a single mode dye
laser.
Received 20 August 2001 and Received in final form 4 December 2001 相似文献
14.
Room temperature stable single-photon source 总被引:2,自引:0,他引:2
A. Beveratos S. Kühn R. Brouri T. Gacoin J.-P. Poizat P. Grangier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):191-196
We report on the realization of a stable solid state room temperature source for single photons. It is based on the fluorescence
of a single nitrogen-vacancy (NV) color center in a diamond nanocrystal. Antibunching has been observed in the fluorescence
light under both continuous and pulsed excitation. Our source delivers 2×104 s-1 single-photon pulses at an excitation repetition rate of 10 MHz. The number of two-photon pulses is reduced by a factor of
five compared to strongly attenuated coherent sources.
Received 1st August 2001 and Received in final form 2 October 2001 相似文献
15.
Faisal A.A. El-Orany J. Peřina V. Peřinová M. Sebawe Abdalla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):141-156
The evolution of the Schr?dinger-cat states in a dissipative parametric amplifier is examined. The main tool in the analysis
is the normally ordered characteristic function. Squeezing, photon-number distribution and reduced factorial moments are discussed
for the single- and compound-mode cases. Also the single-mode Wigner function is demonstrated. In addition to the decoherence
resulting from the interaction with the environment (damped case) there are two sources which can cause such decoherence in
the system even if it is completely isolated: these are the decay of the pump and the relative phases of the initial cat states.
Furthermore, for the damped case there are two regimes, which are underdamped and overdamped. In the first (second) regime
the signal mode or the idler mode “collapses" to a statistical mixture (thermal field).
Received 25 September 2001 / Received in final form 30 May 2002 Published online 13 December 2002
RID="a"
ID="a"e-mail: sebaweh@awalnet.net.sa
RID="b"
ID="b"Joint Laboratory of Optics of Palacky University and Institute of Physics, Academy of Sciences of the Czech Republic,
17. listopadu 50, 772 07 Olomouc, Czech Republic. 相似文献
16.
J.-M. Courty A. Heidmann M. Pinard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(3):399-408
Thermal noise of a mirror can be reduced by cold damping. The displacement is measured with a high-finesse cavity and controlled
with the radiation pressure of a modulated light beam. We establish the general quantum limits of noise in cold damping mechanisms
and we show that the optomechanical system allows to reach these limits. Displacement noise can be arbitrarily reduced in
a narrow frequency band. In a wide-band analysis we show that thermal fluctuations are reduced as with classical damping whereas
quantum zero-point fluctuations are left unchanged. The only limit of cold damping is then due to zero-point energy of the
mirror.
Received 1st August 2001 and Received in final form 12 October 2001 相似文献
17.
F. Grosshans P. Grangier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):119-125
Homodyne detection can be used to perform measurements on various quantum states of the light, such as conditional single
photon states produced by parametric fluorescence processes. In the pulsed regime, the time and frequency overlap between
the single photon wave packet and the local oscillator field plays a crucial role. We show in this paper that this overlap
can be characterized by an effective quantum efficiency, which is explicitly calculated in various situations of experimental
interest.
Received 27 July 2000 and Received in final form 29 November 2000 相似文献
18.
M. Pelton C. Santori G.S. Solomon O. Benson Y. Yamamoto 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):179-190
Current quantum cryptography systems are limited by the attenuated coherent pulses they use as light sources: a security loophole
is opened up by the possibility of multiple-photon pulses. By replacing the source with a single-photon emitter, transmission
rates of secure information can be improved. We have investigated the use of single self-assembled InAs/GaAs quantum dots
as such single-photon sources, and have seen a tenfold reduction in the multi-photon probability as compared to Poissonian
pulses. An extension of our experiment should also allow for the generation of triggered, polarization-entangled photon pairs.
The utility of these light sources is currently limited by the low efficiency with which photons are collected. However, by
fabricating an optical microcavity containing a single quantum dot, the spontaneous emission rate into a single mode can be
enhanced. Using this method, we have seen 78% coupling of single-dot radiation into a single cavity resonance. The enhanced
spontaneous decay should also allow for higher photon pulse rates, up to about 3 GHz.
Received 8 July 2001 and Received in final form 25 August 2001 相似文献
19.
K.-H. Song W.-J. Zhang G.-C. Guo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):267-269
A scheme for preparing entangled coherent states is presented. It is based on the atom-cavity-mode Raman interaction. We also
generalize this method for generating multi-mode entangled coherent states. Finally, our experimental feasibility is discussed.
Received 15 September 2001 and Received in final form 15 November 2001 相似文献
20.
Zhao-xian Yu Zhi-yong Jiao 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(2):277-280
We have studied quantum effects in the interaction of the exciton with a leaky quasi-mode cavity field. When the exciton is
initially prepared in a superposition state which exhibits holes in its photon-number distribution, whereas the cavity field
initially is in the vacuum state, it is found that there exists an energy exchange between the exciton and the cavity field.
The exciton and the cavity field may exhibit sub-Poissonian distributions and quadrature squeezings. It is shown that there
does not exist a violation of the Cauchy-Schwartz inequality, which means that the correlation between the exciton and the
cavity field is classical.
Received 25 November 2000 and Received in final form 1st January 2001 相似文献