共查询到20条相似文献,搜索用时 15 毫秒
1.
Prakash Gupta 《Optik》2010,121(16):1507-1510
The possibility of observing higher order squeezing in different optical processes, such as six-wave mixing and four-wave mixing, has been studied and it is shown that amplitude squared squeezing appears in all these cases. It is also shown that the minimum total noise (Tmin) of a higher order squeezed state, which is a measure of the total fluctuations in the field amplitude, always increases with the increase in depth of nonclassicality associated with higher order squeezing. Thus we can use Tmin as an indirect measure of higher order squeezing. 相似文献
2.
Eyob Alebachew 《Optics Communications》2007,280(1):133-141
We consider a non-degenerate three-level cascade laser coupled to a two-mode squeezed vacuum reservoir via the lossy single-port mirror. Applying the pertinent master equation, we analyze the effects of the injected squeezed light on the quadrature squeezing, entanglement and normalized intensity difference fluctuations. We show that the injected squeezed light considerably enhances the degree of squeezing and entanglement in the two-mode light for certain initial conditions. Moreover, the injected squeezed light increases the mean photon number where the squeezing and entanglement is significant. We also show that the presence of the injected squeezed light greatly reduces the noise in the intensity difference. 相似文献
3.
We study the photon counting noise in optical interferometers used for gravitational wave detection. In order to reduce quantum
noise a squeezed vacuum state is injected into the usually unused input port. Here, we specifically investigate the so-called
“dark port case,” when the beam splitter is oriented close to 90° to the incoming laser beam, such that nearly all photons
go to one output port of the interferometer, and only a small fraction of photons is seen in the other port (“dark port”).
For this case it had been suggested that signal amplification is possible without concurrent noise amplification [R. Barak
and Y. Ben-Aryeh, J. Opt. Soc. Am. B 25, 361 (2008)]. We show that by injection of a squeezed vacuum state into the second input port, counting noise is reduced
for large values of the squeezing factor, however the signal is not amplified. Signal strength only depends on the intensity
of the laser beam. 相似文献
4.
The Squeezing and sub-poissonian photon statistics of an optical field are a purely quantum mechanical phenomenon and has
been accepted as means of achieving noise below the quantum shot-noise limit. The effect of higher-order squeezing and sub-poissonian
nature of an optical field in coherent anti-Stokes Raman scattering (CARS) and coherent anti-Stokes hyper Raman scattering
(CAHRS) are investigated under short-time approximation. The coupled Heisenberg equations of motion involving real and imaginary
parts of the quadrature operators are established and solved under short-time scale. The dependence of squeezing on the number
of photons is also investigated. It is also shown that higher-order squeezing allows a much larger fractional noise reduction
than lower-order squeezing. The occurrence of amplitude squeezing effects of the radiation field in the fundamental mode is
investigated in both the processes. The present work shows that squeezing is greater in CAHRS than the corresponding squeezing
in CARS. It is also shown that squeezing is greater in stimulated process than corresponding squeezing in spontaneous interaction.
The conditions for obtaining maximum and minimum squeezing are obtained. The photon statistics of the pump mode in the processes
has also been investigated and found to be sub-poissonian in nature. 相似文献
5.
J. Milanovic J. Heersink Ch. Marquardt A. Huck U. L. Andersen G. Leuchs 《Laser Physics》2007,17(4):559-566
We report on the generation of polarization squeezing by employing intense, ultrashort light pulses in a single pass method
in photonic crystal fibers. We investigated the squeezing behavior near the zero-dispersion wavelength and in the anomalous
dispersion regime by using two distinct fibers. We observed a maximal squeezing at 810 nm of −3.3 ± 0.3 dB with an excess
noise of +16.8 ± 0.3 dB in the anomalous regime. Correcting for linear and interference losses between the polarization modes,
this corresponds to −6 ± 1 dB. The ratio of squeezing to excess noise indicates the creation of a much purer state; this ratio
indeed lies an order of magnitude below those squeezing experiments that exploit traditional fibers [1]. We attribute this
increased state of purity to increased effective nonlinearity and to the reduction of scattering on acoustic modes in the
fiber.
Original Text ? Astro, Ltd., 2007. 相似文献
6.
McKenzie K Grosse N Bowen WP Whitcomb SE Gray MB McClelland DE Lam PK 《Physical review letters》2004,93(16):161105
We demonstrate the generation of broadband continuous-wave optical squeezing from 280 Hz-100 kHz using a below-threshold optical parametric oscillator (OPO). The squeezed state phase was controlled using a noise locking technique. We show that low frequency noise sources, such as seed noise, pump noise, and detuning fluctuations, present in optical parametric amplifiers, have negligible effect on squeezing produced by a below-threshold OPO. This low frequency squeezing is ideal for improving the sensitivity of audio frequency measuring devices such as gravitational-wave detectors. 相似文献
7.
van Der Lee AM van Druten NJ van Exter MP Woerdman JP Poizat JP Grangier P 《Physical review letters》2000,85(22):4711-4714
We investigate the impact of the Petermann-excess-noise factor K>/=1 on the possibility of intensity noise squeezing of laser light below the standard quantum limit. Using an N-mode model, we show that squeezing is limited to a floor level of 2(K-1) times the shot noise limit. Thus, even a modest Petermann factor significantly impedes squeezing, which becomes impossible when K>/=1.5. This appears as a serious limitation for obtaining sub-shot-noise light from practical semiconductor lasers. We present experimental evidence for our theory. 相似文献
8.
Scattering of charged particles is accompanied by the emission of soft photons. Handel's theory of 1/f noise, based on the infrared quasi-divergent coupling of the system to the electromagnetic field, indicates that the current associated with a beam of scattered particles will exhibit 1/f noise. His derivation is valid in a vacuum. Here we extend his results and obtain the fluctuation spectrum for the fluctuations in cross-section and for the scattering rates w kk′ in k-space, using the Born approximation. Next we consider mobility fluctuations due to these scattering rates, employing the relaxation time solutions of the Boltzmann transport equation, valid in non-degenerate semiconductors. Explicit results are obtained for the mobility-fluctuation noise caused by ionized impurity scattering, acoustic phonon scattering, optical phonon scattering, polar optical phonon scattering, and intervalley scattering. We derive Hooge's law, and the Hooge parameters for the above-mentioned processes are obtained in detail. This is then applied to n-type silicon and n-type gallium arsenide; the overall Hooge parameter, which is a weighted average of the partial α-parameters, is computed as a function of temperature and compared with experiment. For silicon, good agreement is obtained with available data. As a byproduct we also find the mobilities as function of temperature for these materials. Excellent agreement with the well-known experimental data is observed. We still note that this is the first theoretical derivation of Hooge's law and that the magnitude of the noise is obtained in detail without adjustable parameters. We believe that quantum 1/f noise gives the limiting value of 1/f noise that can be observed. 相似文献
9.
P. Kürz R. Paschotta K. Fiedler A. Sizmann G. Leuchs J. Mlynek 《Applied physics. B, Lasers and optics》1992,55(3):216-225
We have measured the intensity fluctuations of the second-harmonic mode generated in a MgO:LiNbO3 external monolithic cavity pumped by a Nd:YAG laser. The cavity has mirror coatings for both the fundamental and the second-harmonic mode. We scan the cavity using the electro-optic effect of the crystal and observe that the second-harmonic beam of 2 mW exhibits a quantum noise reduction of 40(±5)%. In addition, we report on the active frequency stabilization of the monolithic device used in our squeezing experiments. Several fast tuning parameters such as the electro-optic effect, the photo-elastic effect, and the laser frequency have been investigated. With these tuning parameters the monolithic resonator can be locked on double-resonance at the phase-matching temperature, which is a prerequisit for observing squeezing in a cw-regime. 相似文献
10.
S. Banerjee R. Srikanth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):335-344
We study the geometric phase of an open two-level quantum
system under the influence of a squeezed, thermal environment for both
non-dissipative as well as dissipative system-environment
interactions. In the non-dissipative case, squeezing is found to have
a similar influence as temperature, of suppressing geometric phase,
while in the dissipative case, squeezing tends to counteract the
suppressive influence of temperature in certain regimes. Thus, an
interesting feature that emerges from our work is the contrast in the
interplay between squeezing and thermal effects in non-dissipative and
dissipative interactions. This can be useful for the practical
implementation of geometric quantum information processing. By
interpreting the open quantum effects as noisy channels, we make the
connection between geometric phase and quantum noise processes
familiar from quantum information theory. 相似文献
11.
We describe a new approach to spin squeezing based on a double-pass Faraday interaction between an optical probe and an optically dense atomic sample. A quantum eraser is used to remove residual spin-probe entanglement, thereby realizing a single-axis twisting unitary map on the collective spin. This interaction can be phase matched, resulting in exponential enhancement of squeezing as a function of optical density for times short compared to the decoherence time. In practice the scaling and peak squeezing depends on decoherence, technical loss, and noise. Including these imperfections, our model indicates that ~10 dB of squeezing should be achievable with laboratory parameters. 相似文献
12.
We report on a novel and efficient source of polarization squeezing that uses a single pass through an optical fiber. Using the fiber's two orthogonal polarization axes produces two identical squeezed beams. Combining these in a Stokes measurement generates polarization squeezing of up to 5.1 +/- 0.3 dB. Furthermore, this scheme enables us to directly measure, for both polarizations, the noise of any given quadrature. 相似文献
13.
Spatial quantum optics and quantum information based on the high order transverse mode are of importance for the super-resolution measurement beyond the quantum noise level. We demonstrated experimentally the transverse plane TEM01 Hermite-Gauss quantum squeezing. The squeezed TEM01 mode is generated in a degenerate optical parametric amplifier with the nonlinear crystal of periodically poled KTiOPO4. The level of 2.2-dB squeezing is measured using a spatial balance homodyne detection system. 相似文献
14.
The concept of squeezing of the electromagnetic field is investigated in fundamental mode in fifth harmonic generation with the approximation |gt|2?1, where g is coupling constant and t, the interaction time between waves during the process. It has been found that squeezing occurs in amplitude, amplitude-squared, amplitude-cubed and fourth-order amplitude states of the field for selective phase values of field amplitude of fundamental mode. The dependence of squeezing on the photon number has also been investigated and found to be sub-Poissonian in nature. The signal to noise ratio has been studied in different order. It is found that the signal to noise ratio is higher in lower order. 相似文献
15.
Measurement of intensity difference squeezing via non-degenerate four-wave mixing process in an atomic vapor 下载免费PDF全文
We report the measurement of the intensity difference squeezing via the non-degenerate four-wave mixing process in a rubidium atomic vapor medium. Two pairs of balanced detection systems are employed to measure the probe and the conjugate beams, respectively. It is convenient to get the quantum shot noise limit, the squeezed and the amplified noise power spectra. We also investigate the influence of the input extra quadrature amplitude noise of the probe beam. The influence of the extra noise can be minimized and the squeezing can be optimized under the proper parameter condition. We measure the -3.7-dB intensity difference squeezing when the probe beam has a 3-dB extra quadrature amplitude noise. This result is slightly smaller than -4.1 dB when the ideal coherent light (no extra noise) for the probe beam is used. 相似文献
16.
H. Prakash R. Kumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):475-481
Saito and Ueda [Phys. Rev. A 59, 3959 (1999)] studied atomic and
radiation squeezing in interaction of a single mode coherent state
of radiation with two excited two-level atoms, using
the Jaynes Cummings Hamiltonian. They considered α real and studied
squeezing of the Dicke operator Sx using the Kitagawa-Ueda criterion for
squeezing and coupling times less than or nearly equal to
. We obtain results to all orders in coupling time for
atoms, which are initially in (i) fully excited, (ii) superradiant or in
(iii) ground states and obtain more general results. We use our recently
reported criterion for atomic squeezing, of which the Kitagawa-Ueda
criterion is a special case, and obtain a much stronger (nearly 95%)
atomic squeezing than that (nearly 1.1%) reported by Saito and Ueda. 相似文献
17.
Kominis IK 《Physical review letters》2008,100(7):073002
Spin noise sets fundamental limits to the precision of measurements using spin-polarized atomic vapors, such as performed with sensitive atomic magnetometers. Spin squeezing offers the possibility to extend the measurement precision beyond the standard quantum limit of uncorrelated atoms. Contrary to current understanding, we show that, even in the presence of spin relaxation, spin squeezing can lead to a significant reduction of spin noise, and hence an increase in magnetometric sensitivity, for a long measurement time. This is the case when correlated spin relaxation due to binary alkali-atom collisions dominates independently acting decoherence processes, a situation realized in thermal high atom-density magnetometers and clocks. 相似文献
18.
本文研究高阻恒流源驱动的光发射二极管(LED)的输出光场的振幅噪声压缩与电,光量子效率,漏电流效应,泵浦残余噪声频率的关系,指出高阻恒流技术不仅使任意纵模产生振幅噪声压缩,而且由于仅在高阻恒流下各纵模间存在负量子相关,使得LED总输出光场的振幅噪声压缩加深。 相似文献
19.
20.
We examine the dynamics of a wave packet that initially corresponds to a coherent state in the model of a quantum rotator
excited by a periodic sequence of kicks. This model is the main model of quantum chaos and allows for a transition from regular
behavior to chaotic in the classical limit. By doing a numerical experiment we study the generation of squeezed states in
quasiclassical conditions and in a time interval when quantum-classical correspondence is well-defined. We find that the degree
of squeezing depends on the degree of local instability in the system and increases with the Chirikov classical stochasticity
parameter. We also discuss the dependence of the degree of squeezing on the initial width of the packet, the problem of stability
and observability of squeezed states in the transition to quantum chaos, and the dynamics of disintegration of wave packets
in quantum chaos.
Zh. éksp. Teor. Fiz. 113, 111–127 (January 1998) 相似文献