共查询到20条相似文献,搜索用时 31 毫秒
1.
We report the first experimental observation of quantum Talbot effects with single photons and entangled photon pairs. Both the first- and second-order quantum Talbot self-images are observed experimentally. They exhibit unique properties, which are different from those produced by coherent and incoherent classical light sources. In particular, our experiments show that the revival distance of two-photon Talbot imaging is twice the usual classical Talbot length and there is no net improvement in the resolution, due to the near-field effect of Fresnel diffraction, which is different from the case of previous proof-of-principle quantum lithography experiments in the far field. 相似文献
2.
Nonstationary Raman-Induced Kerr Effect in Liquids and Uniaxial Piezocrystals A nonstationary probe-beam method using Raman-induced Kerr effect (RIKE) for measuring the (transversal) relaxation constant Γ (= T) of piezo crystals and Raman active liquids is discussed. In isotropic media, in every scattering geometry phase matching is realised automatically for all frequencies and therefore, in contrast to coherent active Raman spectroscopy (CARS), the complete Raman spectrum is generated simultaneously and also its time behaviour can be studied. (In anisotropic crystals the appearing of RIKE will be drastically reduced.) For arbitrary correlation behaviour of the pump fields the nonstationary signal intensity vanishes exponentially with the effective vibration damping constant and with the delay-time of the testpulse. The dependence of the signal on the characteristic interaction length between the pulses (LS), on the phase modulation times τL,S, and on the probe length L are studied. The analogies between the methods of active Raman spectroscopy (ARS), RIKE, and induced two-photon-emission-experiments will be illustrated. 相似文献
3.
J. Große 《Fortschritte der Physik》2008,56(3):183-301
4.
To investigate how quantum effects might modify special relativity, we will study a Lorentz transformation between classical and quantum reference frames and express it in terms of the four-dimensional (4D) momentum of the quantum reference frame. The transition from the classical expression of the Lorentz transformation to a quantum-mechanical one requires us to symmetrize the expression and replace all its dynamical variables with the corresponding operators, from which we can obtain the same conclusion as that from quantum field theory (given by Weinberg's formula): owing to the Heisenberg's uncertainty relation, a particle (as a quantum reference frame) can propagate over a spacelike interval. 相似文献
5.
The performances of a dual-pump parametric and Raman amplification process and the wavelength conversion in silicon waveguides are investigated. By setting the Raman contribution fraction f to be 0.043 in our analytical model, the amplification gain of the probe signal can be obtained to be over 10 dB. The pump transfer noise (PTN), the quantum noise (QN), and the total noise figure (TNF) are discussed, and the TNF has a constant value of about 4 dB in the gain bandwidth. An idler signal generated during the parametric amplification (PA) process can be used to realize the wavelength conversion in wavelength division multiplexing (WDM) systems. In addition, the pump signal parameters, the generated free carrier lifetime and effective mode area (EMA) of the waveguide are analysed for the optimization of signal gain and noise characteristics. 相似文献
6.
Robert D. Frankel 《Journal of Raman spectroscopy : JRS》2014,45(9):764-772
Stimulated Raman scattering (SRS) scanning microscopy has the potential to enable label‐free in vivo imaging for research and clinical medicine. Volume SRS from focus occurs in the forward scattered direction. Therefore, multiple scattering events are required to direct the light out of the tissue, reducing imaging depth and resolution. Here, a method called Stokes interference SRS (SISRS) is introduced that operates by the addition to the standard pump and stimulated emission probe beams a third beam called the donut beam. The donut is close in wavelength to the probe beam and, after passage through a π phase plate, forms an annular beam in the focal plane with bright nodes above and below focus. The donut beats with the probe beam, and when they destructively interfere with each other, the microscope's 3‐D stimulated emission focal spot is reduced to subwavelength dimensions. A subwavelength focal volume emits a dipole pattern of SRS with forward and backscatter lobes, enabling high‐resolution single‐backscatter imaging from deep within tissues. The reduction of the focal volume also increases the resolution of the scanning image creating imaging beyond the diffraction limit. SISRS imaging may provide in vivo label‐free Raman images comparable with that achieved in stained in vitro tissues in all planes of section. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
7.
Finding the optimal solution to a complex optimisation problem is of great importance in practically all fields of science, technology, technical design and econometrics. We demonstrate that a modified Grover's quantum algorithm can be applied to real problems of finding a global minimum using modest numbers of quantum bits. Calculations of the global minimum of simple test functions and Lennard-Jones clusters have been carried out on a quantum computer simulator using a modified Grover's algorithm. The number of function evaluations N reduced from O(N) in classical simulation to O(N 1/2) in quantum simulation. We also show how the Grover's quantum algorithm can be combined with the classical Pivot method for global optimisation to treat larger systems. 相似文献
8.
We propose a practical scheme for one-way quantum computing based on efficient generation of 2D cluster state in thermal cavities.
We achieve a controlled-phase gate that is neither sensitive to cavity decay nor to thermal field by adding a strong classical
field to the two-level atoms. We show that a 2D cluster state can be generated directly by making every two atoms collide
in an array of cavities, with numerically calculated parameters and appropriate operation sequence that can be easily achieved
in practical Cavity QED experiments. Based on a generated cluster state in Box(4) configuration, we then implement Grover’s search algorithm for four database elements in a very simple way as an example
of one-way quantum computing. 相似文献
9.
P. W. Wachulak M. C. Marconi A. Isoyan L. Urbanski A. Bartnik H. Fiedorowicz R. A. Bartels 《Opto-Electronics Review》2012,20(1):1-14
Imaging systems with nanometer resolution are instrumental to the development of the fast evolving field of nanoscience and
nanotechnology. Decreasing the wavelength of illumination is a direct way to improve the spatial resolution in photon-based
imaging systems and motivated a strong interest in short wavelength imaging techniques in the extreme ultraviolet (EUV) region.
In this review paper, various EUV imaging techniques, such as 2D and 3D holography, EUV microscopy using Fresnel zone plates,
EUV reconstruction of computer generated hologram (CGH) and generalized Talbot self-imaging will be presented utilizing both
coherent and incoherent compact laboratory EUV sources. Some of the results lead to the imaging with spatial resolution reaching
50 nm in a very short exposure time. These techniques can be used in a variety of applications from actinic mask inspection
in the EUV lithography, biological imaging to mask-less lithographic processes in nanofabrication. 相似文献
10.
C. J. Zhu C. Hang G. X. Huang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(2):231-237
We propose a four-level Λ scheme with a one-mode
active Raman gain core and two-folded lower levels to obtain new
linear and nonlinear optical responses. We show that this scheme is
fundamentally different from that based on electromagnetically
induced transparency (EIT). Firstly, it is gain-assisted and thus
capable of eliminating all attenuation of probe field. Furthermore,
due to the quantum interference effect introduced by a coupling
field a gain doublet appears in gain spectrum, and hence the
distortion of the probe field during propagation can be effectively
avoided. In addition, in such system a large and rapidly responding
Kerr nonlinearity can be produced, which is much (more than 10
times) larger than that obtained in the EIT-based scheme with the
same energy-level configuration. 相似文献
11.
12.
We introduce an idea of producing an optical lattice relied on the Talbot effect. Our alternative scheme is based on the interference of light behind a diffraction grating in the near-field regime. We demonstrate 1D and 2D optical lattices with the simulations and experiments. This Talbot optical lattice can be broadly used from quantum simulations to quantum information. The Talbot effect is usually used in lensless optical systems, therefore it provides small aberrations. 相似文献
13.
Abstract Using the Weisskopf-Wigner technique, a self consistent quantum electrodynamic (SCQED) theory of spontaneous emission of radiation and single photon small signal gain is developed for high voltage free electron lasers (FEL). Excellent agreement is obtained simultaneously to our knowledge for the first time between the predictions and the experimental observations for lineshift, linewidth and gain. The SCQED theory predicts lineshift and broadening due to quantum mechanical effects for linear, helical and tapered undulator FELs which are not predicted by the classical/conventional FEL theories, but which have been observed 4,5,18,22,23,45,46. Excellent agreement is obtained between the SCQED theory predicted spontaneous emission spectra and the 1980–81 ACO FEL4,18, ACO Optical Klystron FEL45,46, Stanford 10.6 μm FEL22 and Stanford 3.4 μm FEL23 experimental spectra. This agreement is much better than the prediction from the classical/conventional FEL theory which gives errors of many tens of percent. We show that the spontaneous emission spectrum obtained from classical/conventional FEL theories is valid only in the limit of a short undulator containing a small number of periods. The small signal gain derived from the SCQED theory is shown to reduce to Colson's gain formula12,34 in the classical limit. However, the SCQED theory predicts significant reductions in the small signal gain which agree well with the ACO gain data5, and are not predicted well by Colson's formula. Due to the non-neglible finite electron state lifetime, it is discovered that a fundamental physical gain limit exists which is universal to all types of FELs within the limits of the single photon transition scheme considered (i.e. if multiphoton effects are ignored). Finally, the implications of the theoretically obtained results are discussed for practical conditions of experimental interest. It is shown that under practical experimental conditions quantum effects can be quite important in the FEL. 相似文献
14.
Jason Guicheteau Steven Christesen Darren Emge Ashish Tripathi 《Journal of Raman spectroscopy : JRS》2010,41(12):1632-1637
The ability of normal Raman and surface‐enhanced Raman scattering (SERS) to identify and detect bacteria has shown great success in recent studies. The addition of silver nanoparticles to bacterial samples not only results in an enhanced Raman signal, but it also suppresses the native fluorescence associated with biological material. In this report, Raman chemical imaging (RCI) was used to analyze individual bacteria and complex mixtures of spores and vegetative cells. RCI uses every pixel or a binned pixel group (BPG) of the Raman camera as an independent Raman spectrograph, allowing collection of spatially resolved Raman spectra. The advantage of this technique resides primarily in the analysis of samples in complex backgrounds without the need for physically isolating or purifying the sample. Using a chemical imaging Raman microscope, we compare normal RCI to SERS‐assisted chemical imaging of mixtures of bacteria. In both cases, we are able to differentiate single bacterium in the Raman microscope's field of view, with a 60‐fold reduction in image acquisition time and a factor of 10 increase in the signal‐to‐noise ratio for SERS chemical imaging over normal RCI. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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17.
H.-M. Frey P. Beaud T. Gerber B. Mischler P.P. Radi A.P. Tzannis 《Applied physics. B, Lasers and optics》1999,68(4):735-739
2 , N2, and CO2. For CO2 additional experiments have been performed at reduced pressure and in a molecular beam. By delaying the probe pulse a periodic
recovery of the DFWM signal is observed. The period of these transients can be assigned unambiguously to rotational Raman
transitions of the ground state within the laser bandwidth. The decay of the transients yields the collisional dephasing of
the Raman-induced polarization. At zero delay also optical-field-induced birefringence of electronic nature contributes to
the signal. The different time scales of the Raman and electronic effects allow us to estimate their relative strength.
Received: 3 August 1998 / Revised version: 21 October 1998 / Published online: 24 February 1999 相似文献
18.
We investigate the two-dimensional gain and absorption of a weak probe field via two orthogonal standing-wave lasers in a four-level inverted-Y asymmetric quantum well system. We find that, due to the spatial-dependent quantum interference effect, the spatial distribution of the 2D gain and absorption spectra can be easily controlled by adjusting the system parameters. More importantly, the probe gain-absorption spectrum can be controlled at a particular position and the 2D localization effect is indeed achieved efficiently. Thus, our scheme shows the underlying probability for the formation of the 2D localization effect by using a QW structure. 相似文献
19.
Raman response function for silica fibers 总被引:1,自引:0,他引:1
The commonly used Lorentzian form of the Raman response function for studying propagation of ultrashort pulses in silica fibers does not properly account for the shoulder in the Raman gain spectrum originating from the Boson peak. We propose a more accurate form of this response function and show that its predictions for the Raman-induced frequency shift should be in better agreement with experiments. 相似文献
20.
《Physics letters. A》2006,357(3):171-176
We derive some important features of the standard quantum mechanics from a certain classical-like model—prequantum classical statistical field theory, PCSFT. In this approach correspondence between classical and quantum quantities is established through asymptotic expansions. PCSFT induces not only linear Schrödinger's equation, but also its nonlinear generalizations. This coupling with “nonlinear wave mechanics” is used to evaluate the small parameter of PCSFT. 相似文献