摘要:

The Jaynes-Cummings model (JCM), a soluble fully quantum mechanical model of an atom in a field, was first used (in 1963) to examine the classical aspects of spontaneous emission and to reveal the existence of Rabi oscillations in atomic excitation probabilities for fields with sharply defined energy (or photon number). For fields having a statistical distributions of photon numbers the oscillations collapse to an expected steady value. In 1980 it was discovered that with appropriate initial conditions (e.g. a near-classical field), the Rabi oscillations would eventually revive, only to collapse and revive repeatedly in a complicated pattern. The existence of these revivals, present in the analytic solutions of the JCM, provided direct evidence for discreteness of field excitation (photons) and hence for the truly quantum nature of radiation. Subsequent study revealed further non-classical properties of the JCM field, such as a tendency of the photons to antibunch. Within the last two years it has been found that during the quiescent intervals of collapsed Rabi oscillations the atom and field exist in a macroscopic superposition state (a Schrödinger cat). This discovery offers the opportunity to use the JCM to elucidate the basic properties of quantum correlation (entanglement) and to explore still further the relationship between classical and quantum physics. The relative simplicity of the JCM and the ease with which it can be extended through analytic expressions or numerical computation continues to motivate attention, as evidenced by the growing abundance of publications. We here present an overview of the theory of the JCM and some of the many extensions and generalizations that have appeared.

ISSN:0950-0340    

DOI:10.1080/09500349314551321

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper we present a macroscopic theory for scanning tunnelling optical microscopy where the sample is a grating and the tip is modelled by a dielectric sphere. The sphere is immersed in the near-field above the grating and is excited by the diffracted orders which can be evanescent. The detected signal is supposed to be the diffracted intensity by the sphere which is calculated by using Mie theory. When studying Mie scattering of one evanescent wave we show that the multipolar series is perturbed compared to scattering of a homogeneous wave. Even for a small sphere multipolar terms have to be taken into account. We have then proposed a formula for the intensity leading to calculations of intensity profile and surfaces and to discuss the influence of tip radius on resolution of the images.

ISSN:0950-0340    

DOI:10.1080/09500349314551331

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We report, in this paper, the three-dimensional (3D) coherent functions for a confocal scanning system consisting of two unequal annular lenses. Analytical expressions for the 3D coherent transfer functions are derived for both transmission and reflection cases. Various numerical plots of the 3D coherent transfer function are given for different confocal systems including dark field microscopes. Our method is then generalized to the fibre-optical confocal system in which optical fibres rather than pinholes are employed for illumination and collection. In this case, the 3D coherent transfer function in transmission can also be obtained analytically, whilst that in reflection cannot be expressed by analytical functions, but by a single integral. Finally, images of a grating of periodic square structures are simulated to reveal the significance of the derived 3D coherent transfer functions.

ISSN:0950-0340    

DOI:10.1080/09500349314551341

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A theory describing the diffraction properties of highly conducting wire gratings with arbitrary cross-sections is presented. The method incorporates the surface impedance boundary condition on the field along metallic interfaces and relies on the solution of a coupled system of ordinary differential equations for finding the field between wires. The theory is exemplified numerically for different wire profiles. The numerical results for gold gratings in the resonance region are compared with those obtained from a theory valid for perfectly conducting wires. Comparisons to measurements validate the effectiveness of the developed algorithm and show that it is particularly suited for dealing with metallic gratings in the infrared region.

ISSN:0950-0340    

DOI:10.1080/09500349314551351

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A statistical model is used to study the formation of noise gratings in holograms and the mechanism that causes radiation scattering in them. The theoretical model presented describes noise scattering in terms of diffraction due to the high number of spurious gratings formed during the recording stage by the interference of a single reference beam with its own scattered radiation. Numerical results calculated from the theory showing the dependence of noise grating efficiency on exposure are compared with experimental results obtained with bleached emulsions, and good agreement is found.

ISSN:0950-0340    

DOI:10.1080/09500349314551361

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We show that the resonant interaction between a two-level atom and a quantized field mode via two-photon transitions leads to extreme quantum entanglement between the atom and quantum field. Nevertheless during the time evolution there are moments at which the atom-field system becomes asymptotically disentangled. We investigate statistical properties of the pure-field states generated at such times. We show that at the quarter of the revival time the field is produced in the pure superposition state (Schrödinger cat state) composed of two coherent states with the same amplitude but which are out of phase by 90° (we obtain approximate analytical solution for this superposition state). We show that the interference between component states leads to non-classical oscillations in the photon number distribution. At the revival time the field is again in the pure state (we present an approximate analytical solution for the corresponding state vector). This pure state is not a superposition state. Nevertheless it exhibits a certain degree of sub-Poissonian photon statistics. We briefly discuss the influence of the Stark shift on the production of superposition states.

ISSN:0950-0340    

DOI:10.1080/09500349314551371

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The Bessel beam propagation characteristics are investigated in the presence of azimuthally dependent phase variations of its angular components. The phase variations influence the beam symmetry and strongly reduce an axial intensity. An experimental interpretation of presented results is also discussed.

ISSN:0950-0340    

DOI:10.1080/09500349314551381

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

There have recently been several proposals for generation of optical superposition states in the resonant atom-field interaction and more practically in microwave cavities. In the present paper we study the influence of the vacuum reservoir on properties of the near-superposition state of the cavity field which is described by the Jaynes-Cummings model at one-half of the revival time. Instead of introducing the cavity loss from the first instance of the atom-field interaction we consider the cavity loss only after the near-superposition state is produced and after the atom leaves the cavity. We solve the corresponding master equation with the initial condition being the Jaynes-Cummings field at one-half of the revival time. We find that under the influence of the vacuum reservoir the photon number distribution of the superposition state we study exhibits certain asymmetry around the mean photon induced by the decay process. We show that an analogous effect can be seen when the Jaynes-Cummings superposition state is amplified. For a basic test of our approach we study the dissipation and amplification of Fock states.

ISSN:0950-0340    

DOI:10.1080/09500349314551391

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

By utilizing our previous operator solution [17], we have investigated the squeezing in the radiation field of the Tavis-Cummings model (collective N ≫ 1 two-level atoms interacting with a resonant single cavity quantized mode). With field and atoms initially in coherent field state strong or weak and atomic coherent state (of few excited atoms), periodic time-dependent squeezing in the field and the macroscopic polarization is expressed in terms of Jacobian elliptic functions of the first kind. The statistical investigations are carried out for the quasiprobability distribution functions (Wigner function andQfunction). The distribution function of the field quadrature has a variance less (greater) than that for a coherent state if this quadrature is squeezed (unsqueezed).

ISSN:0950-0340    

DOI:10.1080/09500349314551401

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In the present work we study the effects of squeezing on coherent states, number states, and on the thermal field states related to the time evolution operator, which is the result of the Hamiltonian describing the simultaneous non-degenerate parametric amplifier with mixing of two modesaandbvia a rotation of their polarization. By using the Glauber second-order correlation function we examined the statistical properties of these various squeezed states. The quasi-probabilities of theWWigner andQfunctions are calculated. The GlauberPrepresentation for the squeezed thermal state explicitly shows the limit of its applicability.

ISSN:0950-0340    

DOI:10.1080/09500349314551411

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor