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  • Journal article
    THOMPSON RC, HANSER A, BEKK K, MEISEL G, FROLICH Det al., 1982,

    HIGH-RESOLUTION MEASUREMENTS OF ISOTOPE SHIFTS IN LEAD

    , ZEITSCHRIFT FUR PHYSIK A-HADRONS AND NUCLEI, Vol: 305, Pages: 89-90, ISSN: 0939-7922
  • Journal article
    THOMPSON RC, 1982,

    AN INSTRUMENTAL EFFECT ON SPECTRAL-LINE PROFILES

    , JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, Vol: 27, Pages: 417-421, ISSN: 0022-4073
  • Journal article
    DALTON BJ, KNIGHT PL, 1982,

    POPULATION TRAPPING AND ULTRANARROW RAMAN LINESHAPES INDUCED BY PHASE-FLUCTUATING FIELDS

    , OPTICS COMMUNICATIONS, Vol: 42, Pages: 411-416, ISSN: 0030-4018
  • Journal article
    DALTON BJ, KNIGHT PL, 1982,

    THE EFFECTS OF LASER FIELD FLUCTUATIONS ON COHERENT POPULATION TRAPPING

    , JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 15, Pages: 3997-4015, ISSN: 0953-4075
  • Journal article
    COLEMAN PE, KNIGHT PL, 1982,

    POPULATION TRAPPING IN PHOTOIONIZATION TO DRESSED CONTINUUM STATES

    , JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 15, Pages: L235-L241, ISSN: 0953-4075
  • Journal article
    KNIGHT PL, RADMORE PM, 1982,

    QUANTUM ORIGIN OF DEPHASING AND REVIVALS IN THE COHERENT-STATE JAYNES-CUMMINGS MODEL

    , PHYSICAL REVIEW A, Vol: 26, Pages: 676-679, ISSN: 1050-2947
  • Journal article
    COLEMAN PE, KNIGHT PL, 1981,

    RAMAN COUPLING BETWEEN DRESSED STATES IN RESONANT MULTI-PHOTON IONIZATION

    , PHYSICS LETTERS A, Vol: 81, Pages: 379-382, ISSN: 0375-9601
  • Journal article
    COLEMAN PE, KAGAN D, KNIGHT PL, 1981,

    INTERPRETATION OF SUB-NATURAL LINEWIDTHS IN PULSED-EXCITATION LASER SPECTROSCOPY

    , OPTICS COMMUNICATIONS, Vol: 36, Pages: 127-130, ISSN: 0030-4018
  • Journal article
    COLEMAN PE, KNIGHT PL, 1981,

    INTEGRITY OF DRESSED STATES IN MULTI-PHOTON IONIZATION

    , JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 14, Pages: 2139-2158, ISSN: 0953-4075
  • Journal article
    RADMORE PM, KNIGHT PL, KAGAN D, 1981,

    LINE-NARROWED LASER-ABSORPTION SPECTRA INDUCED BY DECAYING ADIABATIC PULSES

    , PHYSICS LETTERS A, Vol: 82, Pages: 288-290, ISSN: 0375-9601
  • Journal article
    KNIGHT PL, 1980,

    ORIGIN OF QUANTUM BEATS IN PHOTO-IONIZATION

    , OPTICS COMMUNICATIONS, Vol: 32, Pages: 261-265, ISSN: 0030-4018
  • Journal article
    KNIGHT PL, COLEMAN PE, 1980,

    SUBNATURAL LINEWIDTH SPECTROSCOPY

    , JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 13, Pages: 4345-4352, ISSN: 0953-4075
  • Thesis dissertation
    Thompson RC, 1980,

    Pressure broadening in neon at low densities
  • Journal article
    MALVERN AR, PINDER AC, STACEY DN, THOMPSON RCet al., 1980,

    SELF-BROADENING IN SINGLET SPECTRAL-LINES OF HELIUM

    , PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 371, Pages: 259-278, ISSN: 1364-5021
  • Journal article
    KNIGHT PL, 1980,

    THEORY OF NEAR-RESONANT SPONTANEOUS RAMAN-SCATTERING SPECTRA

    , JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 13, Pages: 4551-4565, ISSN: 0953-4075
  • Journal article
    BAIRD PEG, BURNETT K, DAMASCHINI R, STACEY DN, THOMPSON RCet al., 1979,

    RESONANCE BROADENING IN NEON AT LOW-DENSITIES

    , JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 12, Pages: L143-L146, ISSN: 0953-4075
  • Journal article
    STACEY DN, THOMPSON RC, 1978,

    SPECTRAL-LINE BROADENING IN NEON DUE TO THE RESONANCE INTERACTION

    , ACTA PHYSICA POLONICA A, Vol: 54, Pages: 833-839, ISSN: 0587-4246
  • Journal article
    Keitel CH, Zhu SY, Knight PL,

    Total fluorescence inhibition via incoherent dressed population transfer

    , LASER PHYSICS, Vol: 9, Pages: 826-830, ISSN: 1054-660X
  • Journal article
    KIM M, BUZEK V,

    DECAY OF QUANTUM COHERENCES UNDER THE INFLUENCE OF A THERMAL HEATBATH - SCHRODINGER CAT STATES AT FINITE TEMPERATURE

    , JOURNAL OF MODERN OPTICS, Vol: 39, Pages: {1609-1614}-{1609-1614}, ISSN: 0950-0340

    Recently several methods have been proposed for generation of superposition (Schrodinger cat) states in microwave cavities. At microwave frequencies thermal photons can significantly affect statistical properties of superposition states. In the present letter we study the influence of a thermal heatbath on non-classical properties of quantum superposition states. We show that at non-zero temperatures the loss of quantum coherences is much faster than at zero temperature and that the sensitivity of the quantum coherence to the presence of thermal photons can lead to some difficulties in the preparation of Schrodinger cat states in microwave cavities unless the temperature of the microwave cavity is sufficiently low.
  • Journal article
    Kim MS, Antesberger G, Bodendorf CT, Walther Het al.,

    Scheme for direct observation of the Wigner characteristic function in cavity QED

    , PHYSICAL REVIEW A, Vol: 58, Pages: {R65-R68}-{R65-R68}, ISSN: 1050-2947

    We suggest a quantum state reconstruction scheme. Our proposal is applicable to the field inside a microwave cavity as well as to the harmonic motion of a trapped atom. It will be shown that the inversion of two-level atoms after a resonant interaction with a coherently displaced quantum state is directly related to the Wigner characteristic function of the initial state. This method neither requires the preparation of atoms in a quantum superposition of the upper and lower energy levels nor heavy numerical processing of the measured data. We demonstrate the reconstruction scheme for the example of a Schrodinger-cat superposition state.
  • Journal article
    Kim MG, Imoto N, Cho K, Kim MSet al.,

    Quantum noise in optical beam propagation in distributed amplifiers

    , OPTICS COMMUNICATIONS, Vol: 130, Pages: {377-384}-{377-384}, ISSN: 0030-4018

    Quantum effects on optical beam propagation in a gain medium having distributed loss are analyzed using an amplifier-attenuator array model. For the amplifier-attenuator set, the Wigner function of the output field is related to that of the input field by a convolution law. Using this, we derive the Fokker-Planck equation for the beam propagation in the distributed amplifier with loss, and the added quantum noise is analyzed by solving this equation. When the amplification just compensates the attenuation, the mean amplitude of the signal does not change but the mean energy increases due to the added noise. Even in this case, the photon number variance can be reduced when a proper phase-sensitive reservoir is incorporated.
  • Journal article
    Kim MS, Sanders BC,

    Squeezing and antisqueezing in homodyne measurements

    , PHYSICAL REVIEW A, Vol: 53, Pages: {3694-3697}-{3694-3697}, ISSN: 1050-2947

    Squeezing the signal field or the local oscillator can improve the accuracy of homodyne detection. We show that an equivalence exists between antisqueezing the signal field and squeezing the local oscillator state. The importance of this result is illustrated in two contexts: a homodyne measurement of squeezing and the reconstruction of the wave function.
  • Journal article
    Janszky J, Kim MG, Kim MS,

    Quasiprobabilities and the nonclassicality of fields

    , PHYSICAL REVIEW A, Vol: 53, Pages: {502-506}-{502-506}, ISSN: 1050-2947

    The existence of positive well-defined quasiprobabilities is known to be related to the measure of nonclassicality for a given field state. We test the coincidence of the loss of well-known nonclassical properties with the appearance of the positive well-defined quasiprobabilities for various fields influenced by phase-insensitive reservoirs. For Gaussian fields the appearance of a positive Glauber-Sudarshan P function coincides with the loss of nonclassical properties in quadrature fluctuations and in photon statistics. We find that when an initial Fock state dissipates or is amplified the initial field loses its nonclassicality in photon statistics before the P function becomes positive, which is different from the Gaussian field. The Wigner function may be positive even when the decaying Fock state is sub-Poissonian. For the amplification of the Pock state, however, the Wigner function is positive only when the field is super-Poissonian. For the dissipation and amplification of the Fock state the point when a certain quasiprobability function becomes positive definite depends only on the average number of photons N of the heat bath.
  • Journal article
    KIM M, IMOTO N,

    PHASE-SENSITIVE RESERVOIR MODELED BY BEAM-SPLITTERS

    , PHYSICAL REVIEW A, Vol: 52, Pages: {2401-2410}-{2401-2410}, ISSN: 1050-2947

    The superposition of input fields in a lossless beam splitter is studied in the Schrodinger picture by using the convolution of the positive P representations, and the convolution law for these representations is extended to other quasiprobability functions such as the Wigner and Q functions. We show that the reservoir can be modeled by an infinite array of beam splitters, and we use the convolution law and this model to derive the Fokker-Planck equation for a system coupled with a phase-sensitive reservoir. Solving this equation shows that a phase-sensitive attenuation and amplification can be described by the superposition of two independent quantum fields, one of which is the initial signal field and the other the squeezed thermal noise field representing the reservoir.
  • Journal article
    BUZEK V, KIM M, KIM M,

    ENTROPIC UNCERTAINTY RELATIONS FOR OPERATIONAL PHASE-SPACE MEASUREMENT

    , JOURNAL OF THE KOREAN PHYSICAL SOCIETY, Vol: 28, Pages: {529-533}-{529-533}, ISSN: 0374-4884

    We introduce entropic measures of uncertainty related to operational phase-space probability density distributions. With the help of these entropies, we find the entropic uncertainty relation for the position ((q) over cap) and the momentum ((p) over cap) operators of a quantum-mechanical system in the form S-Psi Phi((q)) + S-Psi Phi((p)) greater than or equal to S-Psi Phi((q,p)) greater than or equal to k(B). The fundamental lower bound on the entropic uncertainty relation is equal to the Boltzmann constant k(B).
  • Journal article
    SANDERS B, LEE K, KIM M,

    OPTICAL HOMODYNE MEASUREMENTS AND ENTANGLED COHERENT STATES

    , PHYSICAL REVIEW A, Vol: 52, Pages: {735-741}-{735-741}, ISSN: 1050-2947
  • Journal article
    BUZEK V, KIM M, KIM M,

    DESCRIPTION OF THE INFLUENCE OF A RESERVOIR VIA COARSE-GRAINING IN PHASE-SPACE

    , JOURNAL OF THE KOREAN PHYSICAL SOCIETY, Vol: 28, Pages: {123-127}-{123-127}, ISSN: 0374-4884

    We show that the Q-function of a single-mode field which is attenuated or amplified by a phase-sensitive environment can be expressed through a coarse-grained Q-function with time-dependent coarse-graining parameters. This fact can be utilized for simulation of the decay of quantum systems into various environments. In particular, we have derived an analytical expression describing the time-evolution of the Q-function of the initial Fock state which decays into a phase-sensitive reservoir.
  • Journal article
    BUZEK V, KIM M,

    DECAY WITHOUT LOSSES - MEAN-PHOTON-NUMBER DECAY AND SHANNON ENTROPY DECAY OF MICROMASER FIELDS VIA CONDITIONAL MEASUREMENTS

    , JOURNAL OF THE KOREAN PHYSICAL SOCIETY, Vol: 27, Pages: {215-220}-{215-220}, ISSN: 0374-4884

    We investigate the dynamics of a lossless micromaser when a single-mode cavity field is resonantly coupled via one-photon transitions to two-level atoms crossing the cavity in a sequence. We analyze the statistical properties of the cavity field when the atoms after the interaction are conditionally measured, provided the interaction time is short. Namely, we select only those sequences wherein each atom after the interaction is measured in its initial state. We assume that the total sequence duration is smaller than the cavity decay time so that cavity losses can be neglected. We show that even though there is no direct transfer of the energy from the atoms to the field and vice versa, the mean photon number of the cavity field is reduced due to the conditional measurement. This energy ‘’decay” is accompanied by a reduction of the Shannon entropy of the field. We show that there exists an attractor state of the cavity field which is the Fock state with the smallest photon number which contributes to the initial state of the field. Finally, we find the remarkable result that the time evolution of a field initially prepared in a coherent state which is conditionally measured by the sequence of atoms is exactly the same as the time evolution of a coherent field decaying into a zero-temperature heat bath.
  • Journal article
    BUZEK V, GANTSOG T, KIM M,

    PHASE PROPERTIES OF SCHRODINGER CAT STATES OF LIGHT DECAYING IN PHASE-SENSITIVE RESERVOIRS

    , PHYSICA SCRIPTA, Vol: T48, Pages: {131-142}-{131-142}, ISSN: 0281-1847

    We study phase properties of quantum mechanical superposition states decaying into phase-sensitive reservoirs. We show that the Wigner phase quasiprobability distribution reflects the quantum interference effects very well while the Pegg-Barnett and the Husimi phase probability distributions are quite insensitive with respect to the character of the quantum interference between component states. We study in detail phase properties of the even coherent state which decays into the thermal and the squeezed reservoirs. In thermal reservoirs the phase of the superposition state becomes randomized under the influence of thermal fluctuations. The higher the number of thermal photons the faster the randomization process is. On the other hand we show that depending on the relative phase between the superposition state and the phase-sensitive reservoir the process of phase randomization can be either enhanced or completely s suppressed.
  • Journal article
    BUZEK V, KIM M, GANTSOG T,

    QUANTUM PHASE DISTRIBUTIONS OF AMPLIFIED SCHRODINGER-CAT STATES OF LIGHT

    , PHYSICAL REVIEW A, Vol: 48, Pages: {3394-3397}-{3394-3397}, ISSN: 1050-2947

    We study the phase properties of quantum superpositions of two coherent states (Schrodinger-cat states) amplified by phase-sensitive (squeezed) amplifiers. We show that a phase-sensitive amplifier with a properly chosen phase can preserve the phase distribution of the Schrodinger-cat-state input.

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