118892945
GOVERNING DYNAMICS BY SQUEEZING IN A SYSTEM OF COLD TRAPPED IONS
Department of Physics, Technion–Israel Institute of Technology, Haifa 32000, Israel~Received 4 June 1998!We consider a system of laser-cooled ions in a linear harmonic trap and study the phenomenon of squeezingexchange between their internal and motional degrees of freedom. An interesting relation between the quantumnoise reduction ~squeezing! and the dynamical evolution is found when the internal and motional subsystemsare prepared in properly squeezed ~intelligent! states. Speciﬁcally, the evolution of the system is fully governedby the relative strengths of spectroscopic and motional squeezing, including the phenomenon of total cancel-lation of the interaction when the initial squeezing parameters are equal. @S1050-2947~99!01401-8#PACS number~s!: 03.65.Bz, 42.50.Dv, 42.50.Vk, 32.80.Qk
16820646
Analytic representations based on SU(1,1) coherent states and their applications
We consider two analytic representations of the SU(1,1) Lie group: the representation in the unit disc based on the SU(1,1) Perelomov coherent states and the Barut - Girardello representation based on the eigenstates of the SU(1,1) lowering generator. We show that these representations are related through a Laplace transform. A `weak' resolution of the identity in terms of the Perelomov SU(1,1) coherent states is presented which is valid even when the Bargmann index k is smaller than . Various applications of these results in the context of the two-photon realization of SU(1,1) in quantum optics are also discussed.
119995096
Coherent and thermal coherent state
The characterization of coherent states as the quantum states that split into two uncorrelated beams is considered. The characterization leads to the study of coherent states at finite temperature—thermal coherent states (TCS’s). These TCS’s are defined within the formalism of thermo field dynamics (TFD). TFD allows a generalization of the uncertainty relation that accounts for both thermal and quantum fluctuations. The TCS is shown to be a minimal state for the generalized uncertainty relation.
18649329
Generation of single-mode intelligent states and an analytic approach to their quantum statistical properties
We discuss a scheme for generation of single-mode photon states associated with the two-photon realization of the SU(1,1) algebra. This scheme is based on the process of non-degenerate down-conversion with the signal prepared initially in the squeezed vacuum state and with a measurement of the photon number in one of the output modes. We focus on the generation and properties of single-mode SU(1,1) intelligent states which minimize the uncertainty relations for Hermitian generators of the group. Properties of the intelligent states are studied by using a `weak' extension of the analytic representation in the unit disc. Then we are able to obtain exact analytical expressions for expectation values describing quantum statistical properties of the SU(1,1) intelligent states. Attention is mainly devoted to the study of photon statistics and linear and quadratic squeezing.
16492315
Empirical State Determination of Entangled Two-Level Systems and Its Relation to Information Theory
Theoretical methods for empirical state determination of entangled two-level systems are analyzed in relation to information theory. We show that hidden variable theories would lead to a Shannon index of correlation between the entangled subsystems which is larger than that predicted by quantum mechanics. Canonical representations which have maximal correlations are treated by the use of Schmidt and Hilbert-Schmidt decomposition of the entangled states, including especially the Bohm singlet state and the GHZ entangled states. We show that quantum mechanics does not violate locality, but does violate realism.
40587572
Inverted spectroscopy and interferometry for quantum-state reconstruction of systems with SU(2) symmetry
We consider how the conventional spectroscopic and interferometric schemes can be rearranged to serve for reconstructing quantum states of physical systems possessing SU(2) symmetry. The discussed systems include a collection of two-level atoms, a two-mode quantized radiation field with a fixed total number of photons, and a single laser-cooled ion in a two-dimensional harmonic trap with a fixed total number of vibrational quanta. In the proposed rearrangement, the standard spectroscopic and interferometric experiments are inverted. Usually one measures an unknown frequency or phase shift using a system prepared in a known quantum state. Our aim is just the inverse, i.e., to use a well-calibrated apparatus with known transformation parameters to measure unknown quantum states.
121860583
Measurement of the neutral-current interactions of high-energy neutrinos and antineutrinos
Measurements of the ..nu.. and nu-bar weak hadronic neutral-current total cross sections and hadron energy distributions are consistent with a V - A form for this current. They are three standard deviations from pure V, pure A, or a pure T form and unambiguously exclude V + A and any linear combination of S and P.
121989655
Further observation of dimuon production by neutrinos
By using a quadrupole focused neutrino beam, 61 events with two muons in the final state have been observed at Fermilab. These include seven $mu$$sup - $$mu$$sup -$ events. A comparison of the event rate in two targets of different hadron absorption length indicates that attributing the events to $pi$ or K leptonic decay is ruled out by 4.0 standard deviations. No trimuon events were observed; this circumstance, combined with lepton conservation, indicates an unobserved neutral lepton is present in most of the events. (AIP)
121620440
Study of Approximations in the Nuclear Pairing-Force Problem
123621331
APPROACH TO THE NUCLEAR MANY-BODY PROBLEM BY VARIATIONALLY DETERMINED TRANSFORMATION. II.
We present a generalization of the Hartree-Fock (HF) method incorporating two-body correlations. The correlations are introduced by means of a unitary operator ${e}^{\mathrm{iF}}$, where $F$ is a Hermitian one- and two-body operator to be determined by the variational principle. Assuming that the matrix elements of $F$ are small so that powers of $F$ higher than the second may be neglected, a set of linear equations determining $F$ is obtained. The relation between our method and methods used to treat singular interactions is discussed. The method is applied to two recently suggested models and is compared with the HF method, second-order perturbation theory, and with the random-phase approximation. It is found that our method yields very good results within the range of validity of our approximations, which seems to call forth applications to more realistic problems. Possible applications to the study of collective phenomena in nuclei are indicated.
118537138
Flux independent search for new particle production in high energy neutrino and antineutrino collisions