119480279
Generalized coherent states are unique Bell states of quantum systems with Lie-group symmetries
Entanglement is the main quantum mechanical feature that distinguishes between quantum and classical physics. A state of a quantum system, consisting of two subsystems, is called entangled if it cannot be represented as a direct product of states of the subsystems. The nonclassicality of such a situation is expressed mathematically by the violation of Bell’s inequality @1,2#. More specifically, let us consider a quantum system A ~e.g., a mode of the quantized radiation field or a spin-j particle!, which is split or decays into two subsystems B and C @3#. A pure quantum state that upon splitting will not violate Bell’s inequality ~i.e., a quantum state that possesses the basic attribute of classical physics ! has been called the Bell state @4#. It has been proven @4‐6# that a state that factorizes upon splitting into a direct product cannot violate Bell’s inequality, while a state that gives rise to an entangled ~i.e., nonproduct! state can always, by a suitable choice of local apparatus, be made to violate the inequality. Therefore the Bell state of the system A must factorize upon splitting into the direct product of states of the subsystems.
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.
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.
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.
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.
116058926
Experimental use of neutrinos from ISABELLE beam dumps
The technical feasibility and possible applicability of using ISABELLE beam dumps as powerful sources for directed high-energy neutrino bursts are investigated. In the present machine design two dump systems are applied to absorb the extracted fast beams. The expected normal beam extraction rate is 1 to 2 per day, when about (6.3 to 7.5) x 10/sup 14/ protons are hitting the external targets during a pulse length of approx. 50 ..mu..s. These protons are considered so far to be useless. The neutrinos produced could be used for the following activities: the study of coherent neutrino regeneration, calibration and permanent testing of cosmic-ray and astrophysical neutrino detectors, research on the practical applicability of neutrinos in telecommunication, and certain astro- and geophysical applications. Tailoring the system to meet these activities is illustrated. 6 figures. (RWR)
122959606
New Features of Neutrino Physics as Observed in Fermilab Exp. 1A
With the advent of large counter experiments and high energy accelerators many new phenomena have appeared in neutrino physics. Apart from the discovery of weak neutral currents [1] the most striking development has been the observation of v and v interactions with two muons in the final state [2a] (dimuon events) and more recently of v interactions with a muon and a positron in the final state [3]. Of equal importance has been the observation of departure from the scaling predictions observed in high energy v weak charged current reactions [4].
123939432
Measurement of the radiative electron polarization in a 2.4 GeV storage ring
We have observed the existence of transverse polarization of the electron beam in the SPEAR storage ring resulting from the emission of synchrotron radiation in the magnetic field. The time constant for polarization build-up has been measured for a single circulating electron beam to be approx. 90 min and the corresponding equilibrium polarization to be approx. 0.85. These values are to be compared with the theoretical predictions of 124 min and 0.924, respectively. (AIP)
189916402
The future of neutrino physics
A brief, selective overview is presented of recent progress in neutrino physics, with emphasis on several unanswered questions and possible future experiments which might address them.
123581677
LINEARIZED VERSION OF THE HARTREE--FOCK METHOD.