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Summary form only given. Bosonic stimulation as the principal mechanism for the growth of a Bose-Einstein condensate was first introduced and quantitatively evaluated by Gardiner et al., and this was subsequently experimentally verified by Miesner et al. Although agreement between experiment and theory is not perfect, it is clear that the predicted mechanism of stimulated emission into the condensate...
Summary form only given. We define the premise of "macroscopic local realism" so that its failure is more surprising than failure of the local realism addressed previously. Macroscopic local realism is a premise stating the following. If one can predict the result of a measurement at A by performing a simultaneous measurement on a spatially separated system B, then the result of the measurement...
Summary form only given. One of the key elements of quantum communication is the generation of maximally entangled states between distant nodes of a quantum network. We present an entanglement purification scheme which generates maximally entangled states in finite Hilbert spaces from the continuous two-mode squeezed states. With high probabilities, we get a more entangled stale, and the entanglement...
Summary form only given. In any optical system, quantum and classical theory yield identical predictions for the mean intensity. The quantum mechanical predictions diverge from the classical theory only for higher order correlations. For this reason, typical quantum-interference experiments are performed by measuring coincidence rates between two or more detectors. The usual approximation, following...
Summary form only given. Complementarity is one of the most basic principles of quantum mechanics. A quantum mechanical object, be it a photon or a massive particle, shows position (particle-like) or momentum (wave-like) attributes exclusively depending on the experimental situation. Over the years, Young's two-slit experiment has been emphasized as a good example of complementarity. We report two...
Summary form only given. Design and excitation of novel quantum states and the measurement of those states is driven by both fundamental and technological goals. For example, the study of Schrodinger cat states touches upon the basic measurement hypotheses of quantum mechanics while the establishment of particular coherent superposition states is the starting point for the process of coherent control...
Summary form only given. Using the density matrix formulation of quantum mechanics, the optically-heterodyne-detected coherent Raman scattering signal in the out-of-phase configuration, under the off-resonant condition, is given.
Summary form only given. Quantum coherence effects in atomic media interacting with multiple coherent electromagnetic fields have gained a lot of attention in both theoretical and experimental quantum optics over the last three decades. The absorptive and dispersive properties of coherently prepared media lead. Astonishing effects like electromagnetically induced transparency on extremely narrow dark...
Summary form only given. The dilute gas experiments on the Bose-Einstein condensation of magnetically confined alkali vapors have already generated widespread interest across a broad spectrum of traditional fields of physics. They have provided an exciting stage on which to build bridges linking the theory of complex and collective phenomena in superconducting and superfluid systems with the single...
Summary form only given. Entangled states of multi-particle systems are arguably the quintessential feature of quantum mechanics. In addition to their central role in discussions of non-local quantum correlations, they form the basis of quantum information, and enable such phenomena as quantum cryptography, quantum dense coding, teleportation, and quantum computation. Via the process of spontaneous...
Summary form only given. The notion of entanglement was coined by Erwin Schrodinger in order to signify the peculiar properties of quantum correlations. Entanglement is at the heart of the Einstein-Podolsky-Rosen paradox and Bell's theorem. While, originally, entanglement was considered to be a very important fundamental concept in quantum mechanics leading to such concepts as quantum nonlocality,...
Summary form only given. A chain of ions in a linear trap is ideally suited to process quantum information. Two long-lived internal states in each ion store the quantum bits, which may be coupled by means of the collective vibrational excitation of the chain. A prerequisite for realizing even the simplest two-bit quantum gate is cooling the vibrational degrees of freedom of the ion crystal to the...
Summary form only given. According to Feynman, quantum mechanics teaches us that interference occurs when the relevant amplitudes become indistinguishable. In the case of first-order and second-order interference (order by "intensity"), the relevant amplitudes are one-photon and two-photon amplitudes, respectively. We report a quantum interference experiment in which the relevant amplitudes...
Summary form only given. Quantum cryptographic schemes use fundamental properties of quantum mechanics to ensure the protection of random number keys. In particular the act of measurement in quantum mechanics inevitably disturbs the system. Furthermore, for single quanta such as a photon, simultaneous measurements of non-commuting variables are forbidden. It is of practical and fundamental interest...
Summary form only given. Optical solitons in fibres are attractive macroscopical quantum objects, which are particle-like pulses propagating over large distances without distortion due to the balance between Kerr nonlinearity and group velocity dispersion effects. However, in the frame of the quantum theory, they exhibit a complicated internal quantum structure with nontrivial nonlinear dynamics....
Summary form only given, as follows. Much (indeed most!) of quantum mechanics is concerned with determining the eigenvalues and eigenstates of the system of interest and scattering rates between these states. But in many cases (e.g. in superconductors and lasers) coherent superpositions of states are required to understand the physics. Furthermore some of the deepest issues of physics arise from correlations...
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