76,917 research outputs found
Bose-Einstein Condensation with Entangled Order Parameter
We propose a practically accessible non-mean-field ground state of
Bose-Einstein condensation (BEC), which occurs in an interspecies two-particle
entangled state, and is thus described by an entangled order parameter. A
suitably defined entanglement entropy is used as the characterization of the
non-mean-field nature, and is found to persist in a wide parameter regime. The
interspecies entanglement leads to novel interference terms in the dynamical
equations governing the single particle orbital wavefunctions. Experimental
feasibility and several methods of probe are discussed. We urge the study of
multi-channel scattering between different species of atoms.Comment: V1: 5 pages, 4 figures. Accepted by Phys. Rev. Lett.; V2: A couple of
very minor typos corrected, publishe
Adaptive Ising Model and Bacterial Chemotactic Receptor Network
We present a so-called adaptive Ising model (AIM) to provide a unifying
explanation for sensitivity and perfect adaptation in bacterial chemotactic
signalling, based on coupling among receptor dimers. In an AIM, an external
field, representing ligand binding, is randomly applied to a fraction of spins,
representing the states of the receptor dimers, and there is a delayed negative
feedback from the spin value on the local field. This model is solved in an
adiabatic approach. If the feedback is slow and weak enough, as indeed in
chemotactic signalling, the system evolves through quasi-equilibrium states and
the ``magnetization'', representing the signal, always attenuates towards zero
and is always sensitive to a subsequent stimulus.Comment: revtex, final version to appear in Europhysics Letter
A committee machine gas identification system based on dynamically reconfigurable FPGA
This paper proposes a gas identification system based on the committee machine (CM) classifier, which combines various gas identification algorithms, to obtain a unified decision with improved accuracy. The CM combines five different classifiers: K nearest neighbors (KNNs), multilayer perceptron (MLP), radial basis function (RBF), Gaussian mixture model (GMM), and probabilistic principal component analysis (PPCA). Experiments on real sensors' data proved the effectiveness of our system with an improved accuracy over individual classifiers. Due to the computationally intensive nature of CM, its implementation requires significant hardware resources. In order to overcome this problem, we propose a novel time multiplexing hardware implementation using a dynamically reconfigurable field programmable gate array (FPGA) platform. The processing is divided into three stages: sampling and preprocessing, pattern recognition, and decision stage. Dynamically reconfigurable FPGA technique is used to implement the system in a sequential manner, thus using limited hardware resources of the FPGA chip. The system is successfully tested for combustible gas identification application using our in-house tin-oxide gas sensors
Dicke-like quantum phase transition and vacuum entanglement with two coupled atomic ensembles
We study the coherent cooperative phenomena of the system composed of two
interacting atomic ensembles in the thermodynamic limit. Remarkably, the system
exhibits the Dicke-like quantum phase transition and entanglement behavior
although the governing Hamiltonian is fundamentally different from the
spin-boson Dicke Hamiltonian, offering the opportunity for investigating
collective matter-light dynamics with pure matter waves. The model can be
realized with two Bose-Einstein condensates or atomic ensembles trapped in two
optical cavities coupled to each other. The interaction between the two
separate samples is induced by virtual photon exchange
Tensor Norms and the Classical Communication Complexity of Nonlocal Quantum Measurement
We initiate the study of quantifying nonlocalness of a bipartite measurement
by the minimum amount of classical communication required to simulate the
measurement. We derive general upper bounds, which are expressed in terms of
certain tensor norms of the measurement operator. As applications, we show that
(a) If the amount of communication is constant, quantum and classical
communication protocols with unlimited amount of shared entanglement or shared
randomness compute the same set of functions; (b) A local hidden variable model
needs only a constant amount of communication to create, within an arbitrarily
small statistical distance, a distribution resulted from local measurements of
an entangled quantum state, as long as the number of measurement outcomes is
constant.Comment: A preliminary version of this paper appears as part of an article in
Proceedings of the the 37th ACM Symposium on Theory of Computing (STOC 2005),
460--467, 200
Octet Baryon Charge Radii, Chiral Symmetry and Decuplet Intermediate States
We compute the octet baryon charge radii to O(1/Heavy^3) in heavy baryon
chiral perturbation theory. We examine the effect of including the decuplet of
spin-3/2 baryons explicitly. We find that it does no t improve the level of
agreement between the HBchiPT and experimental values for the Sigma^- charge
radius.Comment: 9 pages, 2 figures. Uses axodraw.sty, include
Local vertical measurements and violation of Bell inequality
For two qubits belonging to Alice and Bob, we derive an approach to setup the
bound of Bell operator in the condition that Alice and Bob continue to perform
local vertical measurements. For pure states we find that if the entanglement
of the two qubits is less than 0.2644 (measured with von Neumann entropy) the
violation of the Bell inequality will never be realized, and only when the
entanglement is equal to 1 the maximal violation () can occur. For
specific form of mixed states, we prove that the bound of the Bell inequality
depends on the concurrence. Only when the concurrence is greater than 0.6 the
violation of the Bell inequality can occur, and the maximal violation can never
be achieved. We suggest that the bound of the Bell operator in the condition of
local vertical measurements may be used as a measure of the entanglement.Comment: 4 pages, 3 figure
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