796 research outputs found
Non-classical properties and algebraic characteristics of negative binomial states in quantized radiation fields
We study the nonclassical properties and algebraic characteristics of the
negative binomial states introduced by Barnett recently. The ladder operator
formalism and displacement operator formalism of the negative binomial states
are found and the algebra involved turns out to be the SU(1,1) Lie algebra via
the generalized Holstein-Primarkoff realization. These states are essentially
Peremolov's SU(1,1) coherent states. We reveal their connection with the
geometric states and find that they are excited geometric states. As
intermediate states, they interpolate between the number states and geometric
states. We also point out that they can be recognized as the nonlinear coherent
states. Their nonclassical properties, such as sub-Poissonian distribution and
squeezing effect are discussed. The quasiprobability distributions in phase
space, namely the Q and Wigner functions, are studied in detail. We also
propose two methods of generation of the negative binomial states.Comment: 17 pages, 5 figures, Accepted in EPJ
Localization of the Activation Gate of a Voltage-gated Ca2+ Channel
Ion channels open and close in response to changes in transmembrane voltage or ligand concentration. Recent studies show that K+ channels possess two gates, one at the intracellular end of the pore and the other at the selectivity filter. In this study we determined the location of the activation gate in a voltage-gated Ca2+ channel (VGCC) by examining the open/closed state dependence of the rate of modification by intracellular methanethiosulfonate ethyltrimethylammonium (MTSET) of pore-lining cysteines engineered in the S6 segments of the α1 subunit of P/Q type Ca2+ channels. We found that positions above the putative membrane/cytoplasm interface, including two positions below the corresponding S6 bundle crossing in K+ channels, showed pronounced state-dependent accessibility to internal MTSET, reacting ∼1,000-fold faster with MTSET in the open state than in the closed state. In contrast, a position at or below the putative membrane/cytoplasm interface was modified equally rapidly in both the open and closed states. Our results suggest that the S6 helices of the α1 subunit of VGCCs undergo conformation changes during gating and the activation gate is located at the intracellular end of the pore
Practical Phase-Coding Side-Channel-Secure Quantum Key Distribution
All kinds of device loopholes give rise to a great obstacle to practical
secure quantum key distribution (QKD). In this article, inspired by the
original side-channel-secure protocol [Physical Review Applied 12, 054034
(2019)], a new QKD protocol called phase-coding side-channel-secure (PC-SCS)
protocol is proposed. This protocol can be immune to all uncorrelated side
channels of the source part and all loopholes of the measurement side. A
finite-key security analysis against coherent attack of the new protocol is
given. The proposed protocol only requires modulation of two phases, which can
avoid the challenge of preparing perfect vacuum states. Numerical simulation
shows that a practical transmission distance of 300 km can be realized by the
PC-SCS protocol
Quantum repeaters free of polarization disturbance and phase noise
Original quantum repeater protocols based on single-photon interference
suffer from phase noise of the channel, which makes the long-distance quantum
communication infeasible. Fortunately, two-photon interference type quantum
repeaters can be immune to phase noise of the channel. However, this type
quantum repeaters may still suffer from polarization disturbance of the
channel. Here we propose a quantum repeaters protocol which is free of
polarization disturbance of the channel based on the invariance of the
anti-symmetric Bell state under collective
noise. Our protocol is also immune to phase noise with the Sagnac
interferometer configuration. Through single-atom cavity-QED technology and
linear optics, this scheme can be implemented easily.Comment: 5 pages, 2 figure
Poly[[[μ-1,1′-(butane-1,4-diyl)diimidazole-κ2 N 3:N 3′](μ-cyclohexane-1,4-dicarboxylato-κ4 O 1,O 1′:O 4,O 4′)nickel(II)] 0.25-hydrate]
In the title coordination polymer, {[Ni(C8H10O4)(C10H14N4)]·0.25H2O}n, the coordination of the NiII ion is distorted octahedral. The 1,1′-(butane-1,4-diyl)diimidazole ligand and the cyclohexane-1,4-dicarboxylate dianion bridge metal centres, forming a two-dimensional (4,4) network. The network is consolidated by O—H⋯O hydrogen bonds between the statistically occupied water molecules and O atoms of the two carboxylate groups
Interferencing intensity in two Bose-Einstein condensates with Josephson-like coupling
Abstract We derive a general expression for interferencing intensity in two Bose -Einstein condensates with Josephson-like coupling when the two Bose -Einstein condensates are initially in arbitrary quantum pure states. The expression can be used to numerically calculate the intensity. As examples, we study the time behaviors of the intensity when the two Bose -Einstein condensates are initially in coherent states, Fock states, and squeezed states, respectively. c 1999 Elsevier Science B.V. All rights reserved. PAC
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