New loophole for the Einstein-Podolsky-Rosen paradox

Using the new concept of "stochastic gauge system", we describe a novel loophole to circumvent the Einstein-Podolsky-Rosen (EPR) paradox. We derive a "realistic" (i.e., classical) model, free from any paradox, which exactly emulates the spin EPR experiment. We conclude that Bell's inequalities are violated in classical physics as well, or, conversely that quantum mechanical theory is logically consistent with relativity.     

The bell inequalities

It is shown that the Bell inequalities are conditions that must be satisfied by the probability functions of certain three-variable systems if they are to be expressible in terms of a single, nonnegative function. The generalized Bell inequalities, or CHSH inequalities, play a similar role for four-variable systems. The physical significance of the results is discussed.     

Complete correlation,detection loophole and Bell's theorem

Two new formulations of Bell's theorem are given here. First, we consider a definite set of two entangled photons with only two polarization directions, for which Bell's locality assumption is violated for the case of perfect correlation. Then, using a different approach, we prove an efficient Bell‐type inequality which is violated by some quantum mechanical predictions, independent of the efficiency factors.     

Hiding bits in bell states.

We present a scheme for hiding bits in Bell states that is secure even when the sharers, Alice and Bob, are allowed to carry out local quantum operations and classical communication. We prove that the information that Alice and Bob can gain about a hidden bit is exponentially small in n, the number of qubits in each share, and can be made arbitrarily small for hiding multiple bits. We indicate an alternative efficient low-entanglement method for preparing the shared quantum states. We discuss how our scheme can be implemented using present-day quantum optics.     

Error correcting bell inequalities

Quantum error-correcting codes can protect multipartite quantum states from errors on some limited number of their subsystems (usually qubits). We construct a family of Bell inequalities which inherit this property from the underlying code and exhibit the violation of local realism, without any quantum information processing (except for the creation of an entangled state). This family shows no reduction in the size of the violation of local realism for arbitrary errors on a limited number of qubits. Our minimal construction requires preparing an 11-qubit entangled state.     

Detection of cosmic ray events by LEP experiments

Accelerator experiments located at LEP collider have been used also to detect cosmic ray events. Various results obtained by Cosmo-ALEPH, DELPHI and L3+C collaborations are described). Emphasis is put on comparisons of various measurements with Monte-Carlo simulations based on current models of primary hadron-hadron interactions. Analysis of muon momentum spectrum by Cosmo-ALEPH is presented and the link of these measurements to various tests of hadron-hadron interactions models is explained using L3+C data. Cosmo-ALEPH studies of coincident events between distant scintillator stations is briey described. The analyses of multi-muon bundles are explained in more details for all three experiments Cosmo-ALEPH, DELPHI and L3+C. Other topics like source searches by L3+C, ALEPH and DELPHI, L3+C results on anti-proton/proton flux, solar are study, etc. demonstrate large variety of cosmic ray studies at LEP.     

Biphoton light generation in polarization-frequency bell states

Four polarization-frequency Bell states are obtained experimentally for photon pairs (biphotons) emitted during spontaneous parametric scattering from continuous pumping in the collinear frequency-nondegenerate regime. The polarization properties of such states are investigated. It is shown that biphoton light in the singlet Bell state is not polarized in the second or fourth order in the field.     

Studies with an eccentric bell

Vibration measurements have been made on a highly eccentric bell. Only negligible splitting of most partials was observed, thus casting doubt on the ability of group theory to handle this type of problem adequately. The implications for warble suppression are discussed.     

Correlation complementarity yields bell monogamy relations

We present a method to derive Bell monogamy relations by connecting the complementarity principle with quantum nonlocality. The resulting monogamy relations are stronger than those obtained from the no-signaling principle alone. In many cases, they yield tight quantum bounds on the amount of violation of single and multiple qubit correlation Bell inequalities. In contrast with the two-qubit case, a rich structure of possible violation patterns is shown to exist in the multipartite scenario.     

大钟拍声的调整实验

阐明大钟拍声的发生原理,并用大钟振动拍的理论模型说明拍的特性,从而控制清晰度。在实验钟上附着质量,根据附着质量位置的不同,能够改变其非对称程度,进一步调整拍频,同时用有限元分析的结果和等效圆环理论计算的结果对比。引入等效圆环理论,通过建立一个理论上带有附加质量的轴对称圆环模型,达到具有和大钟相同的振动特性。根据模型,得到在大钟特定位置附加的质量,以同时调整所需拍的清晰度和周期。在大钟多个位置进行实验,并进行有限元分析,验证了该理论的有效性。     

Bipartite bell inequalities for hyperentangled states

We show that bipartite Bell inequalities based on the Einstein-Podolsky-Rosen criterion for elements of reality and derived from the properties of some hyperentangled states allow feasible experimental verification of the fact that quantum nonlocality grows exponentially with the size of the subsystems, and Bell loophole-free tests with currently available photodetection efficiencies.     

Single-clipped correlation and the bell polynomials

A closed form for the infinite sum occurring in the expression of the single-clipped correlation is derived and its relation with the “exponential Bell polynomials” is established.     

Indistinguishability of orthogonal time-separated bell states

This paper proves that it is impossible to identify orthogonally time-separated Bell states. If two qubits of a Bell state interact with the measurement apparatus at different time, any attempt to identify this state will disturb it.     

Controlling a sine wave gating single-photon detector by exploiting its filtering loophole

GHz single-photon detector(SPD) is a crucial part in the practical high speed quantum key distribution(QKD) system.However, any imperfections in a practical QKD system may be exploited by an eavesdropper(Eve) to collect information about the key without being discovered. The sine wave gating SPD(SG-SPD) based on InGaAs/InP avalanche photodiode,one kind of practical high speed SPD, may also contain loopholes. In this paper, we study the principle and characteristic of the SG-SPD and find out the filtering loophole of the SG-SPD for the first time. What is more, the proof-of-principle experiment shows that Eve could blind and control Bob's SG-SPD by exploiting this loophole. We believe that giving enough attention to this loophole can improve the practical security of the existing QKD system.     

Quantum cryptography using entangled photons in energy-time bell states

We present a setup for quantum cryptography based on photon pairs in energy-time Bell states and show its feasibility in a laboratory experiment. Our scheme combines the advantages of using photon pairs instead of faint laser pulses and the possibility to preserve energy-time entanglement over long distances. Moreover, using four-dimensional energy-time states, no fast random change of bases is required in our setup: Nature itself decides whether to measure in the energy or in the time base, thus rendering eavesdropper attacks based on "photon number splitting" less efficient.     

Normal modes of the Indian elephant bell

The geometrical structure of the Indian elephant bell is presented and the requirements on its normal modes from group representation theory are described. These are in good agreement with the results of a finite-element model (FEM) for a specific 16-tine case. The spectrum consists of a sequence of families of modes lying on saturation curves, completely different from those of conventional bells. Physical explanations for the occurrence of these families are presented in terms of the tines behaving as a closed loop of coupled cantilevers with constraints from the dome. Each family is found to consist of modes in one of two specific sequences of symmetry types. Experimental measurements of the modes of this same 16-tine bell, using electronic speckle pattern interferometry (ESPI), have been made and are compared with the FEM predictions. Although the interpretation of the interferograms is difficult in all but the simpler cases, agreement in terms of frequencies is surprisingly good for the first few family sequences. The ESPI study also showed up numerous harmonics and subharmonics of true normal modes, showing the system to be rather non-linear and making comparisons with the FEM results tricky.     

The geometrical aspects of the bell inequalities

The Bell inequalities of the metric form are introduced. The quantum-mechanical correlations of the particles with s=1/2 and photons are described using the relative measure of probability on the concave surfaces. The relation of the proposed scheme with the Bayes theorem about conditional information entropy and J. von Neumann's postulates is discussed.     

Observation of bunching of two bell states

The bunching of two single photons on a beam splitter is a fundamental quantum effect, first observed by Hong, Ou, and Mandel. It is a unique interference effect that relies only on the photons' indistinguishability and not on their relative phase. We generalize this effect by demonstrating the bunching of two Bell states, created in two passes of a nonlinear crystal, each composed of two photons. When the two Bell states are indistinguishable, phase-insensitive destructive interference prevents the outcome of fourfold coincidence between the four spatial-polarization modes. For certain combinations of the two Bell states, we demonstrate the opposite effect of antibunching. We relate this result to the number of distinguishable modes in parametric down-conversion.     

Solid-state interfacial reaction and asymmetric growth of amorphous interlayers in Ni/Nb multilayers. Molecular-dynamics simulation together with experiments

An embedded-atom potential for the Ni-Nb system is constructed using physical properties obtained from first-principle calculations. Employing the potential, molecular-dynamics simulations are performed to study the interfacial reaction in Ni/Nb multilayers upon annealing at medium temperatures. The results show that a preset disordered interlayer, which is obtained by exchanging Ni and Nb atoms in the interfaces, may act as a nucleus of amorphous phase and is usually necessary for amorphization. It is found that the growth of the amorphous interlayer is in a planar mode and exhibits an asymmetric behavior due to a faster consumption of Ni than that of the Nb layer; this is also indeed observed experimentally. Moreover, performing a simulation with solid solution models, it is found that the Nb lattice can accommodate a large number of Ni atoms and still retain a crystalline structure, while a small amount of Nb atoms induce a spontaneous decay of the Ni lattice. Such differences in solid solubility is thought to be the physical origin of the asymmetric growth observed in experiments and simulations. Received 7 June 1999 and Received in final form 12 January 2000