Dualism in Entanglement and Testing Quantum to Classical Transition of Identicity

We show a hitherto unexplored consequence of the property of identicity in quantum mechanics. If two identical objects, distinguished by a dynamical variable A, are in certain entangled states of another dynamical variable B, then, for such states, they are also entangled in variable A when distinguished from each other by variable B. This dualism is independent of quantum statistics. Departures from identicity of the objects due to arbitrarily small differences in their innate attributes destroy this dualism. A system independent scheme to test the dualism is formulated which is readily realizable with photons. This scheme can be performed without requiring the entangled objects to be brought together. Thus whether two macro-systems behave as quantum identical objects can be probed without the complications of scattering. Such a study would complement the program of testing the validity of quantum superposition principle in the macro-domain which has stimulated considerable experimentation.Comment: 4 pages, 3 figure

Uncovering a Nonclassicality of the Schr\"odinger Coherent State up to the Macro-Domain

The Leggett-Garg inequality (LGI), based on the notions of realism and noninvasive measurability, is applied in the context of a linear harmonic oscillator. It is found that merely through observing at various instants which region of the potential well, the oscillating quantum object is in, the LGI can be violated without taking recourse to any ancillary quantum system. Strikingly, this violation reveals an unexplored nonclassicality of the state which is considered the most "classical-like" of all quantum states, namely the Schr\"odinger coherent state. In the macrolimit, the extent to which such nonclassicality persists for large values of mass and classical amplitudes of oscillation is quantitatively investigated. It is found that while for any given mass and oscillator frequency, a significant quantum violation of LGI can be obtained by suitably choosing the initial peak momentum of the coherent state wave packet, as the mass is sufficiently increased, actual observability of this violation becomes increasingly difficult. A feasible experimental setup for testing the predicted quantum mechanical violation of LGI is suggested using a trapped nano-object of $\sim 10^6-10^9$ amu mass

Interpreting the time of decay measurement: phenomenological significance of the Bohm model

We point out that the spreading of wave packets could be significant in affecting the analysis of experiments involving the measurement of time of decay. In particular, we discuss a hitherto unexplored application of the Bohm model in properly taking into account the nontrivial effect of wave packet spreading in the CP violation experiment.Comment: 8 pages, Late

On the importance of the Bohmian approach for interpreting CP-violation experiments

We argue that the inference of CP violation in experiments involving the $K^0-\bar{K^0}$ system in weak interactions of particle physics is facilitated by the assumption of particle trajectories for the decaying particles and the decay products. A consistent explanation in terms of such trajectories is naturally incorporated within the Bohmian interpretation of quantum mechanics.Comment: 7 pages, latex, to appear in Foundations of Physic

Effect of quantum statistics on the gravitational weak equivalence principle

We study the effect of quantum statistics on the arrival time distribution of quantum particles computed through the probability current density. It is shown that symmetrization or asymmetrization of the wave function affects the arrival time distribution for even freely propagating particles. In order to investigate the effect of statistics on the weak equivalence principle in quantum mechanics (WEQ), we then compute the mean arrival time for wave packets in free fall. The violation of WEQ through the effect of statistics on the mass-dependence of the mean arrival time is clearly exhibited. We finally evaluate the effect of spin on the violation of WEQ using a different approach by including an explicit spin-dependence in the probability current distribution, and compare it with the approach using particle statistics. Our results show WEQ re-emerges smoothly in the limit of large mass.Comment: 12 pages, 5 figures, Accepted by Class. Quantum Gra

Proposal for testing non-locality of single photons in cavities

A scheme is formulated for testing nonlocality of single photons by considering the state of a single photon that could be located within one of two spatially separated cavities. The outcomes of four experiments on this state involving the resonant interactions of two-level atoms with these cavities and a couple of other auxiliary ones is shown to lead to a contradiction with the criterion of locality.Comment: 8 pages, 4 eps figs, accepted for publication in Physics Letters

A testable prediction of the no-signalling condition using a variant of the EPR-Bohm example

Predictive power of the no-signalling condition (NSC) is demonstrated in a testable situation involving a non-ideal Stern-Gerlach (SG) device in one of the two wings of the EPR-Bohm entangled pairs. In this wing, for two types of measurement in the other wing, we consider the spin state of a selected set of particles that are confined to a particular half of the plane while emerging from the SG magnetic field region. Due to non-idealness of the SG setup, this spin state will have superposing components involving a relative phase for which a testable quantitative constraint is obtained by invoking NSC, thereby providing a means for precision testing of this fundamentally significant principle.Comment: 7 page

Communicating with a wave packet using quantum superarrival

An analytical treatment of a propagating wave packet incident on a transient barrier reveals a counterintuitive quantum mechanical effect in which, for a particular time interval, the time-varying transmission probability {\it exceeds} (`superarrival') that for the free propagation of the wave packet. It is found that the speed with which the information about the barrier perturbation propagates across the wave packet can exceed the group velocity of the wave packet. An interesting implication of this effect regarding information transfer is analyzed by showing one-to-one correspondence between the strength of the barrier and the magnitude of `superarrival'.Comment: 4 pages, latex, 3 fig

Probing hierarchy of temporal correlation requires either generalised measurement or nonunitary evolution

Temporal steering and violation of the Leggett-Garg inequality are two different ways of probing the violation of macro-realistic assumptions in quantum mechanics. It is shown here that under unitary evolution and projective measurements the two types of temporal correlations lead to similar results. However, their inequivalence may be exhibited if either one of them is relaxed, i.e., by employing either generalized measurements, or noisy evolution, as we show here using relevant examples.Comment: 8 pages, 3 figure

Sharing of Nonlocality of a single member of an Entangled Pair Is Not Possible by More Than Two Unbiased Observers on the other wing

We address the recently posed question as to whether the nonlocality of a single member of an entangled pair of spin $1/2$ particles can be shared among multiple observers on the other wing who act sequentially and independently of each other [1]. We first show that the optimality condition for the trade-off between information gain and disturbance in the context of weak or non-ideal measurements emerges naturally when one employs a one-parameter class of positive operator valued measures (POVMs). Using this formalism we then prove analytically that it is impossible to obtain violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality by more than two Bobs in one of the two wings using unbiased input settings with an Alice in the other wing