Quantum nonlocality which is conventionally invoked for describing a composite entangled system is shown here to be a possible important characteristic of a single quantum object. To this end, we analyze some interactions of a single photon released
from Fabry Perot resonator with environment. The split photon state with oppositely moving parts is shown to obey quantum nonlocality despite the sharp edges truncating each part. Photon post release reflection from a plane mirror is considered. The changing shape of the form during reflection contains moving discontinuities in electric and magnetic components of the pulse. They originate from preexisting edges of the form and move together, first away from and then back to the mirror. At the end of the process, the pulse restores its original shape, with electric component reversed. Altogether, the process demonstrates conservation of moving discontinuities. The considered experimental setup may be used for some ne
Relativistic kinematics is usually considered only as a manifestation of pseudo-Euclidean (Lorentzian) geometry of space-time. However, as it is explicitly stated in General Relativity, the geometry itself depends on dynamics, specifically, on the en
ergy-momentum tensor. We discuss a few examples, which illustrate the dynamical aspect of the length-contraction effect within the framework of Special Relativity. We show some pitfalls associated with direct application of the length contraction formula in cases when an extended object is accelerated. Our analysis reveals intimate connections between length contraction and the dynamics of internal forces within the accelerated system. The developed approach is used to analyze the correlation between two congruent disks - one stationary and one rotating (the Ehrenfest paradox). Specifically, we consider the transition of a disk from the state of rest to a spinning state under the applied forces. It reveals the underlying physical mechanism in the corresponding transition from Euclidean geometry of stationary disk to Lobachevskys (hyperbolic) geometry of the spinning disk in the process of its rotational boost. A conclusion is made that the rest mass of a spinning disk or ring of a fixed radius must contain an additional term representing the potential energy of non-Euclidean circumferential deformation of its material. Possible experimentally observable manifestations of Lobachevskys geometry of rotating systems are discussed.
The lately developed part of Quantum Bayesianism named QBism has been proclaimed by its authors a powerful interpretation of Quantum Physics. This article presents analysis of some aspects of QBism. The considered examples show inconsistencies in som
e basic statements of the discussed interpretation. In particular, the main quantum mechanical conundrum of measurement and the observer is, contrary to the claims, not resolved within the framework of QBism. The conclusion is made that the basic tenets of QBism as applied in Physics are unsubstantiated.
Known experiments with the path entangled photon pairs are considered here under more general conditions widely broadening the domain of used bases. Starting from symmetric beam splitters and equally weighted superposition in the initial setup, we al
low arbitrary beam splitters and in addition insert the new elements: absorptive plates. The first innovation allows one to vary the amplitudes of local interferences. The second one enables the experimenter to monitor the nonlocal superposition amplitudes, thus varying the entanglement strength from maximal to zero. The generalized scheme reveals an interesting effect: the local coherence observed for independent photons disappears already at infinitesimally weak entanglement between them. Mathematically, local coherence turns out to be a discontinuous function of entanglement strength. The same features are unveiled for a quite different system, spin entangled fermion pair. We can thus conjecture a general rule of total mutual intolerance between local coherence and entanglement: any local coherence must vanish completely not only at maximal, but even at arbitrarily weak entanglement between members of studied pair. Altogether, the generalized thought experiment shows that coherence transfer is a complicated phenomenon with common features for various bipartite systems and different types of observables. Key words: Bi-photon, bi-fermion, entanglement, correlations, coherence transfer
Detailed analysis of behavior of spin-entangled particle pairs under arbitrary rotations in their Hilbert space has been performed. It shows a rich range of varieties (faces) of entanglement in different bases. Analytic criteria are obtained for the
respective faces of an entangled state. The corresponding conditions generally depend on both the state itself and the chosen basis. The most important result is revealing a deep analogy between a spin-entangled electronic qubit pair and momentum-entangled photon pair. Both cases exhibit coherence transfer from individual particles to nonlocal state of the system. This analogy allows us to predict certain features of the interference patterns in spin-entangled qubit pairs.
A thought experiment is considered on observation of instantaneous collapse of an extended wave packet. According to relativity of simultaneity, such a collapse being instantaneous in some reference frame must be a lasting process in other frames. Bu
t according to quantum mechanics, collapse is instantaneous in any frame. Mathematical structure of quantum mechanics eliminates any contradictions between these two apparently conflicting statements. Here the invariance of quantum-mechanical collapse is shown to follow directly from the Born postulate, without any use of mathematical properties of quantum operators. The consistency of quantum mechanics with Relativity is also shown for instant disentanglement of a composite system.
A new causal paradox in superluminal signaling is presented. In contrast to the Tolman paradox with tachyon exchange between two parties, the new paradox appears already in a one-way superluminal signaling, even without creating the time loop. This p
roduces a universal ban on superluminal signals, which is stronger than the ban imposed by the Tolman paradox. The analysis also shows that records of evolution of a superluminal object observed from two different reference frames may be time-reversed with respect to each other. Interactions with such objects could add some new features to spectroscopy. Even though relativity embraces superluminal motions, thus making the world symmetric with respect to the invariant speed barrier, their ineptness for signaling makes the symmetry incomplete. Key words: superluminal signaling, tachyons, the Tolman paradox
Some known relativistic paradoxes are reconsidered for closed spaces, using a simple geometric model. For two twins in a closed space, a real paradox seems to emerge when the traveling twin is moving uniformly along a geodesic and returns to the star
ting point without turning back. Accordingly, the reference frames (RF) of both twins seem to be equivalent, which makes the twin paradox irresolvable: each twin can claim to be at rest and therefore to have aged more than the partner upon their reunion. In reality, the paradox has the resolution in this case as well. Apart from distinction between the two RF with respect to actual forces in play, they can be distinguished by clock synchronization. A closed space singles out a truly stationary RF with single-valued global time; in all other frames, time is not a single-valued parameter. This implies that even uniform motion along a spatial geodesic in a compact space is not truly inertial, and there is an effective force on an object in such motion. Therefore, the traveling twin will age less upon circumnavigation than the stationary one, just as in flat space-time. Ironically, Relativity in this case emerges free of paradoxes at the price of bringing back the pre-Galilean concept of absolute rest. An example showing the absence of paradoxes is also considered for a more realistic case of a time-evolving closed space.
This is an analysis of some aspects of an old but still controversial topic, superluminal quantum tunneling. Some features of quantum tunneling described in literature, such as definition of the tunneling time and a frequency range of a signal, are d
iscussed. The argument is presented that claim of superluminal signaling allegedly observed in frustrated internal reflection experiment was based on the wrong interpretation of the tunneling process. A thought experiment similar to that in the Tolman paradox is discussed. It shows that a new factor, attenuation, comes in the interplay between tunneled signals and macroscopic causality.
The evanescent waves named as EW1, EW2, EW3 are described in 3 respective experimental setups: 1) total internal reflection; 2) scattering on an inhomogeneous planar target; and 3) propagation along a waveguide. Some interactions are considered betwe
en EW2 and the environment. The latter may include a beam of probing particles and/or the screen on which the EW2 are formed. Some new properties of EW are described, such as complex energy eigenvalues in case of a movable screen, and evanescence exchange between the interacting objects. This reveals the connection between evanescent states and the Gamow states of the studied system. The 4-momentum exchange between EW2 and the probe is highly selective and may collapse the superposition of studied EW2- eigenstates to a single EW-eigenstate of the probing particle. Possible imprints of EW2 in the far field are briefly discussed and a simple experiment is suggested for their observation. .
