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A. V. Nikulov

Publications and source records attributed to A. V. Nikulov.

At least 55 records · Page 3Linked to original sources
arXiv2009

Contradiction between assumption on superposition of flux-qubit states and the law of angular momentum conservation

Superconducting loop interrupted by one or three Josephson junctions is considered in many publications as a possible quantum bit, flux qubit, which can be used for creation of quantum computer. But the assumption on superposition of two macroscopically distinct quantum states of superconducting loop contradict to the fundamental law of angular momentum conservation and the universally recognized quantum formalism. Numerous publications devoted to the flux qubit testify to an inadequate interpretation by many authors of paradoxical nature of superposition principle and the subject of quantum description.

physics.gen-ph↗
arXiv2009

Aharonov-Bohm effects in nanostructures

Measurements of the Little-Parks oscillations at measuring current much lower than the persistent current give unambiguous evidence of the dc current flowing against the force of the dc electric field because of the Aharonov-Bohm effect. This result can assume that an additional force is needed for description of the Aharonov-Bohm effect observed in semiconductor, normal metal and superconductor nanostructures in contrast to the experimental result obtained recently for the case of the two-slit interference experiment.

cond-mat.supr-con↗
arXiv2009

Quantum oscillations of the critical current of asymmetric superconducting rings and systems of the rings

The quantum oscillations in magnetic field of the critical current of asymmetric superconducting rings with different widths of the half-rings are shifted to opposite sides for measurement in the opposite direction. The value of this shift found before equal half of the flux quantum for single ring with radius 2 μm has smaller value at lower critical current and for system of the rings with smaller radius.

cond-mat.supr-con↗
arXiv2009

Superposition of flux-qubit states and the law of angular momentum conservation

It is shown that the assumptions on macroscopic quantum tunneling and on superposition of two macroscopically distinct quantum states of superconducting loop, considered as flux qubit by many authors, contradict to the fundamental law of angular momentum conservation and the universally recognized quantum formalism.

cond-mat.supr-con↗
arXiv2009

Magnetic dependence of the critical and persistent current of asymmetric superconducting rings

The obtained periodic magnetic-field dependencies of the critical current, measured in opposite directions on asymmetric superconducting aluminum rings, allow to explain observed earlier quantum oscillations of a dc voltage as a result of alternating current rectification. It is found, that the high efficiency of the rectification of both individual rings and ring systems is connected to a hysteresis of the current-voltage characteristics. The asymmetry of the current-voltage characteristics providing the rectification effect is due to the relative shifts of the magnetic dependencies of the critical current measured in opposite directions. This shift means that position of the critical current minimums does not correspond to n + 0.5 magnetic flux quantum which is in the direct contradiction with measurement results of the Little-Parks resistance oscillations. Despite of this contradiction the amplitude of the critical current anisotropy oscillations and its variations with temperature correspond to expected amplitude of the persistent current oscillations and to its variations with temperature.

cond-mat.supr-con↗
arXiv2008

Bohm's quantum potential and quantum force in superconductor

The Bohm's quantum potential, introduced in 1952, and the quantum force in superconductor, introduced in 2001, allow to describe non-local force-free momentum transfer observed in the Ahronov-Bohm effects. Comparison of the Ahronov-Bohm effects in the two-slit interference experiment and in superconductor ring reveals fundamental difference between the Schrodinger wave function and the wave function describing macroscopic quantum phenomena. The Ginzburg-Landau wave function describing the superconductivity phenomenon can not collapse and an additional postulate, which was implied first by L.D. Landau, must be used for the description of macroscopic quantum phenomena. It is note that quantum principles and postulates should not be universal till the quantum formalism is only phenomenological theory but no description of an unique reality. A simple Gedankenexperiment is considered which challenges the universality of the Heisenberg uncertainty relation and the Bohr's complementarity principle.

quant-ph↗
arXiv2008

Observation of the Little-Parks Oscillations in a System of Asymmetric Superconducting Rings

Little-Parks oscillations are observed in a system of 110 series-connected aluminum rings 2000 nm in diameter with the use of measuring currents from 10 nA to 1000 nA. The measurements show that the amplitude and character of the oscillations are independent of the relation between the measuring current and the amplitude of the persistent current. By using asymmetric rings, it is demonstrated that the persistent current has clockwise or contra-clockwise direction. This means that the total current in one of the semi-rings may be directed against the electric field at measurement of the Little-Parks oscillations. The measurements at zero and low measuring current have revealed that the persistent current, like the conventional circulating current, causes a potential difference on the semi-rings with different cross sections in spite of the absence of the Faraday's voltage.

cond-mat.supr-con↗
arXiv2008

About Essence of the Wave Function on Atomic Level and in Superconductors

The wave function was proposed for description of quantum phenomena on the atomic level. But now it is well known that quantum phenomena are observed not only on atomic level and the wave function is used for description of macroscopic quantum phenomena, such as superconductivity. The essence of the wave function on level elementary particles was and is the subject of heated argument among founders of quantum mechanics and other physicists. This essence seems more clear in superconductor. But impossibility of probabilistic interpretation of wave function in this case results to obvious contradiction of quantum principles with some fundamental principles of physics.

physics.gen-ph↗
arXiv2007

Magnetic field dependence of the electrical conductivity in V3Ge in the vicinity of Hc2

The phase transition from the Abrikosov state to the normal state with superconducting fluctuations observed below the second critical field and well-known as vortex lattice melting was one of the most popular problems in the nineties. This problem had became popular after the discovery of high-Tc superconductors because the fluctuation phenomena are much stronger in the HTSC than in the conventional superconductors. Most people are sure that this sharp transition was observed for the present only in HTSC and are ignorant that it was observed as far back as 1981, before the HTSC discovery. In the last years some papers devoted to the problem of vortex lattice melting in conventional superconductors were published. The authors of these papers and others should be aware of the result obtained before the HTSC discovery. It was found first in the presented paper that the transition into the Abrikosov vortex state is very narrow in high quality samples with weak pinning and it is observed below the second critical field. These results signify that this phase transition can be first-order and it is not connected directly with appearance of a finite density of superconducting pairs.

cond-mat.supr-con↗
arXiv2007

The quantum challenge on mesoscopic level

Most experts reject the quantum potential introduced by David Bohm in 1952. But it is impossible to describe some quantum mesoscopic phenomena observed in superconductor nanostructures without a quantum force.

cond-mat.supr-con↗
arXiv2006

Investigation of possibility of creation of a superconductor quantum register

Multiple and single measurements of quantum states of mesoscopic superconducting loops are carried out in order to investigate a possibility of macroscopic quantum superposition and of creation of a superconductor quantum register. Asymmetric superconducting rings are used in order to be convinced that single measurement gives result corresponding to one of permitted states and multiple one gives an average value on these states. We have measured magnetic dependencies of resistance, rectified voltage and critical current on these rings. The observed quantum oscillations of the resistance and the rectified voltage, corresponding to multiple measurement of quantum states, give evidence of two permitted states at the magnetic flux inside the ring divisible by half of the flux quantum. But the observed quantum oscillations of the critical current, corresponding to single measurement, not only does not confirm these two quantum states, but are in a direct contradiction with the observed oscillations of the resistance. It is assumed that the observed contradiction between the results of measurements made on the same ring can testify to violation of the principle of realism on the mesoscopic level that is a necessary condition for an opportunity of creation of a quantum computer.

cond-mat.supr-con↗
arXiv2006

Multiple and single measurements of a mesoscopic quantum system with two permitted states

Mesoscopic loop is proposed in many works as possible solid-state quantum bit, i.e. two-state quantum system. The quantum oscillations of resistance and of rectified voltage observed on asymmetric superconducting loops give evidence of the two states at magnetic flux divisible by half of the flux quantum. But our measurements of quantum oscillations of the critical current of these loops have given results coming into irreconcilable contradictions with result of the observations of the quantum oscillations of resistance.

cond-mat.supr-con↗
arXiv2006

Could the EPR correlation be in superconducting structures? Possibility of experimental verification

In order to have a chance to make a real quantum computer it is important to find the entanglement phenomenon on mesoscopic level since technology can not be able in the visible future to work on atomic level. It is known that the entanglement (the EPR correlation) violates the principle of local realism. Existence of EPR correlation on a level higher than atomic one violates both local and macroscopic realism. In order to clear possibility of this violation the fundamental difference between applications of the principles of quantum mechanics on atomic and higher level is considered. Mysterious nature of some macroscopic quantum phenomena is accentuated. Experimental verification of the entanglement possibility in superconductor structure is proposed.

cond-mat.supr-con↗
arXiv2006

Could two degenerate energy states be observed for a superconducting ring at $Φ_{0}$/2?

The Little-Parks oscillations of the resistance and the quantum oscillations of the rectified voltage observed for asymmetric superconducting Al rings give experimental evidence of two degenerate energy states at the magnetic flux $Φ_{0}$/2. The quantum oscillations of the critical current as a function of magnetic field have also been measured. On the one hand, these oscillations confirm that the quantum oscillations of the rectified voltage are a consequence of periodical dependence of the asymmetry of the current-voltage curves and, on the other hand, comparison of the oscillations with Little-Parks measurements results in contradiction.

cond-mat.supr-con↗
arXiv2006

Calibration of quantum detector of noise based on a system of asymmetric superconducting loops

The quantum oscillations of the dc voltage are induced on segments of asymmetric superconducting loops by an external ac current or noise. The dependencies of the amplitude of the quantum oscillations on amplitude of inducing ac current are measured at different temperatures below superconducting transition Tc on aluminum asymmetric loops and systems of the loops connected in series. The measured values of the maximum amplitude of the quantum oscillations, the amplitude of the ac current inducing this maximum dc voltage and the critical amplitude of the ac current decrease with temperature increase to Tc. The extrapolation of these measured dependencies to the region near superconducting transition allows to make a calibration of asymmetric superconducting loops as quantum detector of noise. The calibration restores an amplitude profile of the noise pulses from a measured temperature dependence of an amplitude of the quantum oscillations induced by this noise. It is found that rectification efficiency, determined as relation of the maximum amplitude of the quantum oscillations to the ac current amplitude inducing it, decreases near superconducting transition Tc. High efficiency of rectification observed below Tc is consequence of irreversibility of the current-voltage curves. Increase of the rectification efficiency is achieved in multiple series connected loop structures.

cond-mat.supr-con↗