arXiv subjects

S. Yu. Kun

Publications and source records attributed to S. Yu. Kun.

8 recordsLinked to original sources

arXiv2007

Experimental indication of anomalous sensitivity in many-body systems: Deterministic randomness in complex quantum collisions?

We have experimentally tested a recently suggested possibility for anomalous sensitivity of the cross sections of dissipative heavy ion collisions. Cross sections for the $^{19}$F+$^{27}$Al dissipative collisions were measured at the fixed energy 118.75 MeV of the $^{19}$F for the 12 different beam spots on the same target foil. The data demonstrate dramatic differences between the cross sections for the different beam spots. The effect may indicate deterministic randomness in complex quantum collisions. New experiments are highly desirable in a view of the fundamental importance of the problem.

quant-ph↗

arXiv2007

Thermalized non-equilibrated matter and high temperature superconducting state in quantum many-body systems

A characteristic feature of thermalized non-equilibrated matter is that, in spite of energy relaxation--equilibration, a phase memory of the way the many-body system was excited remains. As an example, we analyze data on a strong forward peaking of thermal proton yield in the Bi($γ$,p) photonuclear reaction. New analysis shows that the phase relaxation in highly-excited heavy nuclei can be 8 orders of magnitude or even much longer than the energy relaxation. We argue that thermalized non-equilibrated matter resembles a high temperature superconducting state in quantum many-body systems. We briefly present results on the time-dependent correlation function of the many-particle density fluctuations for such a superconducting state. It should be of interest to experimentally search for manifestations of thermalized non-equilibrated matter in many-body mesoscopic systems and nanostructures.

cond-mat.supr-con↗

arXiv2007

Quantum-classical transition for an analog of double-slit experiment in complex collisions: Dynamical decoherence in quantum many-body systems

We study coherent superpositions of clockwise and anti-clockwise rotating intermediate complexes with overlapping resonances formed in bimolecular chemical reactions. Disintegration of such complexes represents an analog of famous double-slit experiment. The time for disappearance of the interference fringes is estimated from heuristic arguments related to fingerprints of chaotic dynamics of a classical counterpart of the coherently rotating complex. Validity of this estimate is confirmed numerically for the H+D$_2$ chemical reaction. Thus we demonstrate the quantum--classical transition in temporal behavior of highly excited quantum many-body systems in the absence of external noise and coupling to an environment.

quant-ph↗

arXiv2006

Effect of phase relaxation on quantum superpositions in complex collisions

We study the effect of phase relaxation on coherent superpositions of rotating clockwise and anticlockwise wave packets in the regime of strongly overlapping resonances of the intermediate complex. Such highly excited deformed complexes may be created in binary collisions of heavy ions, molecules and atomic clusters. It is shown that phase relaxation leads to a reduction of the interference fringes, thus mimicking the effect of decoherence. This reduction is crucial for the determination of the phase--relaxation width from the data on the excitation function oscillations in heavy--ion collisions and bimolecular chemical reactions. The difference between the effects of phase relaxation and decoherence is discussed.

quant-ph↗

arXiv2006

Anomalously Slow Cross Symmetry Phase Relaxation, Thermalized Non-Equilibrated Matter and Quantum Computing Beyond the Quantum Chaos Border

Thermalization in highly excited quantum many-body system does not necessarily mean a complete memory loss of the way the system was formed. This effect may pave a way for a quantum computing, with a large number of qubits $n\simeq 100$--1000, far beyond the quantum chaos border. One of the manifestations of such a thermalized non-equilibrated matter is revealed by a strong asymmetry around 90$^\circ $ c.m. of evaporating proton yield in the Bi($γ$,p) photonuclear reaction. The effect is described in terms of anomalously slow cross symmetry phase relaxation in highly excited quantum many-body systems with exponentially large Hilbert space dimensions. In the above reaction this phase relaxation is about eight orders of magnitude slower than energy relaxation (thermalization).

quant-ph↗

arXiv2005

Meltdown in quantum computers needs not occur: Nuclear experiments show a way out

We show that phase memory can be much longer than energy relaxation in systems with exponentially large dimensions of Hilbert space; this finding is documented by fifty years of nuclear experiments, though the information is somewhat hidden. For quantum computers Hilbert spaces of dimension $2^{100}$ or larger will be typical and therefore this effect may contribute significantly to reduce the problems of scaling of quantum computers to a useful number of qubits.

quant-ph↗

arXiv2004

Effect of a finite-time resolution on Schrödinger Cat States in complex collisions

We study the effect of finite time resolution on coherent superpositions of rotating clockwise and anticlockwise wave packets in the regime of strongly overlapping resonances of the intermediate complex. Such highly excited deformed complexes may be created in binary collisions of heavy-ions, molecules and atomic clusters. It is shown that time averaging reduces the interference fringes acting effectively as dephasing. We propose a simple estimate of the ``critical'' time averaging interval. For the time averaging intervals bigger than the critical one the interference fringes wash out appreciably. This is confirmed numerically. We evaluate minimal energy intervals for measurements of the excitation functions needed to observe the Schrödinger Cat States. These should be easily observable in heavy-ion scattering. Such an experiment is suggested.

nucl-th↗

arXiv2003

Macroscopic quantum superpositions in highly-excited strongly-interacting many-body systems

We demonstrate a break-down in the macroscopic (classical-like) dynamics of wave-packets in complex microscopic and mesoscopic collisions. This break-down manifests itself in coherent superpositions of the rotating clockwise and anticlockwise wave-packets in the regime of strongly overlapping many-body resonances of the highly-excited intermediate complex. These superpositions involve $\sim 10^4$ many-body configurations so that their internal interactive complexity dramatically exceeds all of those previously discussed and experimentally realized. The interference fringes persist over a time-interval much longer than the energy relaxation-redistribution time due to the anomalously slow phase randomization (dephasing). Experimental verification of the effect is proposed.

quant-ph↗