共查询到20条相似文献,搜索用时 31 毫秒
1.
I. N. Yakunin V. L. Berdinskii 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(3):384-390
Manifestations of the chemical Zeno effect (slowing down of the quantum evolution of radical pairs as a result of spin-selective
recombination of exchange-bounded radical pairs) are considered. In radical pairs created in singlet and random spin states,
the chemical kinetics is described by the sum of kinetic evolution (exponential) and oscillatory functions. The kinetic function
is a superposition of two exponential functions. Recombination monotonically decreases the amplitude of quantum beats in singlet
radical pairs. The dependence of the amplitude of quantum beats in noncorrelated radical pairs on the recombination rate constant
is not monotonic. 相似文献
2.
P.E. Toschek Ch. Wunderlich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):387-396
The evolution of a quantum system under observation becomes retarded or even impeded. We review this “quantum Zeno effect”
in the light of the criticism that has been raised upon a previous attempt to demonstrate it, of later reexaminations of both
the projection postulate and the significance of the observations, and of the results of a recent experiment on an individual cold atom. Here, the micro-state of the quantum system gets unveiled with the observation, and the effect of measurement
is no longer mixed up with dephasing the object's wave function by the reactive effect of the detection. A procedure is outlined
that promises to provide, by observation, an upper limit for the delay of even an exponential decay.
Received 11 January 2001 and Received in final form 28 February 2001 相似文献
3.
John G. Cramer 《Foundations of Physics Letters》2006,19(1):63-73
The transactional interpretation of quantum mechanics is applied to the “interaction-free” measurement scenario of Elitzur
and Vaidman and to the Quantum Zeno effect version of the measurement scenario by Kwiat et al. It is shown that the non-classical information provided by the measurement scheme is supplied by the probing of the intervening
object by incomplete offer and confirmation waves that do not form complete transactions or lead to real interactions. 相似文献
4.
A direct test of the so-called “quantum Zeno effect” is proposed for a truly decaying system. It is suggested that the lifetime
of an unstable atom can be extended by illuminating it with an intense laser beam at the frequency of another of its transitions.
The “Zeno” time is also compared to the lifetime 相似文献
5.
L. S. Schulman 《Foundations of Physics》1997,27(12):1623-1636
The quantum Zeno effect (QZE) is often associated with the ironic maxim, “a watched pot never boils”, although the notion
of “watching” suggests a continuous activity at odds with the usual (pulsed measurement) presentation of the QZE. We show
how continuous watching can provide the same halting of decay as the usual QZE, and, for incomplete hindrance, we provide
a precise connection between the interval between projections and the response time of the continuous observer. Thus, watching
closely, but not so closely as to halt the “boiling”, is equivalent to—gives the same degree of partial hindrance as—pulsed
measurements with a particular pulsing rate. Our demonstration is accomplished by treating the apparatus for the continuous
watching as a fully quantum object. This in turn allows us a second perspective on the QZE, in which it is the modified level
structure of the combined system/apparatus Hamiltonian that slows the decay. This and other considerations favor the characterization
“dominated time evolution” for the QZE. 相似文献
6.
A. A. Prokofiev A. S. Moskalenko I. N. Yassievich W. D. A. M. de Boer D. Timmerman H. Zhang W. J. Buma T. Gregorkiewicz 《JETP Letters》2009,90(12):758-762
The effect of quantum confinement on the direct bandgap of spherical Si nanocrystals has been modelled theoretically. We conclude
that the energy of the direct bandgap at the Γ-point decreases with size reduction: quantum confinement enhances radiative
recombination across the direct bandgap and introduces its “red“ shift for smaller grains. We postulate to identify the frequently
reported efficient blue emission (F-band) from Si nanocrystals with this zero-phonon recombination. In a dedicated experiment, we confirm the “red“ shift of
the F-band, supporting the proposed identification. 相似文献
7.
M. B. Mensky 《Optics and Spectroscopy》2007,103(3):461-467
Conceptual problems in quantum mechanics result from the specific quantum concept of reality and require, for their solution,
including the observer’s consciousness into the quantum theory of measurements. Most naturally, this is achieved in the framework
of Everett’s “many-world interpretation” of quantum mechanics. According to this interpretation, various classical alternatives
are perceived by consciousness separately from each other. In the Extended Everett Concept (EEC) proposed by the present author,
the separation of the alternatives is identified with the phenomenon of consciousness. This explains the classical character of the alternatives and unusual manifestations
of consciousness arising “at the edge of consciousness” (i.e., in sleep or trance) when its access to “other alternative classical
realities” (other Everett’s worlds) becomes feasible. Because of reversibility of quantum evolution in EEC, all time moments
in the quantum world are equivalent, while the impression of flow of time appears only in consciousness. If it is assumed
that consciousness may influence the probabilities of alternatives (which is consistent in case of infinitely many Everett’s
worlds), EEC explains free will, “probabilistic miracles” (observing low-probability events), and decreasing entropy in the
sphere of life.
The text was submitted by the author in English. 相似文献
8.
A. M. M. Pruisken 《International Journal of Theoretical Physics》2009,48(6):1736-1765
It is shown that the “massless chiral edge excitations” are an integral and universal aspect of the low energy dynamics of
the ϑ vacuum that has historically gone unnoticed. Within the SU(M+N)/S(U(M)×U(N)) non-linear sigma model we introduce an effective theory of “edge excitations” that fundamentally explains the quantum Hall
effect. In sharp contrast to the common beliefs in the field our results indicate that this macroscopic quantization phenomenon
is, in fact, a super universal strong coupling feature of the ϑ angle with the replica limit M=N=0 only playing a role of secondary importance. To demonstrate super universality we revisit the large N expansion of the CP
N−1 model. We obtain, for the first time, explicit scaling results for the quantum Hall effect including quantum criticality
of the quantum Hall plateau transition. Consequently a scaling diagram is obtained describing the cross-over between the weak
coupling “instanton phase” and the strong coupling “quantum Hall phase” of the large N theory. Our results are in accordance with the “instanton picture” of the ϑ angle but fundamentally invalidate all the ideas, expectations and conjectures that are based on the historical “large N picture.” 相似文献
9.
The rise of quantum information theory has lent new relevance to experimental tests for non-classicality, particularly in
controversial cases such as adiabatic quantum computing superconducting circuits. The Leggett-Garg inequality is a “Bell inequality
in time” designed to indicate whether a single quantum system behaves in a macrorealistic fashion. Unfortunately, a violation
of the inequality can only show that the system is either (i) non-macrorealistic or (ii) macrorealistic but subjected to a measurement technique that happens to disturb the system. The “clumsiness” loophole
(ii) provides reliable refuge for the stubborn macrorealist, who can invoke it to brand recent experimental and theoretical
work on the Leggett-Garg test inconclusive. Here, we present a revised Leggett-Garg protocol that permits one to conclude
that a system is either (i) non-macrorealistic or (ii) macrorealistic but with the property that two seemingly non-invasive measurements can somehow collude and strongly disturb
the system. By providing an explicit check of the invasiveness of the measurements, the protocol replaces the clumsiness loophole
with a significantly smaller “collusion” loophole. 相似文献
10.
David Finkelstein 《International Journal of Theoretical Physics》1982,21(6-7):489-503
The mathematical language presently used for quantum physics is a high-level language. As a lowest-level or basic language
I construct a quantum set theory in three stages: (1) Classical set theory, formulated as a Clifford algebra of “S numbers” generated by a single monadic operation, “bracing,” Br = {…}. (2) Indefinite set theory, a modification of set theory
dealing with the modal logical concept of possibility. (3) Quantum set theory. The quantum set is constructed from the null
set by the familiar quantum techniques of tensor product and antisymmetrization. There are both a Clifford and a Grassmann
algebra with sets as basis elements. Rank and cardinality operators are analogous to Schroedinger coordinates of the theory,
in that they are multiplication or “Q-type” operators. “P-type” operators analogous to Schroedinger momenta, in that they transform theQ-type quantities, are bracing (Br), Clifford multiplication by a setX, and the creator ofX, represented by Grassmann multiplicationc(X) by the setX. Br and its adjoint Br* form a Bose-Einstein canonical pair, andc(X) and its adjointc(X)* form a Fermi-Dirac or anticanonical pair. Many coefficient number systems can be employed in this quantization. I use the
integers for a discrete quantum theory, with the usual complex quantum theory as limit. Quantum set theory may be applied
to a quantum time space and a quantum automaton.
This material is based upon work supported in part by NSF Grant No. PHY8007921. 相似文献
11.
Fabio Gavarini 《Czechoslovak Journal of Physics》2001,51(12):1330-1335
The “quantum duality principle” states that a quantisation of a Lie bialgebra provides also a quantisation of the dual formal
Poisson group and, conversely, a quantisation of a formal Poisson group yields a quantisation of the dual Lie bialgebra as
well. We extend this to a much more general result: namely, for any principal ideal domainR and for each primepεR we establish an “inner” Galois’ correspondence on the categoryHA of torsionless Hopf algebras overR, using two functors (fromHA to itself) such that the image of the first and the second is the full subcategory of those Hopf algebras which are commutative
and cocommutative, modulop, respectively (i.e., they are“quantum function algebras” (=QFA) and“quantum universal enveloping algebras” (=QUEA), atp, respectively). In particular we provide a machine to get two quantum groups — a QFA and a QUEA — out of any Hopf algebraH over a fieldk: apply the functors tok[ν] ⊗k H forp=ν.
A relevant example occurring in quantum electro-dynamics is studied in some detail.
Presented at the 10th International Colloquium on Quantum Groups: “Quantum Groups and Integrable Systems”, Prague, 21–23 June
2001 相似文献
12.
Michael H. Freedman Alexei Kitaev Zhenghan Wang 《Communications in Mathematical Physics》2002,227(3):587-603
Quantum computers will work by evolving a high tensor power of a small (e.g. two) dimensional Hilbert space by local gates,
which can be implemented by applying a local Hamiltonian H for a time t. In contrast to this quantum engineering, the most abstract reaches of theoretical physics has spawned “topological models”
having a finite dimensional internal state space with no natural tensor product structure and in which the evolution of the
state is discrete, H≡ 0. These are called topological quantum field theories (TQFTs). These exotic physical systems are proved to be efficiently
simulated on a quantum computer. The conclusion is two-fold:
1. TQFTs cannot be used to define a model of computation stronger than the usual quantum model “BQP”.
2. TQFTs provide a radically different way of looking at quantum computation. The rich mathematical structure of TQFTs might
suggest a new quantum algorithm.
Received: 4 May 2001 / Accepted: 16 January 2002 相似文献
13.
M. Combescot O. Betbeder-Matibet 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(1):63-76
The purpose of this paper is to show how the diagrammatic expansion
in fermion exchanges of scalar products of N-composite-boson
(“coboson”) states can be obtained in a practical way. The hard
algebra on which this expansion is based, will be given in an independent publication.
Due to the composite nature of the particles, the scalar products
of N-coboson states do not reduce to a set of Kronecker symbols, as
for elementary bosons, but contain subtle exchange terms between two or
more cobosons. These terms originate from Pauli exclusion between the
fermionic components of the particles. While our many-body
theory for composite bosons leads to write these scalar products as
complicated sums of products of “Pauli scatterings” between
two cobosons, they in fact correspond to fermion exchanges
between any number P of quantum particles, with
2 ≤P≤N. These P-body exchanges are nicely represented by the
so-called “Shiva diagrams”, which are topologically different from
Feynman diagrams, due to the intrinsic many-body nature of the Pauli
exclusion from which they originate. These Shiva diagrams in fact
constitute the novel part of our composite-exciton many-body theory
which was up to now missing to get its full
diagrammatic representation. Using them, we can now “see” through
diagrams the physics of any quantity in which enters N interacting
excitons — or more generally N composite bosons —, with fermion
exchanges included in an
exact — and transparent — way. 相似文献
14.
Quantum theory has the property of “local tomography”: the state of any composite system can be reconstructed from the statistics
of measurements on the individual components. In this respect the holism of quantum theory is limited. We consider in this
paper a class of theories more holistic than quantum theory in that they are constrained only by “bilocal tomography”: the
state of any composite system is determined by the statistics of measurements on pairs of components. Under a few auxiliary assumptions, we derive certain general features of such theories. In particular, we
show how the number of state parameters can depend on the number of perfectly distinguishable states. We also show that real-vector-space
quantum theory, while not locally tomographic, is bilocally tomographic. 相似文献
15.
V. P. Maslov 《Russian Journal of Mathematical Physics》2007,14(3):304-318
We show that the superfluidity effect in nanotubes arises in a classical liquid (regarded as the limit as h → 0 of the quantum liquid) and involves not only the Bogolyubov “running waves,” but also a “standing wave.” This is obtained
from the variational equations in the context of ultrasecondary quantization. It is stressed that the “atomic” size of the
nanotube plays a crucial role in the phenomena. 相似文献
16.
17.
V. P. Maslov 《Russian Journal of Mathematical Physics》2007,14(4):453-464
We show that the superfluidity effect in nanotubes arises in a classical liquid (regarded as the limit as h → 0 of the quantum liquid) and involves not only the Bogolyubov “running waves,” but also a “standing wave.” This is obtained
from the variational equations in the context of ultrasecondary quantization. We consider cases of Bose and Fermi liquids. 相似文献
18.
A. Kh. Inoyatov L. L. Perevoshchikov A. Kovalík O. Dragoun D. V. Filosofov 《The European Physical Journal A - Hadrons and Nuclei》2011,47(7):84
The conversion electron spectrum of the 22.5keV M1 + E2 nuclear transition in 149Sm from the electron capture decay of 149Eu was experimentally studied for the “Eu2O3” and “EuF3” compounds in which 149Eu ions have the same assumed oxidation number +3 . While the energies of the L, M, N, O, and P1 conversion lines for “EuF3” were lower, on average, by 1.7(1), 2.7(2), 2.3(3), 4.1(2), and 5.7(9)eV, respectively, than those for “Eu2O3”, no changes between the two ligand complexes were observed for relative intensities of the conversion lines and their natural
widths within the error limits. 相似文献
19.
R.I. Eglitis E.A. Kotomin G. Borstel 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):483-486
The origin of the intrinsic excitonic (“green”) luminescence in ABO3 perovskites remains a hot topic over the last quarter of a century. We suggest as a theoretical interpretation for the “green”
luminescence in these crystals, the recombination of electron and hole polarons forming a charge transfer vibronic exciton.
In order to check quantitatively the proposed model, we performed quantum chemical calculations using the Intermediate Neglect
of Differential Overlap (INDO) method combined with the periodic defect model. The luminescence energies calculated for four
perovskite crystals are found to be in good agreement with experimental data.
Received 19 December 2001 and Received in final form 14 March 2002 Published online 25 June 2002 相似文献
20.
In order to have well defined rules for the perturbative calculation of quantities of interest in an interacting quantum
field theory in curved spacetime, it is necessary to construct Wick polynomials and their time ordered products for the noninteracting
theory. A construction of these quantities has recently been given by Brunetti, Fredenhagen, and K?hler, and by Brunetti and
Fredenhagen, but they did not impose any “locality” or “covariance” condition in their constructions. As a consequence, their
construction of time ordered products contained ambiguities involving arbitrary functions of spacetime point rather than arbitrary
parameters. In this paper, we construct an “extended Wick polynomial algebra”– large enough to contain the Wick polynomials
and their time ordered products – by generalizing a construction of Dütsch and Fredenhagen to curved spacetime. We then
define the notion of a local, covariant quantum field, and seek a definition of local Wick polynomials and their time ordered products as local, covariant quantum fields. We introduce a new notion of the scaling
behavior of a local, covariant quantum field, and impose scaling requirements on our local Wick polynomials and their time
ordered products as well as certain additional requirements – such as commutation relations with the free field and appropriate
continuity properties under variations of the spacetime metric. For a given polynomial order in powers of the field, we prove
that these conditions uniquely determine the local Wick polynomials and their time ordered products up to a finite number
of parameters. (These parameters correspond to the usual renormalization ambiguities occurring in Minkowski spacetime together
with additional parameters corresponding to the coupling of the field to curvature.) We also prove existence of local Wick
polynomials. However, the issue
of existence of local time ordered products is deferred to a future investigation.
Received: 27 March 2001 / Accepted: 6 June 2001 相似文献