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1.
In this paper we give a logical analysis of both classical and quantum correlations. We propose a new logical system to reason
about the information carried by a complex system composed of several parts. Our formalism is based on an extension of epistemic
logic with operators for “group knowledge” (the logic GEL), further extended with atomic sentences describing the results of “joint observations” (the logic LCK). As models we introduce correlation models, as a generalization of the standard representation of epistemic models as vector models. We give sound and complete axiomatizations
for our logics, and we use this setting to investigate the relationship between the information carried by each of the parts
of a complex system and the information carried by the whole system. In particular we distinguish between the “distributed
information”, obtainable by simply pooling together all the information that can be separately observed in any of the parts,
and “correlated information”, obtainable only by doing joint observations of the parts (and pooling together the results).
Our formalism throws a new light on the difference between classical and quantum information and gives rise to an informational-logical
characterization of the notion of “quantum entanglement”. 相似文献
2.
A remarkable theorem by Clifton et al [Found Phys. 33(11), 1561–1591 (2003)] (CBH) characterizes quantum theory in terms of information-theoretic principles. According to Bub [Stud. Hist. Phil. Mod. Phys. 35 B, 241–266 (2004); Found. Phys. 35(4), 541–560 (2005)] the philosophical significance of the theorem is that quantum theory should be regarded as a “principle” theory about (quantum) information rather than a “constructive” theory about the dynamics of quantum systems. Here we criticize Bub’s principle approach arguing that if the mathematical formalism of quantum mechanics remains intact then there is no escape route from solving the measurement problem by constructive theories. We further propose a (Wigner-type) thought experiment that we argue demonstrates that quantum mechanics on the information-theoretic approach is incomplete. 相似文献
3.
The condition for the appearance of an event horizon is considered in pair-correlated systems (superfluids and superconductors)
in which the fermionic quasiparticles obey “relativistic” equations. In these systems the Landau critical velocity of superflow
corresponds to the speed of light. In conventional systems, such as s-wave superconductors, the superflow remains stable even above the Landau threshold. We show, however, that, in “ relativistic”
systems, the quantum vacuum becomes unstable and the superflow collapses after the “speed of light” is reached, so that the
horizon cannot appear. Thus an equilibrium dissipationless superflow state and the horizon are incompatible on account of
quantum effects. This negative result is consistent with the quantum Hawking radiation from the horizon, which would lead
to a dissipation of the flow.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 2, 124–129 (25 January 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
4.
5.
Thomas Filk 《International Journal of Theoretical Physics》2006,45(6):1166-1180
The famous “spooky action at a distance” in the EPR-scenario is shown to be a local interaction, once entanglement is interpreted as a kind of “nearest neighbor” relation among quantum systems. Furthermore, the wave function itself is interpreted as encoding the “nearest neighbor” relations between a quantum system and spatial points. This interpretation becomes natural, if we view space and distance in terms of relations among spatial points. Therefore, “position” becomes a purely relational concept. This relational picture leads to a new perspective onto the quantum mechanical formalism, where many of the “weird” aspects, like the particle-wave duality, the non-locality of entanglement, or the “mystery” of the double-slit experiment, disappear. Furthermore, this picture circumvents the restrictions set by Bell’s inequalities, i.e., a possible (realistic) hidden variable theory based on these concepts can be local and at the same time reproduce the results of quantum mechanics.
PACS: 03.65.Ud, 04.60.Nc 相似文献
6.
S. Muralidharan S. Karumanchi S. Jain R. Srikanth P. K. Panigrahi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(3):757-763
We introduce a new genuinely 2N qubit state, known as the “mirror state” with interesting entanglement properties.
The well known Bell and the cluster states form a special case of these “mirror states”, for N = 1 and N = 2 respectively.
It can be experimentally realized using SWAP and multiply controlled phase shift
operations. After establishing the general
conditions for a state to be useful for various communicational protocols involving quantum and classical information, it
is shown that the present state can optimally implement algorithms for the quantum teleportation of an arbitrary N qubit state and achieve quantum information splitting in all possible ways. With regard to superdense coding, one can send
2N classical bits
by sending only N qubits and consuming N ebits of entanglement. Explicit comparison of the mirror state with the
rearranged N Bell pairs and the linear cluster states is considered for these quantum protocols. We also show that mirror states are more
robust than
the rearranged Bell pairs with respect to a certain class of collisional
decoherence. 相似文献
7.
S. Dickmann 《JETP Letters》2011,93(2):86-90
Spin relaxation in quantum Hall ferromagnet regimes is studied. As the initial non-equilibrium state, a coherent deviation
of the spin system from the B direction is considered and the breakdown of this Goldstone-mode state due to hyperfine coupling to nuclei is analyzed. The
relaxation occurring non-exponentially with time is studied in terms of annihilation processes in the “Goldstone condensate”
formed by “zero spin excitons”. The relaxation rate is calculated analytically even if the initial deviation is not small.
This relaxation channel competes with the relaxation mechanisms due to spin-orbit coupling, and at strong magnetic fields
it becomes dominating. 相似文献
8.
G. P. Miroshnichenko 《Journal of Experimental and Theoretical Physics》2009,109(2):193-206
A theory of the discrete photodetection of quantum jumps on the V configuration of atomic levels has been developed. A three-level
source atom is placed in a cavity excited by a resonance fluorescence field. The cavity is tuned to exact resonance with an
atomic transition. The cavity mode state is tested by a flux of unexcited (at the entrance) probe atoms passing through the
cavity. The energy states of the outgoing probe atoms are detected by ionization chambers, which are assumed ideal. This a
posteriori statistical information is indirectly related to the numerical characteristics of a measured quantum system consisting
of the source atom and cavity mode. The “tuning” conditions for a discrete photodetector, i.e., the rules for choosing the
parameters and durations of the interactions of the cavity mode with the probe and source atoms, intensities of the pump and
probe fields that are necessary for observing quantum jumps from the “bright” state to the “dark” one and vice versa, have
been determined. A two-state model that describes the dynamics of a quantum jump has been analyzed. The formulas have been
obtained for the observable characteristics of quantum jumps: the mean residence time of the quantum system in quasistationary
states (durations of the bright and dark periods), probabilities of quantum jumps, mean excitation levels of the quantized
cavity mode, etc. 相似文献
9.
The emission of slow secondary electrons excited in efficient photocathodes by fast internal x-ray electrons upon absorption
of x-ray photons having energies in the range 1–10 keV is analyzed. Analytical expressions are derived for the quantum current
yield of the x-ray photoelectric effect for a “point” model and a “non-point” model of energy exchange of fast internal x-ray
electrons. We present some estimates for its parameters in a CsI photocathode.
Fiz. Tverd. Tela (St. Petersburg) 40, 1042–1046 (June 1998) 相似文献
10.
A scheme is proposed for measuring the state of an individual spin (system of spins). The scheme is based on the idea of a
single-electron “turnstile” and the injection of single spin-polarized electrons from the magnetic metallic borders. Applications
to the recently proposed scheme of quantum spin gates based on a silicon matrix are discussed (B. E. Kane, Nature 393, 133 (1998)).
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 2, 141–147 (25 July 1999) 相似文献
11.
Quantum well devices feature heterostructures of very thin epitaxial layers of group III-V and II-VI semiconductor materials.
Quantum well devices are integrated monolithically with various optoelectronics devices to provide photonic integrated circuits.
The representative structure could be realized with GaAs wells with GaAlAs barriers for wavelengths around 0.9 μm and InGaAsP
are used for longer wavelengths. Together with quantum well, superlattice structure is another popular design for InGaAs Avalanche
Photo Diode (APD). Quantum well structures find their applications in improved lasers, superlattice for photodiodes, modulators
and switches. Consequences of quantum well theory are available today in terms of quantum wires and quantum dots. Upon the
application of the normal electric field to quantum well structures, exciton pairs becomes more and more confined and the
sharp exciton absorption peaks are observed. The effect is termed as “Quantum Confined Stark Effect”. The electro-absorption effect is approximately 50 times larger in multiple quantum well structures than it is in bulk semiconductors.
Another electro-absorption effect known as “Franz Keldysh Effect” has been employed in monolithic waveguide detector. These effects lead to electro-absorption lasers (EAL) as well as electro-absorption
laser modulators (EML). 相似文献
12.
We present two equivalent axiomatizations for a logic of quantum actions: one in terms of quantum transition systems, and the other in terms of quantum dynamic algebras. The main contribution of the paper is conceptual, offering a new view of quantum structures in terms of their underlying
logical dynamics. We also prove Representation Theorems, showing these axiomatizations to be complete with respect to the natural Hilbert-space semantics. The advantages of this setting are many: (1) it provides a clear and intuitive dynamic-operational meaning to key postulates
(e.g. Orthomodularity, Covering Law); (2) it reduces the complexity of the Solèr–Mayet axiomatization by replacing some of
their key higher-order concepts (e.g. “automorphisms of the ortholattice”) by first-order objects (“actions”) in our structure;
(3) it provides a link between traditional quantum logic and the needs of quantum computation.
PACS: 02.10.-v Logic; set theory and algebra; 03.65.-w Quantum mechanics; 03.65.Fd Algebraic methods; 03.67.-a Quantum information. 相似文献
13.
14.
We study the effect of photon scattering from a path of a four-beam atomic interference setup, which is based on a cesium
atomic beam and two subsequent optical Ramsey pulses projecting the atoms onto a multilevel dark state. While in two-beam
interference, any attempt to keep track of an interfering path reduces the fringe contrast, we demonstrate that photon scattering
in a multiple-path arrangement cannot only lead to a decrease, but - under certain conditions - also to an increase of the
interference contrast. The results are confirmed by a density-matrix calculation. We are aware that in all cases the “which-path”
information carried away by the scattered photons leads to a loss of information that is contained in the atomic quantum state.
An approach to quantify this “which-path” information using observed fringe signals is presented; it allows for an appropriate
measure of quantum decoherence in multiple-path interference.
Received: 27 July 2000 / Published online: 6 December 2000 相似文献
15.
16.
As quantum information science approaches the goal of constructing quantum computers, understanding loss of information through
decoherence becomes increasingly important. The information about a system that can be obtained from its environment can facilitate
quantum control and error correction. Moreover, observers gain most of their information indirectly, by monitoring (primarily
photon) environments of the “objects of interest.” Exactly how this information is inscribed in the environment is essential
for the emergence of “the classical” from the quantum substrate. In this paper, we examine how many-qubit (or many-spin) environments
can store information about a single system. The information lost to the environment can be stored redundantly, or it can
be encoded in entangled modes of the environment. We go on to show that randomly chosen states of the environment almost always
encode the information so that an observer must capture a majority of the environment to deduce the system’s state. Conversely,
in the states produced by a typical decoherence process, information about a particular observable of the system is stored
redundantly. This selective proliferation of “the fittest information” (known as Quantum Darwinism) plays a key role in choosing
the preferred, effectively classical observables of macroscopic systems. The developing appreciation that the environment
functions not just as a garbage dump, but as a communication channel, is extending our understanding of the environment’s
role in the quantum-classical transition beyond the traditional paradigm of decoherence. 相似文献
17.
The “phase diagram” of a two-dimensional mesoscopic system of bosons is investigated. An example of such a system is a system
of indirect magnetoexcitons in semiconductor double quantum dots. Quantum Monte Carlo calculations show the existence of quantum
orientational melting. At zero (quite low) temperature, as quantum fluctuations of the particles intensify, two quantum disordering
phenomena occur with increasing de Boer parameter q. First, at q≈10−3 the system passes to a radially ordered but orientationally disordered state, where different shells of a cluster rotate
relative to one another. Then at q≈0.16 a transition to a superfluid state occurs.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 11, 817–822 (10 December 1998) 相似文献
18.
S. N. Vergeles 《Journal of Experimental and Theoretical Physics》1998,86(5):854-859
An anomaly-free quantum theory of a relativistic string is constructed in two-dimensional space-time. The states of the string
are found to be similar to the states of a massless chiral quantum particle. This result is obtained by generalizing the concept
of an “operator” in quantum field theory.
Zh. éksp. Teor. Fiz. 113, 1566–1578 (May 1998) 相似文献
19.
In a previous work by one of us (R. Urigu) concerning open quantum systems it was remarked that in processes of the type
, when evaluating the information entropy of the environment as the Shannon entropy of the outcome probabilities
in the channels
, the total information entropy may decrease. We remark here that this decrease is easily excluded by requiring a condition
of quantum modelizability of the environment even with respect to Shannon entropy (“cybernetic interpretability” of the environment).
Further conditions on the quantum model of the environment are defined (“maximal observability” and “Boolean interpretability”),
which are proved to be equivalent, and it turns out that, once satisfied in one model, they also are in any model with pure
initial state; furthermore, these conditions turn out to be equivalent to the condition that the process consists of pure
operations of the first kind. The relevance to the concept of macroscopicity and to the “von Neumann chain” is discussed. 相似文献
20.
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