共查询到20条相似文献,搜索用时 15 毫秒
1.
We discuss a large class of phenomenological models incorporating quantum gravity motivated corrections to electrodynamics.
The framework is that of electrodynamics in a birefringent and dispersive medium with non-local constitutive relations, which
are considered up to second order in the inverse of the energy characterizing the quantum gravity scale. The energy-momentum
tensor, Green functions and frequency dependent refraction indices are obtained, leading to departures from standard physics.
The effective character of the theory is also emphasized by introducing a frequency cutoff Ω. The analysis of its effects
upon the standard notion of causality is performed, showing that in the radiation regime (Ω R ≫ 1) the expected corrections of the order (ω/Ω)
n
get further suppressed by highly oscillating terms proportional to , thus forbiding causality violations to show up in the corresponding observational effects.
Dedicated to Octavio Obregón on his sixtieth birthday. 相似文献
2.
P. Moylan 《Czechoslovak Journal of Physics》1997,47(12):1251-1258
We show that it is possible to express the basis elements of the Lie algebra of the Euclidean group,E(2), as simple irrational functions of certainq deformed expressions involving the generators of the quantum algebraU
q
(so(2, 1)). We consider implications of these results for the representation theory of the Lie algebra ofE(2). We briefly discess analogous results forU
q
(so(2, 2)).
Presented at the 6th International Colloquium on Quantum Groups: “Quantum Groups and Integrable Systems”, Prague, 19–21 June
1997. 相似文献
3.
Claudio Garola 《International Journal of Theoretical Physics》1985,24(5):423-433
It has been proposed that some posets of quantum logic could be embedded into lattices in order to recover the lattice structure avoiding the introduction of ad hoc axioms. We consider here the embedding
s of any posetS into the complete lattice
s of its closed ideals (normal embedding ofS) and show that
s can be characterized (up to a lattice isomorphism) either by means of a density property or by means of a minimality property. Both of these suggest that the normal embedding satisfies some intuitive conditions which make it preferable with respect to other possible embeddings ofS. We consider the poset of all the effects associated to yes-no experiments and briefly comment on the application of the normal embedding in this case. The possibility of giving a physical interpretation to the elements of
is also discussed.Research sponsored by CNR and INFN (Italy). 相似文献
4.
A mixed quantum–classical method for the simulation of laser-induced desorption processes at surfaces is implemented. In this method, the nuclear motion is described classically, while the electrons are treated quantum mechanically. The feedback between nuclei and electrons is taken into account self-consistently. The computational efficiency of this method allows a more realistic multi-dimensional treatment of desorption processes. We apply this method to the laser-induced desorption of NO from NiO(100) using a two-state two-dimensional potential energy surface derived from ab initio quantum chemical calculations; we extend this potential energy surface to seven dimensions employing a physically reasonable model potential. By comparing our method to jumping wave-packet calculations on exactly the same potential energy surface we verify the validity of our method. We focus on the velocity, rotational, and vibrational distributions of the desorbing NO molecules. Furthermore, we model the energy transfer to the substrate by a surface oscillator. Including recoil processes in the simulation has a decisive influence on the desorption dynamics, as far as the velocity and rotational distribution is concerned. In particular, the bimodality in the velocity distribution observed in low dimensions and in the experiment disappears in a high-dimensional treatment. PACS 68.43.Tj; 68.43.Rs; 82.20.Gk; 82.20.Wt 相似文献
5.
M. Fecko 《Czechoslovak Journal of Physics》1985,35(4):378-385
A standard free non-relativistic top is described using a non-traditional set of variables. A quantization is performed via canonical path-integral formalism rather than Lagrangian one [2]. On both classical and quantum levels an agreement with usual approaches is obtained. 相似文献
6.
Koshino K 《Physical review letters》2007,98(22):223902
In order to investigate the nonlinear dynamics of photons, one must in principle solve a quantum many-particle problem, which usually requires intensive computation. In this study, we show that the spatial wave function of photons after nonlinear interaction can be obtained with less computation by assuming a classical input pulse and calculating a correlation function in the output field. This method is particularly useful when nonlinear optical media have many mechanical degrees of freedom, where quantum many-particle problems become extremely difficult. 相似文献
7.
Zhen-Sheng Yuan Xiao-Hui Bao Chao-Yang Lu Jun Zhang Cheng-Zhi Peng Jian-Wei Pan 《Physics Reports》2010
This article reviews the progress of quantum communication that utilizes photonic entanglement. We start with a survey of various methods for generating entangled photons, followed by an introduction of the theoretical principles and the experimental implementations of quantum key distribution. We then move on to a discussion of more involved quantum communication protocols including quantum dense coding, teleportation and quantum communication complexity. After that, we review the progress in free-space quantum communication, decoherence-free subspace, and quantum repeater protocols which are essential ingredients for long-distance quantum communication. Practical realizations of quantum repeaters, which require an interface between photons and quantum memories, are discussed briefly. Finally, we draw concluding remarks considering the technical challenges, and put forward an outlook on further developments of this field. 相似文献
8.
9.
This paper proposes a scheme for secure authentication of classical
messages with single photons and a hashed function. The security
analysis of this scheme is also given, which shows that anyone
cannot forge valid message authentication codes (MACs). In addition,
the lengths of the authentication key and the MACs are invariable
and shorter, in comparison with those presented authentication
schemes. Moreover, quantum data storage and entanglement are not
required in this scheme. Therefore, this scheme is more efficient
and economical. 相似文献
10.
We propose an experiment where a photon is first cloned by stimulated parametric down-conversion, making many (imperfect) copies, and then the cloning transformation is inverted, regenerating the original photon while destroying the copies. Focusing on the case where the initial photon is entangled with another photon, we study the conditions under which entanglement can be proven in the final state. The proposed experiment would provide a clear demonstration that quantum information is preserved in quantum cloning. It would furthermore allow a definitive experimental proof for micro-macro entanglement in the intermediate multiphoton state, which is still an outstanding challenge. Finally, it might provide a quantum detection technique for small differences in transmission (e.g., in biological samples), whose sensitivity scales better with the number of photons used than a classical transmission measurement. 相似文献
11.
M. Pelton C. Santori G.S. Solomon O. Benson Y. Yamamoto 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):179-190
Current quantum cryptography systems are limited by the attenuated coherent pulses they use as light sources: a security loophole
is opened up by the possibility of multiple-photon pulses. By replacing the source with a single-photon emitter, transmission
rates of secure information can be improved. We have investigated the use of single self-assembled InAs/GaAs quantum dots
as such single-photon sources, and have seen a tenfold reduction in the multi-photon probability as compared to Poissonian
pulses. An extension of our experiment should also allow for the generation of triggered, polarization-entangled photon pairs.
The utility of these light sources is currently limited by the low efficiency with which photons are collected. However, by
fabricating an optical microcavity containing a single quantum dot, the spontaneous emission rate into a single mode can be
enhanced. Using this method, we have seen 78% coupling of single-dot radiation into a single cavity resonance. The enhanced
spontaneous decay should also allow for higher photon pulse rates, up to about 3 GHz.
Received 8 July 2001 and Received in final form 25 August 2001 相似文献
12.
A quasi-secure quantum dialogue protocol using single photons was proposed. Different from the previous entanglement-based protocols, the present protocol uses batches of single photons which run back and forth between the two parties. A round run for each photon makes the two parties each obtain a classical bit of information. So the efficiency of information transmission can be increased. The present scheme is practical and well within the present-day technology. 相似文献
13.
A repulsive potential is called reflectionless in the case of classical mechanics if limit velocities of one-dimensional particles as t → ∞ arise from the analogous velocities as t → ? ∞ by changing order. The class reflectionless potentials is investigated inside the classes of potentials with the finite range and potentials decaying as a power function of the distance. 相似文献
14.
15.
Spatially entangled twin photons allow the study of high-dimensional entanglement, and the Laguerre-Gauss modes are the most commonly used basis to discretize the single-photon mode spaces. In this basis, to date only the azimuthal degree of freedom has been investigated experimentally due to its fundamental and experimental simplicity. We show that the full spatial entanglement is indeed accessible experimentally; i.e., we have found practicable radial detection modes with negligible cross correlations. This allows us to demonstrate hybrid azimuthal-radial quantum correlations in a Hilbert space with more than 100 dimensions per photon. 相似文献
16.
We compute quantum dissonance Q (non-entangled quantum correlation), entanglement E, quantum discord D (total quantum correlation) and classical correlation C for spin pairs at any distance in the infinite XY spin-1/2 chains, i.e., the anisotropic XY model and the isotropic XY model with three-spin interactions. We obtain two simple dominance relations: C ≥ E and D ≥ E + Q Except this, there are no other simple ordering relations between them. We also show that Q can detect the special points of the system where the entanglement just appears or completely disappears. In addition, it is worthwhile to mention that dissonance and classical correlation can also clearly spotlight the critical points of quantum phase transitions in XY spin-1/2 chains. 相似文献
17.
18.
Ricci M Sciarrino F Cerf NJ Filip R Fiurásek J De Martini F 《Physical review letters》2005,95(9):090504
An application of quantum cloning to optimally interface a quantum system with a classical observer is presented; in particular, we describe a procedure to perform a minimal disturbance measurement on a single qubit by adopting a 1-->2 cloning machine followed by a generalized measurement on a single clone and the anticlone or on the two clones. Such a scheme can be applied to enhance the transmission fidelity over a lossy quantum channel. 相似文献
19.