Showing papers on "Quantum channel published in 1990"
TL;DR: In this paper, an analytic approximation for the maximum signal information possible with occupation number signal states as a function of mean signal energy is given, and a theorem guaranteeing that these states are optimal for communication is proved.
Abstract: Information must take up space, must weigh, and its flux must be limited. Quantum limits on communication and information storage leading to these conclusions are described here. Quantum channel capacity theory is reviewed for both steady state and burst communication. An analytic approximation is given for the maximum signal information possible with occupation number signal states as a function of mean signal energy. A theorem guaranteeing that these states are optimal for communication is proved. A heuristic "proof" of the linear bound on communication is given, followed by rigorous proofs for signals with specified mean energy, and for signals with given energy budget. And systems of many parallel quantum channels are shown to obey the linear bound for a natural channel architecture. The time-energy uncertainty principle is reformulated in information language by means of the linear bound. The quantum bound on information storage capacity of quantum mechanical and quantum field devices is reviewed. A simplified version of the analytic proof for the bound is given for the latter case. Solitons as information caches are discussed, as is information storage in one-dimensional systems. The influence of signal self-gravitation on communication is considered. Finally, it is shown that acceleration of a receiver acts to block information transfer.
69 citations
TL;DR: In this paper, the quantum supergroupGLcffffq(1/1) in its matrix representation is constructed and the quantum matrix can be written as the exponential of a matrix with non-commuting entries.
Abstract: We construct the quantum supergroupGL
q(1/1) in its matrix representation We investigate properties of powers of 2×2 quantum super-matrices and we show that any element ofGL
q(1/1) can be written as the exponential of a matrix with non-commuting entries An explicit construction of this exponential form is presented Finally, we prove a relation between the quantum superdeterminant of a quantum matrix and the supertrace of the logarithm of the quantum matrix
23 citations
TL;DR: In this article, the authors discussed various asymptotic limits of the classical and quantum Heisenberg model and showed that the quantum model converges to the classical model in the limit of large spins.
Abstract: The authors discuss various asymptotic limits of the classical and quantum Heisenberg model. They give a new proof that the thermodynamic free energy of the quantum model converges to the free energy of the classical model in the limit of large spins. They also obtain Gaussian and free Bose gas limits for the classical and quantum models respectively.
23 citations
TL;DR: The role of completely positive mappings in quantum dynamics and measurement theory is reanalyzed in light of the possibility of a generalized dynamics in this article, where the role of the completely positive mapping in measurement theory and quantum dynamics is discussed.
Abstract: The role of completely positive mappings in quantum dynamics and measurement theory is reanalyzed in light of the possibility of a generalized dynamics
16 citations
22 Jan 1990
TL;DR: In this article, the authors focus on quantum effects such as nonclassical states of light, quantum non-demolition detection, modification of spontaneous emission characteristics, and resonant tunneling.
Abstract: Over the last several years there have been significant advances in quantum optoelectronics. We focus on a number of these advances based on such quantum effects as nonclassical states of light, quantum nondemolition detection, modification of spontaneous emission characteristics, and resonant tunneling. These quantum effects have communication device applications in addition to multiple quantum well lasers including the possibility of zero threshold lasers, efficient photon number detection, and quantum effect logic gates.
01 Jan 1990
TL;DR: In this article, a related quantum mechanical model for which the corresponding semiclassical behaviour clearly differs from the two-level case was studied. But the model was solved exactly the case with equal couplings.
Abstract: In spite of intensive study, the interface between quantum mechanics and classical mechanics still offers questions to be answered. The transition is best investigated with models where both the classical and quantum mechanical versions are solvable. In quantum optics one in this case talks about semiclassical and quantum behaviour which differ in that in the latter case the electromagnetic field is quantized. A well known case is the Jaynes-Cummings model1 in which a two-level system is coupled with a boson mode. One obtains that the model reproduces the corresponding semiclassical behaviour only if the initial conditions are suitable chosen. Otherwise interesting non-classical phenomena like revivals can occur2. In this paper we study a related quantum mechanical model for which the corresponding semiclassical behaviour clearly differs from the two-level case. The two-level system is replaced with an infinite ladder of states and the single quantum field mode is resonantly coupled to each step in the ladder. We solve the problem exactly the case with equal couplings. The corresponding semiclassical model has been used for example to describe optical transitions in molecules. Because of the equal coupling constants the present model dramatically differs from the model of coupled harmonic oscillators.