Showing papers on "Quantum error correction published in 1988"
TL;DR: In this article, a theoretical result for correlated quantum systems is presented which leads to a noise commutation relation and a generalized Heisenberg uncertainty relation, which imply an inherent and unavoidable extra noise in quantum measurements beyond that already included in the lower bound.
Abstract: A theoretical result for correlated quantum systems is presented which leads to a noise commutation relation and a generalized Heisenberg uncertainty relation. These relations imply an inherent and unavoidable extra noise in quantum measurements beyond that already included in the Heisenberg lower bound. These relations lead directly to model-independent lower bounds on inherent noise, useful in a variety of applications, including balanced homodyne detection and quantum optical linear amplifiers.
199 citations
01 Jan 1988
20 citations
TL;DR: The formalism of effects and operations has been shown to be equivalent to the standard rules of quantum mechanics by D'Espagnat et al. as discussed by the authors, who found a discrepancy between an analysis based on the standard quantum rule for calculating probabilities and an analysis that uses a particular operation taken from the work of Barchielli and his collaborators.
Abstract: We review the formalism of Effects and Operations in order to demonstrate that this formalism is equivalent to the standard rules of quantum mechanics. D'Espagnat has studied an example where he finds a discrepancy between an analysis based on the standard quantum rule for calculating probabilities and an analysis that uses a particular Operation taken from the work of Barchielli and his collaborators. We use the formalism of Effects and Operations to explore and explain this discrepancy.
15 citations
TL;DR: The correctness of Handel's quantum 1/f noise theory is demonstrated by direct calculation of the spatial autocorrelation and of the wavenumber spectrum of the particle density in the scattered flux as discussed by the authors.
Abstract: Kiss and Heszler's calculation (see ibid., vol.19, p.L631, 1986) of the expectation value of Handel's quantum 1/f noise effect yields zero because the expectation of quantum noise is always zero. The correctness of Handel's quantum 1/f noise theory is demonstrated by direct calculation of the spatial autocorrelation and of the wavenumber spectrum of the particle density in the scattered flux.
6 citations
TL;DR: In the quantum noise operator approach to many problems in quantum optics, the noise operator in the equation for the field operator is delta-correlated This ignores the atomic memory effects as discussed by the authors.
5 citations
TL;DR: In this article, the reduction process of a wave packet due to measurement is defined as a dynamic process derived from interactions between an object quantum system and a measuring apparatus without ensemble averaging.
Abstract: Quantum theory of phase relaxation (T. Endo: J. Phys. Soc. Jpn 56 (1987) 1684) is applied to reduction process of a wave packet due to measurement. Reduction of a wave packet is a dynamic process derived from interactions between an object quantum system and a measuring apparatus without ensemble averaging.
2 citations
TL;DR: It is predicted that for two-stage free-electron lasers, quantum noise can be comparable to the classical noise due to the thermal spread of the beam or the random initial distribution of electrons in phase.
Abstract: A novel relativistic quantum theory of the free-electron laser is formulated using the Dirac equation. It is shown that the theory has the correct classical limit. It is predicted that for two-stage free-electron lasers, quantum noise can be comparable to the classical noise due to the thermal spread of the beam or the random initial distribution of electrons in phase.
2 citations
01 Jan 1988
TL;DR: In this article, the classical and quantum aspects of the theory are unified by formulating QFT in a large class of accelerated frames, and describing the thermal effects, their asymptotic character and the role of the PCT symmetry.
Abstract: We review recent results in non-inertial quantum field theory By formulating QFT in a large class of accelerated frames, the classical and the quantum aspects of the theory are unified We describe the thermal effects, their asymptotic character and the role of the PCT symmetry A discussion of quantum covariance and detection processes is also given
1 citations
TL;DR: In this paper, it was shown that an arbitrary small disturbance can be recorded with preparation of the system in a quantum state having a negative quantum correlation coefficient between the observable coordinate and momentum.
Abstract: The problem of recording a classical disturbance by tracking the coordinate of a free particle is examined within the scope of nonrelativistic quantum mechanics. The absence of the fundamental limitation on the sensitivity — the “standard quantum limit” — is proven. An arbitrarily small disturbance can be recorded with preparation of the system in a quantum state having a negative quantum correlation coefficient between the observable coordinate and momentum. It is shown that it belongs to the collective coherent states — the condensed states. Arguments are presented for the absence of fundamental quantum limits on the magnitude of the recordable disturbance in the measurement of an arbitrary observable with a continuous spectrum.
1 citations