Showing papers on "Quantum error correction published in 1968"
TL;DR: In this paper, the orthogonality condition for the perturbation expansions of the state vectors for the excited states of stationary quantum systems is established and a common misunderstanding on this subject is discussed and corrected.
Abstract: A theorem establishing the correct orthogonality condition for the perturbation expansions of the state vectors for the excited states of stationary quantum systems is enunciated. A common misunderstanding on this subject is discussed and corrected. Implications of the theorem to the use of the variation perturbation method for calculating approximate eigenvalues and eigenvectors for excited states is discussed.
13 citations
TL;DR: A simple one-dimensional model is taken to illustrate the quantum effects of a narrowband communication system and it is shown that the noise of the channel, due to both thermal and quantum fluctuations, is additive and Gaussian.
Abstract: A simple one-dimensional model is taken to illustrate the quantum effects of a narrowband communication system. The system is quantized, and its dynamics are discussed in terms of the Heisenberg equations for field operators. The detection process of a "coherent joint detector," whose compatibility with quantum physics was justified elsewhere, is discussed. The detector, which is capable of measuring the quadrature-modulating components at Nyquist rate with minimum possible uncertainty allowed by quantum theory and which is most suitable for a continuous channel, is used to determine the channel capacity. It is shown that the noise of the channel, due to both thermal and quantum fluctuations, is additive and Gaussian. The classical concepts and expressions for the average mutual information and channel capacity are still valid, provided that the quantum noise of one quantum is included properly. The results obtained approach straightforwardly Shannon's in the classical limit.
9 citations
TL;DR: Lower bounds to the second-order correction to the eigenvalue of an observable for the ith excited state of a stationary quantum system were given in this article, where the second order correction was shown to be equivalent to the lower bound of the secondorder correction of the eigenthreshold of the Eigenvalue.
Abstract: This letter finds lower bounds to the second-order correction to the eigenvalue of an observable for the ith excited state of a stationary quantum system.
2 citations