Showing papers on "Quantum error correction published in 1992"
TL;DR: In this paper, a quantum stochastic calculus of a posteriori conditional expectations in quantum observed systems is developed and a general quantum filtering equation for 2 QS process is derived, and an application to the description of spontaneous collapse of the quantum spin under continuous observation is given.
316 citations
01 Jan 1992
TL;DR: The new electronic techniques required for quantum nondemolition measurements and the theory underlying them are described and may find application elsewhere in science and technology.
Abstract: Some future gravitational-wave antennas will be cylinders of mass approximately 100 kilograms, whose end-to-end vibrations must be measured so accurately (10(-19) centimeter) that they behave quantum mechanically. Moreover, the vibration amplitude must be measured over and over again without perturbing it (quantum nondemolition measurement). This contrasts with quantum chemistry, quantum optics, or atomic, nuclear, and elementary particle physics, where one usually makes measurements on an ensemble of identical objects and does not care whether any single object is perturbed or destroyed by the measurement. This article describes the new electronic techniques required for quantum nondemolition measurements and the theory underlying them. Quantum nondemolition measurements may find application elsewhere in science and technology.
130 citations
60 citations
TL;DR: This work introduces the notion of a class of abstract digital computers based on quantum reversibility and indeterminism, which are compatible with quantum laws and may perform nondeterministic and non-recursive computation.
Abstract: We introduce the notion of a class of abstract digital computers based on quantum reversibility and indeterminism (not 011 the classical sequential architecture), which are compatible with quantum laws and may perform nondeterministic and non-recursive computation.
7 citations
Journal Article•
TL;DR: In this paper, the Schrodinger equation for interacting systems is used to describe the continuous process of decoherence occurring locally on a very short time scale, while the observer's "increase of information" is appropriately represented by the resulting dynamical decoupling of the corresponding components of the global wave function.
6 citations
Journal Article•
TL;DR: In this article, the role of quantum superpositions in providing new modes of computation, not available to classical computers, is reviewed and some new results on quantum superposition are presented, demonstrating the importance of quantum processes for issues in complexity theory.
Abstract: We review recent work and some new results on the role of quantum superpositions in providing new modes of computation, not available to classical computers. For certain problems, these new modes can provide an exponential reduction in complexity over any classical computer demonstrating the importance of quantum processes for issues in complexity theory.
4 citations
01 Jan 1992
TL;DR: New ideas concerning the peculiar phenomenon of quantum chaos are presented with special emphasis on a number of unsolved problems and current apparent contradictions as mentioned in this paper, with a focus on the unsolved problems of quantum randomness.
Abstract: New ideas concerning the peculiar phenomenon of quantum chaos are presented with special emphasis on a number of unsolved problems and current apparent contradictions
3 citations
01 Feb 1992
TL;DR: In this article, a generalization of previous treatments of quantum phase is presented, in which restrictions on the class of realizable phase statistics are removed, thus permitting phase wave function collapse.
Abstract: A generalization of previous treatments of quantum phase is presented. Restrictions on the class of realizable phase statistics are thereby removed; thus, permitting 'phase wavefunction collapse' (and other advantages). This is accomplished by exciting the auxiliary mode of the measurement apparatus in a time-reversed fashion. The mathematical properties of this auxiliary mode are studied in the hope that they will lead to an identification of a physical apparatus which can realize the quantum phase measurement.
1 citations
16 Nov 1992
TL;DR: In this article, the authors discuss the concepts of received quantum state control and quantum state switches, and propose a new quantum state switch system, which is a quantum conditional unitary system and can overcome the standard quantum limit.
Abstract: The authors discuss the concepts of received quantum state control and quantum state switches, and propose a new quantum state switch system. It is shown that the new system is a quantum conditional unitary system and can overcome the standard quantum limit. >
16 Nov 1992
TL;DR: In this article, the applicability of Caves' formulae for some significant quantum states for a quantum communication viewpoint is clarified. But this method can treat only quantum noise of quadrature components.
Abstract: The phase space representation of quantum states is one of the most useful methods to describe the quantum noise properties in the quantum communication theory, and it enables an understanding of their properties with the classical analogy. In principle, however, this method can treat only quantum noise of quadrature components. Caves has discussed a method of transformation from quantum noises of quadrature amplitudes to those of photon and phase. The authors clarify the applicability of Caves' formulae for some significant quantum states for a quantum communication viewpoint. >