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Showing papers on "Quantum error correction published in 1974"


Journal ArticleDOI
01 Feb 1974
TL;DR: In this article, a simple proof of Schnol's result was given for the general case of (A + V) = 2 V..(r. r.) with V ǫ > 0.
Abstract: We provide a simple proof (and mild improvement) of Schnol's result that L eigenfunctions of — A, + V are 0(exp(— ar)) for any a > 0 whenever V — ooas r — do. Despite a rather large literature (reviewed in [6]) on the exponential falloff of Schrödinger operators, A + V, one of the strongest results is one of the first, that of Schnol [9], who asserts that L solutions of (A + V)i/r = Ei// obey pointwise bounds of the form (1) |i/Xr)| so instead of as y/E which is suggested by spherically symmetric examples and the theory of ordinary differential equations [8]. Much of the literature on the subject deals with these weaknesses. Due to the recent work of O'Connor [6], Combes-Thomas [2] and Simon [lO], we now have nearly maximally good results for the case V(r) = 2 V . .(r. r.) with V ..(x) —> 0 as

35 citations


Journal ArticleDOI
TL;DR: The purpose of the simultaneous measurement of noncommuting quantum observables can be viewed as the joint estimation of parameters of the density operator of the quantum system Joint estimation involves the application of a multiply parameterized operator-valued measure as discussed by the authors.
Abstract: The purpose of the simultaneous measurement of noncommuting quantum observables can be viewed as the joint estimation of parameters of the density operator of the quantum system Joint estimation involves the application of a multiply parameterized operator-valued measure An example related to the simultaneous estimation of the position and velocity of a particle is given Conceptual difficulties attending simultaneous measurement of noncommuting observables are avoided by this formation

24 citations


Journal ArticleDOI
TL;DR: In this article, the effects of the quantum nature of the detector system on the reliability of the detection operation are investigated in the general case in connection with the measurement problem in quantum physics.
Abstract: In a quantum field theory of the photodetection process, we investigate the effects of the quantum nature of the detector system on the reliability of the detection operation. We describe these effects in the general case in connection with the measurement problem in quantum physics.

5 citations