Comments on the Referee's Reports for Manuscript Foop1369, Submitted to Foundations of Physics, Entitled Quantum Weak Values Are Not Unique What Do They Actually Measure?
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چکیده
Most of the comments on the referee's reports will not be meaningful to someone who has not read the paper, so I may as well use the notation of the paper. For the reader's convenience, it is summarized below, but most readers will probably want to skip the summary, referring back to it only if needed. Symbols in the summary (such as A, s, f , etc.) will be used in the comments without further definition. We are given a quantum system S (the " system of interest ") in a given initial state s, and an observable A (like the spin of a particle) whose value is to be measured, with the object of determining its average value s, As. If these measurements are performed normally within S, each measurement may significantly disturb the initial state s of the system S (by " collapsing the wavefunction " to an eigenstate of A). Such measurements are called " strong " measurements. If we want to measure A without significantly disturbing the initial state s of S, it is possible to " weakly couple " S to an auxiliary " meter " system M , and measure a " meter observable " as a proxy for the measurement of A, in such a way that the average of the meter observable is the same as the average s, As of A. For sufficiently weak coupling, it can be arranged that a measurement of the meter observable will not significantly affect the state s of S. The tradeoff is that the meter observable will have a large dispersion, i.e., the individual meter measurements are likely to be very inaccurate approximations to s, As, though a large number of meter measurements will average to s, As. Such measurement are called " weak measurements " of s, As. All this is preliminary to the situation with which the " weak value " literature is typically concerned. Suppose that after making each of " weak measurements " of A in the state s (i.e. measuring the meter observable), we " postselect " the system A to a " final state " f ∈ S. This means that we perform another measurement to answer the question " Is S in state f (" yes " answer) or a state orthogonal to f ? " If the answer is " yes " , we say that the …
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متن کاملar X iv : 0 90 9 . 02 95 v 1 [ qu an t - ph ] 2 S ep 2 00 9 1 Quantum weak values are not unique What do they actually measure ?
Precise definitions of “weak [quantum] measurements” and “weak value” [of a quantum observable] are offered, which seem to capture the meaning of the often vague ways that these terms are used in the literature. Simple finite dimensional examples are given showing that weak values are not unique. They therefore cannot correspond to any physical attribute of the system being “weakly” measured, c...
متن کاملar X iv : 0 90 9 . 02 95 v 2 [ qu an t - ph ] 8 S ep 2 00 9 1 Quantum weak values are not unique What do they actually measure ?
Precise definitions of “weak [quantum] measurements” and “weak value” [of a quantum observable] are offered, which seem to capture the meaning of the often vague ways that these terms are used in the literature. Simple finite dimensional examples are given showing that weak values are not unique. They therefore cannot correspond to any physical attribute of the system being “weakly” measured, c...
متن کاملQuantum weak values are not unique What do they actually measure ?
Precise definitions of “weak [quantum] measurements” and “weak value” [of a quantum observable] are offered, which seem to capture the meaning of the often vague ways that these terms are used in the literature. Simple finite dimensional examples are given showing that weak values of an observable are not unique, and in fact arbitrary weak values can be obtained by appropriate weak measurements...
متن کاملWhat do quantum “ weak ” measurements actually measure ?
A precise definition of “weak [quantum] measurements” and “weak value” (of a quantum observable) is offered, and simple finite dimensional examples are given showing that weak values are not unique and therefore probably do not correspond to any physical attribute of the system being “weakly” measured, contrary to impressions given by most of the literature on weak measurements. A possible math...
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تاریخ انتشار 2010