Papers by Aephraim Steinberg
Physical Review A, 1994
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IEEE Journal of Quantum Electronics, 2001
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Physical Review A, 1992
In the process of spontaneous parametric downconversion, pairs of photons are emitted simultaneou... more In the process of spontaneous parametric downconversion, pairs of photons are emitted simultaneously. Although each photon is broadband, energy conservation requires that the frequencies of the two photons in each pair must always sum to thesame fixed value. It has been shown that due to this anticorrelation," the dispersion experienced by one photon can exactly cancel the dispersion experienced by the other in such a way that their coincidence is maintained,
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Physical Review A, 1995
It is argued that there is a sensible way to define conditional probabilities in quantum mechanic... more It is argued that there is a sensible way to define conditional probabilities in quantum mechanics, assuming only Bayes's theorem and standard quantum theory. These probabilities are equivalent to the ``weak measurement'' predictions due to Aharonov {\it et al.}, and hence describe the outcomes of real measurements made on subensembles. In particular, this approach is used to address the question of the history of a particle which has tunnelled across a barrier. A {\it gedankenexperiment} is presented to demonstrate the physically testable implications of the results of these calculations, along with graphs of the time-evolution of the conditional probability distribution for a tunneling particle and for one undergoing allowed transmission. Numerical results are also presented for the effects of loss in a bandgap medium on transmission and on reflection, as a function of the position of the lossy region; such loss should provide a feasible, though indirect, test of the present conclusions. It is argued that the effects of loss on the pulse {\it delay time} are related to the imaginary value of the momentum of a tunneling particle, and it is suggested that this might help explain a small discrepancy in an earlier experiment.
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Physical Review Letters, 1995
The question in the title may be answered by considering the outcome of a ``weak measurement'' in... more The question in the title may be answered by considering the outcome of a ``weak measurement'' in the sense of Aharonov et al. Various properties of the resulting time are discussed, including its close relation to the Larmor times. It is a universal description of a broad class of measurement interactions, and its physical implications are unambiguous.
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Physical Review A, 1994
Over the past few years, renewed attention has been devoted to the long-standing controversy over... more Over the past few years, renewed attention has been devoted to the long-standing controversy over the dura-tion of the tunneling process [1—9]. Most of the theoreti-cal work has centered on electron tunneling in one dimension, although some recent papers [10—14] have found it advantageous to focus on electromagnetic instances of tunneling. Both one-and two-dimensional tun-neling are importantin solid-state physics as well as in electromagnetism, and analogies between the different processes can be fruitful [15]. ...
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Physical Review A, 1992
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Scientific American, 1993
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Physical Review Letters, 2003
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In these notes, based on lectures given as part of the Les Houches summer school on Quantum Optic... more In these notes, based on lectures given as part of the Les Houches summer school on Quantum Optics and Nanophotonics
in August, 2013, I have tried to give a brief survey of some important approaches and modern tendencies in quantum
measurement. I wish it to be clear from the outset that I shy explicitly away from the “quantum measurement problem,”
and that the present treatment aims to elucidate the theory and practice of various ways in which measurements can,
in light of quantum mechanics, be carried out; and various formalisms for describing them. While the treatment is by
necessity largely theoretical, the emphasis is meant to be on an experimental “perspective” on measurement – that is,
to place the priority on the possibility of gaining information through some process, and then attempting to model that
process mathematically and consider its ramifications, rather than stressing a particular mathematical definition as the
sine qua non of measurement. The textbook definition of measurement as being a particular set of mathematical operations
carried out on particular sorts of operators has been so well drilled into us that many have the unfortunate tendency of
saying “that experiment can’t be described by projections onto the eigenstates of a Hermitian operator, so it is not really
a measurement,” when of course any practitioner of an experimental science such as physics should instead say “that
experiment allowed us to measure something, and if the standard theory of measurement does not describe it, the standard
theory of measurement is incomplete.” Idealisations are important, but when the real world breaks the approximations
made in the theory, it is the theory which must be fixed, and not the real world.
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Papers by Aephraim Steinberg
in August, 2013, I have tried to give a brief survey of some important approaches and modern tendencies in quantum
measurement. I wish it to be clear from the outset that I shy explicitly away from the “quantum measurement problem,”
and that the present treatment aims to elucidate the theory and practice of various ways in which measurements can,
in light of quantum mechanics, be carried out; and various formalisms for describing them. While the treatment is by
necessity largely theoretical, the emphasis is meant to be on an experimental “perspective” on measurement – that is,
to place the priority on the possibility of gaining information through some process, and then attempting to model that
process mathematically and consider its ramifications, rather than stressing a particular mathematical definition as the
sine qua non of measurement. The textbook definition of measurement as being a particular set of mathematical operations
carried out on particular sorts of operators has been so well drilled into us that many have the unfortunate tendency of
saying “that experiment can’t be described by projections onto the eigenstates of a Hermitian operator, so it is not really
a measurement,” when of course any practitioner of an experimental science such as physics should instead say “that
experiment allowed us to measure something, and if the standard theory of measurement does not describe it, the standard
theory of measurement is incomplete.” Idealisations are important, but when the real world breaks the approximations
made in the theory, it is the theory which must be fixed, and not the real world.
in August, 2013, I have tried to give a brief survey of some important approaches and modern tendencies in quantum
measurement. I wish it to be clear from the outset that I shy explicitly away from the “quantum measurement problem,”
and that the present treatment aims to elucidate the theory and practice of various ways in which measurements can,
in light of quantum mechanics, be carried out; and various formalisms for describing them. While the treatment is by
necessity largely theoretical, the emphasis is meant to be on an experimental “perspective” on measurement – that is,
to place the priority on the possibility of gaining information through some process, and then attempting to model that
process mathematically and consider its ramifications, rather than stressing a particular mathematical definition as the
sine qua non of measurement. The textbook definition of measurement as being a particular set of mathematical operations
carried out on particular sorts of operators has been so well drilled into us that many have the unfortunate tendency of
saying “that experiment can’t be described by projections onto the eigenstates of a Hermitian operator, so it is not really
a measurement,” when of course any practitioner of an experimental science such as physics should instead say “that
experiment allowed us to measure something, and if the standard theory of measurement does not describe it, the standard
theory of measurement is incomplete.” Idealisations are important, but when the real world breaks the approximations
made in the theory, it is the theory which must be fixed, and not the real world.