354 research outputs found
Event-based simulation of quantum physics experiments
We review an event-based simulation approach which reproduces the statistical
distributions of wave theory not by requiring the knowledge of the solution of
the wave equation of the whole system but by generating detection events
one-by-one according to an unknown distribution. We illustrate its
applicability to various single photon and single neutron interferometry
experiments and to two Bell test experiments, a single-photon
Einstein-Podolsky-Rosen experiment employing post-selection for photon pair
identification and a single-neutron Bell test interferometry experiment with
nearly detection efficiency.Comment: Lectures notes of the Advanced School on Quantum Foundations and Open
Quantum Systems, Jo\~ao Pessoa, Brazil, July 2012, edited by T. M.
Nieuwenhuizen et al, World Scientific, to appea
Event-based simulation of neutron experiments: interference, entanglement and uncertainty relations
We discuss a discrete-event simulation approach, which has been shown to give
a unified cause-and-effect description of many quantum optics and
single-neutron interferometry experiments. The event-based simulation algorithm
does not require the knowledge of the solution of a wave equation of the whole
system, yet reproduces the corresponding statistical distributions by
generating detection events one-by-one. It is showm that single-particle
interference and entanglement, two important quantum phenomena, emerge via
information exchange between individual particles and devices such as beam
splitters, polarizers and detectors. We demonstrate this by reproducing the
results of several single-neutron interferometry experiments, including one
that demonstrates interference and one that demonstrates the violation of a
Bell-type inequality. We also present event-based simulation results of a
single neutron experiment designed to test the validity of Ozawa's universally
valid error-disturbance relation, an uncertainty relation derived using the
theory of general quantum measurements.Comment: Invited paper presented at the EmQM13 Workshop on Emergent Quantum
Mechanics, Austrian Academy of Sciences (October 3-6, 2013, Vienna
Discrete-event simulation of uncertainty in single-neutron experiments
A discrete-event simulation approach which provides a cause-and-effect
description of many experiments with photons and neutrons exhibiting
interference and entanglement is applied to a recent single-neutron experiment
that tests (generalizations of) Heisenberg's uncertainty relation. The
event-based simulation algorithm reproduces the results of the quantum
theoretical description of the experiment but does not require the knowledge of
the solution of a wave equation nor does it rely on concepts of quantum theory.
In particular, the data satisfies uncertainty relations derived in the context
of quantum theory
Irrelevance of Bell's Theorem for experiments involving correlations in space and time: a specific loophole-free computer-example
John Bell is generally credited to have accomplished the remarkable "proof"
that any theory of physics, which is both Einstein-local and "realistic"
(counterfactually definite), results in a strong upper bound to the
correlations that are measured in space and time. He thus predicts that
Einstein-Podolsky-Rosen experiments cannot violate Bell- type inequalities. We
present a counterexample to this claim, based on discrete-event computer
simulations. Our model-results fully agree with the predictions of quantum
theory for Einstein-Podolsky-Rosen-Bohm experiments and are free of the
detection- or a coincidence-loophole
Discrete-event simulation unmasks the quantum Cheshire Cat
It is shown that discrete-event simulation accurately reproduces the
experimental data of a single-neutron interferometry experiment [T. Denkmayr
{\sl et al.}, Nat. Commun. 5, 4492 (2014)] and provides a logically consistent,
paradox-free, cause-and-effect explanation of the quantum Cheshire cat effect
without invoking the notion that the neutron and its magnetic moment separate.
Describing the experimental neutron data using weak-measurement theory is shown
to be useless for unravelling the quantum Cheshire cat effect
Counterfactual Definiteness and Bell's Inequality
Counterfactual definiteness must be used as at least one of the postulates or
axioms that are necessary to derive Bell-type inequalities. It is considered by
many to be a postulate that is not only commensurate with classical physics (as
for example Einstein's special relativity), but also separates and
distinguishes classical physics from quantum mechanics. It is the purpose of
this paper to show that Bell's choice of mathematical functions and independent
variables implicitly includes counterfactual definiteness and reduces the
generality of the physics of Bell-type theories so significantly that no
meaningful comparison of these theories with actual Einstein-Podolsky-Rosen
experiments can be made
Reply to the Comment by A.J. Leggett and Anupam Garg
In their comment[1] on our Letter [arXiv:0907.0767], Leggett and Garg claim
that they have introduced in their original paper (LG1) a dependence on
measurement times. They also claim that Eqs.(HMDR1) and (LG2a) can therefore
not be linked in such a way that the arguments of [arXiv:0907.0767] can be
transcribed. However, (LG1) distinguishes only three time differences, and all
experimental results corresponding to the same time differences are identically
labeled and therefore treated as mathematically identical. We therefore cannot
agree with the argumentation of Leggett and Garg: except for a change of
nomenclature Eqs.(HMDR1) and (LG2a) are the same. A more extensive discussion
of this point can be found in [arXiv:0901.2546].Comment: Published version with minor correction
Rigorous Bounds on the Free Energy of Electron-Phonon Models
We present a collection of rigorous upper and lower bounds to the free energy of electron-phonon models with linear electron-phonon interaction. These bounds are used to compare different variational approaches. It is shown rigorously that the ground states corresponding to the sharpest bounds do not exhibit Off-Diagonal Long-Range Order in the two-particle density matrix.
Optical absorption in the soliton model for polyacetylene
A quantum molecular dynamics technique is used to compute the optical absorption at room-temperature for the soliton model for trans-polyacetylene in the semiclassical limit. Our simulation data for the optical absorption for dopant concentrations below 6% are in good agreement with experiment
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