50 research outputs found
The interplay between quantum foundations and quantum technologies:Counterfactual communication, and extensions of quantum mechanics
Counterfactuality, Definiteness, and Bell's Theorem
We show counterfactual definiteness separates classical from quantum physics,
by analysing Bell's Theorem. By comparing what it prohibited by various
interpretations, we show most interpretations just require counterfactual
semi-definiteness (the definiteness of possible options available after a
measurement event), rather than full counterfactual indefiniteness. While less
definite than classical counterfactual definiteness, it allows us a far more
sophisticated tool to consider the physical interpretation of multi-valued
variables in a not yet done. Working from this, we further consider its
relation to how counterfactual possibilities interact.Comment: 5+1 pages, edited for clarity and concisenes
Counterfactual Ghost Imaging
We give a protocol for ghost imaging in a way that is always counterfactual -
while imaging an object, no light interacts with that object. This extends the
idea of counterfactuality beyond communication, showing how this interesting
phenomenon can be leveraged for metrology. Given, in the infinite limit, no
photons ever go to the imaged object, it presents a method of imaging even the
most light-sensitive of objects without damaging them. Even when not in the
infinite limit, it still provides a many-fold improvement in visibility and
signal-to-noise ratio over previous protocols, with over an order of magnitude
reduction in absorbed intensity.Comment: 7 pages, 6 figures, matches published versio
Do the laws of physics prohibit counterfactual communication?
It has been conjectured that counterfactual communication is impossible, even
for post-selected quantum particles. We strongly challenge this by proposing
exactly such a counterfactual scheme where---unambiguously---none of Alice's
photons that make it has been to Bob. We demonstrate counterfactuality
theoretically and experimentally by means of weak measurements, as well as
conceptually using consistent histories. Importantly, the accuracy of Alice
learning Bob's bit can be made arbitrarily close to unity with no trace left by
Bob on Alice's photon.Comment: Experiment conducted in the lab, showing no weak trace from Bob at
either D0 or D1. 5 pages, 5 figure
Comment on "Experimentally adjudicating between different causal accounts of Bell-inequality violations via statistical model selection"
In a recent paper (Phys. Rev. A 105, 042220 (2022)), Daley et al claim that
superdeterministic models are disfavoured against standard quantum mechanics,
because such models overfit the statistics of a Bell-type experiment which the
authors conducted. We argue here that their claim is based on a
misunderstanding of what superdeterministic models are.Comment: 4 pages, no figure
Comment on ``Scheme of the arrangement for attack on the protocol BB84"
In a recent paper (Scheme of the arrangement for attack on the protocol BB84,
Optik 127(18):7083-7087, Sept 2016), a protocol was proposed for using weak
measurement to attack BB84. This claimed the four basis states typically used
could be perfectly discriminated, and so an interceptor could obtain all
information carried. We show this attack fails when considered using standard
quantum mechanics, as expected - such ``single-shot" quantum state
discrimination is impossible, even using weak measurement.Comment: 3 pages, 1 figure, accepted for publication by Opti
Comment on "Why interference phenomena do not capture the essence of quantum theory" by Catani et al
It was recently argued by Catani et al that it is possible to reproduce the
phenomenology of the double-slit experiment with a deterministic, local, and
classical model (arXiv:2111.13727). The stated aim of their argument is to
falsify the claim made by Feynman (in his third book of Lectures on Physics)
that the double-slit experiment is "impossible, absolutely impossible, to
explain in any classical way" and that it "contains the only mystery" of
quantum mechanics. We here want to point out some problems with their argument,
and defend Feynman's position.Comment: 3 pages, no figures, comments welcom