17 research outputs found
Measurements on the reality of the wavefunction
Quantum mechanics is an outstandingly successful description of nature,
underpinning fields from biology through chemistry to physics. At its heart is
the quantum wavefunction, the central tool for describing quantum systems. Yet
it is still unclear what the wavefunction actually is: does it merely represent
our limited knowledge of a system, or is it an element of reality? Recent no-go
theorems argued that if there was any underlying reality to start with, the
wavefunction must be real. However, that conclusion relied on debatable
assumptions, without which a partial knowledge interpretation can be maintained
to some extent. A different approach is to impose bounds on the degree to which
knowledge interpretations can explain quantum phenomena, such as why we cannot
perfectly distinguish non-orthogonal quantum states. Here we experimentally
test this approach with single photons. We find that no knowledge
interpretation can fully explain the indistinguishability of non-orthogonal
quantum states in three and four dimensions. Assuming that some underlying
reality exists, our results strengthen the view that the entire wavefunction
should be real. The only alternative is to adopt more unorthodox concepts such
as backwards-in-time causation, or to completely abandon any notion of
objective reality.Comment: 7 pages, 4 figure
Testing foundations of quantum mechanics with photons
The foundational ideas of quantum mechanics continue to give rise to
counterintuitive theories and physical effects that are in conflict with a
classical description of Nature. Experiments with light at the single photon
level have historically been at the forefront of tests of fundamental quantum
theory and new developments in photonics engineering continue to enable new
experiments. Here we review recent photonic experiments to test two
foundational themes in quantum mechanics: wave-particle duality, central to
recent complementarity and delayed-choice experiments; and Bell nonlocality
where recent theoretical and technological advances have allowed all
controversial loopholes to be separately addressed in different photonics
experiments.Comment: 10 pages, 5 figures, published as a Nature Physics Insight review
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