24 research outputs found
Experimental non-classicality of an indivisible quantum system
Quantum theory demands that, in contrast to classical physics, not all
properties can be simultaneously well defined. The Heisenberg Uncertainty
Principle is a manifestation of this fact. Another important corollary arises
that there can be no joint probability distribution describing the outcomes of
all possible measurements, allowing a quantum system to be classically
understood. We provide the first experimental evidence that even for a single
three-state system, a qutrit, no such classical model can exist that correctly
describes the results of a simple set of pairwise compatible measurements. Not
only is a single qutrit the simplest system in which such a contradiction is
possible, but, even more importantly, the contradiction cannot result from
entanglement, because such a system is indivisible, and it does not even allow
the concept of entanglement between subsystems.Comment: 11 pages, 4 figures, 2 table
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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An experimental test of noncontextuality without unphysical idealizations
To make precise the sense in which nature fails to respect classical physics, one requires a formal notion of classicality. Ideally, such a notion should be defined operationally, so that it can be subject to direct experimental test, and it should be applicable in a wide variety of experimental scenarios so that it can cover the breadth of phenomena thought to defy classical understanding. Bell’s notion of local causality fulfils the first criterion but not the second. The notion of noncontextuality fulfils the second criterion, but it is a long-standing question whether it can be made to fulfil the first. Previous attempts to test noncontextuality have all assumed idealizations that real experiments cannot achieve, namely noiseless measurements and exact operational equivalences. Here we show how to devise tests that are free of these idealizations. We perform a photonic implementation of one such test, ruling out noncontextual models with high confidence
Quantum Entanglement of High Angular Momenta
Single photons with helical phase structures may carry a quantized amount of orbital angular momentum (OAM), and their entanglement is important for quantum information science and fundamental tests of quantum theory. Because there is no theoretical upper limit on how many quanta of OAM a single photon can carry, it is possible to create entanglement between two particles with an arbitrarily high difference in quantum number. By transferring polarization entanglement to OAM with an interferometric scheme, we generate and verify entanglement between two photons differing by 600 in quantum number. The only restrictive factors toward higher numbers are current technical limitations. We also experimentally demonstrate that the entanglement of very high OAM can improve the sensitivity of angular resolution in remote sensing
An experimental proposal for revealing contextuality in almost all qutrit states
10.1038/srep02706Scientific Reports3