118 research outputs found
Arbitrarily High Super-Resolving Phase Measurements at Telecommunication Wavelengths
We present two experiments that achieve phase super-resolution at
telecommunication wavelengths. One of the experiments is realized in the space
domain and the other in the time domain. Both experiments show high
visibilities and are performed with standard lasers and single-photon
detectors. The first experiment uses six-photon coincidences, whereas the
latter needs no coincidence measurements, is easy to perform, and achieves, in
principle, arbitrarily high phase super-resolution. Here, we demonstrate a
30-fold increase of the resolution. We stress that neither entanglement nor
joint detection is needed in these experiments, demonstrating that neither is
necessary to achieve phase super-resolution.Comment: 5 pages, 7 figure
Quantum Clock Synchronization with a Single Qudit
Clock synchronization for nonfaulty processes in multiprocess networks is
indispensable for a variety of technologies. A reliable system must be able to
resynchronize the nonfaulty processes upon some components failing causing the
distribution of incorrect or conflicting information in the network. The task
of synchronizing such networks is related to detectable Byzantine agreement
(DBA), which can classically be solved using recursive algorithms if and only
if less than one-third of the processes are faulty. Here we introduce a
nonrecursive quantum algorithm that solves the DBA and achieves clock
synchronization in the presence of arbitrary many faulty processes by using
only a single quantum system
Two Fundamental Experimental Tests of Nonclassicality with Qutrits
We report two fundamental experiments on three-level quantum systems
(qutrits). The first one tests the simplest task for which quantum mechanics
provides an advantage with respect to classical physics. The quantum advantage
is certified by the violation of Wright's inequality, the simplest classical
inequality violated by quantum mechanics. In the second experiment, we obtain
contextual correlations by sequentially measuring pairs of compatible
observables on a qutrit, and show the violation of Klyachko et al.'s
inequality, the most fundamental noncontextuality inequality violated by
qutrits. Our experiment tests exactly Klyachko et al.'s inequality, uses the
same measurement procedure for each observable in every context, and shows that
the violation does not depend on the order of the measurements.Comment: 4 pages, 2 figure
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