30 research outputs found
Spin - Rotation Coupling Observed in Neutron Interferometry
Einstein's theory of general relativity and quantum theory form the two major
pillars of modern physics. However, certain inertial properties of a particle's
intrinsic spin are inconspicuous while the inertial properties of mass are well
known. Here, by performing a neutron interferometric experiment, we observe
phase shifts arising as a consequence of the spin's coupling with the angular
velocity of a rotating magnetic field. The resulting phase shifts linearly
depend on the frequency of the rotation of the magnetic field. Our results
agree well with the predictions derived from the Pauli - Schr\"odinger
equation
Experimental demonstration of direct path state characterization by strongly measuring weak values in a matter-wave interferometer
A novel method was recently proposed and experimentally realized for
characterizing a quantum state by directly measuring its complex probability
amplitudes in a particular basis using so-called weak values. Recently Vallone
and Dequal showed theoretically that weak measurements are not a necessary
condition to determine the weak value [Phys. Rev. Lett. 116, 040502 (2016)].
Here we report a measurement scheme used in a matter-wave interferometric
experiment in which the neutron path system's quantum state was characterized
via direct measurements using both strong and weak interactions. Experimental
evidence is given that strong interactions outperform weak ones. Our results
are not limited to neutron interferometry, but can be used in a wide range of
quantum systems.Comment: 5 pages, 3 figure
Observation of a quantum Cheshire Cat in a matter wave interferometer experiment
From its very beginning quantum theory has been revealing extraordinary and
counter-intuitive phenomena, such as wave-particle duality, Schr\"odinger cats
and quantum non-locality. In the study of quantum measurement, a process
involving pre- and postselection of quantum ensembles in combination with a
weak interaction was found to yield unexpected outcomes. This scheme, usually
referred to as "weak measurements", can not only be used as an amplification
technique and for minimal disturbing measurements, but also for the exploration
of quantum paradoxes. Recently the quantum Cheshire Cat has attracted
attention: a quantum system can behave as if a particle and its property (e.g.
its polarization) are spatially separated. Up to now most experiments studying
weak measurements were done with photonic setups. To reveal the peculiarities
of a quantum Cheshire Cat the use of non-zero mass particles is most appealing,
since no classical description is possible. Here, we report an experiment using
a neutron interferometer to create and observe a purely quantum mechanical
Cheshire Cat. The experimental results suggest that the system behaves as if
the neutrons went through one beam path, while their spin travelled along the
other.Comment: 8 pages, 4 figures and 1 tabl
Search for dark energy with neutron interferometry
We use previously obtained experimental results by neutron interferometry to
effectively constrain the parameter space of several prominent dark energy
models. This investigation encompasses the environment-dependent dilaton field,
a compelling contender for dark energy that emerges naturally within the strong
coupling limit of string theory, alongside symmetron and chameleon fields. Our
study presents substantial improvements over previous constraints of the
dilaton and symmetron fields, improving parameter constraints by several orders
of magnitude. However, the analysis does not yield any new constraints on the
chameleon field. Furthermore, we establish constraints for the projected
neutron split interferometer, which has recently concluded a decisive
proof-of-principle demonstration. Our symmetron simulations reveal that
depending on the parameter values there are multiple static solutions with
increasing number of nodes and increasing energy inside a cylindrical vacuum
chamber. This agrees with results obtained earlier in the literature for
infinitely parallel plates. Interestingly, while these multiple solutions can
correspond to domain walls forming inside the vacuum chamber, we also find
solutions that do not reach their vacuum expectation value inside the vacuum
chamber, but display multiple nodes nonetheless.Comment: 11 pages, 8 figure
Violation of a Leggett-Garg inequality using ideal negative measurements in neutron interferometry
We report on an experiment that demonstrates the violation of a Leggett-Garg
inequality (LGI) with neutrons. LGIs have been proposed in order to assess how
far the predictions of quantum mechanics defy macroscopic realism. With LGIs,
correlations of measurements performed on a single system at different times
are described. The measured value of K = 1.120 +/- 0.007, obtained in a neutron
interferometric experiment, is clearly above the limit K = 1 predicted by
macro-realistic theories.Comment: 6 pages, 8 figure
Three-Path Quantum Cheshire Cat Observed in Neutron Interferometry
The paradoxical phenomenon of the quantum Cheshire Cat (qCC) refers to
situations where different properties of a particle appear to be localised in
different paths of an interferometer and therefore spatially separated. This
observation is obtained by implementing a pre- and postselection procedure. The
localisations are determined qualitatively through conspicuous changes induced
by weak interactions. Previous demonstrations of the qCC only used the path and
spin/polarisation degrees of freedom. In addition, the present experiment uses
the neutron's energy as a third property in a three-path interferometer. It is
demonstrated that the three properties of neutrons are found separated in
different paths in the interferometer; a detailed analysis suggests that the
appearance of a property is strongly related to the geometrical relation
between the state vectors of pre- and postselection with weak interactions in
between. If a weak interaction in a path locally generates a state vector with
a component parallel to the reference state in another path, a conspicuous
intensity oscillation is expected and observed. Therefore, the appearance of
the observed intensity oscillations is attributed solely to the cross-terms
between the reference and the newly generated state via weak interactions