330 research outputs found
On the fluidity of consonance and dissonance: The influence of musical context
The consonance/dissonance (C/D) level of a triadic chord is not a fixed or absolute value. Rather, it is fluid, since C/D depends both on a chord’s sonic characteristics and on the musical context in which it appears. To test the fluidity of C/D—the extent to which C/D perception is dependent on musical context—4 types of chords (major, minor, augmented, and diminished triads) were presented in isolation (“without musical context”) and as part of a short cadence (IV-V-I, “with musical context”). The C/D level of each chord was judged, as was the overall C/D and pleasantness/unpleasantness (P/U) level of the cadences. When isolated, major triads were considered most consonant, followed by minor and diminished triads, while augmented triads were judged most dissonant. In the context of a musical cadence, this rank order remained the same. However, evaluations of the dissonance of augmented and diminished chords varied depending on each chord’s functional position within the cadence. For instance, diminished triads were relatively consonant when on the subdominant, while augmented triads were relatively dissonant when on the tonic. These findings lend support to the hypotheses that: (a) the degree to which the harmonic function of a chord is familiar, and (b) the degree to which a chord’s stability (and hence also the listener’s expectation) is violated contribute to the perception of C/D
Control of Ultra-cold Inelastic Collisions by Feshbash Resonances and Quasi-One-Dimensional Confinement
Cold inelastic collisions of atoms or molecules are analyzed using very
general arguments. In free space, the deactivation rate can be enhanced or
suppressed together with the scattering length of the corresponding elastic
collision via a Feshbach resonance, and by interference of deactivation of the
closed and open channels. In reduced dimensional geometries, the deactivation
rate decreases with decreasing collision energy and does not increase with
resonant elastic scattering length. This has broad implications; e.g.,
stabilization of molecules in a strongly confining two-dimensional optical
lattice, since collisional decay of the highly vibrationally excited states due
to inelastic collisions is suppressed. The relation of our results with those
based on the Lieb-Liniger model are addressed.Comment: 5 pages, 1 figur
Universally valid reformulation of the Heisenberg uncertainty principle on noise and disturbance in measurement
The Heisenberg uncertainty principle states that the product of the noise in
a position measurement and the momentum disturbance caused by that measurement
should be no less than the limit set by Planck's constant, hbar/2, as
demonstrated by Heisenberg's thought experiment using a gamma-ray microscope.
Here I show that this common assumption is false: a universally valid trade-off
relation between the noise and the disturbance has an additional correlation
term, which is redundant when the intervention brought by the measurement is
independent of the measured object, but which allows the noise-disturbance
product much below Planck's constant when the intervention is dependent. A
model of measuring interaction with dependent intervention shows that
Heisenberg's lower bound for the noise-disturbance product is violated even by
a nearly nondisturbing, precise position measuring instrument. An experimental
implementation is also proposed to realize the above model in the context of
optical quadrature measurement with currently available linear optical devices.Comment: Revtex, 6 page
The Standard Model of Quantum Measurement Theory: History and Applications
The standard model of the quantum theory of measurement is based on an
interaction Hamiltonian in which the observable-to-be-measured is multiplied
with some observable of a probe system. This simple Ansatz has proved extremely
fruitful in the development of the foundations of quantum mechanics. While the
ensuing type of models has often been argued to be rather artificial, recent
advances in quantum optics have demonstrated their prinicpal and practical
feasibility. A brief historical review of the standard model together with an
outline of its virtues and limitations are presented as an illustration of the
mutual inspiration that has always taken place between foundational and
experimental research in quantum physics.Comment: 22 pages, to appear in Found. Phys. 199
Simulation results for a low energy nuclear recoil yields measurement in liquid xenon using the MiX detector
Measuring the scintillation and ionization yields of liquid xenon in response
to ultra-low energy nuclear recoil events is necessary to increase the
sensitivity of liquid xenon experiments to light dark matter. Neutron capture
on xenon can be used to produce nuclear recoil events with energies below
keV via the asymmetric emission of rays during nuclear
de-excitation. The feasibility of an ultra-low energy nuclear recoil
measurement using neutron capture was investigated for the Michigan Xenon (MiX)
detector, a small dual-phase xenon time projection chamber that is optimized
for a high scintillation gain. Simulations of the MiX detector, a partial
neutron moderator, and a pulsed neutron generator indicate that a population of
neutron capture events can be isolated from neutron scattering events. Further,
the rate of neutron captures in the MiX detector was optimized by varying the
thickness of the partial neutron moderator, neutron pulse width, and neutron
pulse frequency.Comment: 7 pages, 5 figures. LIDINE 2022 proceeding
Continuous variable quantum cryptography
We propose a quantum cryptographic scheme in which small phase and amplitude
modulations of CW light beams carry the key information. The presence of EPR
type correlations provides the quantum protection.Comment: 8 pages, 3 figure
Interpretation for a positive P representation
We show that a "canonical" form of the positive P representation has a simple interpretation as the statistics of four detectors, two of which make redundant position measurements, while the other two simultaneously make redundant momentum measurements. This interpretation allows us to understand the additional degrees of freedom for the canonical positive P representation
Path integrals on a flux cone
This paper considers the Schroedinger propagator on a cone with the conical
singularity carrying magnetic flux (``flux cone''). Starting from the operator
formalism and then combining techniques of path integration in polar
coordinates and in spaces with constraints, the propagator and its path
integral representation are derived. "Quantum correction" in the Lagrangian
appears naturally and no a priori assumption is made about connectivity of the
configuration space.Comment: LaTeX file, 9 page
Time-of-arrival distributions from position-momentum and energy-time joint measurements
The position-momentum quasi-distribution obtained from an Arthurs and Kelly
joint measurement model is used to obtain indirectly an ``operational''
time-of-arrival (TOA) distribution following a quantization procedure proposed
by Kocha\'nski and W\'odkiewicz [Phys. Rev. A 60, 2689 (1999)]. This TOA
distribution is not time covariant. The procedure is generalized by using other
phase-space quasi-distributions, and sufficient conditions are provided for
time covariance that limit the possible phase-space quasi-distributions
essentially to the Wigner function, which, however, provides a non-positive TOA
quasi-distribution. These problems are remedied with a different quantization
procedure which, on the other hand, does not guarantee normalization. Finally
an Arthurs and Kelly measurement model for TOA and energy (valid also for
arbitrary conjugate variables when one of the variables is bounded from below)
is worked out. The marginal TOA distribution so obtained, a distorted version
of Kijowski's distribution, is time covariant, positive, and normalized
Quantum Communication with Correlated Nonclassical States
Nonclassical correlations between the quadrature-phase amplitudes of two
spatially separated optical beams are exploited to realize a two-channel
quantum communication experiment with a high degree of immunity to
interception. For this scheme, either channel alone can have an arbitrarily
small signal-to-noise ratio (SNR) for transmission of a coherent ``message''.
However, when the transmitted beams are combined properly upon authorized
detection, the encoded message can in principle be recovered with the original
SNR of the source. An experimental demonstration has achieved a 3.2 dB
improvement in SNR over that possible with correlated classical sources.
Extensions of the protocol to improve its security against eavesdropping are
discussed.Comment: 8 pages and 4 figures (Figure 1; Figures 2a, 2b; Figure 2
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