73 research outputs found
Factoring and Fourier Transformation with a Mach-Zehnder Interferometer
The scheme of Clauser and Dowling (Phys. Rev. A 53, 4587 (1996)) for
factoring by means of an N-slit interference experiment is translated into
an experiment with a single Mach-Zehnder interferometer. With dispersive phase
shifters the ratio of the coherence length to wavelength limits the numbers
that can be factored. A conservative estimate permits . It is
furthermore shown, that sine and cosine Fourier coefficients of a real periodic
function can be obtained with such an interferometer.Comment: 5 pages, 2 postscript figures; to appear in Phys.Rev.A, Nov. 1997;
Figures contained only in replaced versio
A Quantum-mechanical description of ion motion within the confining potentials of voltage gated ion channels
Voltage gated channel proteins cooperate in the transmission of membrane
potentials between nerve cells. With the recent progress in atomic-scaled
biological chemistry it has now become established that these channel proteins
provide highly correlated atomic environments that may maintain electronic
coherences even at warm temperatures. Here we demonstrate solutions of the
Schr\"{o}dinger equation that represent the interaction of a single potassium
ion within the surrounding carbonyl dipoles in the Berneche-Roux model of the
bacterial \textit{KcsA} model channel. We show that, depending on the
surrounding carbonyl derived potentials, alkali ions can become highly
delocalized in the filter region of proteins at warm temperatures. We provide
estimations about the temporal evolution of the kinetic energy of ions
depending on their interaction with other ions, their location within the
oxygen cage of the proteins filter region and depending on different
oscillation frequencies of the surrounding carbonyl groups. Our results provide
the first evidence that quantum mechanical properties are needed to explain a
fundamental biological property such as ion-selectivity in trans-membrane
ion-currents and the effect on gating kinetics and shaping of classical
conductances in electrically excitable cells.Comment: 12 pages, 8 figure
Dissipative systems: uncontrollability, observability and RLC realizability
The theory of dissipativity has been primarily developed for controllable
systems/behaviors. For various reasons, in the context of uncontrollable
systems/behaviors, a more appropriate definition of dissipativity is in terms
of the dissipation inequality, namely the {\em existence} of a storage
function. A storage function is a function such that along every system
trajectory, the rate of increase of the storage function is at most the power
supplied. While the power supplied is always expressed in terms of only the
external variables, whether or not the storage function should be allowed to
depend on unobservable/hidden variables also has various consequences on the
notion of dissipativity: this paper thoroughly investigates the key aspects of
both cases, and also proposes another intuitive definition of dissipativity.
We first assume that the storage function can be expressed in terms of the
external variables and their derivatives only and prove our first main result
that, assuming the uncontrollable poles are unmixed, i.e. no pair of
uncontrollable poles add to zero, and assuming a strictness of dissipativity at
the infinity frequency, the dissipativities of a system and its controllable
part are equivalent. We also show that the storage function in this case is a
static state function.
We then investigate the utility of unobservable/hidden variables in the
definition of storage function: we prove that lossless autonomous behaviors
require storage function to be unobservable from external variables. We next
propose another intuitive definition: a behavior is called dissipative if it
can be embedded in a controllable dissipative {\em super-behavior}. We show
that this definition imposes a constraint on the number of inputs and thus
explains unintuitive examples from the literature in the context of
lossless/orthogonal behaviors.Comment: 26 pages, one figure. Partial results appeared in an IFAC conference
(World Congress, Milan, Italy, 2011
Quantum tomography as normalization of incompatible observations
Quantum states are successfully reconstructed using the maximum likelihood
estimation on the subspace where the measured projectors reproduce the identity
operator. Reconstruction corresponds to normalization of incompatible
observations. The proposed approach handles the noisy data corresponding to
realistic incomplete observation with finite resolution.Comment: RevTeX, 4 pages, 3 figure
New intensity and visibility aspects of a double loop neutron interferometer
Various phase shifters and absorbers can be put into the arms of a double
loop neutron interferometer. The mean intensity levels of the forward and
diffracted beams behind an empty four plate interferometer of this type have
been calculated. It is shown that the intensities in the forward and diffracted
direction can be made equal using certain absorbers. In this case the
interferometer can be regarded as a 50/50 beam splitter. Furthermore the
visibilities of single and double loop interferometers are compared to each
other by varying the transmission in the first loop using different absorbers.
It can be shown that the visibility becomes exactly 1 using a phase shifter in
the second loop. In this case the phase shifter in the second loop must be
strongly correlated to the transmission coefficient of the absorber in the
first loop. Using such a device homodyne-like measurements of very weak signals
should become possible.Comment: 12 pages, 9 figures, accepted for publication in the Journal of
Optics B - Quantum and Semiclassical Optic
Zero-field and Larmor spinor precessions in a neutron polarimeter experiment
We present a neutron polarimetric experiment where two kinds of spinor
precessions are observed: one is induced by different total energy of neutrons
(zero-field precession) and the other is induced by a stationary guide field
(Larmor precession). A characteristic of the former is the dependence of the
energy-difference, which is in practice tuned by the frequency of the
interacting oscillating magnetic field. In contrast the latter completely
depends on the strength of the guide field, namely Larmor frequency. Our
neutron-polarimetric experiment exhibits individual tuning as well as specific
properties of each spinor precession, which assures the use of both spin
precessions for multi-entangled spinor manipulation.Comment: 12 pages, 4 figure
Interrelations Between the Neutron's Magnetic Interactions and the Magnetic Aharonov-Bohm Effect
It is proved that the phase shift of a polarized neutron interacting with a
spatially uniform time-dependent magnetic field, demonstrates the same physical
principles as the magnetic Aharonov-Bohm effect. The crucial role of inert
objects is explained, thereby proving the quantum mechanical nature of the
effect. It is also proved that the nonsimply connectedness of the field-free
region is not a profound property of the system and that it cannot be regarded
as a sufficient condition for a nonzero phase shift.Comment: 18 pages, 1 postscript figure, Late
Quantum theory of incompatible observations
Maximum likelihood principle is shown to be the best measure for relating the
experimental data with the predictions of quantum theory.Comment: 3 page
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