669 research outputs found
Problems with interpretation of He ground state
The continuum of He nucleus is studied theoretically in a three-body
He++ model basing on the recent information concerning He
spectrum [Golovkov, \textit{et al.}, Phys. Rev. C \textbf{76}, 021605(R)
(2007)]. The He ground state (g.s.) candidate with structure
for new g.s. energy of He is predicted to be at about
MeV. The peak in the cross section associated with this state may be
shifted to a lower energy (e.g. MeV) when He is populated in
reactions with Li due to peculiar reaction mechanism. Formation of the
low-energy ( keV) ``alternative'' ground state with structure
is highly probable in He in the case of considerable
attraction (e.g. fm) in the s-wave He channel, which properties are
still quite uncertain. This result either questions the existing experimental
low-energy spectrum of He or place a limit on the scattering length in
He channel, which contradicts existing data.Comment: 14 pages, 13 figures, 1 tabl
Hartman effect and spin precession in graphene
Spin precession has been used to measure the transmission time \tau over a
distance L in a graphene sheet. Since conduction electrons in graphene have an
energy-independent velocity v, one would expect \tau > L/v. Here we calculate
that \tau < L/v at the Dirac point (= charge neutrality point) in a clean
graphene sheet, and we interpret this result as a manifestation of the Hartman
effect (apparent superluminality) known from optics.Comment: 6 pages, 4 figures; v2: added a section on the case of
perpendicularly aligned magnetizations; v3: added a figur
Compact and Loosely Bound Structures in Light Nuclei
A role of different components in the wave function of the weakly bound light
nuclei states was studied within the framework of the cluster model, taking
into account of orbitals "polarization". It was shown that a limited number of
structures associated with the different modes of nucleon motion can be of
great importance for such systems. Examples of simple and quite flexible trial
wave functions are given for the nuclei Be, He. Expressions for the
microscopic wave functions of these nuclei were found and used for the
calculation of basic nuclear characteristics, using well known central-exchange
nucleon-nucleon potentials.Comment: 19 pages, 3 ps figure
Quantum Abacus for counting and factorizing numbers
We generalize the binary quantum counting algorithm of Lesovik, Suslov, and
Blatter [Phys. Rev. A 82, 012316 (2010)] to higher counting bases. The
algorithm makes use of qubits, qutrits, and qudits to count numbers in a base
2, base 3, or base d representation. In operating the algorithm, the number n <
N = d^K is read into a K-qudit register through its interaction with a stream
of n particles passing in a nearby wire; this step corresponds to a quantum
Fourier transformation from the Hilbert space of particles to the Hilbert space
of qudit states. An inverse quantum Fourier transformation provides the number
n in the base d representation; the inverse transformation is fully quantum at
the level of individual qudits, while a simpler semi-classical version can be
used on the level of qudit registers. Combining registers of qubits, qutrits,
and qudits, where d is a prime number, with a simpler single-shot measurement
allows to find the powers of 2, 3, and other primes d in the number n. We show,
that the counting task naturally leads to the shift operation and an algorithm
based on the quantum Fourier transformation. We discuss possible
implementations of the algorithm using quantum spin-d systems, d-well systems,
and their emulation with spin-1/2 or double-well systems. We establish the
analogy between our counting algorithm and the phase estimation algorithm and
make use of the latter's performance analysis in stabilizing our scheme.
Applications embrace a quantum metrological scheme to measure a voltage (analog
to digital converter) and a simple procedure to entangle multi-particle states.Comment: 23 pages, 15 figure
New Perturbation Theory for Nonstationary Anharmonic Oscillator
The new perturbation theory for the problem of nonstationary anharmonic
oscillator with polynomial nonstationary perturbation is proposed. As a zero
order approximation the exact wave function of harmonic oscillator with
variable frequency in external field is used. Based on some intrinsic
properties of unperturbed wave function the variational-iterational method is
proposed, that make it possible to correct both the amplitude and the phase of
wave function. As an application the first order correction are proposed both
for wave function and S-matrix elements for asymmetric perturbation potential
of type The transition amplitude
''ground state - ground state'' is analyzed in detail
depending on perturbation parameter (including strong coupling
region ) and one-dimensional refraction coefficient .Comment: LaTeX, 13 page
Peculiar properties of the cluster-cluster interaction induced by the Pauli exclusion principle
Role of the Pauli principle in the formation of both the discrete spectrum
and multi-channel states of the binary nuclear systems composed of clusters is
studied in the Algebraic Version of the resonating-group method. Solutions of
the Hill-Wheeler equations in the discrete representation of a complete basis
of the Pauli-allowed states are discussed for 4He+n, 3H+3H, and 4He+4He binary
systems. An exact treatment of the antisymmetrization effects are shown to
result in either an effective repulsion of the clusters, or their effective
attraction. It also yields a change in the intensity of the centrifugal
potential. Both factors significantly affect the scattering phase behavior.
Special attention is paid to the multi-channel cluster structure 6He+6He as
well as to the difficulties arising in the case when the two clustering
configurations, 6He+6He and 4He+8He, are taken into account simultaneously. In
the latter case the Pauli principle, even in the absence of a potential energy
of the cluster-cluster interaction, leads to the inelastic processes and
secures an existence of both the bound state and resonance in the 12Be compound
nucleus.Comment: 17 pages, 14 figures, 1 table; submitted to Phys.Rev.C Keywords:
light neutron-rich nuclei, cluster model
Traversal time for electron tunneling in water
The traversal time for tunneling is a measure of the time during which the
transmitted particle can be affected by interactions localized in the barrier.
The Buttiker-Landauer approach, which estimates this time by imposing an
internal clock on the system, has been applied so far for relatively simple
1-dimensional models. Here we apply this approach to estimate the traversal
time for electron tunneling through a realistic 3-dimensional model of a water
layer. Observed structure in the energy dependence of times computed reflects
the existence of transient tunneling resonances associated with instantaneous
water structures.Comment: 9 pages, 3 figures. Submitted to the Journal of Chemical Physic
Quantum divisibility test and its application in mesoscopic physics
We present a quantum algorithm to transform the cardinality of a set of
charged particles flowing along a quantum wire into a binary number. The setup
performing this task (for at most N particles) involves log_2 N quantum bits
serving as counters and a sequential read out. Applications include a
divisibility check to experimentally test the size of a finite train of
particles in a quantum wire with a one-shot measurement and a scheme allowing
to entangle multi-particle wave functions and generating Bell states,
Greenberger-Horne-Zeilinger states, or Dicke states in a Mach-Zehnder
interferometer.Comment: 9 pages, 5 figure
Passive sampling of wastewater as a tool for the long-term monitoring of community exposure: Illicit and prescription drug trends as a proof of concept
Embargo until 20 May 2019.A passive sampling device, the Polar Organic Chemical Integrative Sampler (POCIS), was calibrated in-situ over a 4-week period in Oslo (Norway) for 10 illicit drugs and pharmaceuticals with the goal of developing an approach for monitoring long-term wastewater drug loads. The calibrations were performed in triplicate using three different overlapping calibration sets under changing environmental conditions that allowed the uncertainty of the sampling rates to be evaluated. All 10 compounds exhibited linear uptake kinetics and provided sampling rates of between 0.023 and 0.192 L dâ1. POCIS were deployed for consecutive 2-week periods during 2012 and 2013 and the calculated time-weighted average (TWA) concentrations used to define different drug use trends. The relative uncertainty related to the POCIS data was approximately 40% and, except for citalopram, 85% of all the long-term measurements of pharmaceuticals were within the confidence interval levels calculated to evaluate the effects of changing environmental conditions on the TWA estimations. POCIS was demonstrated to be sufficiently robust to provide reliable annual drug use estimates with a smaller number of samplers (n = 24) than recommended for active sampling (n = 56) within an acceptable level of sample size related uncertainty < 10%. POCIS is demonstrated to be a valuable and reliable tool for the long-term monitoring of certain drugs and pharmaceuticals within a defined population.acceptedVersio
Evolution of a Bose-condensed gas under variations of the confining potential
We discuss the dynamic properties of a trapped Bose-condensed gas under
variations of the confining field and find analytical scaling solutions for the
evolving coherent state (condensate). We further discuss the characteristic
features and the depletion of this coherent state.Comment: 4 pages, no postscript figure
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