6,090 research outputs found
Design, fabrication and evaluation of chalcogenide glass Luneburg lenses for LiNbO3 integrated optical devices
Optical waveguide Luneburg lenses of arsenic trisulfide glass are described. The lenses are formed by thermal evaporation of As2S3 through suitably placed masks onto the surface of LiNbO3:Ti indiffused waveguides. The lenses are designed for input apertures up to 1 cm and for speeds of f/5 or better. They are designed to focus the TM sub 0 guided mode of a beam of wavelength, external to the guide, of 633 nm. The refractive index of the As2S3 films and the changes induced in the refractive index by exposure to short wavelength light were measured. Some correlation between film thickness and optical properties was noted. The short wavelength photosensitivity was used to shorten the lens focal length from the as deposited value. Lenses of rectangular shape, as viewed from above the guide, as well as conventional circular Luneburg lenses, were made. Measurements made on the lenses include thickness profile, general optical quality, focal length, quality of focal spot, and effect of ultraviolet irradiation on optical properties
Solid-state memcapacitive system with negative and diverging capacitance
We suggest a possible realization of a solid-state memory capacitive
(memcapacitive) system. Our approach relies on the slow polarization rate of a
medium between plates of a regular capacitor. To achieve this goal, we consider
a multi-layer structure embedded in a capacitor. The multi-layer structure is
formed by metallic layers separated by an insulator so that non-linear
electronic transport (tunneling) between the layers can occur. The suggested
memcapacitor shows hysteretic charge-voltage and capacitance-voltage curves,
and both negative and diverging capacitance within certain ranges of the field.
This proposal can be easily realized experimentally, and indicates the
possibility of information storage in memcapacitive devices
Strongly Incompatible Quantum Devices
The fact that there are quantum observables without a simultaneous
measurement is one of the fundamental characteristics of quantum mechanics. In
this work we expand the concept of joint measurability to all kinds of possible
measurement devices, and we call this relation compatibility. Two devices are
incompatible if they cannot be implemented as parts of a single measurement
setup. We introduce also a more stringent notion of incompatibility, strong
incompatibility. Both incompatibility and strong incompatibility are rigorously
characterized and their difference is demonstrated by examples.Comment: 27 pages (AMSart), 6 figure
Cloning and Joint Measurements of Incompatible Components of Spin
A joint measurement of two observables is a {\it simultaneous} measurement of
both quantities upon the {\it same} quantum system. When two quantum-mechanical
observables do not commute, then a joint measurement of these observables
cannot be accomplished by projective measurements alone. In this paper we shall
discuss the use of quantum cloning to perform a joint measurement of two
components of spin associated with a qubit system. We introduce a cloning
scheme which is optimal with respect to this task. This cloning scheme may be
thought to work by cloning two components of spin onto its outputs. We compare
the proposed cloning machine to existing cloners.Comment: 7 pages, 2 figures, submitted to PR
The Uniqueness Problem of Sequence Product on Operator Effect Algebra
A quantum effect is an operator on a complex Hilbert space that satisfies
. We denote the set of all quantum effects by . In
this paper we prove, Theorem 4.3, on the theory of sequential product on which shows, in fact, that there are sequential products on which are not of the generalized L\"{u}ders form. This result answers a
Gudder's open problem negatively
First-principles study of phase stability of Gd-doped EuO and EuS
Phase diagrams of isoelectronic EuGdO and EuGdS
quasi-binary alloy systems are constructed using first-principles calculations
combined with the standard cluster expansion approach and Monte-Carlo
simulations. The oxide system has a wide miscibility gap on the Gd-rich side
but forms ordered compounds on the Eu-rich side, exhibiting a deep asymmetric
convex hull in the formation enthalpy diagram. The sulfide system has no stable
compounds. The large difference in the formation enthalpies of the oxide and
sulfide compounds is due to the contribution of local lattice relaxation, which
is sensitive to the anion size. The solubility of Gd in both EuO and EuS is in
the range of 10-20% at room temperature and quickly increases at higher
temperatures, indicating that highly doped disordered solid solutions can be
produced without the precipitation of secondary phases. We also predict that
rocksalt GdO can be stabilized under appropriate experimental conditions.Comment: 14 pages, 6 figures (some with multiple panels), revtex4 with
embedded ep
Does My Stigma Look Big in This? Considering the acceptability and desirability in the inclusive design of technology products
This paper examines the relationship between stigmatic effects of design of technology products for the older and disabled and contextualizes this within wider social themes such as the functional, social, medical and technology models of disability. Inclusive design approaches are identified as unbiased methods for designing for the wider population that may accommodate the needs and desires of people with impairments, therefore reducing ’aesthetic stigma’. Two case studies illustrate stigmatic and nonstigmatic designs
Confined Quantum Time of Arrivals
We show that formulating the quantum time of arrival problem in a segment of
the real line suggests rephrasing the quantum time of arrival problem to
finding states that evolve to unitarily collapse at a given point at a definite
time. For the spatially confined particle, we show that the problem admits a
solution in the form of an eigenvalue problem of a compact and self-adjoint
time of arrival operator derived by a quantization of the classical time of
arrival, which is canonically conjugate with the Hamiltonian in closed subspace
of the Hilbert space.Comment: Figures are now include
Wannier functions of elliptic one-gap potentials
Wannier functions of the one dimensional Schroedinger equation with elliptic
one gap potentials are explicitly constructed. Properties of these functions
are analytically and numerically investigated. In particular we derive an
expression for the amplitude of the Wannier function in the origin, a power
series expansion valid in the vicinity of the origin and an asymptotic
expansion characterizing the decay of the Wannier function at large distances.
Using these results we construct an approximate analytical expression of the
Wannier function which is valid in the whole spatial domain and is in good
agreement with numerical results.Comment: 24 pages, 5 figure
Sequential measurements of conjugate observables
We present a unified treatment of sequential measurements of two conjugate
observables. Our approach is to derive a mathematical structure theorem for all
the relevant covariant instruments. As a consequence of this result, we show
that every Weyl-Heisenberg covariant observable can be implemented as a
sequential measurement of two conjugate observables. This method is applicable
both in finite and infinite dimensional Hilbert spaces, therefore covering
sequential spin component measurements as well as position-momentum sequential
measurements.Comment: 25 page
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