4,693 research outputs found
Integrated infrared array technology
An overview of integrated infrared (IR) array technology is presented. Although the array pixel formats are smaller, and the readout noise of IR arrays is larger, than the corresponding values achieved with optical charge-coupled-device silicon technology, substantial progress is being made in IR technology. Both existing IR arrays and those being developed are described. Examples of astronomical images are given which illustrate the potential of integrated IR arrays for scientific investigations
Quantized vortices around wavefront nodes, 2
Quantized vortices can occur around nodal points in wavefunctions. The derivation depends only on the wavefunction being single valued, continuous, and having continuous first derivatives. Since the derivation does not depend upon the dynamical equations, the quantized vortices are expected to occur for many types of waves such as electromagnetic and acoustic. Such vortices have appeared in the calculations of the H + H2 molecular collisions and play a role in the chemical kinetics. In a companion paper, it is shown that quantized vortices occur when optical waves are internally reflected from the face of a prism or particle beams are reflected from potential energy barriers
Low-background performance of a monolithic InSb CCD array
A 20 element monolithic InSb charge coupled device (CCD) detector array was measured under low background conditions to assess its potential for orbital astronomical applications. At a temperature of 64 K, previous results for charge transfer efficiency (CTE) were reproduced, and a sensitivity of about 2 x 10 to the minus 15th power joules was measured. At 27 and 6 K, extended integration times were achieved, but CTE was substantially degraded. The noise was approximately 6000 charges, which was in excess of the level where statistical fluctuations from the illumination could be detected. A telescope demonstration was performed showing that the array sensitivity and difficulty of operation were not substantially different from laboratory levels. Ways in which the device could be improved for astronomical applications were discussed
Performance of charge-injection-device infrared detector arrays at low and moderate backgrounds
Three 2 x 64 element charge injection device infrared detector arrays were tested at low and moderate background to evaluate their usefulness for space based astronomical observations. Testing was conducted both in the laboratory and in ground based telescope observations. The devices showed an average readout noise level below 200 equivalent electrons, a peak responsivity of 4 A/W, and a noise equivalent power of 3x10 sq root of W/Hz. Array well capacity was measured to be significantly smaller than predicted. The measured sensitivity, which compares well with that of nonintegrating discrete extrinsic silicon photoconductors, shows these arrays to be useful for certain astronomical observations. However, the measured readout efficiency and frequency response represent serious limitations in low background applications
Detector arrays for low-background space infrared astronomy
The status of development and characterization tests of integrated infrared detector array technology for astronomy applications is described. The devices under development include intrinsic, extrinsic silicon, and extrinsic germanium detectors, with hybrid silicon multiplexers. Laboratory test results and successful astronomy imagery have established the usefulness of integrated arrays in low-background astronomy applications
Infrared Classification of Galactic Objects
Unbiased analysis shows that IRAS data reliably differentiate between the
early and late stages of stellar evolution because objects at these stages
clearly segregate in infrared color-color diagrams. Structure in these diagrams
is primarily controlled by the density distribution of circumstellar dust. The
density profile around older objects is the steepest, declining as ,
while young objects have profiles that vary as and flatter. The
different density profiles reflect the different dynamics that govern the
different environments. Our analysis also shows that high mass star formation
is strongly concentrated within \about 5 kpc around the Galactic center, in
support of other studies.Comment: 11 pages, 3 Postscript figures (included), uses aaspp4.sty. To appear
in Astrophysical Journal Letter
Dirac Relation and Renormalization Group Equations for Electric and Magnetic Fine Structure Constants
The quantum field theory describing electric and magnetic charges and
revealing a dual symmetry was developed in the Zwanziger formalism. The
renormalization group (RG) equations for both fine structure constants -
electric and magnetic - were obtained. It was shown
that the Dirac relation is valid for the renormalized and at the arbitrary scale, but these RG equations can be considered
perturbatively only in the small region: with given by the Dirac
relation: = 1/4.Comment: 15 pages, 4 figures, made corrections of physics after comments from
Kim Milto
Teleportation-based realization of an optical quantum two-qubit entangling gate
In recent years, there has been heightened interest in quantum teleportation,
which allows for the transfer of unknown quantum states over arbitrary
distances. Quantum teleportation not only serves as an essential ingredient in
long-distance quantum communication, but also provides enabling technologies
for practical quantum computation. Of particular interest is the scheme
proposed by Gottesman and Chuang [Nature \textbf{402}, 390 (1999)], showing
that quantum gates can be implemented by teleporting qubits with the help of
some special entangled states. Therefore, the construction of a quantum
computer can be simply based on some multi-particle entangled states, Bell
state measurements and single-qubit operations. The feasibility of this scheme
relaxes experimental constraints on realizing universal quantum computation.
Using two different methods we demonstrate the smallest non-trivial module in
such a scheme---a teleportation-based quantum entangling gate for two different
photonic qubits. One uses a high-fidelity six-photon interferometer to realize
controlled-NOT gates and the other uses four-photon hyper-entanglement to
realize controlled-Phase gates. The results clearly demonstrate the working
principles and the entangling capability of the gates. Our experiment
represents an important step towards the realization of practical quantum
computers and could lead to many further applications in linear optics quantum
information processing.Comment: 10 pages, 6 figure
- …