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At least 523 records · Page 29

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NASA NTRSDate not supplied

Modeling Electro-Optic Frequency Comb Generation as a Pump Source for Quantum Communications

The Quantum Communications group at NASA GRC is focused on developing technologies and system architectures to enable future space-based quantum networks. High-repetition rate pulsed pump lasers are needed because the signal on the quantum channel cannot be amplified, hence entanglement generation rates can only be increased through high-rate pumping. Additionally, tunability in center frequency, pulse width, and repetition rate allows for a wider parameter space over which to optimize quantum channel frequency conversion efficiency, joint spectral engineering, and channel synchronization for high-fidelity entanglement swapping –a necessary stepping-stone towards quantum repeater development. One of the most flexible methods for high-repetition rate pulse generation is through spectral shaping–generating a frequency comb from a continuous-wave(CW)laser using electro-optic modulators (EOMs). As a result, this project focuses on analytically modeling and simulating the effects various EOMs such as phase and intensity modulators have on a CW source. Generating a tunable frequency comb as the pump source allows us to conveniently fine-tune the central frequency, repetition rate, and the spectral shape of our source to match the strict optimal parameters for any given entanglement source considered in the future. These models and simulations are to be used for comparison purposes for future experiments as well as for providing the Quantum Communications group a convenient tool to understand the effects of manipulating various parameters have on the outgoing frequency comb.

Electro-optic modulator↗

NASA NTRS1994

Growth of delta-doped layers on silicon CCD/S for enhanced ultraviolet response

The backside surface potential well of a backside-illuminated CCD is confined to within about half a nanometer of the surface by using molecular beam epitaxy (MBE) to grow a delta-doped silicon layer on the back surface. Delta-doping in an MBE process is achieved by temporarily interrupting the evaporated silicon source during MBE growth without interrupting the evaporated p+ dopant source (e.g., boron). This produces an extremely sharp dopant profile in which the dopant is confined to only a few atomic layers, creating an electric field high enough to confine the backside surface potential well to within half a nanometer of the surface. Because the probability of UV-generated electrons being trapped by such a narrow potential well is low, the internal quantum efficiency of the CCD is nearly 100% throughout the UV wavelength range. Furthermore, the quantum efficiency is quite stable.

Hoenk, Michael E.↗

NASA NTRS2010

Planar Submillimeter-Wave Mixer Technology with Integrated Antenna

High-performance mixers at terahertz frequencies require good matching between the coupling circuits such as antennas and local oscillators and the diode embedding impedance. With the availability of amplifiers at submillimeter wavelengths and the need to have multi-pixel imagers and cameras, planar mixer architecture is required to have an integrated system. An integrated mixer with planar antenna provides a compact and optimized design at terahertz frequencies. Moreover, it leads to a planar architecture that enables efficient interconnect with submillimeter-wave amplifiers. In this architecture, a planar slot antenna is designed on a thin gallium arsenide (GaAs) membrane in such a way that the beam on either side of the membrane is symmetric and has good beam profile with high coupling efficiency. A coplanar waveguide (CPW) coupled Schottky diode mixer is designed and integrated with the antenna. In this architecture, the local oscillator (LO) is coupled through one side of the antenna and the RF from the other side, without requiring any beam sp litters or diplexers. The intermediate frequency (IF) comes out on a 50-ohm CPW line at the edge of the mixer chip, which can be wire-bonded to external circuits. This unique terahertz mixer has an integrated single planar antenna for coupling both the radio frequency (RF) input and LO injection without any diplexer or beamsplitters. The design utilizes novel planar slot antenna architecture on a 3- mthick GaAs membrane. This work is required to enable future multi-pixel terahertz receivers for astrophysics missions, and lightweight and compact receivers for planetary missions to the outer planets in our solar system. Also, this technology can be used in tera hertz radar imaging applications as well as for testing of quantum cascade lasers (QCLs).

Chattopadhyay, Gautam↗

NASA NTRS2001

Heavy ion induced soft breakdown of thin gate oxides

Heavy ion induced soft and hard breakdown are investigated in thin gate oxides as a function of LET, fluence, and voltage applied during irradiation. It is found that post-irradiation oxide conduction is well described by the Sune quantum point contact model.

radiation↗

NASA NTRS1976

Neutral calcium, strontium and barium - Determination of f values of the principal series by the hook method

The hook method is used to measure the absolute gf values of the following lines: the first 13 members of the principal series, the ground-level transition at 2275.46 A, and the intercombination line at 6572.78 A in Ca I; the first 22 members of the principal series, the ground-level transitions at 2428.1 and 2680.08 A, and the intercombination line at 6892.6 A in Sr I; and the members from principal quantum numbers 12 to 21, inclusive, as well as the ground-level transitions at 2432.5, 2444.6, and 2454.06 A in Ba I. The results are compared with those of previous measurements, and the quantum-defect method is applied to plot the oscillator strengths of the discrete transitions in the principal series of Mg I, Ca I, and Sr I in order to obtain estimates of the photoionization cross sections at the first ionization limit. The resulting cross sections are found to be about twice as large as previous values based on vapor-pressure data.

Parkinson, W. H.↗

NASA NTRS2017

Exponentially-Biased Ground-State Sampling of Quantum Annealing Machines with Transverse-Field Driving Hamiltonians

We study the performance of the D-Wave 2X quantum annealing machine on systems with well-controlled ground-state degeneracy. While obtaining the ground state of a spin-glass benchmark instance represents a difficult task, the gold standard for any optimization algorithm or machine is to sample all solutions that minimize the Hamiltonian with more or less equal probability. Our results show that while naive transverse-field quantum annealing on the D-Wave 2X device can find the ground-state energy of the problems, it is not well suited in identifying all degenerate ground-state configurations associated to a particular instance. Even worse, some states are exponentially suppressed, in agreement with previous studies on toy model problems [New J. Phys. 11, 073021 (2009)]. These results suggest that more complex driving Hamiltonians are needed in future quantum annealing machines to ensure a fair sampling of the ground-state manifold.

Quantum Annealing↗

NASA NTRS1979

The challenge of detecting gravitational radiation is creating a new chapter in quantum electronics: Quantum nondemolition measurements

Future gravitational wave antennas will be approximately 100 kilogram cylinders, whose end-to-end vibrations must be measured so accurately (10 to the -19th power centimeters) that they behave quantum mechanically. Moreover, the vibration amplitude must be measured over and over again without perturbing it (quantum nondemolition measurement). This contrasts with quantum chemistry, quantum optics, or atomic, nuclear, and elementary particle physics where measurements are usually made on an ensemble of identical objects, and care is not given to whether any single object is perturbed or destroyed by the measurement. Electronic techniques required for quantum nondemolition measurements are described as well as the theory underlying them.

Braginsky, V. B.↗

NASA NTRS1982

Can we detect antimatter from other galaxies

A novel particle detection technique employing well established principles of high order quantum electrodynamics for searching for antimatter in cosmic rays is described, and shown to have both collecting power and resolution superior to conventional alternatives. By taking into account various estimates of the metagalactic cosmic-ray energy density, and the possible modulation of metagalactic cosmic rays by a galactic wind within the framework of the dynamical halo model, it is shown that the experiment proposed would be the first to be sensitive to the presence of extragalactic antimatter.

Ahlen, S. P.↗

NASA NTRS1989

Jet-resolved vibronic structure in the higher excited states of N2O - Ultraviolet three-photon absorption spectroscopy from 80,000 to 90,000/cm

Ionization-detected UV multiphoton absorption spectroscopy of the excited states of N2O is presented, showing Rydberg structure within 20,000/cm of the first ionization threshold. Despite evidence for strong Rydberg-continuum coupling in the form of broadened bands and Fano line-shapes, the Rydberg structure persists, with atomic-like quantum defects and vibration structure well-matched with that of the ion. In the most clearly resolved spectrum, corresponding to the 3p(delta)1Pi state, Renner-Teller and Herzberg-Teller coupling of electronic and vibrational angular momentum are revealed. It is suggested that these mixings are properties of the N2O(+)Pi ion core.

Patsilinakou, E.↗

NASA NTRS1960

The Interactions Between Nitrogen and Oxygen Molecules

Lippincott's delta-function model for atomic interactions is analyzed, both physically and mathematically, and extended, by differentiation between K- and L-shell electrons and the introduction of a variable parameter in the expression for the delta-function strength, to cover homonuclear molecules more complex than hydrogen. In addition, modifications are made which allow treatments of diatomic, heteronuclear molecules. This theory, in conjunction with a reasonably extensive study of resonance, dispersion, and configuration interaction phenomena, as well as the use of simple quantum mechanical arguments, is then applied to the N2-N2, N2-O2, and O2-O2 interactions.

Meador, Willard E., Jr.↗

NASA NTRS2018

A Monolithic 2k x 2k LWIR HgCdTe Detector Array for Passively Cooled Space Missions

A 2K x 2K 10 µm cutoﬀ HgCdTe array for background-limited space astronomy has been developed by Teledyne Imaging Sensors to speciﬁcations set by JPL, and demonstrated by University of Rochester at a focal plane temperature of 40K for the proposed JPL Near-Earth Object Camera (NEOCam) survey mission under the NASA Planetary Defense Coordination Oﬃce. We describe the detector performance for the ﬁrst large format monolithic HgCdTe detector array tested, including the dark current, well depth, dark current vs. temperature, quantum eﬃciency, latent image performance, and read noise.

Pan, Jianmei↗

NASA NTRS2018

A Monolithic 2k x 2k LWIR HgCdTe Detector Array for Passively Cooled Space Missions

Pan, Jianmei↗

NASA NTRS2020

On Perspectives of Generating Quasi-Fock State via Resonant Self-Phase-Modulation

Optical resonators with cubic nonlinearity were among the ?rst simplest physical systems proposed for generation of squeezed states of light as well as for veri?cation of quantum nondemolition measurement concept. These conventional squeezed states are characterized with Gaussian statistics and positive Wigner function and are frequently treated as semiclassical. In contrast, it is known that the quantum states resulting from the higher order self-phase modulation are characterized with negative Wigner function. Such states can be transformed to an imperfect Fock state via classical biasing. Using these known features, we have developed an experiment strategy for observation and characterization of the nonclassical state in a system based on a high-Q nonlinear optical microcavity. We discuss technical limitations for the state observation associated with the losses in the system and technical noise of the classical optical sources involved in the measurement.

Bilenko, I. A.↗

NASA NTRS1960

Energies of Various Interactions Between Hydrogen and Helium Atoms and Ions

A compilation is made of those interactions between hydrogen and helium atoms and ions whose potential curves are well established by virtue of being based on experimental data or on essentially exact quantum-mechanical calculations. These potential curves have been fitted with well-known empirical forms which should be useful in calculations of transport properties involving these interactions.

Fallon, Robert J.↗

NASA NTRS2016

Explorations of Quantum-Classical Approaches to Scheduling a Mars Lander Activity Problem

An effective approach to solving problems involving mixed (continuous and discrete) variables and constraints, such as hybrid systems, is to decompose them into subproblems and integrate dedicated solvers geared toward those subproblems. Here, we introduce a new framework based on a tree search algorithm to solve hybrid discrete-continuous problems that incorporates: (1) a quantum annealer that samples from the configuration space for the discrete portion and provides information about the quality of the samples, and (2) a classical computer that makes use of information from the quantum annealer to prune and focus the search as well as check a continuous constraint. We consider four variants of our algorithm, each with progressively more guidance from the results provided by the quantum annealer. We empirically test our algorithm and compare the variants on a simplified Mars Lander task scheduling problem. Variants with more guidance from the quantum annealer have better performance.

scheduling↗

NASA NTRS1977

Detection of long wavelength infrared at moderate temperatures

Technical approaches for the advanced development of 8-12 micrometer detectors operating at elevated temperatures were defined. The theoretical limits to performance of 8-12 micrometer quantum detectors (photoconductive and photovoltaic) and thermal detectors (pyroelectrics, bolometers etc). An analytic model of signal and noise in both quantum detectors and pyroelectric detectors was developed and candidate materials for both detector types were identified and examined. The present status of both quantum and thermal detectors was assessed as well as the parameters limiting operating temperature and detectivity. The areas of research and development likely to lead to detector performance near the theoretical limit are identified.

Tredwell, T. J.↗

NASA NTRS2001

Kelvin Probe Measurements on Solar Cells and Other Thin Film Devices

The Kelvin Probe (KP) has been used for years to measure the surface potential of metals and semiconductors. The KP is an elegantly simple but powerful tool invented by Lord Kelvin around the turn of the century. Using changes in surface potentials as a result of changing the intensity and wavelength of illumination, the KP returns data on material parameters such as band gap energies and the energy levels of interface states. We have employed the KP in the study of CdTe-based solar cells and quantum dot-based solar cells, as well as other thin-film devices. We hope eventually that the KP will be used as an in-line testing station for a fabrication process so that unfinished devices that will not meet requirements can be thrown out before the processing is completed, thus saving resources. Results of these studies will be presented.

Delk, John↗

NASA NTRS2005

Characterization of InGaAs Linear Array for Applications to Remote Sensing

An Indium Gallium Arsenide linear photodiode array in the 1.1-2.5 micron spectral range was characterized. The array has 1024x1 pixels with a 25 micron pitch and was manufactured by Sensors Unlimited, Inc. Characterization and analysis of the electrical and optical properties of a camera system were carried out at room temperature to obtain detector performance parameters. The signal and noise were measured while the array was uniformly illuminated at varying exposure levels. A photon transfer curve was generated by plotting noise as a function of average signal to obtain the camera gain constant. The spectral responsivity was also measured, and the quantum efficiency, read noise and full-well capacity were determined. This paper describes the characterization procedure, analyzes the experimental results, and discusses the applications of the InGaAs linear array to future earth and planetary remote sensing mission.

Garcia, Christopher S.↗