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DOE OSTI2023

A Verified Optimizer for Quantum Circuits

We present VOQC, the first verified optimizer for quantum circuits, written using the Coq proof assistant. Quantum circuits are expressed as programs in a simple, low-level language called SQIR, a small quantum intermediate representation, which is deeply embedded in Coq. Optimizations and other transformations are expressed as Coq functions, which are proved correct with respect to a semantics of SQIR programs. SQIR programs denote complex-valued matrices, as is standard in quantum computation, but we treat matrices symbolically to reason about programs that use an arbitrary number of quantum bits. SQIR’s careful design and our provided automation make it possible to write and verify a broad range of optimizations in VOQC, including full-circuit transformations from cutting-edge optimizers.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2024

Direct detection system for full-field nanoscale X-ray diffraction-contrast imaging

Recent developments in X-ray science provide methods to probe deeply embedded mesoscale grain structures and spatially resolve them using dark field X-ray microscopy (DFXM). Extending this technique to investigate weak diffraction signals such as magnetic systems, quantum materials and thin films prove challenging due to available detection methods and incident X-ray flux at the sample. We present a direct detection method developed in conjunction with KAImaging which focuses on DFXM studies in the hard X-ray range of 10s of keV and above capable of approaching nanoscale resolution. Additionally, we compare this direct detection scheme with routinely used scintillator-based optical detection and achieve an order of magnitude improvement in exposure times allowing for imaging of weakly diffracting ordered systems.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

Chandra Resolves the Double FU Orionis System RNO 1B/1C in X-Rays

We present new Chandra X-ray observations of the close pair of young stars RNO 1B and 1C (6″ separation) located in the L1287 cloud. RNO 1B erupted in 1978–1990 and is classified as an FU Orionis star (FUor). RNO 1C also shows most of the properties of an FUor but no eruption has been seen yet. Only a few dozen FUors are known and the presence of two such objects with a small angular separation is rare, suggesting a common origin. Both stars were faintly detected by Chandra and we summarize their X-ray properties within the framework of other previously detected FUors. We also report other X-ray detections in L1287 including the deeply embedded young star RNO 1G, the jet-like radio source VLA 3, and an enigmatic hard flaring source with no Two Micron All Sky Survey counterpart that was only detected in the second of the two Chandra exposures.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1983

The depletion of calcium in the Rho Ophiuchi cloud

Data on the interstellar Ca II H and K lines toward HD 147889, a star deeply embedded in the rho Ophiuchi dark cloud, were obtained at the Mauna Kea Observatory of the University of Hawaii, using a multi-anode microchannel array (MAMA) detector. An upper limit on the Ca II column density of 1.7 x 10 to the 11th/sq cm was derived, which, together with ionization considerations and an estimated lower limit on the total hydrogen column density, implies that the calcium-to-hydrogen ratio in this line of sight is 0.00000795 or less, relative to the solar value. The logarithmic depletion is up to -5.10, the largest yet measured, and implies that gas-grain interaction in this region has proceeded to a much greater degree than is typical of diffuse clouds.

Snow, T. P.↗

NASA NTRS1983

The unique cometary nebula Parsamian 13

Parsamian 13 is found to be a cometary nebula, with a deeply embedded star suffering strong absorption by silicate grains. A feature near 2.7 microns, attributed to absorption by terminal OH groups, may represent the first detection in an astrophysical environment of water ice grains diluted by another molecule, for example by CO. The bolometric luminosity suggests that this star is either an extremely young T Tauri star or an evolved low-mass star, now a red giant, high on its convective track. Most unusual is the presence of cold (50 K) TiO gas in sufficient abundance to show in absorption in the optical and very near-infrared regions; this material probably represents very recently expelled photospheric layers.

Cohen, M.↗

NASA NTRS1983

Far-infrared detection of low-luminosity star formation in the Bok globule B335

Measurements of far-infrared intensities in the Bok globule B335, made with higher spatial and spectral resolution than two earlier studies, are described. The NASA 3-m Infrared Telescope Facility was used in February 1981 and the Kuiper Airborne Observatory 0.9-m telescope was used in October 1981 and August 1982 for the observations. The far-infrared source in B335 was revealed to be more compact than previously assumed, ruling out the interstellar radiation field as the dominant heat source. The new far-infrared size, luminosity, and temperature derived suggest that these may be the first observations of low-mass star formation embedded deeply within a Bok globule. The far-infrared source does not have a near-infrared or radio continuum counterpart. High angular resolution at submillimeter wavelengths will be critical in further studies of low-mass star formation.

Davidson, J. A.↗

NASA NTRS1985

A study of depletions within the RHO Ophiuchi cloud based on IUE observations of HD 147889

Archival IUE data on the deeply embedded Rho Oph cloud star HD 147889 have been used to derive column densities for several species. The poor data quality and limited useful spectral coverage made unambiguous abundances very difficult to deduce, but firm limits could be set. Absolute depletions have been estimated, based on an assumed value of the total hydrogen column density, but they are uncertain due to uncertainty in N(H). The data appear to indicate that depletions are generally very large in this line of sight. There is also some indication that the relative depletions are enhanced in the densest portions of the cloud.

Snow, T. P.↗

NASA NTRS1987

Radio emission from pre-main-sequence stars in Corona Australis

The central region of the Corona Australis molecular cloud surrounding the stars R and TY CrA has been studied using the VLA at 6 cm. Eleven radio sources are detected including five associated with pre-main-sequence objects. The most striking is associated with the near-IR source IRS 7 and shows a complex structure comprising two strong pointlike sources positioned either side of the deeply embedded IR source and two extended lobes of radio emission. The IRS 7 radio source appears to be similar to that associated with Lynds 1551 IRS 5 but has a considerably larger angular size. The other detected sources include the massive pre-main-sequence star TY CrA, the near-IR sources IRS 1 and IRS 5, and the Herbig-Haro object HH 101. The stars R and T CrA were not detected.

Brown, Alexander↗

NASA NTRS1988

Far-infrared observations of a luminous dust-shrouded source in the nucleus of NGC 4945

High-resolution far-infrared observations of the galaxy NGC 4945 have been obtained from the Kuiper Airborne Observatory. Using new observational techniques and nonlinear deconvolution routines, it is found that virtually all of the far-infrared luminosity originates from a nuclear source no larger than 12 arcsec x 9 arcsec (225 pc x 170 pc) in extent. This size constraint, coupled with the far-infrared dust temperature, indicates that the source is deeply embedded in dust: the lower limit for the 100 micron optical depth is 0.35, which is by far the largest yet measured in an external galaxy. Published optical spectra of NGC 4945 reveal a heavily obscured nonthermal source which exhibits broad line profiles typical of a Seyfert 2 active nucleus; it is concluded that the far-infrared emission is probably due to thermal radiation from dust grains surrounding the nonthermal nuclear source. A compact cluster of massive young stars may also contribute to the infrared luminosity, but the evidence for such star-forming activity is weak.

Brock, David↗

NASA NTRS1989

Aerolastic tailoring and integrated wing design

Much has been learned from the TSO optimization code over the years in determining aeroelastic tailoring's place in the integrated design process. Indeed, it has become apparent that aeroelastic tailoring is and should be deeply embedded in design. Aeroelastic tailoring can have tremendous effects on the design loads, and design loads affect every aspect of the design process. While optimization enables the evaluation of design sensitivities, valid computational simulations are required to make these sensitivities valid. Aircraft maneuvers simulated must adequately cover the plane's intended flight envelope, realistic design criteria must be included, and models among the various disciplines must be calibrated among themselves and with any hard-core (e.g., wind tunnel) data available. The information gained and benefits derived from aeroelastic tailoring provide a focal point for the various disciplines to become involved and communicate with one another to reach the best design possible.

Love, Mike H.↗

NASA NTRS1989

Interstellar and cometary dust

Aspects of interstellar dust which are known from direct observation will be discussed. Some specific difficulties that various theories have in explaining the observations will be presented. Several theoretical interpretations which have been advanced will be discussed, highlighting first their similarities and then their differences. Also discussed will be the author's ideas about the conditions of interstellar dust throughout its life cycle, from origin to incorporation in pre-cometary ices. Dust is primarily observed by its effects on the spectra of background stars, so observations at optical and ultraviolet (UV) wavelengths are confined to the diffuse interstellar medium (ISM) or to the outer regions of dense clouds. Within this somewhat limited range of environments there are very few lines of sight which show any evidence for icy mantles, but there are major variations in the wavelength dependence of the extinction. In the infrared region of the spectrum, it is possible to observe a few stellar sources deeply embedded within molecular clouds.

Mathis, John S.↗

NASA NTRS1990

Laboratory simulation of interstellar grain chemistry and the production of complex organic molecules

During the past 15 years considerable progress in observational techniques has been achieved in the middle infrared (5000 to 500 cm(-1), 2 to 20 microns m), the spectral region most diagnostic of molecular vibrations. Spectra of many different astronomical infrared sources, some deeply embedded in dark molecular clouds, are now available. These spectra provide a powerful probe, not only for the identification of interstellar molecules in both the gas solid phases, but also of the physical and chemical conditions which prevail in these two very different domains. By comparing these astronomical spectra with the spectra of laboratory ices one can determine the composition and abundance of the icy materials frozen on the cold (10K) dust grains present in the interior of molecular clouds. These grains and their ice mantles may well be the building blocks from which comets are made. As an illustration of the processes which can take place as an ice is irradiated and subsequently warmed, researchers present the infrared spectra of the mixture H2O:CH3OH:CO:NH3:C6H14 (100:50:10:10:10). Apart from the last species, the ratio of these compounds is representative of the simplest ices found in interstellar clouds. The last component was incorporated into this particular experiment as a tracer of the behavior of a non-aromatic hydrocarbon. The change in the composition that results from ultraviolet photolysis of this ice mixture using a UV lamp to simulate the interstellar radiation field is shown. Photolysis produces CO, CO2, CH4, HCO, H2CO, as well as a family of moderately volatile hydrocarbons. Less volatile carbonaceous materials are also produced. The evolution of the infrared spectrum of the ice as the sample is warmed up to room temperature is illustrated. Researchers believe that the changes are similar to those which occur as ice is ejected from a comet and warmed up by solar radiation. The warm-up sequence shows that the nitrile or iso-nitrile bearing compound produced during photolysis evaporates between 200 and 250K, suggesting that it is carried by a small molecular species. These molecules could be similar to the source material in Comet Halley that is ejected in grains into the coma, freed by sublimation, and photolyzed by solar radiation to produce the observed jets.

Allamandola, L. J.↗

NASA NTRS1990

The circumstellar environment of TMR-1 - A young, low-mass star in the Taurus molecular ring

Near-infrared camera and Owens Valley millimeter interferometer data are presented that reveal the circumstellar environment of TMR-1 on scales of roughly 1000 AU. TMR-1 is a deeply embedded, young, low-mass star located in a rotating ring of material in the TMC-1/Heiles Cloud 2 region of the Taurus molecular cloud. The stellar wind cavity, as outlined by the extended infrared continuum emission at 2.2 microns, overlaps with the redshifted outflow detected in the (C-12)O data. High-density circumstellar material is seen in (C-13)O in emission and at 2.2 microns in absorption. The morphology suggests the high-density gas may either be part of a 1000 AU disk or may represent infalling material from the molecular cloud core. TMR-1 appears to be in an early wind-clearing phase of protostar formation.

Terebey, S.↗

NASA NTRS1992

Fate of a perched crystal layer in a magma ocean

The pressure gradients and liquid compressibilities of deep magma oceans should sustain the internal flotation of native crystals owing to a density crossover between crystal and liquid. Olivine at upper mantle depths near 250 km is considered. The behavior of a perched crystal layer is part of the general question concerning the fate of any transient crystal carried away from a cooling surface, whether this be a planetary surface or the roof of an intrusive magma body. For magma bodies thicker than a few hundred meters at modest crustal depths, the major cooling surface is the roof even when most solidification occurs at the floor. Importation of cool surroundings must also be invoked for the generation of a perched crystal layer in a magma ocean, but in this case the perched layer is deeply embedded in the hot part of the magma body, and far away from any cooling surface. Other aspects of this study are presented.

Morse, S. A.↗

NASA NTRS1992

Star formation in Taurus. I - The IRAS Faint Source Survey

A deep infrared survey of a 187 sq deg region in Taurus using the IRAS Faint Source Survey reveals 63 multiband objects selected on the basis of their infrared properties. Two-thirds of the sample are previously uncataloged and are most likely either deeply embedded objects or unidentified T Tauri stars. Complete IRAS data are presented for these objects. The sample is estimated to be more than 90 percent complete for objects emitting L equal to or greater than 0.1 solar luminosity between 12 and 60 microns. The luminosity function shows a decline at luminosities below 0.3 solar luminosity. The formation of a massive, 0.1 solar mass, disk of circumstellar material serving as a reservoir for infalling cloud material represents a possible resolution of the problem. A population of unresolved sources emitting only at 60 microns is also identified. If any of these objects are self-luminous, they may represent the youngest protostellar objects yet observed.

Beichman, C. A.↗

NASA NTRS1992

Methanol ice in the protostar GL 2136

We present ground-based spectra in the 10 and 20 micron atmospheric windows of the deeply embedded protostar GL 2136. These reveal narrow absorption features at 9.7 and 8.9 microns, which we ascribe to the CO-stretch and CH3 rock (respectively) of solid methanol in grain mantles. The peak position of the 9.7 micron band implies that methanol is an important ice mantle component. However, the CH3OH/H2O abundance ratio derived from the observed column densities is only 0.1. This discrepancy suggests that the solid methanol and water ice are located in independent grain components. These independent components may reflect chemical differentiation during grain mantle formation and/or partial outgassing close to the protostar.

Skinner, C. J.↗

NASA NTRS1993

Infrared and optical imaging of IRAS sources with CO outflow - A snapshot of early star formation

We present multiband imaging of three IRAS sources associated with CO molecular outflows. We find stellar density enhancements around all three IRAS sources. Optical and near-IR photometry indicates that at least 60 percent of the near-IR sources in the vicinity of the IRAS sources are pre-main-sequence stars. Using the photometric data at nbL and M, we are able to identify candidates for the near-IR counterparts of the IRAS sources. We also find that (1) the spectral energy distribution of the deeply embedded sources could be complicated by source confusion and scattered light from the young stellar objects; (2) star formation in the vicinity of the IRAS sources is a continuous process with an age span of 0.5-3 Myr; and (3) stellar density enhancement is probably a phenomenon found at the earliest stage of star formation.

Chen, H.↗

NASA NTRS1992

An IRAS study of pre-main sequence stars in B209

We have constructed high resolution IRAS maps of the B209 star forming region in the Taurus complex. By combining survey scans with pointed observations using advanced techniques specially developed to handle IRAS data in crowded fields, we have constructed images that reveal two new premain-sequence (PMS) objects. One of these, IRAS 04114+2757G, has FIR colors close to those of typical T Tauri stars and is probably associated with a faint stellar object visible on the POSS prints. The other new PMS source, IRAS 04111+2800G, is a deeply embedded object not detected at 12 microns and not optically visible. The object is projected close to the center of an ammonia core. Our detection of compact blue and red shifted (C-12)O emission peaks around the position of IRAS 04111+2800G confirms the PMS nature and youth of this object. We have examined the reasons for the exclusion of IRAS 04111+2800G and IRAS 04114+2757G from the IRAS Point Source Catalog and estimated the incompleteness of the currently known sample of embedded PMS stars in Taurus. The implications for the determination of evolutionary time scales in low mass star formation are discussed.

Prusti, T.↗