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Results for “Induced coherence”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Quantifying trapped magnetic vortex losses in niobium resonators at mK temperatures

Trapped magnetic vortices in niobium introduce microwave losses that degrade the performance of superconducting resonators. While such losses have been extensively studied above 1 K, we report here their direct quantification in the millikelvin and low-photon regime relevant to quantum devices. Using a high-quality factor 3D niobium cavity cooled through its superconducting transition in controlled magnetic fields, we isolate vortex-induced losses and find the resistive component of the sensitivity to trapped flux S to be approximately 2 n Ω/mG at 10 mK and 6 GHz. The decay rate is initially dominated by two-level system (TLS) losses from the native niobium pentoxide, with vortex-induced degradation of T 1 occurring above B trap ∼ 50 mG. In the absence of the oxide, even 10 mG of trapped flux limits performance, Q 0 ∼ 10 10 , or T 1 ∼ 350 ms, underscoring the need for stringent magnetic shielding. The resistive sensitivity, S, decreases with temperature and remains largely field-independent, whereas the reactive component, S′, exhibits a maximum near 0.8 K. These behaviors are well modeled within the Coffey–Clem framework in the zero-creep limit, under the assumption that vortex pinning is enhanced by thermally activated processes. Our results suggest that niobium-based transmon qubits can tolerate vortex-induced dissipation at trapped field levels up to several hundred mG, but achieving long coherence times still requires careful magnetic shielding to suppress lower-field losses from other mechanisms.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Amplified spontaneous emission in the extreme ultraviolet by expanding xenon clusters

Focused short-wavelength free-electron laser (FEL) pulses interacting with gas phase samples can induce by inner-shell ionization a short-lived population inversion, followed by coherent collective emission of directed, short, and strong radiation bursts. We extend our studies into the warm-dense matter (WDM) regime by investigating the nanoplasmas produced in an ensemble of nanometer-sized clusters by FEL irradiation. Here, additional pathways can also lead to strong, laserlike emission: Electron-ion collisions can yield a long-lived population inversion, and subsequent amplified spontaneous emission. We observe amplified spontaneous emission (ASE) in the extreme ultraviolet in xenon clusters excited by soft x-ray FEL pulses, we diagnose the generated nanoplasmas by fluorescence spectroscopy, and we study under various cluster and FEL parameters the directed ASE from the Xe 2+ 65 nm line. We show its exponential increase as a function of FEL irradiation power, and an accompanying collisional broadening of the emission spectra. These findings are corroborated by extensive numerical simulations based on theory, combining detailed hydrodynamic and kinetic simulations with time-dependent calculations of radiation transport, amplification, and collective emission in the WDM nanoplasma. Furthermore, our theoretical findings underline that population inversion is due to electron-ion collisions and that the observed decoherence processes can be empirically characterized by a phenomenological decoherence time in the range of 100–200 fs.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

The Optical Signatures of Stochastic Processes in Many-Body Exciton Scattering

We review our recent quantum stochastic model for spectroscopic lineshapes in the presence of a coevolving and nonstationary background population of excitations. Starting from a field theory description for interacting bosonic excitons, we derive a reduced model whereby optical excitons are coupled to an incoherent background via scattering as mediated by their screened Coulomb coupling. The Heisenberg equations of motion for the optical excitons are then driven by an auxiliary stochastic population variable, which we take to be the solution of an Ornstein–Uhlenbeck process. Here, we present an overview of the theoretical techniques we have developed as applied to predicting coherent nonlinear spectroscopic signals. We show how direct (Coulomb) and exchange coupling to the bath give rise to distinct spectral signatures and discuss mathematical limits on inverting spectral signatures to extract the background density of states.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Role of nanoscale coherent precipitates on the thermo-mechanical response of martensitic materials (Final Report)

Coherent second phases can have a profound effect on the properties and performance of martensitic materials, and we lack a comprehensive, mechanistic understanding of the underlying processes. This limits our ability to rationally design second phases to tailor the response of martensitic materials. To address this situation, this project sought to develop a mechanistic, predictive understanding of the thermal and mechanical response of martensitic materials with nanoscale coherent heterogeneities. A synergistic combination of atomistic simulations and experiments was used to relate the local properties of each phase (in particular, their free energy landscape) and the material nanostructure (volume fraction, shape and size of second phase precipitates, and defects that may disrupt coherency) to the overall materials response. The focus was on second phases expected to induce phenomena or properties not otherwise achievable: second order martensitic transformation in SMAs, ultra-low stiffness, increased control of transition temperatures, and fatigue resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Quantifying Trapped Magnetic Vortex Losses in Niobium Resonators at mK Temperatures

Trapped magnetic vortices in niobium introduce microwave losses that degrade the performance of superconducting resonators. While such losses have been extensively studied above 1 K, we report here their direct quantification in the millikelvin and low-photon regime relevant to quantum devices. Using a high-quality factor 3D niobium cavity cooled through its superconducting transition in controlled magnetic fields, we isolate vortex-induced losses and find the resistive component of the sensitivity to trapped flux S to be approximately 2 nOhm/mG at 10 mK and 6 GHz. The decay rate is initially dominated by two-level system (TLS) losses from the native niobium pentoxide, with vortex-induced degradation of T1 occurring above Btrap~50 mG. In the absence of the oxide, even 10 mG of trapped flux limits performance, Q0 ~ 1010, or T1 ~350 ms, underscoring the need for stringent magnetic shielding. The resistive sensitivity, S, decreases with temperature and remains largely field-independent, whereas the reactive component, S , exhibits a maximum near 0.8 K. These behaviors are well modeled within the Coffey Clem framework in the zero-creep limit, under the assumption that vortex pinning is enhanced by thermally activated processes. Our results suggest that niobium-based transmon qubits can tolerate vortex-induced dissipation at trapped field levels up to several hundred mG, but achieving long coherence times still requires careful magnetic shielding to suppress lower-field losses from other mechanisms

Bafia, Daniel P. [Fermilab]↗
NASA NTRS1982

The self-excited axisymmetric jet

The results of a number of investigations suggest that large-scale coherent structures and their interactions play key roles in the transport of heat, mass, and momentum, and in the generation of aerodynamic noise. Investigations related to the study of a large-scale coherent structure in the circular jet are considered, taking into account the advantages of inducing controlled perturbation through self-sustained excitation with the whistler nozzle. The primary objective of the present study was to document the jet response to self-excitation and the sensitivity of this response to the initial condition and the Reynolds number R(D). It was also felt that the results would find use in the control of mixing and aerodynamic noise in a jet.

Hasan, M. A. Z.↗
NASA NTRS1982

Thematic mapper flight model preshipment review data package. Volume 3, part B: System data

Procedures and results are presented for performance and systems integration tests of flight model-1 thematic mapper. Aspects considered cover electronic module integration, radiometric calibration, spectral matching, spatial coverage, radiometric calibration of the calibrator, coherent noise, dynamic square wave response, band to band registration, geometric accuracy, and self induced vibration. Thermal vacuum tests, EMI/EMS, and mass properties are included. Liens are summarized.

Source record↗
NASA NTRS1998

Transfer function analysis of dynamic cerebral autoregulation in humans

To test the hypothesis that spontaneous changes in cerebral blood flow are primarily induced by changes in arterial pressure and that cerebral autoregulation is a frequency-dependent phenomenon, we measured mean arterial pressure in the finger and mean blood flow velocity in the middle cerebral artery (VMCA) during supine rest and acute hypotension induced by thigh cuff deflation in 10 healthy subjects. Transfer function gain, phase, and coherence function between changes in arterial pressure and VMCA were estimated using the Welch method. The impulse response function, calculated as the inverse Fourier transform of this transfer function, enabled the calculation of transient changes in VMCA during acute hypotension, which was compared with the directly measured change in VMCA during thigh cuff deflation. Beat-to-beat changes in VMCA occurred simultaneously with changes in arterial pressure, and the autospectrum of VMCA showed characteristics similar to arterial pressure. Transfer gain increased substantially with increasing frequency from 0.07 to 0.20 Hz in association with a gradual decrease in phase. The coherence function was > 0.5 in the frequency range of 0.07-0.30 Hz and < 0.5 at < 0.07 Hz. Furthermore, the predicted change in VMCA was similar to the measured VMCA during thigh cuff deflation. These data suggest that spontaneous changes in VMCA that occur at the frequency range of 0.07-0.30 Hz are related strongly to changes in arterial pressure and, furthermore, that short-term regulation of cerebral blood flow in response to changes in arterial pressure can be modeled by a transfer function with the quality of a high-pass filter in the frequency range of 0.07-0.30 Hz.

NASA Discipline Cardiopulmonary↗
NASA NTRS2015

Development of a Premixed Combustion Capability for Scramjet Combustion Experiments

Hypersonic air-breathing engines rely on scramjet combustion processes, which involve high speed, compressible, and highly turbulent flows. The combustion environment and the turbulent flames at the heart of these engines are difficult to simulate and study in the laboratory under well controlled conditions. Typically, wind-tunnel testing is performed that more closely approximates engine testing rather than a careful investigation of the underlying physics that drives the combustion process. The experiments described in this paper, along with companion data sets being developed separately, aim to isolate the chemical kinetic effects from the fuel-air mixing process in a dual-mode scramjet combustion environment. A unique fuel injection approach is taken that produces a nearly uniform fuel-air mixture at the entrance to the combustor. This approach relies on the precombustion shock train upstream of the dual-mode scramjet combustor. A stable ethylene flame anchored on a cavity flameholder with a uniformly mixed combustor inflow has been achieved in these experiments allowing numerous companion studies involving coherent anti-Stokes Raman scattering (CARS), particle image velocimetry (PIV), and planar laser induced fluorescence (PLIF) to be performed.

Rockwell, Robert D.↗
DOE OSTI2024

Impact of beam coupling impedance on crab cavity noise induced emittance growth

Crab cavities will be deployed as a part of the High Luminosity Large Hadron Collider (HL-LHC) upgrade to mitigate the luminosity reduction induced by the crossing angle at the main experiments (ATLAS and CMS). Two prototype crab cavities have been installed in the CERN Super Proton Synchrotron (SPS) in 2018 for studies with proton beams. An issue of concern is the transverse emittance growth induced by noise in the crab cavity radio frequency (rf) system, which is anticipated to limit the performance of the HL-LHC. In measurements conducted in the SPS in 2018, the crab cavity noise-induced emittance growth was measured to be a factor of 4 lower than predicted from the existing analytical models. In this paper, it is shown that the observed discrepancy is explained by damping effects from the beam coupling impedance, which were not included in the models up to now. Using the van Kampen mode approach, a new theory is developed, suggesting that the impedance can separate the coherent tune from the incoherent spectrum leading to an effective reduction of the crab cavity rf noise-induced emittance growth. This mechanism is validated in tracking simulations using the SPS impedance model as well as in dedicated experimental measurements conducted in the SPS in 2022. The implications for the HL-LHC project are discussed. Published by the American Physical Society 2024

Physics↗
DOE OSTI2024

Fast Z Z free entangling gates for superconducting qubits assisted by a driven resonator

Engineering high-fidelity two-qubit gates is an indispensable step toward practical quantum computing. For superconducting quantum platforms, one important setback is the stray interaction between qubits, which causes significant coherent errors. For transmon qubits, protocols for mitigating such errors usually involve fine-tuning the hardware parameters or introducing usually noisy flux-tunable couplers. In this work, we propose a simple scheme to cancel these stray interactions. The coupler used for such cancelation is a driven high-coherence resonator, where the amplitude and frequency of the drive serve as control knobs. Through the resonator-induced-phase interaction, the static Z Z coupling can be entirely neutralized. We numerically show that such a scheme can enable short and high-fidelity entangling gates, including cross-resonance controlled-not (cnot) gates within 40 ns and adiabatic controlled- Z gates within 140 ns. Our architecture is not only Z Z -free, but also contains no extra noisy components, such that it preserves the coherence times of fixed-frequency transmon qubits. With the state-of-the-art coherence times, the error of our cross-resonance cnot gate can be reduced to below 10 − 4 .

Huang, Ziwen↗
DOE OSTI2025

Superconducting coherence peak in near-field radiative heat transfer

Enhancement and peaks in near-field radiative heat transfer (NFRHT) typically arise due to surface phonon-polaritons, plasmon-polaritons, and electromagnetic (EM) modes in structured materials. However, the role of material quantum coherence in enhancing near-field radiative heat transfer remains unexplored. Here, we unravel that NFRHT in superconductor-ferromagnetic systems displays a unique peak at the superconducting phase transition that originates from the quantum coherence of Bogoliubov quasiparticles in superconductors. Our theory takes into account evanescent EM radiation emanating from fluctuating currents related to Cooper pairs and Bogoliubov quasiparticles in stark contrast to the current-current correlations induced by free electrons in conventional materials. Our proposed NFRHT configuration exploits ferromagnetic resonance at frequencies deep inside the superconducting band gap to isolate this superconducting coherence peak. Furthermore, we reveal that Cooper pairs and Bogoliubov quasiparticles have opposite effects on near-field thermal radiation and isolate their effects on many-body radiative heat transfer near superconductors. As a result, our proposed phenomenon can have applications for developing thermal isolators and heat sinks in superconducting circuits.

Dipole approximation↗
DOE OSTI2021

Quantum system engineering for a next-generation search for axion dark matter. Final report

This project pursued two major experimental goals related to the quantum engineering of the ensemble of nuclear spin qubits, as a potential sensing platform for axion-like dark matter: (1) control the fidelity of spin ensemble state preparation, (2) characterize the coherence time of the spin ensemble under different drive conditions. We have successfully achieved these goals. We have experimentally demonstrated control over the polarization of the 207 Pb nuclear spin ensemble, using light-induced transient paramagnetic centers. We have also performed NMR measurements on the 207 Pb spin ensemble in solid ferroelectric PMN-PT, demonstrating the T 2 coherence time of 16.7 ms. We have used this approach to set new experimental limits on the EDM and the gradient interactions of axion-like dark matter in the mass range 162 neV to 166 neV. In addition, having characterized the magnetic resonance properties of the 207 Pb spin ensemble in solid ferroelectric PMN-PT, we have formulated the technical requirements needed to reach the quantum sensitivity limits in a magnetic resonance-based search for axion-like dark matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Electron charge coherence on a solid neon surface

Recent experiments show ∼0.1 ms coherence time for a single electron charge qubit on a solid neon surface. This remarkably long coherence time is believed to result from the intrinsic purity of solid neon as a qubit host. In this paper, we present theoretical studies on the decoherence mechanisms of an electron’s charge (lateral motional) states on solid neon. At the typical experimental temperature of ∼10 mK, the two main decoherence mechanisms are the phonon-induced displacement of neon surface and phonon-induced modulation of neon permittivity (dielectric constant). With a qubit frequency increasing from 1 GHz to 10 GHz, the charge coherence time decreases from about 366 s to 7 ms and from about 864 s to 24 ms, respectively, limited by the two mechanisms above. Here, the calculated coherence times are at least one order longer than the observed ones at ∼6.4 GHz qubit frequency, suggesting plenty of room for experimental improvement.

Zou, Shan [University of Notre Dame, IN (United St↗
DOE OSTI2024

Correlating aluminum layer deposition rates, Josephson junction microstructure, and superconducting qubits’ performance

An ultra-thin aluminum oxide layer is a key component for Josephson junctions (JJ) in superconducting quantum bits (qubits). This layer serves as a barrier layer for Cooper pairs tunneling between the superconducting electrodes and significantly influences the overall performance of the junction. In this study, we investigate the impact of aluminum deposition rates on the microstructure and chemical variation of the aluminum oxide layer, as well as the device's yields and qubits’ lifetimes. Surprisingly, although the oxide layer roughness and thickness variation improve noticeably with an increasing Al deposition rate from 0.5 Å/s to 5 Å/s, the qubit's coherence time is almost unchanged. We attribute this to the fact that Cooper pairs tunnel only through the thinnest region of the barrier. Additionally, we revealed a stress-induced grain boundary sliding short-circuit failure mechanism in the JJ. Our discovery provides a vital understanding of oxide microstructure and JJ functionality, which are critical for improving the coherence time of superconducting qubits.

Coherence time↗
DOE OSTI2024

One-dimensional mapping of femtosecond laser filaments using coherent microwave scattering

Here, this paper reports on the use of coherent microwave scattering (CMS) for spatially resolved electron number density measurements of elongated plasma structures induced at mid-IR femtosecond filamentation in air. The presented studies comprise one-dimensional mapping of laser filaments induced via 3.9 µm, 127.3 fs laser pulses at output energies up to 15 mJ. The axial electron number density was measured to be invariant (about 2 × 10 15 c⁢m −3 ) along the entire filament length and for all tested laser pulse energies 5–15 mJ, and the corresponding laser intensity in the middle portion of the filament was estimated to be nearly constant for 5–15 mJ pulse energies (about 30−40 TW/c⁢m 2 ). These findings support that intensity clamping conditions were achieved in the experiments. The proposed approach enables capabilities that are currently unavailable to perform absolute and longitudinally resolved measurements of electron number density in laser filaments and to precisely characterize conditions associated with self-focusing and intensity clamping.

plasma diagnostic techniques↗
DOE OSTI2026

Molecular origin of anisotropic shear elastoplasticity in chitin

Chitin nano- and mesoscale structures present in the exoskeleton of crustaceans exhibit exceptional longitudinal stiffness and toughness, rivaling or even exceeding that of many synthetic polymer architectures. Here, we reveal the origin of the asymmetric shear response in chitin multiscale architectures, marked by pronounced anisotropy in deformation. Under shear aligned with the molecular axis, chitin accommodates strain through coherent atomic rearrangements that enable elastic recovery. In contrast, shear applied perpendicular to this axis induces liquid-like plasticity via localized sliding. These results demonstrate the intrinsic mechanical anisotropy of chitin, underpinning a dual function in resisting repetitive loading while dissipating internal stress during high-strain events. Our findings establish the molecular basis of shear elastoplasticity in multiscale chitin structures, wherein axial elasticity supports energy storage in load-bearing regions, whereas transverse plasticity enables controlled energy dissipation. These atomic-scale insights lay a foundation for the predictive design of chitin-based materials with tunable strength-toughness profiles.

Wan, Zhangmin [University of British Columbia, Van↗