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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Anisotropic transport in modulation-doped quantum-well structures

Anisotropic electron transport has been observed in GaAs modulation-doped quantum wells grown by molecular-beam epitaxy on a thick (001) Al(0.3)Ga(0.7)As buffer grown at 620 C. Thicker quantum wells (150, 200, and 300 A) show progressively less anisotropy, which vanishes for a 300-A quantum well. The degree of anisotropy is also reduced or eliminated by suspending growth of the Al(0.3)Ga(0.7)As for a period of 300 s prior to growing the GaAs quantum well. Growing the Al(0.3)Ga(0.7)As buffer at higher temperatures (680 C) also reduces the degree of anisotropy. Higher two-dimensional electron gas sheet densities result in less anisotropy.The anisotropy is eliminated by replacing the thick Al(0.3)Ga(0.7)As buffer with a periodic multilayer structure comprising 15 A of GaAs and 200 A of Al(0.3)Ga(0.7)As. The degree of anisotropy is related to the thickness and growth parameters of the Al(0.3)Ga(0.7)As layer grown just prior to the growth of the GaAs.

Radulescu, D. C.↗
DOE OSTI2023

PV module spectral response measurements - Data and Resources

"This dataset includes spectral response curves for 12 commercial silicon module types that are deployed at SNL in Albuquerque. The modules chosen for evaluation were originally purchased by SNL for the PV Lifetime project (renamed to Systems Long-Term Evaluation [SLTE]). The majority of those modules are deployed outdoors for long-term evaluation, but several modules of each type were placed in storage for future comparison purposes. One stored module of each type was sent to NREL for the spectral response measurements. NREL used the recently developed Module Quantum Efficiency (QE) test bed. What makes this system unique is that it scans the entire module automatically, taking one or more measurements on each cell. Using the mean of these measurements at each wavelength leads to improvements in spectral mismatch correction and module power measurements but having the individual measurements also makes it possible to identify outlier cells, which could be useful for investigating underperforming modules. All measurements were performed nominally at 25°C"

14 SOLAR ENERGY↗
NASA NTRS1994

Quantum propagation in single mode fiber

This paper presents a theory for quantum light propagation in a single-mode fiber which includes the effects of the Kerr nonlinearity, group-velocity dispersion, and linear loss. The theory reproduces the results of classical self-phase modulation, quantum four-wave mixing, and classical solution physics, within their respective regions of validity. It demonstrates the crucial role played by the Kerr-effect material time constant, in limiting the quantum phase shifts caused by the broadband zero-point fluctuations that accompany any quantized input field. Operator moment equations - approximated, numerically, via a terminated cumulant expansion - are used to obtain results for homodyne-measurement noise spectra when dispersion is negligible. More complicated forms of these equations can be used to incorporate dispersion into the noise calculations.

Joneckis, Lance G.↗
NASA NTRS1987

Effects of substrate misorientation and background impurities on electron transport in molecular-beam-epitaxial grown GaAs/AlGaAs modulation-doped quantum-well structures

The effects of substrate misorientation off the (001) plane and of background impurities on electron transport in MBE-grown GaAs/AlGaAs modulation-doped superlattice-buffered quantum-well structures were investigated. Low-field transport data were obtained on GaAs/AlGaAs structures grown on substrates oriented 0, 2, 4, and 6.5 deg off the (001) plane towards either (111)A or (111)B. It is shown that the low-field two-dimensional electron gas (2DEG) mobility is a function of the angle and direction of the substrate orientation, and that the 2DEG mobility is a function of the direction of the applied electric field in the GaAs quantum well. The anisotropy in the 2DEG mobility is also a function of the tilt angle and tilt azimuth direction of the substrate from the (001) plane. In addition, it is shown that the amount of interface scattering from the inverted interface is a sensitive function of the amount of background impurities in the MBE machine.

Radulescu, D. C.↗
DOE OSTI2023

PyQMC : An all-Python real-space quantum Monte Carlo module in PySCF

We describe a new open-source Python-based package for high accuracy correlated electron calculations using quantum Monte Carlo (QMC) in real space: PyQMC. PyQMC implements modern versions of QMC algorithms in an accessible format, enabling algorithmic development and easy implementation of complex workflows. Tight integration with the PySCF environment allows for a simple comparison between QMC calculations and other many-body wave function techniques, as well as access to high accuracy trial wave functions.

Wheeler, William A. (ORCID:0000000283910530)↗
NASA NTRS1998

Ultrafast Modulation and Switching of Quantum-Well Lasers using Terahertz Fields

Modulation and switching of semiconductor lasers are important for laser-based information technology. Typically the speed of modulation and switching is limited by interband processes such as stimulated and spontaneous recombinations which occur on a nanosecond time scale. This is why the diode laser modulation has been restricted to tens of GHz. Modulation at higher speed is highly desirable as the information technology enters into the so-called tera-era. In this paper, we study the possibility of utilizing THz-field-induced plasma heating to modulate quantum-well lasers. This is a timely study since, with the advancement of THz solid-state sources and free-electron lasers, THz physics and related technology is currently coming out of its infancy. The investigation of interplaying THz and optical fields is also of intruiging fundamental interest. First, we introduce theoretical plasma heating results for the quantum-well optical amplifier in the presense of an intense half-cycle THz pulse. The heated carrier distributions are then utilized to calculate the THz-pulse-induced change in refractive index and gain profile. Since the electron-hole-plasma is heated using intraband transitions, we circumvent the usual complications due to an overall change in density, and the nonlinear recovery is governed solely by the carrier-LO-phonon interactions, typically 5 ps for a complete recovery. This procedure implies THz and sub-THz switching and recovery rates, respectively; using either gain modulation or index modulation. Plasma heating via steady-state THz fields is also studied. Finally, numerical simulation of a coupled set of equations to investigate the THz modulation based on a simplified model for quantum-well lasers is presented. Our results show that a semiconductor laser can be modulated at up to 1 THz with little distortion with a THz field amplitude at the order of a few kV/cm. Laser responses to a change in THz frequency will be shown. Constraints, practicalities, and applications will be discussed.

Ning, Cun-Zheng↗
DOE OSTI2025

Modulating Oxide‐Based Quantum Materials by Ion Implantation

Ion implantation has emerged as a powerful tool for manipulating and investigating oxide quantum materials, where strong electron correlations give rise to exotic phases and functionalities. This Review examines how controlled ion bombardment enables targeted modulation of structural, electronic, and magnetic properties in complex oxides. Recent advances in ion beam techniques is analyzed that provide unprecedented control over defect profiles, from point defects to extended damage cascades. In application, ion irradiation has demonstrated the ability to tune quantum phenomena including metal‐insulator transitions, magnetism, and superconductivity through selective doping, defect creation, and lattice strain. The ability to write quantum states with nanoscale precision using focused ion beams is opening new paths for quantum device fabrication. Challenges in understanding radiation damage mechanisms in strongly correlated systems is discussed, and identify opportunities for designing quantum functionality through defect‐engineering approaches. The technique's demonstrated capability to write quantum states with nanoscale precision, combined with its compatibility with existing semiconductor processing infrastructure, suggests a clear pathway for translating fundamental discoveries in quantum materials into practical technological applications.

defect engineering↗
NASA NTRS1986

Low-noise behavior of InGaAs quantum-well-structured modulation-doped FET's from 10 to the -2nd to 10 to the 8 Hz

Equivalent gate noise voltage spectra of 1-micron gate-length modulation-doped FET's with pseudomorphic InGaAs quantum-well structure have been measured for the frequency range of 0.01 Hz to 100 MHz and commpared with the noise spectra of conventional AlGaAs/GaAs MODFET's and GaAs MESFET's. The prominent generation-recombination (g-r) noise bulge commonly observed in the vicinity of 10 kHz in conventional MODFET's at 300 K does not appear in the case of the new InGaAs quantum-well MODFET. Instead, its noise spectra indicate the presence of low-intensity multiple g-r noise components superimposed on a reduced 1/f noise. The LF noise intensity in the new device appears to be the lowest among those observed in any MODFET or MESFET. The noise spectra at 82 K in the new device represent nearly true 1/f noise. This unusual low-noise behavior of the new structure suggests the effectiveness of electron confinement in the quantum well that significantaly reduces electron trapping in the n-AlGaAs, and thus eliminates the g-r noise bulge observed in conventional MODFET's.

Liu, Shih-Ming J.↗
NASA NTRS1990

Multi-Quantum-Well Spatial Light Modulators On Si Substrates

Proposed new class of two-dimensional spatial light modulators (SLM's) based on fabrication of multi-quantum-well (MQW) structures (e.g. of AlGaAs and InGaAs) on silicon substrates. Concept makes two-dimensional SLM arrays by taking advantage of mature technology of silicon charge-coupled devices (CCD's). Features include short response times, high resolution, and low switching energies.

Cutts, James A.↗
DOE OSTI2023

Low-loss interconnects for modular superconducting quantum processors

Low-loss superconducting aluminium cables and on-chip impedance transformers can be used to link qubit modules and create superconducting quantum computing networks with high-fidelity intermodule state transfer. Scaling is now a key challenge in superconducting quantum computing. One solution is to build modular systems in which smaller-scale quantum modules are individually constructed and calibrated and then assembled into a larger architecture. This, however, requires the development of suitable interconnects. Here we report low-loss interconnects based on pure aluminium coaxial cables and on-chip impedance transformers featuring quality factors of up to 8.1 x 10 5 , which is comparable with the performance of our transmon qubits fabricated on a single-crystal sapphire substrate. We use these interconnects to link five quantum modules with intermodule quantum state transfer and Bell state fidelities of up to 99%. To benchmark the overall performance of the processor, we create maximally entangled, multiqubit Greenberger-Horne-Zeilinger states. The generated intermodule four-qubit Greenberger-Horne-Zeilinger state exhibits 92.0% fidelity. We also entangle up to 12 qubits in a Greenberger-Horne-Zeilinger state with 55.8 ± 1.8% fidelity, which is above the genuine multipartite entanglement threshold of 1/2.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Light-wave control of correlated materials using quantum magnetism during time-periodic modulation of coherent transport

Light–wave quantum electronics utilizes the oscillating carrier wave to control electronic properties with intense laser pulses. Without direct light–spin interactions, however, magnetic properties can only be indirectly affected by the light electric field, mostly at later times. A grand challenge is how to establish a universal principle for quantum control of charge and spin fluctuations, which can allow for faster-than-THz clock rates. Using quantum kinetic equations for the density matrix describing non–equilibrium states of Hubbard quasiparticles, here we show that time–periodic modulation of electronic hopping during few cycles of carrier–wave oscillations can dynamically steer an antiferromagnetic insulating state into a metalic state with transient magnetization. While nonlinearities associated with quasi-stationary Floquet states have been achieved before, magneto–electronics based on quasiparticle acceleration by time–periodic multi–cycle fields and quantum femtosecond/attosecond magnetism via strongly–coupled charge–spin quantum excitations represents an alternative way of controlling magnetic moments in sync with quantum transport.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

HetArch: Heterogeneous Microarchitectures for Superconducting Quantum Systems

Noisy Intermediate-Scale Quantum Computing (NISQ) has dominated headlines in recent years, with the longer-term vision of Fault-Tolerant Quantum Computation (FTQC) offering significant potential but at currently intractable resource costs and quantum error correction (QEC) overheads. For problems of interest, FTQC will require millions of physical qubits with long coherence times, high-fidelity gates, and compact sizes to surpass classical systems. Just as heterogeneous specialization has offered scaling benefits in classical computing, it is likewise gaining interest in FTQC. However, systematic use of heterogeneity in either hardware or software elements of FTQC systems remains a serious challenge due to the vast design space and the variable physical constraints. This paper meets the challenge of making heterogeneous FTQC design practical by introducing HetArch, a toolbox for designing heterogeneous quantum systems, and using it to explore heterogeneous design scenarios. Using a hierarchical approach, we successively break quantum algorithms into smaller operations (akin to classical application kernels), thus greatly simplifying the design space and resulting tradeoffs. Specializing to superconducting systems, we then design optimized heterogeneous hardware composed of varied superconducting devices, abstracting physical constraints into design rules that enable devices to be assembled into standard cells optimized for specific operations, which, in turn, form heterogeneous modules optimized for quantum subroutines. Finally, we provide a heterogeneous design space exploration framework which reduces the simulation burden by a factor of 10^4 or more and allows us to characterize optimal design points. We use these techniques to design superconducting quantum modules for entanglement distillation, error correction, and code teleportation, reducing error rates by 2.6×, 10.7×, and 3.4× compared to homogeneous systems.

Quantum Computing, Quantum Physics, Computer Archi↗
NASA NTRS1989

Photodiode-Coupled Light Modulator

Absorption of one light beam controls transmission of another. High-performance monolithic light modulator comprised of p-doped/intrinsic/n-doped (PIN) GaAs photodiode grown directly over InAs/GaAs PIN multiple-quantum-well (MQW) diode. Photodiode-coupled multiple-quantum-well modulator includes advanced semi-conductor microstructures enhancing electro-optical properties. Using standard lithographic and etching techniques for defining picture elements, structures fabricated into two-dimensional arrays for use as spatial light modulators.

Maserjian, Joseph↗
DOE OSTI2023

Non-commutative disintegrations: Existence and uniqueness in finite dimensions

Motivated by advances in categorical probability, we introduce non-commutative almost everywhere (a.e.) equivalence and disintegrations in the setting of C*-algebras. We show that C*-algebras (resp. W*-algebras) and a.e. equivalence classes of 2-positive (resp. positive) unital maps form a category. We prove non-commutative disintegrations are a.e. unique whenever they exist. We provide an explicit characterization for when disintegrations exist in the setting of finite-dimensional C*-algebras, and we give formulas for the associated disintegrations.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Photoinduced frustration modulation in 𝜅-type quantum spin liquid candidates

Geometric frustration is a key parameter controlling electronic and magnetic properties of quantum spin liquid systems, yet remains challenging to tune. Here, we coherently drive molecular vibrations with midinfrared pulses in two organic quantum spin liquid candidates, the insulating 𝜅−(BEDT−TTF) 2⁢ Cu 2 ⁢(CN) 3 and the metallic 𝜅−(BEDT−TTF) 4 ⁢Hg 2.89 ⁢Br 8 , and probe their electronic response through ultrafast reflectivity measurements. We observe a nonlinear coupling between local molecular vibrations and nonlocal phonons, which is expected to directly modulate the geometric frustration of their triangular lattice. Furthermore, our findings establish a promising route to dynamically control frustration in nonbipartite quantum materials.

Frustrated magnetism↗
DOE OSTI2025

An integrated photonic engine for programmable atomic control

Abstract Solutions for scalable, high-performance optical control are important for the development of scaled atom-based quantum technologies. Modulation of many individual optical beams is central to applying arbitrary gate and control sequences on arrays of atoms or atom-like systems. At telecom wavelengths, miniaturization of optical components via photonic integration has pushed the scale and performance of classical and quantum optics far beyond the limitations of bulk devices. However, material platforms for high-speed telecom integrated photonics lack transparency at the short wavelengths required by leading atomic systems. Here, we propose and implement a scalable and reconfigurable photonic control architecture using integrated, visible-light modulators based on thin-film lithium niobate. We combine this system with techniques in free-space optics and holography to demonstrate multi-channel, gigahertz-rate visible beamshaping. When applied to silicon-vacancy artificial atoms, our system enables the spatial and spectral addressing of a dynamically-selectable set of these stochastically-positioned point emitters.

Science & Technology - Other Topics↗
NASA NTRS1991

Optically induced absorption modulation in a periodically delta-doped InGaAs/GaAs multiple quantum well structure

Strong optically induced absorption modulation has been achieved in a periodically delta-doped InGaAs/GaAs multiple quantum well structure. The use of delta-doping has enabled efficient modulation in short-period structures using a low-power semiconductor laser. With an excitation intensity of 100 mW/sq cm an absolute quantum well absorption change of more than 9000 cm has been measured corresponding to a differential absorption change as high as 58 percent at the excitonic resonance.

Larsson, A.↗