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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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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Half-quantum vortices in nematic and chiral phases of 3 He

In this work, we report theoretical results for the stability of half-quantum vortices (HQVs) in the superfluid phases of 3 He confined in highly anisotropic Nafen aerogel. Superfluidity of 3 He confined in Nafen is the realization of a “nematic superfluid” with Cooper pairs condensed into a single p -wave orbital aligned along the anisotropy axis of the Nafen aerogel. In addition to the nematic phase, we predict a second “chiral” phase that onsets at a lower transition temperature. This chiral phase spontaneously breaks time-reversal symmetry and is a topological superfluid. Both superfluid phases are equal-spin pairing condensates that host arrays of HQVs as equilibrium states of rotating superfluid 3 He. We present results for the structure of HQVs, including magnetic and topological signatures of HQVs in both the nematic and chiral phases of 3 He-Nafen.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Extraction of the higher-twist parton distribution $e(x)$ from CLAS data

We present the first point-by-point extraction of a twist-3 PDF. The scalar PDF, e(x), is accessed through the analysis of the data for the sin φR-moment of the beam-spin asymmetry for dihadron production in semi-inclusive DIS off proton target at CLAS and CLAS12. The dihadron formalism allows for use of collinear framework, hence calling for a minimal set of approximations and hypotheses. The extracted PDF e(x) carries insights into the physics of the largely-unexplored quark-gluon correlations, and its first Mellin moment is related to the marginally known scalar charge of the nucleon. We show that the proton flavor combination of the scalar PDF is nonzero at more than 74% probability.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Free Space Ramsey Spectroscopy in Rubidium with Noise below the Quantum Projection Limit

In this work, we demonstrate the utility of optical cavity generated spin-squeezed states in free space atomic fountain clocks in ensembles of 390 000 87 Rb atoms. Fluorescence imaging, correlated to an initial quantum nondemolition measurement, is used for population spectroscopy after the atoms are released from a confining lattice. For a free fall time of 4 milliseconds, we resolve a single-shot phase sensitivity of 814(61) microradians, which is 5.8(0.6) decibels (dB) below the quantum projection limit. We observe that this squeezing is preserved as the cloud expands to a roughly 200 μ m radius and falls roughly 300 μm in free space. Ramsey spectroscopy with 240 000 atoms at a 3.6 ms Ramsey time results in a single-shot fractional frequency stability of 8.4(0.2) × 10 –12 , 3.8(0.2) dB below the quantum projection limit. The sensitivity and stability are limited by the technical noise in the fluorescence detection protocol and the microwave system, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

QCD Running Coupling in the Nonperturbative and Near-Perturbative Regimes

We use analytic continuation to extend the gauge-gravity duality nonperturbative description of the strong force coupling into the transition, near-perturbative, regime where perturbative effects become important. By excluding the unphysical region in coupling space from the flow of singularities in the complex plane, we derive a specific relation between the scales relevant at large and short distances; this relation is uniquely fixed by requiring maximal analyticity. The unified effective coupling model gives an accurate description of the data in the nonperturbative and the near-perturbative regions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Quantum Spin Ice in Three-Dimensional Rydberg Atom Arrays

Quantum spin liquids are exotic phases of matter whose low-energy physics is described as the deconfined phase of an emergent gauge theory. With recent theory proposals and an experiment showing preliminary signs of Z 2 topological order [G. Semeghini , ], Rydberg atom arrays have emerged as a promising platform to realize a quantum spin liquid. In this work, we propose a way to realize a U(1) quantum spin liquid in three spatial dimensions, described by the deconfined phase of U(1) gauge theory in a pyrochlore lattice Rydberg atom array. We study the ground state phase diagram of the proposed Rydberg system as a function of experimentally relevant parameters. Within our calculation, we find that by tuning the Rabi frequency, one can access both the confinement-deconfinement transition driven by a proliferation of “magnetic” monopoles and the Higgs transition driven by a proliferation of “electric” charges of the emergent gauge theory. We suggest experimental probes for distinguishing the deconfined phase from ordered phases. This work serves as a proposal to access a confinement-deconfinement transition in three spatial dimensions on a Rydberg-based quantum simulator. Published by the American Physical Society 2025

Shah, Jeet (ORCID:0000000158738129)↗
DOE OSTI2026

Subterahertz Spin Relaxation Dynamics of Boron-Vacancy Centers in Hexagonal Boron Nitride

Quantum sensors based on spin defects have become powerful tools for detecting faint magnetic signals, yet their operation remains confined to low magnetic fields and gigahertz frequencies. Extending such sensors into high-field (>0.3 T) and subterahertz regimes would enable quantum metrology across a wide range of electromagnetic phenomena and scientific applications, but has proven challenging. Here, we demonstrate that negatively charged boron vacancies ($V^−_B$) in hexagonal boron nitride can function as relaxation-based quantum sensors operating up to 0.2 terahertz and 7 T fields. Their uniform spin-orientation and persistent spin-contrast at high fields enable measurement of intrinsic spin relaxation across unexplored field regimes. We reveal a crossover in relaxation behavior, initially decreasing at low fields before rising at higher fields, consistent with the emergence of single-phonon-induced resonant noise at subterahertz frequencies. These results establish $V^−_B$ centers as a versatile platform for quantum sensing in the subterahertz, high-field regime.

boron-vacancies↗
NASA NTRS1998

Modeling and Simulation of Semiconductor Quantum Well Structures and Lasers

In this talk I will cover two aspects of modeling and simulation efforts at NASA Ames Research Center. In the quantum well structure simulation, we typically start from the quantum mechanical calculation of the quantum well structures for the confined/and unconfined eigen states and functions. A bandstructure calculation of the k*p type is then performed for the confined valence states. This information is then used to computer the optical gain and refractive index of the quantum well structures by solving the linearized multiband semiconductor Bloch equations with the many-body interactions included. In our laser simulation, we typically solve the envelope equations for the laser field in space-time domain, coupled with a reduced set of material equations using the microscopic calculation of the first step. Finally I will show some examples of both aspects of simulation and modeling.

Ning, Cun-Zheng↗
DOE OSTI2023

Preparations for quantum simulations of quantum chromodynamics in 1+1 dimensions. I. Axial gauge

Here, tools necessary for quantum simulations of 1+1 dimensional quantum chromodynamics are developed. When formulated in axial gauge and with two flavors of quarks, this system requires 12 qubits per spatial site with the gauge fields included via nonlocal interactions. Classical computations and D-wave’s quantum annealer advantage are used to determine the hadronic spectrum, enabling a decomposition of the masses and a study of quark entanglement. Color “edge” states confined within a screening length of the end of the lattice are found. IBM’s seven-qubit quantum computers, ibmq_jakarta and ibm_perth, are used to compute dynamics from the trivial vacuum in one-flavor QCD with one spatial site. More generally, the Hamiltonian and quantum circuits for time evolution of 1+1 dimensional SU(N c ) gauge theory with Nf flavors of quarks are developed, and the resource requirements for large-scale quantum simulations are estimated.

1+1 dimensions↗
NASA NTRS2001

Quantum dots based rad-hard computing and sensors

Quantum Dots (QDs) are solid state structures made of semiconductors or metals that confine a small number of electrons into a small space. The confinement of electrons is achieved by the placement of some insulating material(s) around a central, well conducting region. Thus, they can ve viewed as artificial atoms.

quantum↗
DOE OSTI2025

Upper critical magnetic field and multiband superconductivity in artificial high-𝑇 𝑐 superlattices of nano quantum wells

Artificial high-T c superlattices (AHTS) composed of quantum building blocks with tunable superconducting critical temperature have been synthesized by engineering their nanoscale geometry using the Bianconi-Perali Valletta (BPV) two-gap superconductivity theory. These quantum heterostructures consist of quantum wells made of superconducting, modulation-doped Mott insulators (S), confined by a metallic (N) potential barrier. The lattice geometry has been carefully engineered to induce the predicted Fano-Feshbach shape resonance between the gaps, near a topological Lifshitz transition. Here, we validate the BPV theory by providing compelling experimental evidence that AHTS samples, at the peak of the superconducting dome, exhibit resonant two-band, two-gap superconductivity. This is demonstrated by measuring the temperature dependence of the upper critical magnetic field, μ 0 H c2 , in samples with superlattice periods 3.3 < d < 5.28 nm and L/d ratios close to the magic value 2/3 (where L is the thickness of the superconducting La 2 CuO 4 layer and d is the superlattice period). Here, the data reveal the predicted upward concavity in H c2 (T) and a characteristic kink in the coherence length as a function of temperature, confirming the predicted two-band superconductivity with Fermi velocity ratio ≈ 0.25 and significant pair-exchange term among the two condensates.

Heterostructures↗
DOE OSTI2024

Phonon Screening of Excitons in Atomically Thin Semiconductors

Atomically thin semiconductors, encompassing both 2D materials and quantum wells, exhibit a pronounced enhancement of excitonic effects due to geometric confinement. Consequently, these materials have become foundational platforms for the exploration and utilization of excitons. Recent ab initio studies have demonstrated that phonons can substantially screen electron-hole interactions in bulk semiconductors and strongly modify the properties of excitons. While excitonic properties of atomically thin semiconductors have been the subject of extensive theoretical investigations, the role of phonon screening on excitons in atomically thin structures remains unexplored. In this Letter, we demonstrate via ab initio GW-Bethe-Salpeter equation calculations that phonon screening can have a significant impact on optical excitations in atomically thin semiconductors. We further show that the degree of phonon screening can be tuned by structural engineering. We focus on atomically thin GaN quantum wells embedded in AlN and identify specific phonons in the surrounding material, AlN, that dramatically alter the lowest-lying exciton in monolayer GaN via screening. Our studies provide new intuition beyond standard models into the interplay among structural properties, phonon characteristics, and exciton properties in atomically thin semiconductors, and have implications for future experiments.

2-dimensional systems↗
DOE OSTI2026

Creation of depth-confined, shallow nitrogen-vacancy centers in diamond with tunable density

Engineering shallow nitrogen-vacancy (NV) centers in diamond holds the key to unlocking new advances in nanoscale quantum sensing. We find that the creation of near-surface NVs through delta doping during diamond growth allows for tunable control over both NV depth confinement (with a twofold improvement relative to low-energy ion implantation) and NV density, ultimately resulting in highly sensitive single defects and ensembles with coherence limited by NV–NV interactions. Additionally, we demonstrate the utility of our shallow delta-doped NVs by imaging magnetism in few-layer CrSBr, a two-dimensional magnet. Here, we anticipate that the control afforded by near-surface delta doping will enable new developments in NV quantum sensing from nanoscale nuclear magnetic resonance to entanglement-enhanced metrology.

Chemical vapor deposition↗
NASA NTRS1989

Monolithic III-V/Silicon Spatial Light Modulator

Current techniques for growth of device-quality GaAs on silicon substrates enables fabrication of silicon-based version of photodiode-coupled spatial light modulator. Monolithic photodiode-coupled light-modulator array constructed on silicon substrate by growing InAs/GaAs multiple-quantum-wells over silicon PIN diode layer. Intermediate GaAs buffer layer confines attice-misfit dislocations to vicinity of silicon. Use of silicon makes available wider range of auxiliary on-chip signal-processing circuitry for coding and decoding of data, addition or subtraction of brightness levels, spatial reformatting, and rescaling.

Maserjian, Joseph↗
NASA NTRS1990

Diode laser array

A diode laser array comprises a substrate of a semiconductor material having first and second opposed surfaces. On the first surface is a plurality of spaced gain sections and a separate distributed Bragg reflector passive waveguide at each end of each gain section and optically connecting the gain sections. Each gain section includes a cavity therein wherein charge carriers are generated and recombine to generate light which is confined in the cavity. Also, the cavity, which is preferably a quantum well cavity, provides both a high differential gain and potentially large depth of loss modulation. Each waveguide has a wavelength which is preferably formed by an extension of the cavity of the gain sections and a grating. The grating has a period which provides a selective feedback of light into the gain sections to supporting lasing, which allows some of the light to be emitted from the waveguide normal to the surface of the substrate and which allows optical coupling of the gain sections. Also, the grating period provides an operating wavelength which is on the short wavelength side of the gain period of the gain sections required for laser oscillation. An RF pulse is applied so as to maximize the magnitude of the loss modulation and the differential gain in the gain sections. The array is operated by applying a DC bias to all the gain sections at a level just below the threshold of the gain sections to only one of the gain sections which raises the bias in all of the gain sections to a level that causes all of the gain sections to oscillate. Thus, a small bias can turn the array on and off.

Carlson, Nils W.↗
DOE OSTI2024

Quantum Information for Fusion Energy Sciences (Final Technical Report)

The simulation of plasma dynamics is a critical area of Fusion Energy Sciences (FES) due to it’s usefulness in predicting, controlling, and confining plasmas in the context of potential fusion reactors. The simulation of plasmas is a computationally difficult problem in both classical and quantum physics, motivating investigation into the potential of quantum computers to simulate these systems. This project took several concrete steps towards this goal by developing tools for improving the control, characterization, and calibration of quantum gates on a superconducting quantum computer, developing error suppression and mitigation tools to reduce errors on the quantum computer, and utilizing these advancements to simulate reduced models of plasma dynamics on the quantum computer.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗