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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Spin Qubits in Germanium Structures with Phononic Gap

We propose qubits based on shallow donor electron spins in germanium structures with phononic gap. We consider a phononic crystal formed by periodic holes in Ge plate or a rigid cover / Ge layer / rigid substrate structure with gaps approximately a few GHz. The spin relaxation is suppressed dramatically, if the Zeeman frequency omegaZ is in the phononic gap, but an effective coupling between the spins of remote donors via exchange of virtual phonons remains essential. If omegaZ approaches to a gap edge in these structures, a long-range (limited by detuning of omegaZ) resonant exchange interaction takes place. We estimate that ratio of the exchange integral to the longitudinal relaxation rate exceeds 10(exp 5) and lateral scale of resonant exchange 0.1 mm. The exchange contribution can be verified under microwave pumping through oscillations of spin echo signal or through the differential absorption measurements. Efficient manipulation of spins due to the Rabi oscillations opens a new way for quantum information applications.

Qubit↗
DOE OSTI2024

Single-photon superradiance in individual caesium lead halide quantum dots

The brightness of an emitter is ultimately described by Fermi’s golden rule, with a radiative rate proportional to its oscillator strength times the local density of photonic states. As the oscillator strength is an intrinsic material property, the quest for ever brighter emission has relied on the local density of photonic states engineering, using dielectric or plasmonic resonators. By contrast, a much less explored avenue is to boost the oscillator strength, and hence the emission rate, using a collective behaviour termed superradiance. Recently, it was proposed that the latter can be realized using the giant oscillator-strength transitions of a weakly confined exciton in a quantum well when its coherent motion extends over many unit cells. Here we demonstrate single-photon superradiance in perovskite quantum dots with a sub-100 picosecond radiative decay time, almost as short as the reported exciton coherence time. The characteristic dependence of radiative rates on the size, composition and temperature of the quantum dot suggests the formation of giant transition dipoles, as confirmed by effective-mass calculations. The results aid in the development of ultrabright, coherent quantum light sources and attest that quantum effects, for example, single-photon emission, persist in nanoparticles ten times larger than the exciton Bohr radius.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Quantum Squeezing and Sensing with Pseudo-Anti-Parity-Time Symmetry

The emergence of parity-time (PT) symmetry has greatly enriched our study of symmetry-enabled non-Hermitian physics, but the realization of quantum PT symmetry faces an intrinsic issue of unavoidable symmetry-breaking Langevin noises. Here we construct a quantum pseudo-anti-PT (pseudo-APT) symmetry in a two-mode bosonic system without involving Langevin noises. We show that the spontaneous pseudo-APT symmetry breaking leads to an exceptional point, across which there is a transition between different types of quantum squeezing dynamics; i.e., the squeezing factor increases exponentially (oscillates periodically) with time in the pseudo-APT-symmetric (broken) region. Such dramatic changes of squeezing factors and quantum dynamics near the exceptional point are utilized for ultraprecision quantum sensing. These exotic quantum phenomena and sensing applications can be experimentally observed in two physical systems: spontaneous wave mixing nonlinear optics and atomic Bose-Einstein condensates. Furthermore, our Letter offers a physical platform for investigating exciting APT symmetry physics in the quantum realm, paving the way for exploring fundamental quantum non-Hermitian effects and their quantum technological applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1985

Optimization of SIS mixer elements

Superconductor-Insulator-Superconductor (SIS) quantum mixers provide an approach to millimeter wave mixing - potentially offering conversion gain, a low local oscillator power demand, and potential mixer noise temperatures near the quantum limit. The development of a reliable fabrication technology for producing such high quality SIS devices for mixer applications in radio astronomy is the focus of the work.

Mattauch, Robert J.↗
DOE OSTI2021

A Tunable Unidirectional Source for GUSTO's Local Oscillator at 4.74 THz

The Galactic/Extra Ultra long Duration Balloon Spectroscopic-Stratospheric Terahertz Observatory (GUSTO), is a NASA balloon-borne project and is scheduled for launch in late 2022. The balloon will carry a spectroscopic telescope that will detect three brightest emission lines from interstellar medium. GUSTO measurements will shed light on the life-cycle of the gases in the Milky Way and Large Magellanic Cloud (LMC). In this study, we will discuss the details of a quantum cascade laser used in the local oscillator for detecting the oxygen line at 4.74 THz.

42 ENGINEERING↗
DOE OSTI2023

Quantum information and quantum simulation of neutrino physics

In extreme astrophysical environments such as core-collapse supernovae and binary neutron star mergers, neutrinos play a major role in driving various dynamical and microphysical phenomena, such as baryonic matter outflows, the synthesis of heavy elements, and the supernova explosion mechanism itself. The interactions of neutrinos with matter in these environments are flavor-specific, which makes it of paramount importance to understand the flavor evolution of neutrinos. Flavor evolution in these environments can be a highly nontrivial problem thanks to a multitude of collective effects in flavor space, arising due to neutrino-neutrino ($v$-$v$) interactions in regions with high neutrino densities. A neutrino ensemble undergoing flavor oscillations under the influence of significant $v$-$v$ interactions is somewhat analogous to a system of coupled spins with long-range interactions among themselves and with an external field (‘long-range’ in momentum-space in the case of neutrinos). As a result, it becomes pertinent to consider whether these interactions can give rise to significant quantum correlations among the interacting neutrinos, and whether these correlations have any consequences for the flavor evolution of the ensemble. In particular, one may seek to utilize concepts and tools from quantum information science and quantum computing to deepen our understanding of these phenomena. In this article, we attempt to summarize recent work in this field. In conclusion, we also present some new results in a three-flavor setting, considering complex initial states.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

The response field and the saddle points of quantum mechanical path integrals

Highlights: • Moyal quantum mechanics and Marinov’s path integral. • Classical and semiclassical limits of Marinov’s path integral. • Oscillating functional integrals. • Instantons of the Marinov’s path integral. In quantum statistical mechanics, Moyal’s equation governs the time evolution of Wigner functions and of more general Weyl symbols that represent the density matrix of arbitrary mixed states. A formal solution to Moyal’s equation is given by Marinov’s path integral. In this paper we demonstrate that this path integral can be regarded as the natural link between several conceptual, geometric, and dynamical issues in quantum mechanics. A unifying perspective is achieved by highlighting the pivotal role which the response field, one of the integration variables in Marinov’s integral, plays for pure states even. The discussion focuses on how the integral’s semiclassical approximation relates to its strictly classical limit; unlike for Feynman type path integrals, the latter is well defined in the Marinov case. The topics covered include a random force representation of Marinov’s integral based upon the concept of “Airy averaging”, a related discussion of positivity-violating Wigner functions describing tunneling processes, and the role of the response field in maintaining quantum coherence and enabling interference phenomena. The double slit experiment for electrons and the Bohm–Aharonov effect are analyzed as illustrative examples. Furthermore, a surprising relationship between the instantons of the Marinov path integral over an analytically continued (“Wick rotated”) response field, and the complex instantons of Feynman-type integrals is found. The latter play a prominent role in recent work towards a Picard–Lefschetz theory applicable to oscillatory path integrals and the resurgence program.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1986

Quantum mechanical signature in exclusive coherent pion production

We calculate the coherent production of pions from subthreshold to relativistic energies in heavy-ion collisions using a quantum, microscopic, many-body model. For the first time, in this approach, we use harmonic oscillator wave functions to describe shell-model information. The theoretical quantum mechanical results obtained for the pion spectra represent an important improvement over our previous microscopic, many-body calculations.

NASA Discipline Radiation Health↗
DOE OSTI2026

Squeezing-Enhanced Sensing at an Exceptional Point

Pushing the boundaries of measurement precision is central for sensing and metrology, pursued by nonclassical resources such as squeezing, as well as non-Hermitian degeneracies with distinct spectral response. Their convergence, however, remains challenging. We find extraordinary enhancement of sensitivity by unifying both effects in a general framework for quantum sensing in open systems. At the parametric oscillation threshold and an exceptional point, the sensing precision exhibits a unique quartic scaling with the perturbation strength. The result generalizes to multimode squeezed-state sensors with higher-order exceptional points catered to various quantum sensing platforms.

Wang, Changqing [Fermilab] (ORCID:0000000198073045↗
DOE OSTI2023

Quantum Sensing of Electric Fields Using Spin-Correlated Radical Ion Pairs

Quantum sensing affords the possibility of using quantum entanglement to probe electromagnetic fields with exquisite sensitivity. In this work, we show that a photogenerated spin-correlated radical ion pair (SCRP) can be used to sense an electric field change created at one radical ion of the pair using molecular recognition. The SCRP is generated within a covalent donor–chromophore–acceptor system PXX–PMI–NDI, 1, where PXX = peri-xanthenoxanthene, PMI = 1,6-bis(p-t-butylphenoxy)perylene-3,4-dicarboximide, and NDI = naphthalene-1,8:4,5-bis(dicarboximide). The electron-rich PXX donor in 1 acts as a guest molecule that can be encapsulated selectively by a tetracationic cyclophane ExBox4+ host to give a supramolecular complex 1 ⊂ ExBox 4+ . Selective photoexcitation of the PMI chromophore results in ultrafast generation of the PXX •+ –PMI–NDI •– SCRP. When PXX is encapsulated by ExBox 4+ , the cyclophane generates an electric field that repels the positive charge on PXX •+ within PXX •+ –PMI–NDI •– , reducing the SCRP distance, i.e., the distance between the centers-of-charge on the donor and acceptor. Pulse-EPR measurements are used to measure the coherent oscillations created primarily by the electron–electron dipolar coupling in the SCRP, which yields the distance between the two charges (spins) of PXX •+ –PMI–NDI •– . Here, the experimental results show that the distance between PXX •+ and NDI •– decreases when ExBox 4+ encapsulates PXX •+ , which demonstrates that the SCRP can function as a quantum sensor to detect electric field changes in the vicinity of the radical ions.

Anions↗
DOE OSTI2022

Construction of bias-preserving operations for pair-cat codes

Fault-tolerant quantum computation with depolarization error often requires demanding error threshold and resource overhead. If the operations can maintain high noise bias—dominated by dephasing error with small bit-flip error—we can achieve hardware-efficient fault-tolerant quantum computation with a more favorable error threshold. Distinct from two-level physical systems, multilevel systems (such as harmonic oscillators) can achieve a desirable set of bias-preserving quantum operations while using continuous engineered dissipation or Hamiltonian protection to stabilize to the encoding subspace. For example, cat codes stabilized with driven-dissipation or Kerr nonlinearity can possess a set of bias-preserving gates while continuously correcting bosonic dephasing error. However, cat codes are not compatible with continuous quantum error correction against excitation loss error, because it is challenging to continuously monitor the parity to correct photon loss errors. In this work, we generalize the bias-preserving operations to pair-cat codes, which can be regarded as a multimode generalization of cat codes, to be compatible with continuous quantum error correction against both bosonic loss and dephasing errors. In conclusion, our results open the door towards hardware-efficient robust quantum information processing with both bias-preserving operations and continuous quantum error correction simultaneously correcting bosonic loss and dephasing errors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Effects of Autoionizing Resonances on Wave-Packet Dynamics Studied by Time-Resolved Photoelectron Spectroscopy

Here, we report a combined experimental and theoretical study on the effect of autoionizing resonances in time-resolved photoelectron spectroscopy. The coherent excitation of N 2 by ~14.15 eV extreme-ultraviolet photons prepares a superposition of three dominant adjacent vibrational levels (v'=14–16) in the valence b' 1 $Σ^+_u$ state, which are probed by the absorption of two or three near-infrared photons (800 nm). The superposition manifests itself as coherent oscillations in the measured photoelectron spectra. A quantum-mechanical simulation confirms that two autoionizing Rydberg states converging to the excited A 2 Π u and B 2 $Σ^+_u$ $N^+_2$ cores are accessed by the resonant absorption of near-infrared photons. We show that these resonances apply different filters to the observation of the vibrational wave packet, which results in different phases and amplitudes of the oscillating photoelectron signal depending on the nature of the autoionizing resonance. This work clarifies the importance of resonances in time-resolved photoelectron spectroscopy and particularly reveals the phase of vibrational quantum beats as a powerful observable for characterizing the properties of such resonances.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Coherent spin states and emergent de Sitter quasinormal modes

As a toy model for the microscopic description of matter in de Sitter space, we consider a Hamiltonian acting on the spin-j representation of SU(2). This is a model with a finite-dimensional Hilbert space, from which quasinormal modes emerge in the large-spin limit. The path integral over coherent spin states can be evaluated at the semiclassical level and from it we find the single-particle de Sitter density of states, including 1/j corrections. Along the way, we discuss the use of quasinormal modes in quantum mechanics, starting from the paradigmatic upside-down harmonic oscillator.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Quantum algorithm for the linear Vlasov equation with collisions

The Vlasov equation is a nonlinear partial differential equation that provides a first-principles description of the dynamics of plasmas. Its linear limit is routinely used in plasma physics to investigate plasma oscillations and stability. In this paper, we present a quantum algorithm that simulates the linearized Vlasov equation with and without collisions, in the one-dimensional electrostatic limit. Rather than solving this equation in its native spatial and velocity phase space, we adopt an efficient representation in the dual space yielded by a Fourier-Hermite expansion. For a given simulation time, the Fourier-Hermite representation is exponentially more compact, thus yielding a classical algorithm that can match the performance of a previously proposed quantum algorithm for this problem. Further, this representation results in a system of linear ordinary differential equations (ODEs) which can be solved with well-developed quantum algorithms: a Hamiltonian simulation in the collisionless case, and quantum ODE solvers in the collisional case. In particular, we demonstrate that a quadratic speedup in system size is attainable.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Minkowski vacuum entanglement and accelerated oscillator chains

Minkowski vacuum is empty from the perspective of Unruh-Minkowski photons, however, in the Rindler picture, it is filled with entangled pairs of Rindler photons. A ground-state atom uniformly accelerated through Minkowski vacuum can become excited by absorbing a Rindler photon (Unruh effect) or, in the alternative description, by emitting an Unruh-Minkowski photon (Unruh-Wald effect). We find an exact solution for the quantum evolution of a long chain of harmonic oscillators accelerated through Minkowski vacuum and for two chains accelerated in the opposite directions. We show how entanglement of Rindler photons present in Minkowski vacuum is transferred to the oscillators moving in causally disconnected regions. We also show that in the Unruh-Minkowski photon picture the process can be interpreted as if initial correlations between collective oscillator modes are transferred to the generated Unruh-Minkowski photons. Published by the American Physical Society 2025

Svidzinsky, Anatoly A. (ORCID:0000000247756767)↗
DOE OSTI2023

Aggregation‐Induced Stimulated Emission of 100% Dye Microspheres

Dyes with aggregation-induced emission (AIE) properties have gained interest due to their bright luminescence in solid-state aggregates. While fluorescence from AIE dyes is widely exploited, relatively little is known about aggregation-induced stimulated emission. Here, stimulated emission of tetraphenylethene (TPE)-based organoboron AIE dyes, TPEQBN, in thin films and in microcavity lasers is investigated. Using femtosecond pump–probe spectroscopy, gain coefficients up to 230 cm -1 at 500 nm are measured. Using rate equations, concentration- and pump-dependent gain dynamics as well as laser build-up dynamics are analyzed. During laser oscillation, radiative stimulated emission allows high instantaneous quantum yield greater than 90% to be achieved. Solid-state microspheres made of 100% AIE dyes are fabricated via microfluidic emulsion and solvent evaporation method. Coupled with high gain and high refractive index of 1.76, microspheres as small as 2 µm in diameter show lasing by nanosecond pumping with a threshold of ≈10 pJ µm –2 . Polymer coated, but not bare, microspheres are internalized by live cells and generate narrowband cavity-mode emission from within the cytoplasm. This work shows the potential of AIE dyes as laser materials.

36 MATERIALS SCIENCE↗