Complementarity Probably Survives Challenge
In their Nature article of Sept. 3rd, S. Durr et al. report the results of an experiment involving the recombination of two quantum atomic beams.
Complementarity Heisenberg uncertainty principle i↗
SEARCH · Search NASA
Results for “Quantum interference”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Tunable Optical True-Time Delay Devices Would Exploit EIT
Tunable optical true-time delay devices that would exploit electromagnetically induced transparency (EIT) have been proposed. Relative to prior true-time delay devices (for example, devices based on ferroelectric and ferromagnetic materials) and electronically controlled phase shifters, the proposed devices would offer much greater bandwidths. In a typical envisioned application, an optical pulse would be modulated with an ultra-wideband radio-frequency (RF) signal that would convey the information that one seeks to communicate, and it would be required to couple differently delayed replicas of the RF signal to the radiating elements of a phased-array antenna. One or more of the proposed devices would be used to impose the delays and/or generate the delayed replicas of the RF-modulated optical pulse. The beam radiated or received by the antenna would be steered by use of a microprocessor-based control system that would adjust operational parameters of the devices to tune the delays to the required values. EIT is a nonlinear quantum optical interference effect that enables the propagation of light through an initially opaque medium. A suitable medium must have, among other properties, three quantum states (see Figure 1): an excited state (state 3), an upper ground state (state 2), and a lower ground state (state 1). These three states must form a closed system that exhibits no decays to other states in the presence of either or both of two laser beams: (1) a probe beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 1; and (2) a coupling beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 2. The probe beam is the one that is pulsed and modulated with an RF signal.
Kulikov, Igor↗
Momentum space AC Josephson effect and intervalley coherence in multilayer graphene
Electron transport driven by the phase coherence and interference of quantum many-body wavefunctions is a fascinating phenomenon with potential technological significance. Superconductivity, for example, enables dissipationless transport through macroscopic phase twisting, while charge-density waves show broadband noise and AC-DC interference once their phase is depinned. We identify an analogous phase-coherent dynamics in the intervalley-coherent (IVC) state frequently observed in rhombohedral multilayer graphene. We show that a static magnetic field drives an oscillating intervalley current, which produces an oscillating orbital magnetization and thereby a detectable AC Hall response. This mechanism is similar to the Josephson effect observed in superconductors but now happening in momentum space. In this analogy, the static magnetic field acts as the DC voltage, while the oscillating intervalley current is the AC Josephson current. We provide microscopic calculations of all the phase-number free-energy parameters in rhombohedral trilayer graphene, establishing this effect as an experimental signature of IVC order.
electronic properties and materials↗
Proposal for a QND which-path measurement using photons
A scheme is proposed for experimentally realizing the famous two-slit gedaenken experiment using photons. As elegantly discussed for electrons by Feynman, a particle's quantum pathways interfere to produce fringes in the probability density for the particle to be found at a particle location. If the path taken by the particle is experimentally determined, the complementarity principle says that the fringes must disappear. To carry out this experiment with photons is difficult because normally the act of determining a photon's location destroys it. We propose to overcome this difficulty by putting a type-2 optical parametric amplifier (OPA) in each arm of a Mach-Zehnder interferometer, and observing fringes at the output. An OPA responds to an input photon by increasing its probability to produce a pair of photons with polarization orthogonal to the input, the detection of which allows partial inference about the path taken by the input photon without destroying it. Thus, the measurement is of the quantum nondemolition (QND) type.
Raymer, M. G.↗
Dichotomy of flat bands in the van der Waals ferromagnet Fe 5 GeTe 2
Quantum materials with bands of narrow bandwidth near the Fermi level represent a promising platform for exploring a diverse range of fascinating physical phenomena, as the high density of states within the small energy window often enables the emergence of many-body physics. On one hand, flat bands can arise from strong Coulomb interactions that localize atomic orbitals. On the other hand, quantum destructive interference can quench the electronic kinetic energy. Although both have a narrow bandwidth, the two types of flat bands should exhibit very distinct spectral properties arising from their distinctive origins. So far, the two types of flat bands have only been realized in very different material settings and chemical environments, preventing a direct comparison. Here, in this study, we report the observation of the two types of flat bands within the same material system—an above-room-temperature van der Waals ferromagnet, Fe 5−x GeTe 2 , distinguishable by a switchable iron site order. The contrasting nature of the flat bands is also identified by the remarkably distinctive temperature evolution of the spectral features, indicating that one arises from electron correlations in the Fe(1) site-disordered phase, while the other geometrical frustration in the Fe(1) site-ordered phase. Our results therefore provide a direct juxtaposition of the distinct formation mechanism of flat bands in quantum materials and an avenue for understanding the distinctive roles flat bands play in the presence of magnetism, topology, and lattice geometrical frustration, utilizing sublattice ordering as a key control parameter.
Wu, Han [Rice Univ., Houston, TX (United States)] ↗
Spin excitations and flat electronic bands in a Cr-based kagome superconductor
In the quest for topology- and correlation-driven quantum states, kagome lattice materials have garnered significant interest for their band structures, featuring flat bands (FBs) from the quantum destructive interference of the electronic wavefunction. Tuning an FB to the chemical potential could induce electronic instabilities and emergent orders. Despite extensive studies, direct evidence of FBs tuned to the chemical potential and their role in emergent orders in bulk materials remains lacking. Using angle-resolved photoemission spectroscopy, resonant inelastic X-ray scattering, and density functional theory, we show that the low-energy structure of the Cr-based kagome metal superconductor CsCr 3 Sb 5 is dominated by FBs at the Fermi level. We also observe low-energy magnetic excitations evolving across the low-temperature transition, largely consistent with the FB shift. Our results suggest that the low-temperature order contains a magnetic origin and that the kagome FBs may play a role in the emergence of this order.
electronic properties and materials↗
Search for light sterile neutrinos with two neutrino beams at MicroBooNE
The existence of three distinct neutrino flavours, ν e , ν μ and ν τ , is a central tenet of the Standard Model of particle physics. Quantum-mechanical interference can allow a neutrino of one initial flavour to be detected sometime later as a different flavour, a process called neutrino oscillation. Several anomalous observations inconsistent with this three-flavour picture have motivated the hypothesis that an additional neutrino state exists, which does not interact directly with matter, termed as ‘sterile’ neutrino, ν s . This includes anomalous observations from the Liquid Scintillator Neutrino Detector (LSND)3 experiment and Mini-Booster Neutrino Experiment (MiniBooNE), consistent with ν μ → ν e transitions at a distance inconsistent with the three-neutrino picture. Here we use data obtained from the MicroBooNE liquid-argon time projection chamber in two accelerator neutrino beams to exclude the single light sterile neutrino interpretation of the LSND and MiniBooNE anomalies at the 95% confidence level (CL). Moreover, we rule out a notable portion of the parameter space that could explain the gallium anomaly. This is one of the first measurements to use two accelerator neutrino beams to break a degeneracy between ν e appearance and disappearance, which would otherwise weaken the sensitivity to the sterile neutrino hypothesis. We find no evidence for either ν μ → ν e flavour transitions or ν e disappearance that would indicate non-standard flavour oscillations. Our results indicate that previous anomalous observations consistent with ν μ → ν e transitions cannot be explained by introducing a single sterile neutrino state.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Superconducting (Ba,K)Fe 2 As 2 epitaxial films on single and bicrystal SrTiO 3 substrates
The realization of single crystal and bicrystal films of superconducting materials is of great interest because they allow the investigation of the intragrain performance as well as the understanding of potential limitations in the grain boundary transparency. For many years, the realization of a high-quality (Ba,K)Fe 2 As 2 film has been challenging. Here, the realization of (Ba,K)Fe 2 As 2 epitaxial thin films on single crystal SrTiO 3 (001) and [001]-tilt-type SrTiO 3 bicrystal substrates with high superconducting properties is demonstrated. The epitaxial growth of (Ba,K)Fe 2 As 2 was enabled by implementing an undoped BaFe 2 As 2 buffer layer between the SrTiO 3 substrate and (Ba,K)Fe 2 As 2 film. The film exhibits a high T c of 38.0 K and an extremely high J c of 14.3 MA/cm 2 at 4.2 K. Artificial grain boundaries of (Ba,K)Fe 2 As 2 were also successfully achieved on bicrystals with misorientation angles up to 36.8° by the same preparation methods. The artificial grain boundaries exhibited an identical T c of 38.0 K and an excellent transfer of the grain orientation from the bicrystal substrates with high crystallinity comparable to that of the high-quality Ba(Fe,Co) 2 As 2 films. Furthermore, this enables the investigation of the intrinsic (Ba,K)Fe 2 As 2 grain boundary nature, which will clarify its potential for superconducting applications, like Josephson junctions, wires, and magnets.
(Ba,K)Fe2As2↗
Flat-band driven Kondo breakdown and reentrant effects in heavy-fermion moiré superlattices
Moiré superlattices (MSLs) in van der Waals heterostructures have demonstrated their incredible power in driving emergent electronic phenomena, some of which are reminiscent of those usually only observed in bulk strongly correlated quantum materials. With the recent discovery of van der Waals 𝑓-electron materials, the design of novel MSLs of intrinsic strong correlation is now within the reach. Here we study the novel electron phases of two-dimensional heavy-fermion MSL with increasingly diluted 𝑓-electron local moments. By applying dynamical mean-field theory with numerical renormalization group as an impurity solver, we demonstrate the appearance of a different energy scale and a reentrant Kondo breakdown in connection with the emergence of a flat band in the system. We further compare our numerical findings with predictions derived from the Lieb-Mattis theorem and show the necessity of this energy scale to consistently reconcile the predictions with the conventional single-impurity limit for exceedingly large unit cells.
36 MATERIALS SCIENCE↗
Anisotropic weak antilocalization in thin films of the Weyl semimetal TaAs
Device applications of topological semimetals await the development of epitaxial films in the ultrathin limit. Weak antilocalization (WAL) has been extensively utilized in the understanding of surface states in topological insulators and shows promise for use in elucidating the properties of thin film topological semimetals. Here, we report insights from WAL in the surface state and interface transport properties of our recently synthesized single-crystal-like thin films of the Weyl semimetal TaAs(001) grown on GaAs(001). We observe robust, anisotropic WAL in the magnetoconductance from 2 to 20 K in films from 10 to 200 nm thick. We link the anisotropic WAL magnetoconductance to anisotropic mobility stemming from film topography. We conclude that WAL in the films likely originates from the antilocalization of topological surface states. The WAL magnetoconductance is impacted by the film thickness and topography, solidifying the useful role of WAL in the study of topological semimetal/semiconductor heterointerfaces. Published by the American Physical Society 2024
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Third-order nonlinearities in molecular hydrogen - Two-photon resonance enhanced third-harmonic generation and Raman scattering
Effects of quantum mechanical interferences on third-order susceptibilities in molecules are studied. First principle calculations for molecular hydrogen are presented and shown to agree with results derived from experimental stimulated Raman gain and spontaneous Raman cross-section data. 10 percent third-harmonic conversion efficiency in H2 at 1 atm without phase matching should require a 150 MW per sq cm at 4.81 microns. As little as 5.9-MW power is sufficient when the beam is properly focused. Resonance Raman scattering (RRS) is proposed for experimentally investigating the interference effects, which tend to reduce the strength of third-order nonlinear susceptibilities.
Pan, C.-L.↗
Recent Results of a New Microwave SQUID Multiplexer
We are developing a proof-of-concept microwave SQUID multiplexer containing four SQUIDs coupled to GHz frequency resonant circuits and fed with a single microwave readout line. The resonators are half-wave coplanar waveguide sections and are similar to the structures used for the microwave kinetic inductance detectors developed in our group. Optimal values for the interdigital gap capacitors were determined to maximize the sensitivity of the transmitted and reflected microwave signal with respect to changes in the dynamic resistance of the SQUID. The dc current-bias line for the SQUID has an in-line inductive high frequency filter to minimize coupling between the bias line and resonator. A high frequency modulation scheme is proposed to eliminate the need for individual flux biasing of the SQUIDs, which extends the dynamic range of the readout. In this scheme a common modulation signal is imposed on each SQUID and the received signal is demodulated at one and two times the modulation frequency to maintain sensitivity at any flux state. We present the recent results of the microwave SQUID multiplexer system operating at a readout frequency range of 10 - 11GHz.
superconducting quantum interference device (SQUID↗
Mitigation of Finite Bandwidth Effects in Time-Division-Multiplexed SQUID Readout of TES Arrays
Time division multiplexing (TDM) is being developed as the readout technology of the X-ray integral field unit (X-IFU), a 3,168-pixel X-ray transition-edge sensor (TES) imaging spectrometer that is part of the European Space Agency's Athena satellite mission. Recent improvements in the low X-ray event count rate performance of TDM have been driven by increases in multiplexer bandwidth and the mitigation of settling transients. These methods and design changes have improved the 32-row multiplexed resolution of a NASA LPA 2.5a array from an initial (2.73 ± 0.03) eV to (1.97 ± 0.01) eV resolution at 5.9 keV. We discuss these recent advances in TDM readout, which have been implemented in an 8-column × 32-row spectrometer that will be deployed at the Lawrence Livermore National Laboratory electron beam ion trap (EBIT) facility, and present a model that will inform the design of future systems.
Transition-edge sensors↗
Probing quantum phenomena through photoproduction in relativistic heavy-ion collisions
Photoproduction in ultra-peripheral relativistic heavy-ion collisions displays many unique features, often involving quantum mechanical coherence and two-source interference between photon emission from the two ions. We review the recent experimental results from RHIC and the LHC and theoretical studies of coherent vector meson photoproduction, emphasizing the quantum mechanical aspects of the interactions and the entanglement between the final state particles. These studies enrich our understanding of non-local realism, underscore the critical role of the polarization of the photon source, quantum interference and nuclear effect on the gluon distribution. It paves a way for quantitatively probing the quantum nature of these high-energy nuclear collisions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Quantum Random Walk Simulator Using Ultrafast Optical Switches
Quantum random walk processes have many intriguing applications in high energy physics including the simulation of parton shower evolution. We will present the design and initial results of a fiber loop time-bin quantum walk architecture using the hardware platform already in operation at the Fermilab Quantum Network in which the state of the photon is defined by its time-of-arrival. The fiber loop consists of an unbalanced Mach-Zehnder interferometer implemented using an ultrafast electro-optical switch. The input switch controls the photon path within the interferometer, while the output switch will direct the photon back into the interferometer or to single photon detectors to measure the probability distribution of arrival times. Depending on which path the photon takes each pass through the loop, its wave function will interfere on these optical switches similar to quantum interference on a beam splitter. This work is an important step towards utilizing real-world advantages of quantum information protocols to solve problems in high energy physics.
Cameron, Andrew [Fermilab]↗
A phaseonium magnetometer: A new optical magnetometer based on index enhanced media
An optical magnetometer based on quantum coherence and interference effects in atoms is proposed. The sensitivity of this device is potentially superior to the present state-of-the-art devices. Optimum operating conditions are derived, and a comparison to standard optical pumping magnetometers is made.
Scully, Marlan O.↗
Measurement and feedback-driven adaptive dynamics in the classical and quantum kicked top
In classical dynamical systems, stochastic feedback can stabilize otherwise unstable periodic orbits, giving rise to distinct controlled and uncontrolled phases as the rate of control application is varied. In this work, we apply these control protocols in classical, semiclassical, and quantum regimes to the kicked top, a paradigmatic model of quantum chaos. The quantum kicked top, modeled as the dynamics of a spin-S object, naturally interpolates between these regimes with the spin size S acting as an effective Planck constant. We show that the dynamics of the kicked top in classical, semiclassical, and fully quantum limits can all be controlled using stochastic feedback protocols. Comparing the full quantum dynamics to a truncated Wigner approximation that captures quantum noise but neglects interference beyond the Ehrenfest time, we find that low-moment observables are largely accounted for semiclassically, while the remaining discrepancy in higher moments is consistent with contributions from interference and possibly nonlinearities in rare trajectories that explore the compact phase space. We also find rapid purification in the numerics studied for all rates of control considered, suggesting that control quenches the top's ability to encode a qubit of quantum information even in the uncontrolled phase.
Prasad, Mahaveer [Tata Inst.; Singapore U. Tech. D↗
Fast quantum interferometry at the nanometer and attosecond scales with energy-entangled photons
In classical optical interferometry, loss and background complicate achieving fast nanometer-resolution measurements with illumination at low light levels. Conversely, quantum two-photon interference is unaffected by loss and background, but nanometer-scale resolution is physically difficult to realize. As a solution, we enhance two-photon interference with highly nondegenerate energy entanglement featuring photon frequencies separated by 177 THz. We observe measurement resolution at the nanometer (attosecond) scale with only O(10 4 ) photon pairs, despite the presence of background and loss. Our nondestructive thickness measurement of a metallic thin film agrees with atomic force microscopy, which often achieves better resolution via destructive means. With contactless, nondestructive measurements in seconds or faster, our instrument enables metrological studies in optically challenging contexts where background, loss, or photosensitivity are factors.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗