Pulse Profile Research Articles

Realization of the iSWAP-like gate among the superconducting qutrits

High-dimensional quantum systems, such as qutrits (quantum three-level systems), have multiple accessible energy levels beyond the two-level qubits. Therefore, qutrits can offer a larger state space to improve the efficiency of quantum computation. Here, we demonstrate a high-fidelity iSWAP-like gate operation on a frequency-tunable superconducting qutrits system. The superconducting quantum system consists of two qutrits that are coupled via a resonator with fixed qutrit-resonator coupling strengths. Through designing the frequency pulse profile and optimizing the parameter values, the gate error can be suppressed below 1.5 × 10−3. To bear out the feasibility of the proposal, we have conducted our study with experimentally accessible parameters. As the resonator can mediate the interaction between the irrelevant qutrits, the presented approach can also be used to couple multiple qutrits together, providing a good platform for quantum information processing.

Spectral and timing analysis of Be/X-ray binary EXO 2030+375 during its giant 2021 outburst

ABSTRACT We report the X-ray spectral and timing analysis of the high mass X-ray binary EXO 2030+375 during the 2021 type II outburst. We have incorporated NuSTAR, NICER, Swift/BAT, and Fermi/GBM observations to carry out a comprehensive analysis of the source. Pulse profiles in different energy ranges and time intervals have been generated and analysed. We have performed a brief comparison of the observations amidst the peak outburst condition and also during the decaying state of the outburst. Pulse profiles are found to evolve with time and energy. An iron emission line at (6–7) keV is observed in the X-ray continuum. Distinct absorption features were observed in the spectra corresponding to the peak outburst state while such features were not detected during the later decaying phase of the outburst. We have estimated the characteristic spin-up time-scale to be ∽ 60 yr. The continuum flux of the system and the varying luminosities covering the entire outburst period have been used to interpret the characteristics of the source. We have summarized the variability of various parameters along with their underlying physical implications.

XMM–Newton observations of PSR J0554+3107: pulsing thermal emission from a cooling high-mass neutron star

ABSTRACT XMM–Newton observations of the middle-aged radio-quiet γ-ray pulsar J0554+3107 allowed us, for the first time, firmly identify it in X-rays by detection of pulsations with the pulsar period. In the 0.2–2 keV band, the pulse profile shows two peaks separated by about a half of the rotation phase with the pulsed fraction of 25 ± 6 per cent. The profile and spectrum in this band can be mainly described by thermal emission from the neutron star with the hydrogen atmosphere, dipole magnetic field of ∼1013 G, and non-uniform surface temperature. Non-thermal emission from the pulsar magnetosphere is marginally detected at higher photon energies. The spectral fit with the atmosphere+power-law model implies that J0554+3107 is a rather heavy and cool neutron star with the mass of 1.6–2.1 M⊙, the radius of ≈13 km, and the redshifted effective temperature of ≈50 eV. The spectrum shows an absorption line of unknown nature at ≈350 eV. Given the extinction–distance relation, the pulsar is located at ≈2 kpc and has the redshifted bolometric thermal luminosity of ≈2 × 1032 erg s−1. We discuss cooling scenarios for J0554+3107 considering plausible equations of state of superdense matter inside the star, different compositions of the heat-blanketing envelope, and various ages.

Pulse-Profile-Maintaining Characteristics of Gain-Switched Nanosecond Raman Fiber Laser and Amplifier

This paper investigates pulse-profile-maintaining characteristics of a gain-switched nanosecond Raman fiber laser (RFL) and its Raman fiber amplifier (RFA). It is found that the pulse profiles can be precisely maintained after the gain-switched Raman conversion, only if the pump pulse repetition frequency (PRF) is an integer multiple of, a unit fraction of, or multiple unit fractions of the fundamental cavity-defined PRF. The produced Raman pulses are then amplified in an RFA, and the pulse profiles can also be precisely maintained. However, it is further noticed that the detuning-induced defects can be amplified if they are with the pulse itself. All these observed phenomena should originate from the transient property of Raman gain, not involving any notable delaying or saturation effects that are typically seen with rare-earth-doped gain fibers. Our results demonstrate that, in the nanosecond scale, the Raman-converted pulse can well maintain its profile and shows strong resistance to detune between PRFs of the pump and Raman pulses. Benefiting from that, we can reasonably neglect the pump depletion effect due to walk-off effect typically seen in various short pulse regimes, which can largely simplify the design of nanosecond pulsed pumping Raman sources.

Double-lens scintillometry: the variable scintillation of pulsar B1508 + 55

ABSTRACT We report on observations of PSR B1508 + 55’s scintillation at the Effelsberg 100-m telescope spanning from early 2020 to early 2022. In the autumn of 2020, close to the time the pulsar was predicted to cross echoes in its pulse profile, a sudden transition in the scintillation arcs from peculiar stripe-like features to parabolic arclets was observed. To infer a geometric model of the scattering, we measure the effects of the annual velocity curve of Earth, of the relative movement of the line of sight, and of the projection of points on a second scattering screen and develop novel methods to do so. The latter phenomenon was discovered by this study and strongly indicates a two-screen scattering geometry. We derive an analytical two-screen model and demonstrate in a Markov chain Monte Carlo analysis as well as simulations that it can be successfully applied to explain the observations by interpreting the transition as a change of relative amplitudes of images as well as a shift in the orientation of anisotropy. The collection of methods, we demonstrate here is transferable to other pulsars with the potential to strongly improve constraints on scattering models.

Timing Properties of the X-Ray Accreting Pulsar 1A 0535+262 Studied with Insight-HXMT

We report results on the timing analysis of the 2020 giant outburst of 1A 0535+262, using broadband data from Insight-HXMT. The analysis of the pulse profile evolution from the subcritical-luminosity to the supercritical-luminosity regime is presented for the first time. We found that the observed pulse profile exhibits a complex dependence on both energy and luminosity. A dip structure at the energy of the cyclotron resonant scattering features is found for the first time in the pulse fraction–energy relation of 1A 0535+262, when the outburst evolves in a luminosity range from 4.8 × 1037 to 1.0 × 1038 erg s−1. The observed structure is luminosity dependent and appears around the source critical luminosity (∼6.7 × 1037 erg s−1).

Discovery of γ-Ray Pulsations from PSR J1835–3259B in the Globular Cluster NGC 6652

Motivated by the recent discovery of the pulsar J1835−3259B with a spin period 1.83 ms in the globular cluster (GC) NGC 6652, we analyze the γ-ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi) for the GC and detect the pulsations of this millisecond pulsar (MSP) at a 5.4σ confidence level (the weighted H-test value is ∼41). From timing analysis of the data, a pulse profile that is similar to the radio one is established. We thus consider that we have detected the γ-ray emission of the MSP, and discuss the implications. Based on the results of our analysis and different studies of the sources in the GC, the observed γ-ray emission from the GC could mainly arise from this MSP, like the previous two cases in the GCs NGC 6624 and NGC 6626. Assuming this is the case, the pulsar, at the GC’s distance of 9.46 kpc and having a spin-down luminosity of ≤4.3 × 1035 erg s−1, would have a γ-ray luminosity of ≃(5.04 ± 0.44) × 1034 erg s−1 and a γ-ray efficiency of ≳0.12.

Discovery of a 584.65 Hz Burst Oscillation in the Low-mass X-Ray Binary 4U 1730–22

Type-I X-ray burst oscillations are powered by thermonuclear energy released on the neutron star (NS) surface in low-mass X-ray binaries (LMXBs), where the burst oscillation frequencies are close to the NS spin rates. In this work, we report the detection of oscillation at 584.65 Hz during the cooling tail of type-I X-ray bursts observed from the accreting NS LMXB 4U 1730–22 on 2022 March 20, by the Neutron star Interior Composition Explorer telescope. The oscillation signal showed a strong Leahy power, P m ∼ 54.04, around 584.65 Hz, which has single-trial and multiple-trial confidence levels of 7.05σ and 4.73σ, respectively. The folded pulse profile of the oscillation in the 0.2–10 keV band showed a sinusoidal shape with the fractional rms amplitude of (8.0 ± 1.1)%. We found the oscillation frequency showed insignificant upward drifting, i.e., less than 0.3 Hz, during the cooling tail, similar to the behavior appearing in accreting millisecond X-ray pulsars (AMXP), and indicate the source could be an AMXP spinning at 1.71 ms.

Compressed Sensing Based RFI Mitigation and Restoration for Pulsar Signals

In pulsar signal processing, two primary difficulties are (1) radio-frequency interference (RFI) mitigation and (2) information loss due to preprocessing and mitigation itself. Linear mitigation methods have a difficulty in RFI modeling, and accommodate a limited range of RFI morphologies. Thresholding methods suffer from manual factors and adaptability. There is also a distinct lack of methods dedicated to information loss. In this paper, a novel method “CS-Pulsar” is proposed. It carries out compressed sensing (CS) on time-frequency signals to accomplish RFI mitigation and signal restoration simultaneously. Curvelets allow an optimal sparse representation for multichannel pulsar signals containing the time-of-arrival dispersion relationship. CS-Pulsar mitigation is implemented using a regularized least-squares framework that does not require the statistics of RFI to be known beforehand. CS-Pulsar implements channel restoration, and useful signal contents are retrieved from the measurement error by a morphological component analysis aided by the root-mean-square envelope. These two steps allow CS-Pulsar to provide key signal details for special astrophysical purposes. Experiments of signal restoration for pulsar data from the Nanshan 26 m radio telescope reveal the advantage of CS-Pulsar. The method successfully removes false peaks due to on-pulse RFI in multipeaked pulsar profiles. CS-Pulsar also increases the timing accuracy and signal-to-noise ratio proving its feasibilities and prospects in astrophysical measurements.

Physics-based deep learning for modeling nonlinear pulse propagation in optical fibers.

A physics-based deep learning (DL) method termed Phynet is proposed for modeling the nonlinear pulse propagation in optical fibers totally independent of the ground truth. The presented Phynet is a combination of a handcrafted neural network and the nonlinear Schrödinger physics model. In particular, Phynet is optimized through physics loss generated by the interaction between the network and the physical model rather than the supervised loss. The inverse pulse propagation problem is leveraged to exemplify the performance of Phynet when in comparison to the typical DL method under the same structure and datasets. The results demonstrate that Phynet is able to precisely restore the initial pulse profiles with varied initial widths and powers, while revealing a similar prediction accuracy compared with the typical DL method. The proposed Phynet method can be expected to break the severe bottleneck of the traditional DL method in terms of relying on abundant labeled data during the training phase, which thus brings new insight for modeling and predicting the nonlinear dynamics of the fibers.

Hydrodynamic Impacts of Short Laser Pulses on Plasmas

We determine conditions allowing for simplification of the description of the impact of a short and arbitrarily intense laser pulse onto a cold plasma at rest. If both the initial plasma density and pulse profile have plane symmetry, then suitable matched upper bounds on the maximum and the relative variations of the initial density, as well as on the intensity and duration of the pulse, ensure a strictly hydrodynamic evolution of the electron fluid without wave-breaking or vacuum-heating during its whole interaction with the pulse, while ions can be regarded as immobile. We use a recently developed fully relativistic plane model whereby the system of the Lorentz–Maxwell and continuity PDEs is reduced into a family of highly nonlinear but decoupled systems of non-autonomous Hamilton equations with one degree of freedom, the light-like coordinate ξ=ct−z instead of time t as an independent variable, and new a priori estimates (eased by use of a Liapunov function) of the solutions in terms of the input data (i.e., the initial density and pulse profile). If the laser spot radius R is finite and is not too small, the same conclusions hold for the part of the plasma close to the axis z→ of cylindrical symmetry. These results may help in drastically simplifying the study of extreme acceleration mechanisms of electrons.

A Modified Ultra-Sensitive ELISA for Measurement of LH in Mice.

A major obstacle to monitoring pulsatile luteinizing hormone (LH) secretion in mice has been an assay with sufficient sensitivity in small blood volumes. In 2013, Steyn and colleagues published a highly sensitive enzyme-linked immunosorbent assay (ELISA) that overcame this barrier by coupling a duo of LH antibodies effective in accurately measuring LH in 4-µL whole-blood aliquots. To address the unavailability of the original detection antibody, AFP240580Rb, we validated a replacement detection antibody, biotinylated-5303 SPRN-5, to be used within the established ELISA. This modified LH ELISA demonstrated a minimum detection limit of 0.0028 ng/mL and a limit of quantification of 0.0333 ng/mL or 0.0666 ng/mL in diluted whole-blood samples of volume 6.4 µL (1:10) or 3.2 µL (1:20), respectively. Detection antibody 5303 SPRN-5 demonstrated parallelism, high precision, and accuracy across the standard curve. LH concentrations in comparison assays, using either 5303 SPRN-5 or AFP240580Rb, were highly correlated (R2 = 0.9829) and demonstrated LH pulse profiles from gonadectomized mice that were nearly superimposable. Pulsatile LH secretion was demonstrated in gonad-intact males and diestrous females and basal LH levels measured with 5303 SPRN-5 were approximately 5-fold higher than the limit of quantification. In addition, we document utility of this new LH ELISA to accurately measure LH in whole blood or serum across multiple sampling sites, as well as in pituitary extracts, LβT2 cells, or media. In summary, the modified LH ELISA described here is highly effective in measuring LH across a range of sample types and small volumes in mice.

Watt-level, green-pumped optical parametric oscillator based on periodically poled potassium titanyl phosphate with high extraction efficiency

We report a compact, efficient optical parametric oscillator (OPO) based on a periodically poled potassium titanyl phosphate (PPKTP) crystal pumped by a 532 nm laser, which generated 1.51 W of average power at the signal wavelength of 709 nm with the pulse duration of ∼ 1.0 ns. The extraction efficiency was up to 59%. To the best of our knowledge, this is the first report on Watt-level green-pumped PPKTP-based singly resonant oscillator OPO (SRO-OPO). The precise build-up time of OPO was determined to be 1.6 ns benefitting from the characteristic of twin-peak pulse profile of pump beam. The spectrum width of the idler was also measured to be 4.2 nm with the central wavelength of 2134 nm at 0.2 nm spectral resolution of optical spectrum analyzer. In addition, the beam quality of M 2 < 1.9 of generated signal exhibits a good consistency with M 2 < 1.5 for the pump source.

Sub-second periodicity in a fast radio burst.

Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that are visible at distances of billions of light years1. The nature of their progenitors and their emission mechanism remain open astrophysical questions2. Here we report the detection of the multicomponent FRB 20191221A and the identification of a periodic separation of 216.8(1) ms between its components, with a significance of 6.5σ. The long (roughly 3 s) duration and nine or more components forming the pulse profile make this source an outlier in the FRB population. Such short periodicity provides strong evidence for a neutron-star origin of the event. Moreover, our detection favours emission arising from the neutron-star magnetosphere3,4, as opposed to emission regions located further away from the star, as predicted by some models5.

Arecibo and FAST timing follow-up of 12 millisecond pulsars discovered in Commensal Radio Astronomy FAST Survey

ABSTRACT We report the phase-connected timing ephemeris, polarization pulse profiles, Faraday rotation measurements, and Rotating-Vector-Model (RVM) fitting results of 12 millisecond pulsars (MSPs) discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the Commensal Radio Astronomy FAST survey (CRAFTS). The timing campaigns were carried out with FAST and Arecibo over 3 yr. 11 of the 12 pulsars are in neutron star–white dwarf binary systems, with orbital periods between 2.4 and 100 d. 10 of them have spin periods, companion masses, and orbital eccentricities that are consistent with the theoretical expectations for MSP–Helium white dwarf (He WD) systems. The last binary pulsar (PSR J1912−0952) has a significantly smaller spin frequency and a smaller companion mass, the latter could be caused by a low orbital inclination for the system. Its orbital period of 29 d is well within the range of orbital periods where some MSP–He WD systems have shown anomalous eccentricities, however, the eccentricity of PSR J1912−0952 is typical of what one finds for the remaining MSP–He WD systems.

Revisiting the 1899 earthquake series using integrative geophysical analysis in Yakutat Bay, Alaska, USA

AbstractA series of large earthquakes in 1899 affected southeastern Alaska near Yakutat and Disenchantment Bays. The largest of the series, a MW 8.2 event on 10 September 1899, generated an ~12-m-high tsunami and as much as 14.4 m of coseismic uplift in Yakutat Bay, the largest coseismic uplift ever measured. Several complex fault systems in the area are associated with the Yakutat terrane collision with North America and the termination of the Fairweather strike-slip system, but because faults local to Yakutat Bay have been incompletely or poorly mapped, it is unclear which fault system(s) ruptured during the 10 September 1899 event. Using marine geophysical data collected in August 2012, we provide an improved tectonic framework for the Yakutat area, which advances our understanding of earthquake hazards. We combined 153 line km of 2012 high-resolution multichannel seismic (MCS) reflection data with compressed high-intensity radar pulse (Chirp) profiles, basin-scale MCS data, 2018 seafloor bathymetry, published geodetic models and thermochronology data, and previous measurements of coseismic uplift to better constrain fault geometry and subsurface structure in the Yakutat Bay area. We did not observe any active or concealed faults crossing Yakutat Bay in our high-resolution data, requiring faults to be located entirely onshore or nearshore. We interpreted onshore faults east of Yakutat Bay to be associated with the transpressional termination of the Fairweather fault system, forming a series of splay faults that exhibit a horsetail geometry. Thrust and reverse faults on the west side of the bay are related to Yakutat terrane underthrusting and collision with North America. Our results include an updated fault map, structural model of Yakutat Bay, and quantitative assessment of uncertainties for legacy geologic coseismic uplift measurements. Additionally, our results indicate the 10 September 1899 rupture was possibly related to stress loading from the earlier Yakutat terrane underthrusting event of 4 September 1899, with the majority of 10 September coseismic slip occurring on the Esker Creek system on the northwest side of Yakutat Bay. Limited (~2 m) coseismic or postseismic slip associated with the 1899 events occurred on faults located east of Yakutat Bay.

Ultra-wide Bandwidth Observations of 19 Pulsars with Parkes Telescope

Flux densities are basic observation parameters to describe pulsars. In the most updated pulsar catalog, 24% of the listed radio pulsars have no flux density measurement at any frequency. Here, we report the first flux density measurements, spectral indices, pulse profiles, and correlations of the spectral index with pulsar parameters for 19 pulsars employing the Ultra-Wideband Low receiver system installed on the Parkes radio telescope. The results for spectral indices of 17 pulsars are in the range between −0.6 and −3.10. The polarization profiles of thirteen pulsars are shown. There is a moderate correlation between the spectral index and spin frequency. For most pulsars detected, the signal-to-noise ratio of pulse profile is not high, so DM, Faraday rotation measure, and polarization cannot be determined precisely. Twenty-nine pulsars were not detected in our observations. We discuss the possible explanations for why these pulsars were not detected.

Spectral and timing analysis of BeXRB eRASSU J050810.4–660653 recently discovered in the Large Magellanic Cloud (LMC)

ABSTRACT We have studied the Be/X-ray binary (BeXRB) pulsar eRASSU J050810.4–660653 recently discovered in the Large Magellanic Cloud (LMC). Timing and spectral features of the source have been discussed in detail using NuSTAR and XMM–Newton observations. Coherent pulsation of the source was detected at ∼40.578 ± 0.001 s using NuSTAR observation. We analysed pulse profiles of the source in different energy bands using NuSTAR and XMM–Newton data. The pulse-profile evolved with time but was generally suggestive of a pencil-beam dominated pattern, which combined with the measured luminosity, indicates that the source may be accreting in the sub-critical regime. The pulse fraction follows a linearly increasing trend with photon energy and is anticorrelated with luminosity. In the 1-yr interval between the XMM and NuSTAR observations, the pulse period shortened by 0.021 s which could be consistent with spin-up or orbital Doppler effect. The average flux of the source in (3–50) keV energy range is found to be $\sim 5.56 \times 10^{-11}\, {\rm erg}\, {\rm cm}^{-2}\, \mathrm{s}^{-1}$ and the corresponding luminosity is $\sim 1.66 \times 10^{37}\, {\rm erg}\, \mathrm{s}^{-1}$. The variation of spectral parameters with pulse phase is studied using phase resolved spectroscopy which reveals that the observed photon index becomes harder with increasing flux.

Nutritional and Food Composition Survey of Major Pulses Toward Healthy, Sustainable, and Biofortified Diets

The world's food demand is increasing rapidly due to fast population growth that has posed a challenge to meeting the requirements of nutritionally balanced diets. Pulses could play a major role in the human diet to combat these challenges and provide nutritional and physiological benefits. Pulses such as chickpeas, green gram, peas, horse gram, beans, lentils, black gram, etc., are rich sources of protein (190–260 g kg−1), carbohydrates (600–630 g kg−1), dietary fibers, and bioactive compounds. There are many health benefits of phytochemicals present in pulses, like flavonoids, phenolics, tannins, phytates, saponins, lectins, oxalates, phytosterols peptides, and enzyme inhibitors. Some of them have anti-inflammatory, anti-ulcerative, anti-microbial, and anti-cancer effects. Along with these, pulses are also rich in vitamins and minerals. In this review, we highlight the potential role of pulses in global food systems and diets, their nutritional value, health benefits, and prospects for biofortification of major pulses. The food composition databases with respect to pulses, effect of processing techniques, and approaches for improvement of nutritional profile of pulses are elaborated.

Polarimetric Observations of PSR J0614+2229 and PSR J1938+2213 Using FAST

We presented observations of PSRs J0614+2229 and J1938+2213 using the Five-hundred-meter Aperture Spherical radio Telescope. PSR J0614+2229 shows two distinct emission states, in which the emission of state A occurs earlier than that of state B in longitude. The phase offset between the average pulse profile peaks of the two states is about 1.°05. The polarization properties of the average pulse profile of the two states are different with different linear position angle swings. We found that the emission becomes brighter during the transition between the two states, which has never been seen in other mode-changing pulsars before. PSR J1938+2213 appears to consist of a weak emission state superposed by brighter burst emissions. The weak state is always present and the energy of the strongest pulse in the burst state is about 57 times larger than that of the average pulse energy. The polarization properties of the two states are also different, and orthogonal polarization modes can be seen only in the burst state, rather than both states. Our results suggest that, for the two pulsars, the emissions of the two states may be generated in different regions in the pulsar magnetosphere.