Conventional Pulse Shaping Research Articles

Reducing Leakage of Single-Qubit Gates for Superconducting Quantum Processors Using Analytical Control Pulse Envelopes

Improving the speed and fidelity of quantum logic gates is essential to reach quantum advantage with future quantum computers. However, fast logic gates lead to increased leakage errors in superconducting quantum processors based on qubits with low anharmonicity, such as transmons. To reduce leakage errors, we propose and experimentally demonstrate two new analytical methods, Fourier ansatz spectrum tuning derivative removal by adiabatic gate (FAST DRAG) and higher-derivative (HD) DRAG, both of which enable shaping single-qubit control pulses in the frequency domain to achieve stronger suppression of leakage transitions compared to previously demonstrated pulse shapes. Using the new methods to suppress the ef transition of a transmon qubit with an anharmonicity of −212 MHz, we implement RX(π/2) gates achieving a leakage error below 3.0×10−5 down to a gate duration of 6.25 ns without the need for iterative closed-loop optimization. The obtained leakage error represents a 20-fold reduction in leakage compared to a conventional cosine DRAG pulse. Employing the FAST DRAG method, we further achieve an error per gate of (1.56±0.07)×10−4 at a 7.9-ns gate duration, outperforming conventional pulse shapes both in terms of error and gate speed. Furthermore, we study error-amplifying measurements for the characterization of temporal microwave control-pulse distortions, and demonstrate that non-Markovian coherent errors caused by such distortions may be a significant source of error for sub-10-ns single-qubit gates unless corrected using predistortion. Published by the American Physical Society 2024

Neutron detection in mixed short-pulsed fields with intense photon flashes for LINAC-based active interrogation applications

High-energy photon interrogation has established itself as a valuable tool for detecting special nuclear materials and characterizing nuclear waste. Previous research predominantly uses around 9-MV linear electron accelerators (LINACs) as photon sources and limited exploration has been conducted on the use of organic scintillators to determine the energy deposited in the detector and to separate photon and neutron radiation, crucial when the photon interrogation is based on the measurement of the neutron emission. The challenge arises from the intense photon flux typically produced by electron accelerators, resulting in issues such as pulse pile-up, detector saturation, and a suboptimal signal-to-background ratio. This study aims to extend the applicability of the conventional Active Photon Interrogation (API) techniques by introducing a novel method enabling the detection, in addition to nuclear materials, of light elements—specifically nitrogen, oxygen, and carbon—known to be present in conventional explosives, narcotics, and chemical weapons. The approach relies on active photon interrogation at high energies above 12 MeV, coupled with photoneutron spectrometry. Using a 22-MV electron LINAC, pulse shape discrimination with an organic liquid scintillator demonstrated promising performance. Our results highlight that the conventional pulse shape discrimination capabilities and rapid time-scale operation of organic scintillators enable the detection of fast neutrons from (γ,Xn) reactions, even in a mixed short-pulsed field of photon and neutron radiation with intense photon flashes. This exploration of the initial experimental aspects of photoneutron detection induced by high-energy photons establishes a foundation for a promising new method for the detection of illicit materials.

Spectrally Efficient Pulse Shaping for Beamspace Space Shift Keying in Single-RF ESPAR Systems

A novel spectrally efficient pulse shaping technique for space shift keying (SSK) in single radio frequency (single-RF) antenna systems is proposed. This technique is important since a key issue often overlooked in most single-RF systems, including SSK, is pulse shaping. The proposed pulse shaping technique is based on using an electronically steerable parasitic array radiator (ESPAR). It can avoid the bandwidth expansion arising from switching in SSK while enhancing spectral efficiency (SE) compared to conventional time-limited pulse shaping. In the proposed approach, we pulse shape the parasitic loads of the antennas in the ESPAR by using pulse shaped baseband control voltages to continuously vary the parasitic loads. This is enabled by developing an approximate linear mapping from the baseband control voltages to the ESPAR element currents. Simulation results of the proposed technique are provided, including the continuous-time ESPAR current and its power spectrum density, adjacent channel power ratio, symbol error rate (SER), SE, and energy efficiency (EE). It is shown that the proposed technique can perform spectrally efficient pulse shaping for beamspace SSK and achieve higher SE and EE than time-limited pulse shaping while maintaining the same SER.

High-speed optical pulse shaping based on programmable lithium niobate spatial light modulators.

Pulse shaping plays a key role in various applications of ultrafast lasers, such as optical communications, laser micromachining, microscopy, and quantum coherent control. Conventional pulse shaping devices based on liquid crystal spatial light modulators (LCSLMs) or digital micromirror devices (DMDs) only have the shaping speed of several hertz to kilohertz, which is not suitable for applications requiring a high-speed response. Here, we demonstrate a high-speed programmable lithium niobate spatial light modulator (LNSLM) with 128 individual modulation channels and a modulation speed that can reach 1 MHz. Then we establish a high-speed LNSLM-based Fourier-transform (FT) pulse shaper to realize high-speed pulse shaping, and the update rate can reach 350 kHz, only limited by the electric circuit. The proposed high-speed pulse shaper scheme opens new avenues for future applications of ultrafast science, such as microscopic imaging, interaction between light and matter, and spectroscopy.

High-stable and reconfigurable photonic generation of radio-frequency arbitrary waveforms with multi-tone inputs

Conventional temporal pulse shaping (TPS) for radio frequency (RF) arbitrary waveform generation (RF AWG) based on the Fourier transform relation between the input–output waveform pair requires the electronic AWG to generate RF input signal, which greatly limits the output waveform diversity due to the relative low sampling rate and bit resolution of electronic AWG, i.e., high-fidelity square waveforms are hard to be achieved since high-resolution broadband Sinc input signals are difficult to be generated by current commercial electronic AWGs. The approaches based on TPS with phase modulation incorporating with iterative algorithms can relatively improve the waveform diversity by applying the optimal phase information. However, time-consuming iterative algorithms significantly restrict the waveform reconfigurability, i.e., desired RF waveforms cannot be generated in real-time. We propose a novel high-stable and reconfigurable RF AWG scheme with multi-tone inputs, which aims to improve the output waveform diversity with simple manipulation and high stability. In our design, any desired RF waveform can be achieved in real-time by simply adjusting the power values of multi-tone inputs. A proof-of-concept experiment was implemented, which fully verified the feasibility of the approach. The system performance in terms of output waveform stability was investigated in detail. As no electronic AWG is employed and no iterative algorithms are required, the proposed design provides a promising solution for high-performance reconfigurable photonic-based RF arbitrary waveforms generation.

Experimental Verification of Pulse Shaping in Elastic Metamaterials Under Impact Excitation

Abstract We present experimental verification of pulse shaping in elastic metamaterials together with a procedure to design, fabricate, and verify metamaterial pulse shapers under impact excitation. The split Hopkinson pressure bar (SHPB) test, a fundamental dynamic test introduced more than 70 years ago, often incorporates pulse shaping as a means to alter a stress wave, providing the primary motivation for the presented study. Elastic metamaterials hold promise for enhancing conventional pulse shaping abilities and improving capabilities of the SHPB test. We first design the pulse shaper by numerically optimizing its response using finite element analysis. The pulse shaper consists of repeated unit cells based on a combination of a phononic crystal and a local resonator. Then, we fabricate and test pulse shaper candidates to validate the procedural efficacy. An iterative element corrects inaccuracies in input force and material properties and allows convergence on an appropriate pulse shaper. We carry out this procedure by designing pulse shapers fabricated from 3D-printed polylactic acid (PLA) to achieve an extended dwell acceleration pulse shape. In experimental impact tests, the procedure results in rise, dwell, and fall behaviors comparable to that predicted, effectively confirming the efficacy of the presented procedure and verifying the performance of metamaterial-based pulse shapers.

C-band 120-Gb/s PAM-4 transmissions over a 100-km dispersion-uncompensated SSMF using joint combined pulse shaping and low-complexity nonlinear equalization.

In C-band intensity modulation and direct detection (IM/DD) systems, the frequency-dependent power fading induced by chromatic dispersion (CD) and square-law detection limits the transmission capacity and distance, especially for beyond 100-Gb/s transmissions over a 100-km dispersion-uncompensated link. To reach this goal, we propose a scheme of nonlinear pre-distortion, novel, to the best of our knowledge, combined pulse shaping, and post nonlinear equalization for four-level pulse amplitude modulation (PAM-4)-based IM/DD systems. At the transmitter, the nonlinear pre-distortion is used to generate unequally spaced PAM-4 symbols for pre-compensating the nonlinearities. While the novel pulse shaping, simply shaped by the linear combination of two inter-symbol interference (ISI)-free pulses, alters the frequency-domain power distribution of the PAM-4 signal and results in performance improvement. At the receiver, low-complexity post nonlinear equalization using an absolute-term based nonlinear equalizer with weight sharing (AT-NLE-WS) is performed to eliminate CD-induced power fading and residual nonlinear impairments. With the cooperation of these techniques, record 120-Gb/s PAM-4 signals are successfully transmitted over a 100-km standard single-mode fiber (SSMF) with the measured bit error ratio (BER) below 3.8 × 10-3, achieving >9% improvement of system capacity in comparison with the conventional pulse shaping schemes.

Characterization of the neutron/[formula omitted]-ray discrimination performance in an EJ-301 liquid scintillator for application to prompt fission neutron spectrum measurements at CSNS

The FIssion Neutron spectrum Detector Array (FINDA) has been designed for measurement of prompt fission neutron spectrum on the Back-n beam line at the China Spallation Neutron Source (CSNS). In order to test the neutron-γ discrimination performance of the EJ301 scintillator that will be used as a detector unit in the FINDA, a comparative study using three conventional digital pulse shape discrimination (PSD) methods has been carried out. An Am–Be source has been used to generate the mixed neutron-γ radiation and the waveform data has been obtained with a fast digitizer. Pulse interpolation, baseline restoration and pulses pile-up rejection have been applied for digital pulse processing. Charge comparison (CC) method and simplified charge comparison(SCC) method show a better capability of neutron-γ discrimination than rise time comparison(RTC) method over the entire energy range. Rise time comparison method needs a very fast digitizer or pulse interpolation to improve the PSD ability. The analysis of neutron-γ discrimination performance of the EJ301 scintillator provides a strong technical support for fast neutron measurement using the FINDA at CSNS.

Temporal shaping of narrow-band picosecond pulses via noncolinear sum-frequency mixing of dispersion-controlled pulses

A long-sought-after goal for photocathode electron sources has been to improve performance by temporally shaping the incident excitation laser pulse. The narrow bandwidth, short wavelength, and picosecond pulse duration make it challenging to employ conventional spectral pulse shaping techniques. We present a novel and efficient intensity-envelope shaping technique achieved during nonlinear upconversion through opposite-chirp sum-frequency mixing. We also present a numerical case study of the linac coherent light source-II photoinjector where transverse electron emittance is improved by at least 25%.

Measurement of light output response in scintillator based neutron detectors using quasi-monoenergetic neutrons

Conventional liquid scintillator (BC501A) and pulse shape discrimination capable plastic scintillator (EJ-299-33A) based detector of dimension; 5 inch diameter and 5 inch long, have been used to study pulse height response for quasi-monoenergetic neutrons of energy in the range 3 to 15 MeV generated using 7Li(p,n)7Be reaction. Scintillation light output of plastic scintillator having pulse shape discrimination property is found to be 75% of the liquid scintillator at neutron energy (maximum recoil proton energy) of 3 MeV which improves with the increase in energy. Functional dependence of the scintillation light output in terms of recoil protons energy has been determined for the liquid and the plastic scintillator detectors for neutron energy in the range 3 to 15 MeV. This functional dependences were used in the Geant4 simulation to calculate the pulse height responses at several neutron energies.

Systematic Evaluation of DBS Parameters in the Hemi-Parkinsonian Rat Model.

Electrical stimulation of the subthalamic nucleus (STN) is clinically employed to ameliorate several symptoms of manifest Parkinson’s Disease (PD). Stimulation parameters utilized by chronically implanted pulse generators comprise biphasic rectangular short (60–100 μs) pulses with a repetition frequency between 130 and 180 Hz. A better insight into the effect of electrical stimulation parameters could potentially reveal new possibilities for the improvement of deep brain stimulation (DBS) as a treatment. To this end, we employed single-sided 6-hydroxidopamine (6-OHDA) lesioning of the medial forebrain bundle (MFB) in rats to systematically investigate alternative stimulation parameters. These hemi-parkinsonian (hemi-PD) rats underwent individualized, ipsilateral electrical stimulation to the STN of the lesioned hemisphere, while the transiently induced contralateral rotational behavior was quantified to assess the effect of DBS parameter variations. The number of induced rotations during 30 s of stimulation was strongly correlated with the amplitude of the stimulation pulses. Despite a general linear relation between DBS frequency and rotational characteristics, a plateau effect was observed in the rotation count throughout the clinically used frequency range. Alternative waveforms to the conventional biphasic rectangular (Rect) pulse shapes [Triangular (Tri), Sinusoidal (Sine), and Sawtooth (Lin.Dec.)] required higher charges per phase to display similar behavior in rats as compared to the conventional pulse shape. The Euclidean Distance (ED) was used to quantify similarities between different angular trajectories. Overall, our study confirmed that the effect of different amplitude and frequency parameters of STN-DBS in the hemi-PD rat model was similar to those in human PD patients. This shows that induced contralateral rotation is a valuable readout in testing stimulation parameters. Our study supports the call for more pre-clinical studies using this measurement to assess the effect of other DBS parameters such as pulse-width and interphase intervals.

Dual Pulse Shaping Transmission and Equalization for High-Speed Wideband Wireless Communication Systems

Analog-to-digital and digital-to-analog conversion devices for signals with very large bandwidth are not always available due to technical or cost issues. This limits the realization of very high data-rate digital communication systems. In this paper, we propose a dual pulse shaping (DPS) transmission scheme, which can achieve full Nyquist rate transmission with only a half of the sampling rate for each of the two data streams. Two classes of ideal complementary Nyquist pulses are formulated assuming raised-cosine (RC) pulse shaping. The condition for cross-symbol interference (CSI) free transmission is derived and validated for the proposed pulses. Structures of the DPS transmitter and receiver are described and low-complexity equalization techniques tailored to DPS are proposed. With DPS, a millimeter wave system with commercially available and affordable data conversion devices is exemplified for achieving high-speed low-cost wireless communications. Simulation results with two sets of practical dual spectral shaping pulses are provided. The results verify the effectiveness of the proposed scheme, with comparison to the benchmark conventional Nyquist pulse shaping system.

A new positron-gamma discriminating phoswich detector based on wavelength discrimination (WLD)

Abstract The intra-operative positron probe, used in the field of nuclear medicine, has been developed to localize positron ( β +) emitted from positron emission tomography (PET) radiopharmaceuticals by selectively detecting β + particles in the presence of background gamma ( γ ) radiation. In this research, we propose a new method for real-time discrimination of radiation types in a mixed radiation field of positron ( β +) and gamma ( γ ) radiation, based on simple electronics and signal processing. Scintillators often have distinct emission wavelengths, and this method exploits the scintillator’s emission wavelength, as opposed to conventional pulse shape discrimination (PSD) approach. In this study, we used a two-layer phoswich detector consisting of europium-doped calcium fluoride (CaF2(Eu)) and Ce 3 + doped Lu3Al5O12 (Ce:LuAG), with dimensions of 3 mm × 3 mm × 0.5 mm and 3 mm × 3 mm × 10 mm, and emission wavelengths of 380–450 nm and 480–700 nm respectively. This phoswich detector was placed at the center of two adjacent optical filters (one short pass and one long pass filter), and each coupled to a silicon photomultiplier (SiPM). The optical filters are used for directing a specific scintillator photon wavelength to its corresponding SiPM for identification of the crystal of interaction. This proposed method allows us to realize a high sensitivity (true positive rate) positron probe, that can also double as a γ -probe, while simplifying readout electronic and signal processing. A Na-22 positron( β +) source and Cs-137 γ -source were used to validate the proposed approach experimentally. Results indicate the possibility of discriminating β + and γ -radiations in real time, with an excellent γ -rejection ratio exceeding 99.9 %.

Beam modulation: A novel ToF-technique for high resolution diffraction at the Beamline for European Materials Engineering Research (BEER)

The Beamline for European Materials Engineering Research (BEER) is under construction at the European Spallation Source (ESS) in Lund, Sweden. A basic requirement on BEER is to make best use of the long ESS pulse (2.86 ms) for engineering investigations. High-resolution diffraction, however, demands timing resolution up to 0.1% corresponding to a pulse length down to about 70 μs for the case of thermal neutrons (λ∼ 1.8 Å). Such timing resolution can be achieved by pulse shaping techniques cutting a short section out of the long pulse, and thus paying for resolution by strong loss of intensity. In contrast to this, BEER proposes a novel operation mode called pulse modulation technique based on a new chopper design, which extracts several short pulses out of the long ESS pulse, and hence leads to a remarkable gain of intensity compared to nowadays existing conventional pulse shaping techniques. The potential of the new technique can be used with full advantage for investigating strains and textures of highly symmetric materials. Due to its instrument design and the high brilliance of the ESS pulse, BEER is expected to become the European flagship for engineering research for strain mapping and texture analysis.

A Retention-Aware Multilevel Cell Phase Change Memory Program Evaluation Metric

Multilevel cell (MLC) phase change memory (PCM) offers many potential advantages in scalability, bit-alterability, non-volatility, and high program speed. While many program approaches had been proposed, they were usually evaluated in energy, delay, or energy-delay product (EDP). These metrics, however, often overlook the data integrity maintenance (DIM) overhead caused by the resistance drift (R-drift) phenomenon in the MLC PCM. This letter proposes a program-maintenance (PM) metric, which is a modified EDP metric with DIM consideration. Furthermore, we evaluated the PM metric of various pulse shapes in iterative program–verify scheme. From the measured data of a 128M-cell MLC PCM chip, we showed that the PM metric of optimized pulse shape is better than those of the conventional SET and RESET pulse shapes up to 86.7%.

Rapid short-pulse sequences enhance the spatiotemporal uniformity of acoustically driven microbubble activity during flow conditions.

Despite the promise of microbubble-mediated focused ultrasound therapies, in vivo findings have revealed over-treated and under-treated regions distributed throughout the focal volume. This poor distribution cannot be improved by conventional pulse shapes and sequences, due to their limited ability to control acoustic cavitation dynamics within the ultrasonic focus. This paper describes the design of a rapid short-pulse (RaSP) sequence which is comprised of short pulses separated by μs off-time intervals. Improved acoustic cavitation distribution was based on the hypothesis that microbubbles can freely move during the pulse off-times. Flowing SonoVue® microbubbles (flow velocity: 10 mm/s) were sonicated with a 0.5 MHz focused ultrasound transducer using RaSP sequences (peak-rarefactional pressures: 146-900 kPa, pulse repetition frequency: 1.25 kHz, and pulse lengths: 5-50 cycles). The distribution of cavitation activity was evaluated using passive acoustic mapping. RaSP sequences generated uniform distributions within the focus in contrast to long pulses (50 000 cycles) that produced non-uniform distributions. Fast microbubble destruction occurred for long pulses, whereas microbubble activity was sustained for longer durations for shorter pulses. High-speed microscopy revealed increased mobility in the direction of flow during RaSP sonication. In conclusion, RaSP sequences produced spatiotemporally uniform cavitation distributions and could result in efficient therapies by spreading cavitation throughout the treatment area.

Microring-based reconfigurable optical pulse shaper

Based on the amplitude and phase-shift characteristics of microring (MR) resonator, a novel reconfigurable optical pulse shaping approach is proposed. By adjusting the variable attenuators to set the proper relative weights, a transform-limited Gaussian input optical pulse can be shaped into flat-top waveform or triangular waveform flexibly. In contrast to the conventional pulse shaping method, only positive real relative weights are used in the proposed pulse shaper, which not only facilitates the reconfigurable adjustment, but also is robust to the wavelength detuning and temporal duration variations of the input pulse.

Solitonic Pulse Generation for Optical Wireless Communication Using Microring Resonator

In this paper, a system of microring resonator (MRR) is presented to generate picosecond solitonic pulse for optical wireless communication. When a Gaussian pulse is circulated inside the first ring in the proposed system, chaotic signals are generated because of the nonlinear Kerr effect. Then next MRR in the system filters the chaotic signals and the solitonic pulse shape is generated. Then an add/drop filter is used to tune soliton pulses where the accurate FWHM of 130 ps and FSR of 3.7 ns with power of 2.45 W will be filtered. The performance of the proposed solitonic pulse shape is analysed in terms of bit error rate (BER). During the analysis, the proposed pulse shape is compared against the conventional rectangular and Gaussian pulse shapes in an optical wireless communication system (OWC) with an additive white Gaussian noise (AWGN) channel. Results show the superiority of the proposed solitonic pulse shape for OWC.

A Side-Impact Torsion Kolsky Bar

A novel variant of the torsion Kolsky bar which utilizes a side-impact mechanism to achieve a more tractable torsional pulse-shaping technique has been developed. Integration of components from the well-established compression Kolsky bar experimental technique with the torsion Kolsky bar method allows conventional compression techniques to be applied to a torsion experiment. Typical considerations involving striker length, striker velocity, and pulse-shaper geometry, which are used to generate a desired waveform in a compression bar, can be directly applied to the side-impact torsion technique to control pulse length, rotational velocity, and waveform profile. The results from experiments show that the apparatus successfully generates torsional waveforms using conventional pulse shaping techniques.

Exploiting flow to control the in vitro spatiotemporal distribution of microbubble-seeded acoustic cavitation activity in ultrasound therapy

Focused ultrasound and microbubbles have been extensively used to generate therapeutic bioeffects. Despite encouraging in vivo results, there remains poor control of the magnitude and spatial distribution of these bioeffects due to the limited ability of conventional pulse shapes and sequences to control cavitation dynamics. Thus current techniques are restricted by an efficacy-safety trade-off. The primary aim of the present study was to incorporate the presence of flow in the design of new short pulse sequences, which can more uniformly distribute the cavitation activity. Microbubbles flowing (fluid velocity: 10 mm s−1) through a 300 μm tube were sonicated with a focused 0.5 MHz transducer while acoustic emissions were captured with an inserted focused 7.5 MHz passive cavitation detector. The two foci were co-axially aligned and their focal points were overlapped. Whereas conventional sequences are composed of a long burst (>10 000 cycles) emitted at a low burst repetition frequency (<10 Hz), we decomposed this burst into short pulses by adding intervals to facilitate inter-pulse microbubble movement. To evaluate how this sequence influenced cavitation distribution, we emitted short pulses (peak-rarefactional pressure (PRP): 40–366 kPa, pulse length (PL): 5–25 cycles) at high pulse repetition frequencies (PRF: 0.625–10 kHz) for a burst length of 100 ms. Increased cavitation persistence, implied by the duration of the microbubble acoustic emissions, was a measure of improved distribution due to the presence of flow. Sonication at lower acoustic pressures, longer pulse intervals and lower PLs improved the spatial distribution of cavitation. Furthermore, spectral analysis of the microbubble emissions revealed that the improvement at low pressures is due to persisting stable cavitation. In conclusion, new short-pulse sequences were shown to improve spatiotemporal control of acoustic cavitation dynamics during physiologically relevant flow. This could lead to adjustable distribution of the generated in vivo bioeffect and therefore efficient and safe treatment of a wide range of pathologies.