Control Pulse Research Articles

Quantum sensing of control errors in three-level systems by coherent control techniques

Quantum coherent control of a quantum system with high-fidelity is rather important in quantum computation and quantum information processing. There are many control techniques to reach these targets, such as resonant excitation, adiabatic passages, shortcuts to adiabaticity, and so on. However, for a single pulse to realize population transfer, the external tiny error has a trivial influence on the final population. The repeated application of the same pulse will greatly amplify the error effect, making it easy to be detected. Here, we propose to measure small control errors in three-level quantum systems by coherent amplification of their effects, using several coherent control techniques. For the two types of Hamiltonian with SU(2) dynamic symmetry, we analyze how the fidelity of population transfer are affected by Rabi frequencies fluctuation and static detuning deviation, based on the pulse sequence with alternating and same phases, respectively. It is found that the sensitivity of detecting these errors can be effectively amplified by the control pulse sequences. Furthermore, we discuss the efficiency of sensing the two errors with these control techniques by comparing the full width at half maximum of the population profiles. The results provide an accurate and reliable way for sensing the weak error in three-level quantum systems by applying repeatedly the coherent control pulse.

A novel PWM technique for reduced switch count multilevel inverter in renewable power applications

This paper described a novel pulse width modulation (PWM) technique in reduced switch count multilevel inverter (MLI) for renewable power applications. Therefore, the proposed technique finds a better solution in the multilevel inverters used for improving power quality, efficiency and reduction of switching and conduction losses. It produces a smoother sinusoidal output waveform with reduced total harmonic distortion (THD) using different modulation technique. The novel PWM technique consists of nearest level control (NLC) and level shift pulse width modulation (LSPWM). Normally semiconducting devices are added for increasing number of levels. It affects the power quality and efficiency due to losses. In this work, MLI topology with reduced number of switches count for NLC and LSPWM is presented. The single-phase and three-phase inverter configuration is used in proposed mythology. Detailed simulation results for 7-level inverter of single and three-phase inverters are presented in this paper. It is observed that NLC method is better efficiency and reduced THD than LSPWM for better utilization in renewable power applications.

Coherent control of symmetry breaking in transverse-field Ising chains using few-cycle pulses

Abstract Coherent control of quantum systems with phase-stable pulses offers enticing new opportunities for lightwave electronics. Here we extend this approach to many-body systems with spin degrees of freedom, demonstrating that a single few-cycle control pulse can create a sizable population asymmetry between the two degenerate polar ground states of the Ising model. This opens a route for femtosecond-scale data processing and storage, allowing one to control the final ground state of a correlated system in an all-optical way.

Experimental quantum end-to-end learning on a superconducting processor

Machine learning can be enhanced by a quantum computer via its inherent quantum parallelism. In the pursuit of quantum advantages for machine learning with noisy intermediate-scale quantum devices, it was proposed that the learning model can be designed in an end-to-end fashion, i.e., the quantum ansatz is parameterized by directly manipulable control pulses without circuit design and compilation. Such gate-free models are hardware friendly and can fully exploit limited quantum resources. Here, we report the experimental realization of quantum end-to-end machine learning on a superconducting processor. The trained model can achieve 98% recognition accuracy for two handwritten digits (via two qubits) and 89% for four digits (via three qubits) in the MNIST (Mixed National Institute of Standards and Technology) database. The experimental results exhibit the great potential of quantum end-to-end learning for resolving complex real-world tasks when more qubits are available.

Feed scheduling for time-dependent machining processes by optimization of bulk removal and NC blocks

Time-dependent processes such as CNC fluid jet polishing require feed-rate scheduling through deconvolution of a target removal profile and tool influence function. The dynamic constraints associated with the machine tool driving the process should be considered when solving this numerical problem. This research investigates how material bulk removal affects the scheduled feed-rate and acceleration both in the spatial and time domain, and proposes a method for matching exactly the maximum acceleration with the machine tool limit. Furthermore, the influence of CNC interpolator dynamics is investigated by means of the controller pulse response method. An optimization method for NC blocks is then proposed in order to achieve feed-rates that best match the intended profile. The benefit of bulk removal and NC blocks optimization is validated by fabrication, with and without optimization, of cylindrical Fresnel lenses. Both the shape accuracy and optical performance of the optimally fabricated lens are shown to substantially improve, suggesting that the proposed optimization method has strong potential for industrial application.

Saturable Purcell filter for circuit quantum electrodynamics

We consider a typical circuit QED setup where an artificial atom encodes a qubit and is dispersively coupled to a measurement resonator that in turn is coupled to a transmission line. We show theoretically that by placing another artificial atom in this transmission line to act as a filter, the Purcell decay of the qubit into the transmission line is suppressed. When strong control fields are applied in the transmission line, the filter is saturated and effectively switched off. Such a Purcell filtering capability permits both the control and measurement of the qubit using the single transmission line, while maintaining the long coherence time of the qubit in the absence of the control pulses. We show that high fidelity Pauli ${\ensuremath{\sigma}}_{x}$ gates on the qubit can be realized using simple pulse shapes. For devices that already use one transmission line both for control and measurement of the qubit, our paper provides a way to completely filter out the qubit frequency without removing the possibility of controlling the system. Further, combining the proposed filter with frequency multiplexing potentially enables both control and measurement of several qubits using a single Purcell-filtered transmission line. This will enhance the scalability of superconducting quantum processors by decreasing the number of the required transmission lines.

Methylprednisolone pulse therapy for critically ill patients with COVID-19: a cohort study.

The guidelines recommend the use of dexamethasone 6 mg or an equivalent dose in patients with coronavirus disease 2019 (COVID-19) who require supplemental oxygen. Given that the severity of COVID-19 varies, we investigated the effect of a pulse dose of corticosteroids on the clinical course of critically ill patients with COVID-19. This single-center, retrospective cohort study was conducted between September and December 2021, which was when the Delta variant of the COVID-19 virus was predominant. We evaluated the mortality and oxygenation of severe to critical COVID-19 cases between groups that received dexamethasone 6 mg for 10 days (control group) and methylprednisolone 250 mg/day for 3 days (pulse group). Among 44 patients, 14 and 30 patients were treated with control steroids and pulse steroids, respectively. There was no difference in disease severity, time from COVID-19 diagnosis to steroid administration, or use of remdesivir or antibacterial agents between the two groups. The pulse steroid group showed a significant improvement in oxygenation before and after steroid treatment (P<0.001) compared with the control steroid group (P=0.196). There was no difference in in-hospital mortality (P=0.186); however, the pulse steroid group had a lower mortality rate (23.3%) than the control steroid group (42.9%). There was a significant difference in the length of hospital stay between both two groups (P=0.039). Pulse steroids showed no mortality benefit but were associated with oxygenation improvement and shorter hospital stay than control steroids. Hyperglycemia should be carefully monitored with pulse steroids.

Composite pulses for optimal robust control in two-level systems

In this work, we put forward an approach of constructing the optimal composite pulse sequence for robust population transfer in two-level systems. This approach is quite universal and applicable to a variety of systems, because the modulation parameters of composite pulses are obtained by minimizing the homemade cost function rather than nullifying the error coefficients of the transition probability. Specifically, we design different forms of the cost function for implementing optimal robustness with respect to the single or multiple errors. When slightly adjusting the constraints of the cost function, this approach can be easily extended to achieve arbitrary population transfer. The numerical results demonstrate that the optimized sequences are immune from various systematic errors, allowing us to produce a broadening excitation range of the transition probability. Therefore, this work offers an optimal robust design for controlling quantum states in error-prone environments.

Universal Time-Dependent Control Scheme for Realizing Arbitrary Linear Bosonic Transformations.

We study the implementation of arbitrary excitation-conserving linear transformations between two sets of N stationary bosonic modes, which are connected through a photonic quantum channel. By controlling the individual couplings between the modes and the channel, an initial N-partite quantum state in register A can be released as a multiphoton wave packet and, successively, be reabsorbed in register B. Here we prove that there exists a set of control pulses that implement this transfer with arbitrarily high fidelity and, simultaneously, realize a prespecified N×N unitary transformation between the two sets of modes. Moreover, we provide a numerical algorithm for constructing these control pulses and discuss the scaling and robustness of this protocol in terms of several illustrative examples. By being purely control-based and not relying on any adaptations of the underlying hardware, the presented scheme is extremely flexible and can find widespread applications, for example, for boson-sampling experiments, multiqubit state transfer protocols, or in continuous-variable quantum computing architectures.

Load Voltage Control of a Wind Turbine-driven Three-phase Squirrel-Cage Induction Generator in an Islanded Microgrid

The intermittent nature of the wind resources and reactive power consumptions are major issues associated with squirrel cage induction generator wind power system when operated in an island microgrid mode. The resultant effect of these two issues are continuous fluctuations of load voltage which has adverse effects on electrical devices. This paper proposes a voltage regulation technique based on proportional controller and phase deposition sine pulse width modulation (PDSPWM) for the control of 5-level neutral point clamped multilevel inverter. The instantaneous voltage tracking strategy based on root mean square value of microgrid voltage was adopted to regulate and maintain the output load voltage at 400 𝑉𝑟𝑚𝑠 despite rotor fluctuations with wind speeds. The simulation was carried out in a MATLAB/SIMULINK environment and the performance of the control scheme was found to be excellent.

A Single-Coil Multi-Tapped PDM-Based Induction Heating System for Domestic Applications

The conventional heating system is inefficient as the major part of the heating coil lies out-side the vessel it is placed on. This research article proposes a new single-coil multi-tapped induction heating system. This novel induction heating system is facilitated by a half-bridge resonant converter controlled by zero-voltage switching (ZVS). The multi-tapping winding system ensures an effective heat transfer between the coil and the working vessel with the windings of the induction coil segmented to an equivalent size of the vessel. The pulse density modulation (PDM) scheme employed here as the control proves to be the most versatile one. The whole system is duly simulated for an 850 W IH setup in MATLAB Simulink and implemented as a hardware prototype using a half-bridge resonant converter. The control pulses are developed through the PDM in a PIC16F877A controller. The simulation and experimental results prove the credibility of the proposed induction heating (IH) scheme, and during heavy loading conditions, it outperforms the single-coil IH system by gaining an efficiency of 89.29%

Binary Control Pulse Optimization for Quantum Systems

Quantum control aims to manipulate quantum systems toward specific quantum states or desired operations. Designing highly accurate and effective control steps is vitally important to various quantum applications, including energy minimization and circuit compilation. In this paper we focus on discrete binary quantum control problems and apply different optimization algorithms and techniques to improve computational efficiency and solution quality. Specifically, we develop a generic model and extend it in several ways. We introduce a squared L2-penalty function to handle additional side constraints, to model requirements such as allowing at most one control to be active. We introduce a total variation (TV) regularizer to reduce the number of switches in the control. We modify the popular gradient ascent pulse engineering (GRAPE) algorithm, develop a new alternating direction method of multipliers (ADMM) algorithm to solve the continuous relaxation of the penalized model, and then apply rounding techniques to obtain binary control solutions. We propose a modified trust-region method to further improve the solutions. Our algorithms can obtain high-quality control results, as demonstrated by numerical studies on diverse quantum control examples.

DESIGN AND PERFORMANCE OF A 110 N ATTITUDE CONTROL THRUSTER FOR LUNAR MISSIONS

The design and development of an attitude control thruster, designated A110, developed for broad attitude control applications, including lunar landers, is described. The A110 thruster produces 110 N (25 lbf) of nominal thrust and in-excess of 305.5 s of specific impulse (I&lt;sub&gt;sp&lt;/sub&gt;) while operating on a fuel blend of 20&amp;#37; monomethylhydrazine-80&amp;#37; hydrazine (M20) with mixed oxides of nitrogen containing 3&amp;#37; nitric oxide (MON3) as the oxidizer. The injector and combustion chamber are additively manufactured with cobalt-chrome and niobium C103, respectively, to enable the rapid development required of the industry. The thruster is capable of response times of under 10 ms and currently produces a minimum impulse bit (MIB) of 0.436 N.s and has demonstrated operation in pulse-mode with a variety of duty cycles during development testing. These capabilities allow for the generation of precise pulses for accurate control of a lander. The testing of this thruster is used to evaluate steady-state and pulse-mode specific impulse, impulse repeatability, and combustion stability. The measured performance (i.e., specific impulse and characteristic velocity (C*), are compared with theoretical values. The capabilities demonstrated by the A110 thruster are applicable to a wide range of lunar lander missions and can be qualified for minor changes in thruster requirements for additional missions without the need for major design changes. This article is published with the permission of the authors granted to 3AF - Association A&amp;#233;ronautique et Astronautique de France (www.3AF.fr) organizer of the Space Propulsion International Conference.

A Chaotic Pulse Train Generator Based on Henon Map

The Henon map forms one of the most-studied two-dimensional discrete-time dynamical systems that exhibits chaotic behavior. The Henon map takes a point in the plane and maps it to a new point . In this paper, a chaotic pulse generator based on the chaotic Henon map is proposed. It consists of a Henon map function subcircuit to realize the Henon map and another subcircuit to perform the iterative operation. The Henon map subcircuit comprises operational amplifiers, multipliers, delay elements and resistors, whereas, the iterative subcircuit is implemented with a simple design that comprises of an edge forming circuit followed by a monostable multivibrator and a voltage controlled switch without the use of any clock control. The proposed design can be used to realize the Henon map and also to generate a chaotic pulse train, with a controllable time interval and pulse position. The proposed circuit is implemented and simulated using Multisim 13.0 and MATLAB R2019b. The chaotic nature of the generated pulse train and also the time interval between the consecutive pulses is verified by the calculation of its Lyapunov exponents.

High strain rate deformation of conductive materials with use of pulse magnetic fields

The study of metal deformation processes under extreme impacts is relevant due to the need to predict the behavior of materials in operational and critical modes using various deformation models. In this case, the key factor is to expand the range of experimentally determined/achievable parameters for their verification. The high energy density of the magnetic field and a reliable and simple technique for monitoring its parameters make it possible to use the magnetic pulse method of generating controlled pressure pulses of microsecond duration with an amplitude of ∼1 GPa. A classification of methods for high strain rate deformation of conductive materials by magnetic-pulse loading is carried out and features of magnetic-mechanical. An analysis of the experimental results showed the applicability of the magnetic-pulse method for studying plastic deformation processes with strain rates up to 104 1/s and more and the possibility to formulate requirements for the magnetic system and pulse current sources.

A systematic review of the effect of pulse waveform of controllable pulse parameter TMS devices on cortical excitability and neuroplasticity

A systematic review of the effect of pulse waveform of controllable pulse parameter TMS devices on cortical excitability and neuroplasticity

Modification of anode material VK8 by silicon for electric spark alloying of steel 35

Metal-ceramic coatings on steel 35 were obtained by the method of electric spark processing with different duration of control pulses, using a new electrode material WC—7.5 % Co—7.5 % Si for applying electric spark coatings on steel 35. It is shown that WC particles were deposited into the coating as a result of solid-phase transfer, which intensified with increasing discharge duration. The addition of silicon to WC—Co electrode materials can significantly reduce the coefficient of friction of the formed coatings. In general, the use of WC—Co—Si coatings can increase the heat resistance of steel up to 5 times, reduce the coefficient of friction of steel 35 to 47 %, and increase the wear resistance of its surface from 3 to 10 times.

High-fidelity single-qubit gates of a strong driven singlet-triplet qubit

Semiconductor quantum dot qubits are one of the most promising candidates for quantum computing. Among them, singlet-triplet qubits have attracted much attention due to their excellent properties of all-electric control and accurate readout. To improve qubit immunity to charge noise, strong driving pulses are usually introduced to make operation as fast as possible. However, the complex dynamics induced by strong driving pulses make the rotating wave approximation inapplicable and hinder the implementation of high-fidelity qubit operation. In this work, we present a method of utilizing simple quadrature pulses to correct errors of high-frequency oscillatory terms induced by strong driving. A scheme to obtain these pulses is proposed based on a full quantization of the system and derivative removal by adiabatic gate (DRAG) theory, as the former clarifies the elementary processes of strong driving effects and enables the latter to find correction pulse shapes. The numerical simulation results show that, a NOT gate with 99.99% fidelity and gate time as short as 2 ns can be achieved with the help of the control pulses of this method, which indicates that the control error brought by strong driving is no longer a limiting factor. In particular, NOT gate fidelity higher than 99.9% is achievable even when the charge noise is at a level of &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}$ 2\ \mu{\rm{eV}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="20-20230906_M2.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="20-20230906_M2.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;. Notice that this method can be applied to any resonant-driving single-qubit rotation but not just NOT gates. Therefore, our approach will facilitate qubits to realize fast, high-fidelity single-qubit gates under charge noise.

Effect of energy level configuration on storage of optical solitons in InAs/GaAs quantum dot electromagnetically induced transparency medium

Based on the current growth technology of quantum dot in the experiment, considering that the probe fields and control fields at different frequencies are coupled between different energy levels of the InAs/GaAs quantum dot, the ladder-type, Λ-type and V-type energy level configurations can be formed. The linear and nonlinear properties of these energy level configurations of InAs/GaAs quantum dots are studied by using semiclassical theory combined with multiple scale method. It is shown that in the linear case, electromagnetic induction transparency windows can be formed among ladder-type, Λ-type and V-type energy level configurations. And the width of the transparent window increases with the strength of the control pulse increasing. For the nonlinear case, under the current experimental condition, optical solitons can be formed and stored in ladder-type configuration and &lt;inline-formula&gt;&lt;tex-math id="M6"&gt;\begin{document}$ {{\Lambda }} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20221965_M6.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20221965_M6.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;-type energy level configuration. However, optical solitons cannot be formed in the V-type energy level configurations, which is because the nonlinear effect of the system is very weak. Furthermore, it is demonstrated that the fidelity of the storage and retrieval of the optical solitons is higher than that of linear optical pulse and strongly nonlinear optical pulse. Interestingly, it is also found that the amplitude of stored optical solitons in &lt;inline-formula&gt;&lt;tex-math id="M8"&gt;\begin{document}$ {{\Lambda }} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20221965_M8.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20221965_M8.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;-type energy level configuration is higher than that in ladder-type energy level configuration. This study provides a theoretical basis for semiconductor quantum dot devices to modulate the amplitude of the stored optical solitons.

Study on observation method of injection pressure curve in high pressure common rail system

The performance of the diesel engine was determined by the injection pressure of the high pressure common rail system. The observation method of the injection pressure curve was of great value in evaluating the operating conditions of the diesel engine. However, the observation method could make it impossible to directly observe the injection pressure data on a high pressure common rail system in operation. In this paper, common rail pressure signals and control pulse widths, which were easy to collect, were used as the basis for proposing a GRU (Gated Recurrent Unit) based model for the observation of injection pressure curves of high pressure common rail system in order to solve the above problem. The accuracy and precision of the model was verified by the experiments and compared with commonly used simulation models. From the results, it was concluded that the overall accuracy of the injection pressure curve observation was similar to that of the simulation model, but the accuracy was higher around the peak of the injection pressure, as well as the equipment requirement was low and the calculation speed was fast. The mean EMD of the curvilinear observation model of injection pressure of high pressure common rail system is similar to that of the 1D simulation model, with 37.88 and 33.62 respectively. The overall difference in injection pressure between the two models is similar with 53.62 and 54.23 MPa respectively. On the same computing platform, the average computation time of the test set containing five states is 0.0113 s, and the simulation time of each running state is 12951.6 s using AMESim software.