External Oscillator Research Articles

Beating the Standard Quantum Limit Electronic Field Sensing by Simultaneously Using Quantum Entanglement and Squeezing.

Quantum entanglement and quantum squeezing are two typical approaches to beat the standard quantum limit (SQL) for the sensitive phase estimations in quantum metrology. Each of them has already been utilized individually and sequentially to improve the sensitivity of electric field sensing with the trapped ion platform. However, the upper bound of the demonstrated sensitivity gain is still limited, i.e., the theoretical 6dB and experimental 3dB over the corresponding SQL, for electric field sensing. By simultaneously using the internal (spin)-external (oscillator) state entanglement and the oscillator squeezing to effectively amplify the accumulation phase, we show here that such a theoretical sensitivity gain upper bound can be significantly surpassed. The proposal provides a novel approach to implement the stronger beat of the SQL and even approach the Heisenberg limit, for the sensitive sensings of the desired electric field and also the other metrologies.

Multi-sensor Attitude Estimation using Quaternion Constrained GNSS Ambiguity Resolution and Dynamics-Based Observation Synchronization

Recently, high accuracy and low-cost navigation hardware is becoming increasingly available that can be efficiently used for the control of autonomous vehicles. We present a sensor fusion method providing tightly coupled integration of pseudorange, carrier phase, and Doppler satellite measurements taken at multiple vehicle-mounted GNSS antennas with onboard inertial sensor observations. The key of accurate GNSS position and orientation estimation is the successful integer ambiguity resolution. We propose a method that uses the quaternion states as constraints to improve ambiguity resolution and to increase the accuracy of the GNSS based attitude determination. Generally, the low-cost hardware neither allows a hardware-level time synchronization between the GNSS receivers due to a lack of a common external oscillator nor provides the clock steering function available in geodetic GNSS receivers. The lack of observation synchronization causes several degrees of error in attitude estimation. To eliminate this effect, a dynamics-based solution is presented that synchronizes the observations by taking the dynamics of the moving platform into account. Compared to common external oscillator based sensor setups, our solution allows to increase both the number of rover receivers on the platform and the baselines between them easily, thus it opens up new possibilities in the attitude determination of large vehicles. We validate our approach against a tactical grade inertial navigation system. The results show that our approach using low-cost sensors provides the ambiguity success rate of 100% for the moving baselines, and the positioning and attitude error reached the centimeter and half a degree level, respectively.

Development of a networked photonic‐enabled staring radar testbed for urban surveillance

AbstractUrban surveillance of slow‐moving small targets such as drones and birds in low to medium airspace using radar presents significant challenges. Detecting, locating and identifying such low observable targets in strong clutter requires both innovation in radar hardware design and optimisation of processing algorithms. To this end, the University of Birmingham (UoB) has set‐up a testbed of two L‐band staring radars to support performance benchmarking using datasets of target and clutter from realistic urban environment. This testbed is also providing the vehicle to understand how novel radar architectures can enhance radar capabilities. Some of the challenges in installing the radar at the UoB campus are highligted. Detailed benchmarking results are provided from urban monostatic and bistatic field trials that form the basis for performance comparison against future hardware modification. The solution to the challenge of interfacing the radar to the external oscillators is described and stand‐alone bench tests with the candidate oscillators are reported. The testbed provides a valuable capability to undertake detailed analysis of performance of Quantum photonic‐enabled radar and allows for its comparison with conventional oscillator technology for surveillance of low observable targets in the presence of urban clutter.

Low-Frequency Oscillations for Nonlocal Neuronal Coupling in Shared Intentionality Before and After Birth: Toward the Origin of Perception

The theoretical study observes literature to understand whether or not low-frequency oscillations can simultaneously alter the excitability of neurons from peripheral nervous subsystems in different individuals to provide Shared Intentionality in recipients (e.g., fetuses and newborns) and what are the attributes of ecological context for Shared Intentionality. To grasp the perception of objects during environmental learning at the onset of cognition, a fetus needs exogenous factors that could stimulate her nervous system to choose the relevant sensory stimulus. Low-frequency brain oscillations can cause the nonlocal coupling of neurons in peripheral and central nervous subsystems that provide subliminal perception. An external low-frequency oscillator and the proximity of individuals can stimulate the coordination of their heart rates and modulate neuronal excitability. External low-frequency oscillations can increase the cognitive performance of the subjects. The characteristics of this pulsed low-frequency field are oscillations with 400 and 700 nm wavelengths alternately with the pulsed frequency ranging from 1 to 1.6 Hz. This theoretical work contributes to knowledge about nonlocal neuronal coupling in different organisms that can appear due to low-frequency oscillations. The significance of the article is that it explains the neurophysiological processes occurring during Shared Intentionality - one of the central issues in understanding the cognitive development of young children, as the conventional view in cognitive sciences argues. The article's impact is a proposal of the universal mechanism of nonlocal neuronal coupling in shaping the embryonal nervous system in animals of all species, which opens new directions for research on the origin of perception of objects.

On the influence of internal oscillators on the performance of metastructures: Modelling and tuning conditions

A longitudinally excited metastructure with periodically distributed internal oscillators is considered with a view to determining how the tuning condition between their frequency and the frequency of the metastructure as a whole affects vibration attenuation. First, the mechanical model is created, and the tuning condition related to the first resonance frequency of the metastructure with blocked internal oscillators and the first resonance frequency of internal oscillators themselves is obtained in an original analytical form. Then, this condition is used to design the stiffness of the internal oscillators and they are allowed to oscillate in the metastructure, yielding vibration attenuation around the first resonance. The influence of the number of internal oscillators as well as the mass ratio between the mass of one internal oscillator and external oscillator of the metastructure is investigated. Experimental validations, accompanied with numerical results, of these theoretical results are provided subsequently. In addition, the theoretical concept is extended to other resonances, demonstrating its adaptivity and generality, and these cases are then validated via numerical experiments in FEM simulations.

Shared Intentionality Modulation at the Cell Level: Low-Frequency Oscillations for Temporal Coordination in Bioengineering Systems

The theoretical article aims to develop knowledge about the modulation of shared intentionality at the cellular level. A hypothesis about the neurobiological processes during shared intentionality argues that this pre-perceptual communication occurs through nonlocal neuronal coupling in an ecosystem that can be described as the mother-fetus communication model. The current theoretical study analyses literature to discuss recent findings on the effect of oscillations on neuronal temporal coordination to verify whether external low-frequency oscillations can only synchronize specific local neuronal networks from peripheral and central nervous subsystems for modulating shared intentionality. The review discusses 4 findings. First, gamma oscillations are associated with the temporal coordination of local ensembles of cells. Second, there is a relationship between low-frequency brain oscillations and the temporal coordination of peripheral and central nervous subsystems. Third, delta oscillations influence neuronal activity by modulating gamma activity. Fourth, external delta and gamma oscillations increase cortical excitability. The article concludes that delta oscillations can modulate gamma oscillations in the different subsystems of the nervous system, providing temporal network coordination. An external low-frequency oscillator can coordinate only relevant local neuronal networks in various subsystems already exhibiting gamma activity.

Entrainment of Mutually Synchronized Spatially Distributed 24 GHz Oscillators

Synchronization is one of the most challenging aspects of distributed systems in terms of their scalability. Minimal uncertainties can lead to problems or failures regarding data consistency in globally operating data centers or in distributed sensor arrays. Existing approaches to address these challenges are based on hierarchical synchronization concepts which are well understood and have reached technical maturity, but have the disadvantage of having a single point of failure. However, especially for critical infrastructure or backup more resilient solutions are required. Mutual synchronization where oscillators in a network are coupled bidirectionally without a reference have been considered. Due to the flat hierarchy such systems do not have a single point of failure. This work studies how hierarchical synchronization can be combined with architectures implementing mutual synchronization. A network of three mutually coupled 24 GHz oscillators is used to study how injecting a reference signal into one oscillator affects the dynamics. This can be quantified by analyzing in which range of frequencies the network of mutually coupled oscillators can follow the reference frequency. Measurements on a ring and chain network topology forced by an external reference oscillator shown here are in good agreement with the predictions of a nonlinear dynamical model.

High‐order subharmonic injection locking using a rotary topological defect in an oscillator lattice loop

AbstractThis study proposes a scheme for high‐order subharmonic injection locking in a tunnel diode oscillator lattice loop. The loop supports a rotary pulse resulting from mutual synchronization between the component oscillators. A topological defect in the form of a dislocation is observed to rotate within the loop in a direction opposite to that of the background rotary pulse. The defect is mutually synchronized with the rotary pulse. In addition, the defect velocity is considerably slower than that of the pulse. Upon injection locking of the rotary behavior of the defect using an external oscillator, the rotary pulse can also be locked via the same oscillator. This facilitates a high‐order subharmonic injection locking of the oscillating pulse through the intermediation of a topological defect. Herein, the operation principle is described, followed by its experimental validation.

Squeezed state generation using cryogenic InP HEMT nonlinearity

This study focuses on generating and manipulating squeezed states with two external oscillators coupled by an InP HEMT operating at cryogenic temperatures. First, the small-signal nonlinear model of the transistor at high frequency at 5 K is analyzed using quantum theory, and the related Lagrangian is theoretically derived. Subsequently, the total quantum Hamiltonian of the system is derived using Legendre transformation. The Hamiltonian of the system includes linear and nonlinear terms by which the effects on the time evolution of the states are studied. The main result shows that the squeezed state can be generated owing to the transistor’s nonlinearity; more importantly, it can be manipulated by some specific terms introduced in the nonlinear Hamiltonian. In fact, the nonlinearity of the transistors induces some effects, such as capacitance, inductance, and second-order transconductance, by which the properties of the external oscillators are changed. These changes may lead to squeezing or manipulating the parameters related to squeezing in the oscillators. In addition, it is theoretically derived that the circuit can generate two-mode squeezing. Finally, second-order correlation (photon counting statistics) is studied, and the results demonstrate that the designed circuit exhibits antibunching, where the quadrature operator shows squeezing behavior.

Investigation of pulse-to-pulse timing jitter in an ultrafast Cr:LiSAF laser for synchronization of radiation pulses

Timing jitter is closely related to the phase noise of ultrafast laser pulse train under different mode-locking regimes. Investigations have been made towards timing jitter for pulse-to-pulse Cr:LiSAF femtosecond laser, for usage as a seed laser in synchrotron light source. The laser produced about 180 fs of pulses with an 83.27 MHz pulse repetition rate, which corresponds to a 1.80 m cavity length. Mode-locking was passively achieved using semiconductor saturable absorber mirror (SESAM) optimized for low threshold and stability operation. Active timing-jitter stabilization to an external high precision electronic oscillator was attained with a cavity length control loop using a piezoelectric actuator. Phase noise detection has been evaluated using a timing stabilizer system (CLX-1100) and a phase detector (AD8302). According to the results, the AD8302 phase detector has superior timing jitter sensitivity than the CLX-1100 timing stabilizer system. Ultra low-noise oscillator was introduced to improve the performance of the CLX-1100 timing stabilizer system, which has been evaluated from the phase noise of spectral density and reflected in the root mean square timing jitter. The low timing jitter of the laser pulses was sufficient to accomplish the synchrotron of the radiation source.

Hybrid Control of Self-Oscillating Resonant Converters With Three-Level Input

We propose a hybrid feedback law inducing self-oscillating behavior in second-order resonant converters. With our controller, the converter switches at the resonant frequency of its tank, without the need of external oscillators. In addition, the output amplitude can be adjusted by a reference signal ranging from zero to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\scriptstyle {}^{\scriptstyle \pi }}\hspace {-0.224em}/\hspace {-0.112em}{\scriptstyle 2}$ </tex-math></inline-formula> . The amplitude modulation is then performed while maintaining an approximately constant switching frequency. Theoretical results show uniqueness and almost global asymptotic stability of a nontrivial hybrid limit cycle. Experimental results show that a circuit implementing the new controller successfully matches the desirable simulated behavior.

Resonance in bounded nonlinear pendulum-type systems

Solving nonlinear differential equations with external forces is important for understanding resonant phenomena in the physics of oscillations. The article analyzes this problem basing on example of an ordinary second-order differential equation of the pendulum type, where the nonlinearity is described by a sinusoidal term. The phase plane of such an oscillator is constructed and its periodic trajectories are studied. It is illustrated that bounded nonlinearity matters only at intermediate amplitudes. The excitation of a nonlinear oscillator is carried out using a limited two–component force; the first its component corresponds to an oscillation at the resonant frequency of a linear oscillator, and the second is a limited function with a variable frequency. It is shown that with the appropriate choice of an external force, it is possible to obtain unlimited amplification of oscillations in a pendulum-type oscillator with amplitude linearly proportional to time. Spectral composition of the external force is investigated using short-time Fourier transform. It is demonstrated that in order to maintain the resonant mode, the frequency of the external force must continuously increase. Energy estimates of the external force and oscillator fluctuations depending on time are performed. The considered example is important for understanding resonant conditions in nonlinear problems.

Hermitian and non-Hermitian normal-mode splitting in an optically-levitated nanoparticle

Normal-mode splitting is a hallmark of strong coupling between two coupled harmonic oscillators. Here, we report the realization of strong coupling in the optically-levitated nanoparticle system via feedback. A silica nanoparticle is trapped by a tightly focused laser travelling in free space, which is regarded as a harmonic oscillators. An external electric oscillator is then phase-locked to the nanoparticle’s motion as another harmonic oscillator, which is modulated on the trapping laser to feedback and interact with the nanoparticle. Therefore, a highly manipulatable coupled-harmonic oscillator system is built in our platform and the normal-mode splitting is realized with strong coupling in both Hermitian and non-Hermitian cases. Moreover, since the coupling between the two harmonic oscillators induced by the feedback is flexibly manipulated, the normal-mode splitting following the cooling or heating effect is simultaneously observed. This method could be useful for further studying quantum mechanical Hamiltonian and non-Hermitian phenomena of an optically-levitated nanoparticle.

Two-body continuum states in noninteger geometry

Wave functions, phase shifts and corresponding elastic cross sections are investigated for two short-range interacting particles in a deformed external oscillator field. For this we use the equivalent $d$-method employing a non-integer dimension $d$. Using a square-well potential, we derive analytic expressions for scattering lengths and phase shifts. In particular, we consider the dimension, $d_E$, for infinite scattering length, where the Efimov effect occurs by addition of a third particle. We give explicitly the equivalent continuum wave functions in $d$ and ordinary three dimensional (3D) space, and show that the phase shifts are the same in both methods. Consequently the $d$-method can be used to obtain low-energy two-body elastic cross sections in an external field.

On the Motion of Two Microspheres in a Stokes Flow Driven by an External Oscillator Field

Hydrodynamic interactions of a two-solid microspheres system in a viscous incompressible fluid at low Reynolds number is investigated analytically. One of the spheres is conducting and assumed to be actively in motion under the action of an external oscillator field, and as the result, the other nonconducting sphere moves due to the induced flow oscillation of the surrounding fluid. The fluid flow past the spheres is described by the Stokes equation and the governing equation in the vector form for the two-sphere system is solved asymptotically using the two-timing method. For illustrations, applying a simple oscillatory external field, a systematic description of the average velocity of each sphere is formulated. The trajectory of the sphere was found to be inversely proportional to the frequency of the external field. The results demonstrated that no collisions occur between the spheres as the system moves in a circular motion with a fixed separation distance.

Study of internal oscillations in a dynamic system through an external signal implemented in circadian rhythms

Through the analysis carried out on a dynamic model that is represented as a system of ordinary differential equations that describes the behavior of the circadian cycles; we will show and analyze in the next document what are the conditions that allow the synchronization of the circadian clock oscillator with the external modification oscillator. The implementation of this type of techniques in anatomical problems is highlighted, which are rare in the literature. The implementations will be carried out through different simulations using numerical techniques and the way in which we will determine the coupling conditions of an internal cycle of the system versus external cycles will be detailed. In the final development of this work, we will be able to see in the model without an external modification signal the existence of stable limit cycles and discover the moment in which the synchronization of the internal oscillator and the external modification signal occurs. These types of problems are common when making biological models that are described by a physical analysis.

Asymmetry Induced Suppression of Chaos in an Electro-Chemo-Mechanical System

Multiple unconnected chaotic relaxation oscillators realized by an electro-chemo-mechanical system (Mercury Beating heart) is coupled to a markedly different common external chaotic system realized by an electronic circuit. Upon exploring the resultant dynamics, it is found that, for sufficiently strong coupling, oscillatory activity of the group of oscillators is quenched by a single dissimilar chaotic oscillator. The results are corroborated numerically using model relaxation oscillator systems mimicking the interaction through coupled ordinary differential equations. A completely distinct chaotic external system is able to quench the ensemble’s oscillations most efficiently rather than a regular external oscillator or a system identical to the ensemble. This control of a group of oscillators using a dissimilar external system points to a powerful control strategy which is experimentally demonstrable. The general principle of emergent symmetry from asymmetric constituent systems which is illustrated here suggests that diversity or heterogeneity is a crucial factor in interactive systems exhibiting regularity.

All-solid-state 589-nm pulse generation using sum frequency of Stokes Raman lasers

We report a 589-nm laser using the sum-frequency generation (SFG) of 1.158- and 1.197-μm Stokes Raman lasers. These Stokes lasers are based on two KGd(WO4)2 and Ba(NO3)2 external Raman laser oscillators. First, a high-energy 1064-nm source was built to pump stimulated Raman scattering. Multiorder Stokes lasers with pulse energies of 402 and 220 mJ were generated from Raman laser oscillators with 2.26-J pumping. Furthermore, these two Stokes beams were simultaneously delivered into a potassium dihydrogen phosphate crystal for SFG. Finally, a 31.7-mJ laser at 589 nm was achieved with pulse duration of 6.9 ns and repetition rate of 1 Hz. These experimental results provide practical alternative to generate high-energy short-pulse 589-nm laser beams for related applications.

A tale of two rhythms: Locked clocks and chaos in biology.

The fundamental mechanisms that control and regulate biological organisms exhibit a surprising level of complexity. Oscillators are perhaps the simplest motifs that produce time-varying dynamics and are ubiquitous in biological systems. It is also known that such biological oscillators interact with each other-for instance, circadian oscillators affect the cell cycle, and somitogenesis clock proteins in adjacent cells affect each other in developing embryos. Therefore, it is vital to understand the effects that can emerge from non-linear interaction between oscillations. Here, we show how oscillations typically arise in biology and take the reader on a tour through the great variety in dynamics that can emerge even from a single pair of coupled oscillators. We explain how chaotic dynamics can emerge and outline the methods of detecting this in experimental time traces. Finally, we discuss the potential role of such complex dynamical features in biological systems.

Xenon lamp control signal and drive circuit design of Er: YAG laser

When the Er: YAG laser pumped by a xenon lamp emits laser light, the energy, frequency and pulse width of the emitted light are closely related to the discharge of the xenon lamp. This article uses the 8MHz external crystal oscillator that comes with the STM32F4 development board, generates a clock source through frequency division and frequency multiplication, and configures a pulse width modulation (PWM) signal to control the laser. Since the signals sent by the development board are weak signals, it is necessary to design a corresponding drive circuit to amplify the power of the signal. Finally, the voltage of the pulsed xenon lamp is adjustable from 0 to 1400V, and the pulse width is adjustable from 50 to 300μs to achieve stable laser output.