Phase Drift Research Articles

Robust frame synchronization for continuous-variable quantum key distribution with coherent states.

In a practical continuous variable quantum key distribution (CVQKD) system, frame synchronization is crucial for its operation, especially in conditions of low signal-to-noise ratio (SNR) and phase drift. This paper introduces a robust frame synchronization scheme for CVQKD systems that only utilizes quantum signals. The proposed scheme effectively employs randomly selected segments of quantum signals to achieve frame synchronization, eliminating the need for additional modulation. The performance of this scheme applied in a local local oscillator scenario is thoroughly analyzed through numerical simulations. The results demonstrate that the proposed scheme is capable of withstanding low SNR and arbitrary slow phase drift, as well as fast phase drift originates from two independent lasers, while also slightly improving the secret key rate compared to the scheme using inserted synchronization frames. These findings validate the feasibility of implementing the proposed scheme for long-distance CVQKD in practical scenarios.

Further Evidence for the ∼9 s Pulsation in LS 5039 from NuSTAR and ASCA

The present study aims to reinforce the evidence for the ∼9 s pulsation in the gamma-ray binary LS 5039, derived from a Suzaku observation in 2007 and a NuSTAR observation in 2016. Through a reanalysis of the NuSTAR data incorporating the orbital Doppler correction, the 9.0538 s pulsation was confirmed successfully even in the 3–10 keV range, where it was undetectable previously. This was attained by perceiving an energy-dependent drift in the pulse phase below 10 keV and correcting the pulse timing of individual photons for that effect. Similarly, an archival 0.7–12 keV data set of LS 5039, taken with the ASCA Gas Imaging Spectrometer in 1999 October, was analyzed. The data showed possible periodicity at about 8.882 s, but again the energy-dependent phase drift was noticed below 10 keV. By correcting for this effect, and for the orbital Doppler delays in the LS 5039 system, the 2.8–12 keV periodicity became statistically significant at 8.891 ± 0.001 s. The periods measured with ASCA, Suzaku, and NuSTAR approximately follow an average period derivative of s s−1. These results provide further evidence for the pulsation in this object and strengthen the scenario proposed by Yoneda et al. that the compact object in LS 5039 is a strongly magnetized neutron star.

A quantum ticking self-oscillator using delayed feedback

Self-sustained oscillators (SSOs) is a commonly used method to generate classical clock signals and SSOs using delayed feedback have been developed commercially which possess ultra-low phase noise and drift. Research into the development of quantum self-oscillation, where one can also have a periodic and regular output tick, that can be used to control quantum and classical devices has received much interest and quantum SSOs so far studied suffer from phase diffusion which leads to the smearing out of the quantum oscillator over the entire limit cycle in phase space seriously degrading the system’s ability to perform as a self-oscillation. In this paper, we explore quantum versions of time-delayed SSOs, which has the potentials to develop a ticking quantum clock. We first design a linear quantum SSO which exhibits perfect oscillation without phase diffusion. We then explore a nonlinear delayed quantum SSO but find it exhibits dephasing similar to previously studied non-delayed systems.

Quantum Communications Feasibility Tests over a UK-Ireland 224 km Undersea Link.

The future quantum internet will leverage existing communication infrastructures, including deployed optical fibre networks, to enable novel applications that outperform current information technology. In this scenario, we perform a feasibility study of quantum communications over an industrial 224 km submarine optical fibre link deployed between Southport in the United Kingdom (UK) and Portrane in the Republic of Ireland (IE). With a characterisation of phase drift, polarisation stability and the arrival time of entangled photons, we demonstrate the suitability of the link to enable international UK-IE quantum communications for the first time.

Numerical simulation of slug flow in pipelines using drift flux constitutive equations for gas-viscous oil two-phase flow

Transient simulation of multiphase flow in pipes has been performed using Two-Fluid Model and Drift-Flux Model. The main advantage of the Drift-Flux Model is the reduced number of differential equations, which results in a lower computational time. However, the accuracy of the model depends on a suitable constitutive equation for the velocity of the dispersed phase, commonly, the gas phase. The gas velocity constitutive equation includes two important parameters, namely, the distribution coefficient and the void-fraction-weighted drift velocity.A drift-flux-model code was developed, by using the Finite Volume Method (FVM) with staggered grid system, to evaluate the effect of highly viscous liquid and pipe geometry (pipe diameter and pipe inclination) in the prediction of liquid hold-up and pressure drop gradient. The gas phase compressibility was also included in the model.The results show that the energy consumption to pump the fluids through the lift system has been overestimated when highly viscous liquids are produced. For the case of a vertical upward flow, the overestimation can be up to 10 % of energy consumption. We strongly recommend incorporating the effects of pipe inclination and liquid viscosity into the estimation of the Distribution Coefficient of the dispersed phase, encompassing both C0 and gas drift velocity.

Practical Real-Time Phase Drift Compensation Scheme for Quantum Communication Systems.

Quantum communication systems are susceptible to various perturbations and drifts arising from the operational environment, with phase drift being a crucial challenge. In this paper, we propose an efficient real-time phase drift compensation scheme in which only existing data from the quantum communication process is used to establish a stable closed-loop control subsystem for phase tracking. This scheme ensures the continuous operation of transmission by tracking and compensating for phase drift in the phase-encoding quantum communication system. The experimental results demonstrate the effectiveness and feasibility of the proposed scheme with an average quantum bit error rate of 1.60% and a standard deviation of 0.0583% for 16 h of continuous operation.

Matching pursuit algorithm for cement evaluation behind the casing

The oil and gas sector makes extensive use of ultrasonic tool technology for casing and cement examination for well integrity. This requires the determination of the thickness of the casing, its internal structure, and the mechanical properties of the cement behind the casing. In essence an ultrasonic instrument analyses the ultrasonic pulse echoes returned off the internal surface of the casing. To determine the acoustic impedance of the material behind the casing, it can be difficult to distinguish between the primary reflection from the interior surface of the casing and the ones due to the ringing inside the casing wall itself. The primary reflection offers details regarding the internal geometry of the casing, and the decay of the energy within the casing wall reveals more about how well the cement is bonded to the casing. The ultrasonic signals that the transducer receives when it functions as a receiver are easily contaminated by noise, or part of the reflection may be blocked, or the main waveform and the many ringing waveforms are difficult to separate. As a result, the echo signals will have frequency and phase drift or be deformed. To address the various energy packets and extract the pertinent component independently, a matching pursuit algorithm was developed with a specific dictionary to deal with the different energy packets and extract the relevant component separately. The algorithm was tested on simulated and field data.

Phase drift and noise suppression method based on SEE-SGMD-PCC in a distributed acoustic sensor

The problems of laser source frequency drift (LSFD) and phase noise in distributed acoustic sensor (DAS) make it difficult to recover the true vibration phase curve, which limits its application scope in the field of seismic exploration. In order to suppress the influence of phase noise and phase drift on the phase signal and improve the signal-to-noise ratio (SNR) of the phase curve, this paper proposes a method based on symmetric extreme value expansion, symplectic geometry mode decomposition and Pearson correlation coefficient (SEE-SGMD-PCC). Firstly, the mathematical principles and processing flow of the SEE-SGMD-PCC algorithm were introduced, and the effectiveness of this method was verified through multiple sets of simulation experiments. Secondly, The DAS system implemented using digital heterodyne coherent detection technology was used as the experimental platform, and the phase drift and phase noise sources of the phase signal were analyzed in detail. Next, in single frequency and multi frequency vibration signal experiments, compared with other methods, the SNR of the phase signal is significantly improved, and the phase information is effectively restored. Finally, the feasibility of the proposed method was demonstrated through two on-site experiments. The proposal of this method further promotes the application process of DAS in complex seismic exploration environments.

Punctuated chaos and the unpredictability of the Galactic Centre S-star orbital evolution

ABSTRACT We investigate the chaotic behaviour of the S-star cluster in the Galactic Centre using precise N-body calculations, free from round-off or discretization errors. Our findings reveal that chaos among the Galactic Centre S-stars arises from close encounters, particularly among pairs and near the massive central body. These encounters induce perturbations, causing sudden changes in the orbital energies of the interacting stars. Consequently, neighbouring solutions experience roughly exponential growth in separation. We propose a theory of ‘punctuated chaos’ that describes the S-star cluster’s chaotic behaviour. This phenomenon results from nearly linear growth in the separation between neighbouring orbits after repeated finite perturbations. Each participating star’s orbit experiences discrete, abrupt changes in energy due to the perturbations. The cumulative effect of these events is further amplified by the steady drift in orbital phase. In the Galactic Centre, perturbations originate from coincidental encounters occurring within a distance of ≲100 au between at least two stars (in some cases, three stars). Our model satisfactorily explains the observed exponential growth in the 27 S-stars cluster. We determine that the S-star system has a Lyapunov time-scale of approximately 462 ± 74 yr. For the coming millennium, chaos in the S-star cluster will be driven mainly by a few of the closest orbiting stars: S2, S5, S6, S8, S9, S14, S18, S31, S21, S24, S27, S29, and S38.

PSR J0026−1955: A curious case of evolutionary subpulse drifting and nulling

ABSTRACT PSR J0026−1955 was independently discovered by the Murchison Widefield Array recently. The pulsar exhibits subpulse drifting, where the radio emission from a pulsar appears to drift in spin phase within the main pulse profile, and nulling, where the emission ceases briefly. The pulsar showcases a curious case of drift rate evolution as it exhibits rapid changes between the drift modes and a gradual evolution in the drift rate within a mode. Here, we report new analysis and results from observations of J0026−1955 made with the upgraded Giant Metrewave Radio Telescope at 300–500 MHz. We identify two distinct subpulse drifting modes: A and B, with mode A subcategorized into A0, A1, and A2, depending upon the drift rate evolutionary behaviour. Additionally, the pulsar exhibits short and long nulls, with an estimated overall nulling fraction of ∼58 per cent, which is lower than the previously reported value. Our results also provide evidence of subpulse memory across nulls and a consistent behaviour where mode A2 is often followed by a null. We investigate the drift rate modulations of J0026−1955 and put forward two different models to explain the observed drifting behaviour. We suggest that either a change in polar gap screening or a slow relaxation in the spark configuration could possibly drive the evolution in drift rates. J0026−1955 belongs to a rare subset of pulsars which exhibit subpulse drifting, nulling, mode changing, and drift rate evolution. It is therefore an ideal test bed for carousel models and to uncover the intricacies of pulsar emission physics.

Nonlinear dynamic characteristics analysis of the surge motion of a tender-assisted drilling operation system

ABSTRACT In this study, a numerical analysis is carried out to investigate the coupled behaviour of a TLP (tension leg platform) -TAD (tender-assisted drilling) system under a series of regular waves in surge direction. The numerical model is established in the time domain considering the nonlinear characteristics of the mooring systems and the hydrodynamic interference. After the case validations, the effects of the wave periods and amplitudes on the nonlinear dynamic characteristics of the surge motions are investigated in detail. Then, the observed nonlinear dynamic characteristics are interpreted in detail through the existing theory of phase dynamics. The surge motions of the coupled system can show multiperiod nonlinear characteristics under regular waves in certain wave periods. Three forms of phase dynamic characteristics: phase locking, phase trapping, and phase drifting and slipping are observed in the surge motions of the tender-assisted drilling operation system.

Paradoxical roles of inhibitory autapse and excitatory synapse in formation of counterintuitive anticipated synchronization

Different from the common delayed synchronization (DS) in which response appears after stimulation, anticipated synchronization (AS) in unidirectionally coupled neurons denotes a counterintuitive phenomenon in which response of the receiver neuron appears before stimulation of the sender neuron, showing an interesting function of brain to anticipate the future. The dynamical mechanism for the AS remains unclear due to complex dynamics of inhibitory and excitatory modulations. In this article, the paradoxical roles of excitatory synapse and inhibitory autapse in the formation of AS are acquired. Firstly, in addition to the common roles such that inhibitory modulation delays and excitatory modulation advances spike, paradoxical roles of excitatory stimulation to delay spike via type-II phase response and of inhibitory autapse to advance spike are obtained in suitable parameter regions, extending the dynamics and functions of the excitatory and inhibitory modulations. Secondly, AS is related to the paradoxical roles of the excitatory and inhibitory modulations, presenting deep understandings to the AS. Inhibitory autapse induces spike of the receiver neuron advanced to appear before that of the sender neuron at first, and then excitatory synapse plays a delay role to prevent the spike further advanced, resulting in the AS as the advance and delay effects realize a dynamic balance. Lastly, inhibitory autapse with strong advance, middle advance, and weak advance and delay effects induce phase drift (spike of the receiver neuron advances continuously), AS, and DS, respectively, presenting comprehensive relationships between AS and other behaviors. The results present potential measures to modulate AS related to brain function.

Photonic Phase-Stabled Transmission of Broadband Signals Based on Passive Compensation

A photonic phase-stabled transmission of broadband signal based on passive frequency mixing compensation is proposed. The mechanism of jitter compensation of aimed broadband signal transmission relies on an adaptive cancellation by mixing two signals under approximately the same external time jittering. A theoretical model is built and the frequency dependent jitter suppression is analyzed and verified. Compared with previous methods, the proposed photonic phase-stabled transmission of broadband signal can withstand faster jittering frequency up to 1 kHz. The experimental results show that the proposed method can significantly reduce the phase drift of the broadband signal of 400 MHz bandwidth. The measured overlapping Allan deviation at the center frequency of 7.2 GHz shows a stability of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.53\times 10 ^{-14}$ </tex-math></inline-formula> at 100 s average time.

Modeling of three-dimensional betatron oscillation and radiation reaction in plasma accelerators

Betatron oscillation is a commonly known phenomenon in laser or beam driven plasma wakefield accelerators. In the conventional model, the plasma wake provides a linear focusing force to a relativistic electron, and the electron oscillates in one transverse direction with the betatron frequency proportional to $1/\sqrt{\gamma}$, where $\gamma$ is the Lorentz factor of the electron. In this work, we extend this model to three-dimensional by considering the oscillation in two transverse and one longitudinal directions. The long-term equations, with motion in the betatron time scale averaged out, are obtained and compared with the original equations by numerical methods. In addition to the longitudinal and transverse damping due to radiation reaction which has been found before, we show phenomena including the longitudinal phase drift, betatron phase shift and betatron polarization change based on our long-term equations. This work can be highly valuable for future plasma based high-energy accelerators and colliders.

Self-Referenced Method for Geometrical Distortion Removal in THz Time-Domain Reflection Imaging

In this article, we develop a method for removing the phase drift induced by physically distorted object in terahertz time-domain reflection imaging (THz-TDRI). The proposed approach is defined as self-referenced, as it does not rely on any numerical parameter optimization nor extra instrumental components, and it is based on the unique manipulation of time-domain imaging data. In fact, we demonstrate that the problem can be solved assuming a linear contribution of the temporal shift induced by surface curvature. We illustrate how the self-referenced method is modeled and implemented, and we report the results obtained on two objects with different characteristics: a tilted and highly reflective surface, and a warped and heterogeneous surface. The proposed method demonstrates how to successfully remove the phase alterations induced on the reflected electric field, and how to repair the heavily corrupted images in the frequency-domain.

Temperature-immune Fabry-Perot cavity sensor based on an opened hollow-core anti-resonant fiber.

A new approach to conquer the thermal phase drift of an optical fiber Fabry-Perot interferometer (FPI) sensor is proposed and experimentally demonstrated. By employing a hollow-core anti-resonant fiber (HC-ARF) and optimizing the fusion splicing (includes mode field adaptation) between the lead-in single-mode fiber (SMF) and the HC-ARF, a high spectral resolution (λ/Δλ ≈ 3.8 × 104) optical fiber air-cavity FPI sensor with a fringe visibility higher than 7 dB is constructed. To eliminate the thermal phase drift (i.e. temperature crosstalk) of the sensor that originates from the intrinsic thermal expansion effect of the silica material of the HC-ARF, the FPI air cavity is connected to the external environments, by which the effect of air expelling from the cavity with temperature increasing can well compensate the temperature-induced cavity elongation. As a result, the thermal phase drift of the FPI is reduced to zero at a temperature range of ∼ 80-110 °C and within the temperature range of 40-80 °C, the thermal phase drift is still halved compared with the sealed FPI cavity. The nearly zero thermal phase drift of a FPI at such a temperature range has never been achieved before, to our best knowledge. As a proof of concept, a temperature-immune fiber-optic strain sensor is demonstrated. This work offers a new and efficient approach to eliminate the thermal phase drift (i.e. temperature crosstalk) of a fiber-optic device, which may significantly improve the measurement accuracy and detection limit of fiber-optic FPI sensors. Furthermore, the principle and schema can be generalized to a wide variety of fiber-optic devices.

Phase randomness in a semiconductor laser: Issue of quantum random-number generation

Gain-switched lasers are in demand in numerous quantum applications, particularly, in systems of quantum key distribution and in various optical quantum random number generators. The reason for this popularity is natural phase randomization between gain-switched laser pulses. The idea of such randomization has become so familiar that most authors use it without regard to the features of the laser operation mode they use. However, at high repetition rates of laser pulses or when pulses are generated at a bias current close to the threshold, the phase randomization condition may be violated. This paper describes theoretical and experimental methods for estimating the degree of phase randomization in a gain-switched laser. We consider in detail different situations of laser pulse interference and show that the interference signal remains quantum in nature even in the presence of classical phase drift in the interferometer provided that the phase diffusion in a laser is efficient enough. Moreover, we formulate the relationship between the previously introduced quantum reduction factor and the leftover hash lemma. Using this relationship, we develop a method to estimate the quantum noise contribution to the interference signal in the presence of phase correlations. Finally, we introduce a simple experimental method based on the analysis of statistical interference fringes, providing more detailed information about the probabilistic properties of laser pulse interference.

Real-time suppression of random phase drift for laser ranging with high-frequency intermode beats

Laser ranging with frequency comb intermode beats (IMBs) has been suffering from random phase drifts (RPDs) for two decades. In this study, we reveal the influence of signal transmission path on the RPDs and propose a real-time suppression method using two IMBs of similar frequencies from different combs. As the two IMBs obtain similar RPDs during their transmission through same signal paths, the RPD of the original probing signal IMB is suppressed by deducting the RPD of the newly added local IMB in real time. In our experiments, a real-time suppression of RPDs is achieved using IMBs of 1001 and 1000 MHz. For the sampling time of 100 s, the effect of 19-fold suppression has been achieved. The proposed method provides a new solution for the long-standing phase drift problem in laser ranging with comb IMBs.

Resonances in asymptotically autonomous systems with a decaying chirped-frequency excitation

&lt;p style='text-indent:20px;'&gt;The influence of oscillatory perturbations on autonomous strongly nonlinear systems in the plane is investigated. It is assumed that the intensity of perturbations decays with time, and their frequency increases according to a power law. The long-term behaviour of perturbed trajectories is discussed. It is shown that, depending on the structure and the parameters of perturbations, there are at least two different asymptotic regimes: a phase locking and a phase drifting. In the case of phase locking, resonant solutions with an unlimitedly growing energy occur. The stability and asymptotics at infinity of such solutions are investigated. The proposed analysis is based on a combination of the averaging technique and the method of Lyapunov functions.&lt;/p&gt;

Toward a Phase Adaptive Stabilization System for Next-Generation Single-Dish Sub-mm Telescope Part—I: Multipath Phase Measurements Based on Ultrastable Microwave Signal Distribution

Large-aperture, single-dish, submillimeter-wave (sub-mm) telescopes are important to our understanding of the universe, but it is a long-term outstanding challenge to make the single-dish sub-mm telescopes larger while keeping a high accuracy of their surfaces. A bottleneck in the context of the size and the operating wavelengths of such telescopes is the deterioration of wavefront errors (phase shift) due to the deformation of reflective surfaces. Here proposed is a phase adaptive stabilization system (PASS), functioning as adaptive optics system of radio frenquency, an essential tool for overcoming the challenge, which is based on a state-of-the-art ultra-stable microwave signal distribution (UMSD) technology. The UMSD system with a phase drift of less than 11 fsec rms over 600 sec, is specially proposed for the PASS, which is an innovation. The results of outfield experiments have shown that the PASS is sufficiently accurate to measure the changes in the excess path length down to the level of 20 μm, which is the highest accuracy reported up to now. Our study marks a major step towards the phase adaptive stabilization system.