Dragging of inertial frames by matter and waves

In this paper, we review and analyze four specific general-relativistic problems in which gravitomagnetism plays an important role: the dragging of magnetic fields around rotating black holes, dragging inside a collapsing slowly rotating spherical shell of dust, compared with the dragging by rotating gravitational waves. We demonstrate how the quantum detection of inertial frame dragging can be accomplished by using the Unruh–DeWitt detectors. Finally, we shall briefly show how “instantaneous Machian gauges” can be useful in the cosmological perturbation theory.

Imprinting the quantum statistics of photons on free electrons

The interaction between free electrons and light stands at the base of both classical and quantum physics, with applications in free-electron acceleration, radiation sources, and electron microscopy. Yet, to this day, all experiments involving free-electron–light interactions are fully explained by describing the light as a classical wave. Here, we observe quantum statistics effects of photons on free-electron–light interactions. We demonstrate interactions passing continuously from Poissonian to super-Poissonian and up to thermal statistics, revealing a transition from quantum walk to classical random walk on the free-electron energy ladder. The electron walker serves as the probe in non-destructive quantum detection, measuring the second order photon-correlation g(2)(0) and higher-orders g(n)(0). Unlike conventional quantum-optical detectors, the electron can perform both quantum weak measurements and projective measurements by evolving into an entangled joint-state with the photons. These findings inspire hitherto inaccessible concepts in quantum optics, including free-electron-based ultrafast quantum tomography of light.

Measurement of the Probability of a Binary Symbol «0» Erasing in a Single-Photon Asynchronous Communication Channel with a Receiver Based on a Photon Counter

Receiving modules of single-photon communication channels should provide the least loss of transmitted information when measuring low-power optical signals. In this regard, it is advisable to use photon counters. They are highly sensitive, but are characterized by data logging errors. Therefore, the purpose of this work was to investigate the effect of the intensity of the recorded optical radiation during the transmission of binary symbols «0» on the probability of erasing these symbols in a single-photon communication channel containing a photon counter based on an avalanche photodetector as a receiving module with a passive avalanche suppression scheme.The lower and upper threshold levels of pulses recorded at the output of the photon counter, as well as the statistical distributions of the mixture of the number of dark and signal pulses at the output of the photon counter when registering binary symbols «0» Pst0( N ) and «1» Pst1( N ) were determined. For this, a technique was used to reduce information loss. As a result, the minimum probability of erasing binary symbols «0» P(–/0) was achieved.The performed experimental results showed that to achieve the minimum probability of erasing binary symbols «0» P(–/0) = 0,11·10−2, it is important to select not only the intensity of the used optical radiation J , but also the supply voltage of the avalanche photodetector U, at which the dead time of the photon counter is −2 minimal, and its quantum detection efficiency is maximum: J0 ≥ 98,94·10−2 rel. units and U = 52,54 V.

The Recent Progress of MEMS/NEMS Resonators

MEMS/NEMS resonators are widely studied in biological detection, physical sensing, and quantum coupling. This paper reviews the latest research progress of MEMS/NEMS resonators with different structures. The resonance performance, new test method, and manufacturing process of single or double-clamped resonators, and their applications in mass sensing, micromechanical thermal analysis, quantum detection, and oscillators are introduced in detail. The material properties, resonance mode, and application in different fields such as gyroscope of the hemispherical structure, microdisk structure, drum resonator are reviewed. Furthermore, the working principles and sensing methods of the surface acoustic wave and bulk acoustic wave resonators and their new applications such as humidity sensing and fast spin control are discussed. The structure and resonance performance of tuning forks are summarized. This article aims to classify resonators according to different structures and summarize the working principles, resonance performance, and applications.

Estimating the Product of the X-ray Spectrum and Quantum Detection Efficiency of a CT System and Its Application to Beam Hardening Correction

Lab-based X-ray computed tomography (XCT) systems use X-ray sources that emit a polychromatic X-ray spectrum and detectors that do not detect all X-ray photons with the same efficiency. A consequence of using a polychromatic X-ray source is that beam hardening artefacts may be present in the reconstructed data, and the presence of such artefacts can degrade XCT image quality and affect quantitative analysis. If the product of the X-ray spectrum and the quantum detection efficiency (QDE) of the detector are known, alongside the material of the scanned object, then beam hardening artefacts can be corrected algorithmically. In this work, a method for estimating the product of the X-ray spectrum and the detector’s QDE is offered. The method approximates the product of the X-ray spectrum and the QDE as a Bézier curve, which requires only eight fitting parameters to be estimated. It is shown experimentally and through simulation that Bézier curves can be used to accurately simulate polychromatic attenuation and hence be used to correct beam hardening artefacts. The proposed method is tested using measured attenuation data and then used to calculate a beam hardening correction for an aluminium workpiece; the beam hardening correction leads to an increase in the contrast-to-noise ratio of the XCT data by 41% and the removal of cupping artefacts. Deriving beam hardening corrections in this manner is more versatile than using conventional material-specific step wedges.

Machine learning studies for the effects of probes and cavity on quantum synchronization

As an important technology of the quantum detection, the quantum synchronization detection is always used in the detection or measurement of some quantum systems. A probing model is established to describe the probing of a qubit system in the cavity field and to reveal the effect of the environment (cavity) on the quantum synchronization occurrence, as well as the interactions among environment, a qubit system, and probing equipment. By adjusting the frequency of the probe, the in-phase, anti-phase, and out-of-phase synchronization can be achieved. Simultaneously, the effect of γ 3 ${\gamma }_{3}$ which describes the interaction strength between the probe and environments for quantum synchronization is discussed under different Ohmic dissipation index s . Finally, the machine learning method is applied to present an optimization for classification and regression of synchronization transition dependent on s and γ 3 ${\gamma }_{3}$ .