Weak Measurements Research Articles

Experimental Test of Nonlocality Limits from Relativistic Independence

Quantum correlations, like entanglement, represent the characteristic trait of quantum mechanics and pose essential issues and challenges to the interpretation of this pillar of modern physics. Although quantum correlations are largely acknowledged as a major resource to achieve quantum advantage in many tasks of quantum technologies, their full quantitative description and the axiomatic basis underlying them are still under investigation. Previous works have suggested that the origin of nonlocal correlations is grounded in principles capturing (from outside the quantum formalism) the essence of quantum uncertainty. In particular, the recently introduced principle of relativistic independence has given rise to a new bound intertwining local and nonlocal correlations. Here, we test such a bound by realizing together sequential and joint weak measurements on entangled photon pairs, allowing us to simultaneously quantify both local and nonlocal correlations by measuring incompatible observables on the same quantum system without collapsing its state, a task typically forbidden in the traditional (projective) quantum measurement framework. Our results demonstrate the existence of a fundamental limit on the extent of quantum correlations, shedding light on the profound role of uncertainty in both enabling and balancing them. Published by the American Physical Society 2024

In‐Situ Constructed Core‐Shell Catalyst Enabling Subzero Capacity Unlocking of Cost‐Effective and Long‐Life Vanadium Flow Batteries

AbstractVanadium flow battery (VFB) promises a route for achieving grid‐scale power storage by harnessing renewable energy sources. However, the sluggish reaction kinetics of vanadium redox couples and serious hydrogen evolution reaction (HER) still restrict the further development of VFB. Addressing these challenges requires not only effective solutions but also ones that are cost‐efficient and scalable to meet the demands of affordable energy storage. Here, we present an in situ constructed Cu@Cu6Sn5 core‐shell catalyst by incorporating metal ions into the electrolyte. The Cu core, encapsulated by the Cu6Sn5 shell, forms an excellent conductive pathway to the graphite felt electrode. Charge transfer between Cu and Sn within Cu6Sn5 shell accelerates the reaction kinetics of V2+/V3+ redox couple and selectively inhibits HER, as confirmed through in situ weak measurement imaging method. The Cu@Cu6Sn5 battery achieves a peak power density of 1119.1 mW cm−2 at 1350 mA cm−2, operates stably for 1200 cycles without catalyst failure, and is available over a wide‐temperature range. Furthermore, we identify a demand of subzero capacity unlocking. Achieving a 23.4 % theoretical capacity unlocking at −10 °C with a cut‐off voltage up to 1.75 V, bespeaking a crucial breakthrough toward cost‐effective VFB.

Direct Purification of Bell and Multipartite GHZ States via Weak Measurement

AbstractMaximally entangled states are crucial for various quantum information processing, yet their quality suffers from entanglement loss due to decoherence. In this paper, a direct purification technique that utilizes weak measurement and requires only two copies of the entangled state is proposed. The method involves transforming the damped entangled state with weak measurements and then applying a direct purification process. This approach yields a maximally entangled state with a certain probability. In the context of Bell state purification, two weak measurement‐based operations designed to convert amplitude‐damped Bell states into the desired state for direct purification method are presented. The first operation is applied prior to the noisy channel, while the second is employed after the noisy channel. Through comprehensive analysis, the performances of these two schemes are evaluated and compared and benchmarked them against a pioneering weak measurement‐based scheme. The findings demonstrate that the proposed methods exhibit superior performance in terms of both fidelity and probability. Additionally, a novel technique for purifying multipartite amplitude‐damped Greenberger–Horne–Zeilinger (GHZ) states is introduced, which existing methods cannot address. By employing only two copies of the entangled states and harnessing the unique advantages of weak measurement operations, the method achieves both resource efficiency and effectiveness.

Weak Value Quantum Metrology beyond Weak Interaction

Abstract Weak value amplification is crucial in quantum metrology because it enhances the detection of subtle interactions between quantum entities. However, current weak value quantum metrology techniques are only effective for extremely weak interactions, significantly narrowing its range of potential applications. 
In this work, we present the `metrological weak value,' designed for use with quantum interactions of any strengths, making it unnecessary to have prior knowledge of how strong or weak a quantum interaction might be.
Additionally, we demonstrate an adaptive estimation scheme for weak value quantum metrology tailored for gauging an undetermined interaction strength. This scheme, rooted in metrological weak value measurements, aligns perfectly with the quantum Cramér-Rao lowest bound. 
The versatility and effectiveness of the metrological weak value enables weak value quantum metrology beyond weak interactions, paving the way for precision in quantum measurement and broadening its utility across various quantum systems.

In-Situ Constructed Core-Shell Catalyst Enabling Subzero Capacity Unlocking of Cost-Effective and Long-Life Vanadium Flow Batteries.

Vanadium flow battery (VFB) promises a route for achieving grid-scale power storage by harnessing renewable energy sources. However, the sluggish reaction kinetics of vanadium redox couples and serious hydrogen evolution reaction (HER) still restrict the further development of VFB. Addressing these challenges requires not only effective solutions but also ones that are cost-efficient and scalable to meet the demands of affordable energy storage. Here, we present an in situ constructed Cu@Cu6Sn5 core-shell catalyst by incorporating metal ions into the electrolyte. The Cu core, encapsulated by the Cu6Sn5 shell, forms an excellent conductive pathway to the graphite felt electrode. Charge transfer between Cu and Sn within Cu6Sn5 shell accelerates the reaction kinetics of V2+/V3+ redox couple and selectively inhibits HER, as confirmed through in situ weak measurement imaging method. The Cu@Cu6Sn5 battery achieves a peak power density of 1119.1 mW cm-2 at 1350 mA cm-2, operates stably for 1200 cycles without catalyst failure, and is available over a wide-temperature range. Furthermore, we identify a demand of subzero capacity unlocking. Achieving a 23.4 % theoretical capacity unlocking at -10 °C with a cut-off voltage up to 1.75 V, bespeaking a crucial breakthrough toward cost-effective VFB.

Analytical noise bias correction for precise weak lensing shear inference

Abstract Noise bias is a significant source of systematic error in weak gravitational lensing measurements that must be corrected to satisfy the stringent standards of modern imaging surveys in the era of precision cosmology. This paper reviews the analytical noise bias correction method and provides analytical derivations demonstrating that we can recover shear to its second order using the ‘renoising’ noise bias correction approach introduced by METACALIBRATION. We implement this analytical noise bias correction within the AnaCal shear estimation framework and propose several enhancements to the noise bias correction algorithm. We evaluate the improved AnaCal using simulations designed to replicate Rubin LSST imaging data. These simulations feature semi-realistic galaxies and stars, complete with representative distributions of magnitudes and Galactic spatial density. We conduct tests under various observational challenges, including cosmic rays, defective CCD columns, bright star saturation, bleed trails, and spatially variable point spread functions. Our results indicate a multiplicative bias in weak lensing shear recovery of less than a few tenths of a percent, meeting LSST DESC requirements without requiring calibration from external image simulations. Additionally, our algorithm achieves rapid processing, handling one galaxy in less than a millisecond.

Compton scattering from proton pairs – illustrating weak and strong measurements

Abstract Neutrons interacting with protons in Compton scattering is here chosen as an example of a non-trivial quantum measurement. It illustrates a situation where a probe particle makes an observation (a weak measurement) of the studied protons, preparing for a final state in which one of them takes up the recoil in the collision. The proton is ejected during a strong (projective) measurement that selects one particular momentum value out of the proton’s initial distribution of momentum states. This course of events in the measurement process is evidenced by the observation that destructive interference appears during the weak interaction stage which leads to a strongly reduced neutron cross section for the proton system.

Observation of single-photon azimuthal backflow with weak measurement

Observation of single-photon azimuthal backflow with weak measurement

Research on Array Magnetometer Spectroscopy Technology Based on Diffractive Optical Elements

Abstract With the development of Spin-Exchange Relaxation Free (SERF) atomic magnetometers, human weak magnetic measurement has become a hot research direction in the medical field. Cardio-cerebromagnetic monitoring is a new medical detection method in the medical field. Array magnetometer is the core device of cardio-cerebromagnetic accurate monitoring. The volume and accuracy of the array magnetometer directly determine the wearability and sensitivity of the device, and the laser beam splitting system has a great influence on its accuracy and volume. Because the diffraction beam splitting method has the advantages of high beam splitting efficiency, good beam performance consistency, small space occupation, etc., it is suitable for the laser beam splitting module of array magnetometer, which does not reduce the accuracy while reducing the volume. In this paper, we innovatively apply the diffraction beam splitting scheme to the laser beam splitting module of the array magnetometer, with the goal of miniaturizing the integration of the beam splitting module and improving the output accuracy of the array magnetometer. The design and fabrication of a high-performance diffraction beam splitter applied to the beam splitting system of the SERF atomic magnetometer, as well as the output beam quality and power balance of multiple laser beams, ensure the detection accuracy of the array magnetometer. It is important to carry out related studies of laser beam splitter technology for magnetometer development.

Is it feasible to prolong the flushing interval for totally implantable venous access devices (TIVADs)? A systematic review and meta-analysis.

To ascertain the effects of prolonging flushing intervals (FIs) for Totally Implantable Venous Access Devices (TIVADs) on catheter-related complications in the off-treatment period. A preliminary search of PubMed, EMBASE, Cochrane, Web of Science, Web of Science, Scopus, CNKI, and SinoMed was conducted from inception to 6th June 2023, using the keywords "vascular access devices", "interval", "occlusion", and "complication". Two independent reviewers performed studies screening, quality assessment, and data extraction. The methodological quality of included articles was assessed using the Newcastle-Ottawa Scale (NOS) and Risk of Bias (ROB) tools. Meta-analysis and trial sequential analysis (TSA) was performed to calculate the risk ratios and 95% confidence interval (CI). Eleven studies with 4,924 participants were included. Extending FIs to two or three months increased the risk of catheter occlusion compared to one-month intervals [RR = 1.50 (1.18-1.92), P = 0.001], but this finding was not confirmed by sensitivity analysis and TSA. Extending FIs to three months showed no significant effect on overall complications rates [RR = 1.21 (0.99-1.48), P = 0.49], consistent with sensitivity analysis and TSA results. For other catheter-related complications, the results showed extending the FIs to three months was feasible, but with weak measurements due to insufficient data. Data from the current included studies tended to support the feasibility of extending the flushing interval to every three months, with no expected increase in catheter occlusion or overall catheter complications. However, due to the inherent limitations of the included study, the findings of the current study should be interpreted with caution.

Quantum weak measurement enhanced distributed acoustic sensing.

An enhanced distributed acoustic sensing (DAS) is proposed based on an extended Mach-Zehnder interferometer utilizing quantum weak measurement. The acoustic signals are encoded as the relative phase of the polarized light in several channels by fibers between optical fiber Bragg gratings (FBGs). With appropriate preselection and postselection, the acoustic signal can be extracted by performing the Fourier transform on the contrast ratio of the detected light intensity. Theoretical analysis shows that the scheme can achieve a spatial resolution of 1 m, and the system noise can be decreased by three orders of magnitude compared to classical distributed acoustic sensing. Moreover, this scheme might have potential application in long-distance acoustic source localization.

High-precision measurement of the magneto-optical Faraday effect via difference weak measurements

We propose a modified difference weak measurement scheme that permits precise measurements of the magneto-optical Faraday effect. By making normalized difference processing for a set of post-selected light intensity, a linear-response regime with a significant weak-value amplification effect is established. In the proof-of-principle experiment, we measure the magnetic intensity using the polarization system and achieve precision at the order of ∼10−7 T. Our scheme can be applied to measure other magneto-optical effects, providing a method for future ultra-sensitive sensing and metrology in magnetic physics.

The Impact of Microfinance on Community Welfare: A Bibliometric Analysis and Systematic Literature Review (SLR)

ABSTRACT Over the years, microfinance programs have been the major strategy of many developing countries to improve people’s welfare and reduce poverty. Yet several studies on the welfare impacts of microfinance result in contradictory conclusions. While some studies support the mainstream view that microfinance improves the welfare of the unbankable poor, others criticize its limited effect on business development and weak impact measurement methods. This study analyzes 409 articles to bridge the empirical gaps between mainstream and critical views of microfinance impacts on society through synthesizing major themes in existing research and their interconnections and provides recommendations for future research. Using bibliometric and systematic literature review (SLR) approaches, this study found five clusters of empirical research on microfinance impacts, including entrepreneurship and poverty alleviation; self-help groups and women empowerment; financial inclusion; household income; and community welfare. The study also suggests that microfinance programs have positive impacts on welfare across countries. However, future research needs to more deeply focus on the impact of microfinance programs on agricultural finance, specifically financial efficiency, and social efficiency.

Multi-layer controlled remote implementation of partially unknown single-qudit operations

Our concern is to investigate controlled remote implementation of partially unknown operations with multiple layers. We first propose a scheme to realize the remote implementation of single-qubit operations belonging to the restricted sets. Then, the proposed scheme is extended to the case of single-qudit operations. As long as the controller and the higher-layer senders consent, the receiver can restore the desired state remotely operated by the sender. It is worth mentioning that the recovery operation is deduced by general formulas which clearly reveal the relationship with the measurement outcomes. For the sake of clarity, two specific examples with two levels are given respectively. In addition, we discuss the influence of amplitude-damping noise and utilize weak measurement and measurement reversal to effectively resist noise.

A dual-tier adaptive one-class classification IDS for emerging cyberthreats

In today’s digital age, our dependence on IoT (Internet of Things) and IIoT (Industrial IoT) systems has grown immensely, which facilitates sensitive activities such as banking transactions and personal, enterprise data, and legal document exchanges. Cyberattackers consistently exploit weak security measures and tools. The Network Intrusion Detection System (IDS) acts as a primary tool against such cyber threats. However, machine learning-based IDSs, when trained on specific attack patterns, often misclassify new emerging cyberattacks. Further, the limited availability of attack instances for training a supervised learner and the ever-evolving nature of cyber threats further complicate the matter. This emphasizes the need for an adaptable IDS framework capable of recognizing and learning from unfamiliar/unseen attacks over time. In this research, we propose a one-class classification-driven IDS system structured on two tiers. The first tier distinguishes between normal activities and attacks/threats, while the second tier determines if the detected attack is known or unknown. Within this second tier, we also embed a multi-classification mechanism coupled with a clustering algorithm. This model not only identifies unseen attacks but also uses them for retraining them by clustering unseen attacks. This enables our model to be future-proofed, capable of evolving with emerging threat patterns. Leveraging one-class classifiers (OCC) at the first level, our approach bypasses the need for attack samples, addressing data imbalance and zero-day attack concerns and OCC at the second level can effectively separate unknown attacks from the known attacks. Our methodology and evaluations indicate that the presented framework exhibits promising potential for real-world deployments.

Measurement of the Weyl potential evolution from the first three years of Dark Energy Survey data

The Weyl potential, which is the sum of the spatial and temporal distortions of the Universe’s geometry, provides a direct way of testing the theory of gravity and the validity of the ΛCDM (Lambda Cold Dark Matter) model. Here we present measurement of the Weyl potential at four redshifts bins using data from the first three years of observations of the Dark Energy Survey. We find that the measured Weyl potential is 2 σ, respectively 2.8 σ, below the ΛCDM predictions in the two lowest redshift bins. We show that these low values of the Weyl potential are at the origin of the tension between Cosmic Microwave Background measurements and weak lensing measurements, regarding the parameter σ8 which quantifies the clustering of matter. Interestingly, we find that the tension remains if no information from the Cosmic Microwave Background is used. Dark Energy Survey data on their own prefer a high value of the primordial fluctuations, together with a slow evolution of the Weyl potential. An important feature of our method is that the measurements of the Weyl potential are model-independent and can therefore be confronted with any theory of gravity, allowing efficient tests of models beyond General Relativity.

Observation of the Goos-Hänchen shift in monolayer WSe2 for an arbitrary linearly polarized incident light beam using weak measurement

We report, to our knowledge, the first experimental investigation of the spatial Goos-Hänchen (GH) shift at an absorbing material interface comprised of monolayer (ML) tungsten di-selenide (WSe2) on a SiO2/Si substrate under a total internal reflection (TIR) condition. The critical angle for this design is drastically shifted to 23.31°, compared to the glass-air interface, which was at 41.3°. Utilizing the weak value amplification (WVA) approach, the behavior of spatial GH shifts at this interface with various regulating parameters such as angle of incidence, polarization angle, and post-selection angle has systematically been studied. At critical incidence, the greatest shift of approximately 116 µm exceeds the maximum limit of beam shift w0/2, where w0 is the beam waist (180 µm). A generic theoretical model compatible with polarization-dependent studies is also established that has demonstrated excellent agreement with experimental results. Moreover, this work established three distinct features that allow us to readily tweak the value of spatial GH shifts. The observation of a controllable spatial GH shift at the ML WSe2-SiO2/Si configuration has potential implications for optical sensors, optical differential operation, and other photonic manipulations.

Separation of measurement uncertainty into quantum and classical parts based on Kirkwood–Dirac quasiprobability and generalized entropy

Abstract Measurement in quantum mechanics is notoriously unpredictable. The uncertainty in quantum measurement can arise from the noncommutativity between the state and the measurement basis which is intrinsically quantum, but it may also be of classical origin due to the agent’s ignorance. It is of fundamental as well as practical importance to cleanly separate the two contributions which can be directly accessed using laboratory operations. Here, we propose two ways of decomposition of the total measurement uncertainty additively into quantum and classical parts. In the two decompositions, the total uncertainty of a measurement described by a positive-operator-valued measure (POVM) over a quantum state is quantified respectively by two generalized nonadditive entropies of the measurement outcomes; the quantum parts are identified, respectively, by the nonreality and the nonclassicality—which captures simultaneously both the nonreality and negativity—of the associated generalized Kirkwood–Dirac quasiprobability relative to the POVM of interest and a projection-valued measure and maximized over all possible choices of the latter; and, the remaining uncertainties are identified as the classical parts. Both decompositions are shown to satisfy a few plausible requirements. The minimum of the total measurement uncertainties in the two decompositions over all POVM measurements are given by the impurity of the quantum state quantified by certain generalized quantum entropies, and are entirely classical. We argue that nonvanishing genuine quantum uncertainty in the two decompositions are sufficient and necessary to prove quantum contextuality via weak measurement with postselection. Finally, we suggest that the genuine quantum uncertainty is a manifestation of a specific measurement disturbance.

Euclid preparation

LENSMC is a weak lensing shear measurement method developed for Euclid and Stage-IV surveys. It is based on forward modelling in order to deal with convolution by a point spread function (PSF) with comparable size to many galaxies, sampling the posterior distribution of galaxy parameters via Markov chain Monte Carlo, and marginalisation over nuisance parameters for each of the 1.5 billion galaxies observed by Euclid. We quantified the scientific performance through high-fidelity images based on the Euclid Flagship simulations and emulation of the Euclid VIS images, realistic clustering with a mean surface number density of 250 arcmin−2 (IE < 29.5) for galaxies, and 6 arcmin−2 (IE < 26) for stars, and a diffraction-limited chromatic PSF with a full width at half maximum of 0′.′2 and spatial variation across the field of view. LENSMC measured objects with a density of 90 arcmin−2 (IE < 26.5) in 4500 deg2. The total shear bias was broken down into measurement (our main focus here) and selection effects (which will be addressed in future work). We found measurement multiplicative and additive biases of m1 = (−3.6 ± 0.2) × 10−3, m2 = (−4.3 ± 0.2) × 10−3, c1 = (−1.78 ± 0.03) × 10−4, and c2 = (0.09 ± 0.03) × 10−4; a large detection bias with a multiplicative component of 1.2 × 10−2 and an additive component of −3 × 10−4; and a measurement PSF leakage of α1 = (−9 ± 3) × 10−4 and α2 = (2 ± 3) × 10−4. When model bias is suppressed, the obtained measurement biases are close to Euclid requirement and largely dominated by undetected faint galaxies (−5 × 10−3). Although significant, model bias will be straightforward to calibrate given its weak sensitivity on galaxy morphology parameters. LENSMC is publicly available at gitlab.com/gcongedo/LensMC.

The Orlicz–Pettis theorem for locally convex cones

The Orlicz–Pettis theorem for locally convex cones