Metrological Precision Research Articles

Enhanced super-Heisenberg scaling precision by nonlinear coupling and postselection

In quantum metrology, the famous result of Heisenberg limit, scaling as 1/N (with N the number of probes), can be surpassed by considering nonlinear coupling measurement. In this work, we consider the most practice-relevant quadratic nonlinear coupling and show that the metrological precision can be enhanced from the 1/N32 super-Heisenberg scaling to 1/N2, by simply employing a pre- and post-selection (PPS) strategy, but not using any expensive quantum resources such as quantum entangled state of probes.

Contextual quantum metrology

We demonstrate that the contextuality of measurement selection can enhance the precision of quantum metrology with a simple linear optical experiment. Contextuality is a nonclassical property known as a resource for various quantum information processing tasks. Recent studies show that contextuality by anomalous weak values can be utilized to enhance metrological precision, unraveling the role of contextuality in quantum metrology. Our contextual quantum metrology (coQM) scheme can elevate the precision of the optical polarimetry as much as 6 times the precision limit given by the Quantum Fisher Information. We achieve the contextuality-enabled enhancement with two mutually complementary measurements, whereas, in the conventional method, some optimal measurements to achieve the precision limit are either theoretically challenging to find or experimentally infeasible to realize. These results highlight that the contextuality of measurement selection is applicable in practice for quantum metrology.

Quality analysis for precision metrology based on joint weak measurements without discarding readout data

We present a theoretical analysis for the metrology quality of joint weak measurements (JWMs), in close comparison with the weak-value-amplification technique. We point out that the difference probability function employed in the JWM scheme cannot be used to calculate the uncertainty variance and Fisher information (FI). In order to carry out the metrological precision, we reformulate the problem in terms of difference-combined stochastic variables, which makes all calculations well defined. We reveal that, in general, the metrological precision of the JWM scheme cannot reach that indicated by the total FI, despite that all the readouts are collected without discarding. We also analyze the effect of technical noise, showing that the technical noise cannot be removed by the subtracting procedure, which yet can be utilized to outperform the conventional measurement, when considering the imaginary weak value measurement.

Fisher information of correlated stochastic processes

Many real-world tasks include some kind of parameter estimation, i.e. the determination of a parameter encoded in a probability distribution. Often, such probability distributions arise from stochastic processes. For a stationary stochastic process with temporal correlations, the random variables that constitute it are identically distributed but not independent. This is the case, for instance, for quantum continuous measurements. In this article, we derive the asymptotic Fisher information rate for a stationary process with finite Markov order. We give a precise expression for this rate which is determined by the process’ conditional distribution up to its Markov order. Second, we demonstrate with suitable examples that correlations may both enhance or hamper the metrological precision. Indeed, unlike for entropic information quantities, in general nothing can be said about the sub- or super-additivity of the joint Fisher information in the presence of correlations. To illustrate our results, we apply them to thermometry on an Ising spin chain, considering nearest-neighbour and next-to-nearest neighbour coupling. In this case, the asymptotic Fisher information rate is directly connected to the specific heat capacity of the spin chain. We observe that the presence of correlations strongly enhances the estimation precision in an anti-ferromagnetic chain, while in a ferromagnetic chain this is not the case.

Influence of the dissipative topological edge state on quantized transport in MnBi2Te4

The beauty of the quantum Hall (QH) effect is the metrological precision of Hall resistance quantization that originates from the topological edge states. Understanding the factors that lead to quantization breakdown not only provides important insights on the nature of the topological protection of these edge states, but is beneficial for device applications involving such quantized transport. In this work, we combine conventional transport and real space conductivity mapping to investigate whether the quantization breakdown is tied to the disappearance of edge state in the hotly studied ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ system. Our experimental results unambiguously show that topological edge state does exist when quantization breakdown occurs. Such edge state is dissipative in nature and could lead to a quantization breakdown due to its diffusive character causing overlapping with bulk and other edge states in real devices. Our findings bring attention to issues that are generally inaccessible in the transport study of QH, but can play important roles in practical measurements and device applications.

The Metrological Traceability, Performance and Precision of European Radon Calibration Facilities.

An interlaboratory comparison for European radon calibration facilities was conducted to evaluate the establishment of a harmonized quality level for the activity concentration of radon in air and to demonstrate the performance of the facilities when calibrating measurement instruments for radon. Fifteen calibration facilities from 13 different European countries participated. They represented different levels in the metrological hierarchy: national metrology institutes and designated institutes, national authorities for radiation protection and participants from universities. The interlaboratory comparison was conducted by the German Federal Office for Radiation Protection (BfS) and took place from 2018 to 2020. Participants were requested to measure radon in atmospheres of their own facilities according to their own procedures and requirements for metrological traceability. A measurement device with suitable properties was used to determine the comparison values. The results of the comparison showed that the radon activity concentrations that were determined by European calibration facilities complying with metrological traceability requirements were consistent with each other and had common mean values. The deviations from these values were normally distributed. The range of variation of the common mean value was a measure of the degree of agreement between the participants. For exposures above 1000 Bq/m3, the variation was about 4% for a level of confidence of approximately 95% . For lower exposure levels, the variation increased to about 6%.

Quantum anomalous Hall edge channels survive up to the Curie temperature

Achieving metrological precision of quantum anomalous Hall resistance quantization at zero magnetic field so far remains limited to temperatures of the order of 20 mK, while the Curie temperature in the involved material is as high as 20 K. The reason for this discrepancy remains one of the biggest open questions surrounding the effect, and is the focus of this article. Here we show, through a careful analysis of the non-local voltages on a multi-terminal Corbino geometry, that the chiral edge channels continue to exist without applied magnetic field up to the Curie temperature of bulk ferromagnetism of the magnetic topological insulator, and that thermally activated bulk conductance is responsible for this quantization breakdown. Our results offer important insights on the nature of the topological protection of these edge channels, provide an encouraging sign for potential applications, and establish the multi-terminal Corbino geometry as a powerful tool for the study of edge channel transport in topological materials.

SI-traceable frequency dissemination at 1572.06 nm in a stabilized fiber network with ring topology.

Frequency dissemination in phase-stabilized optical fiber networks for metrological frequency comparisons and precision measurements are promising candidates to overcome the limitations imposed by satellite techniques. However, in an architecture shared with telecommunication data traffic, network constraints restrict the availability of dedicated channels in the commonly-used C-band. Here, we demonstrate the dissemination of an SI-traceable ultrastable optical frequency in the L-band over a 456 km fiber network with ring topology, in which data traffic occupies the full C-band. We characterize the optical phase noise and evaluate a link instability of 4.7 × 10-16 at 1 s and 3.8 × 10-19 at 2000 s integration time, and a link accuracy of 2 × 10-18. We demonstrate the application of the disseminated frequency by establishing the SI-traceability of a laser in a remote laboratory. Finally, we show that our metrological frequency does not interfere with data traffic in the telecommunication channels. Our approach combines an unconventional spectral choice in the telecommunication L-band with established frequency-stabilization techniques, providing a novel, cost-effective solution for ultrastable frequency-comparison and dissemination, and may contribute to a foundation of a world-wide metrological network.

Effect of Welding Orientation in Angular Distortion in Multipass GMAW

The use of the welding process on an industrial scale has become significant over the years and is currently among the main processes for joining metallic materials. Along the weld, structural changes occur in the vicinity of the joint. These thermal stresses and geometric distortions are mostly undesirable and are complex to predict with precision. Using S235JR steel as the base material, laboratory experiments were carried out using the multipass GMAW process, with the aim of investigating the influence of the welding direction on angular distortion. To measure the distortions, a methodology was applied using equipment to identify the coordinates in the operational space with metrological precision. Through metrological and statistical analyses, we found that the orientation factor significantly influenced the final distortions and that the alternated orientation sequence resulted in less distortions.

Elaboration of an App for calculations of dosimetric quantities aiming at radiological protection

In routine operations of services and standard practices that use ionizing radiation sources, safety is required in relation to the calculations of the variables, according to the operation. The safe distance to operate at, the conversions of units and other important quantities need metrological precision, to avoid any unfortunate unwanted affects. In this sense, this work aims to demonstrate the benefits of an App that can be used free of charge for calculating dosimetric quantities. This App proved to be efficient and accurate in tests, for example, in calculations for Gammagraphy.

Robust Interferometric Sensing Using Two-Photon Interference

Precise measurement of the angular deviation of an object is a common task in science and technology. Many methods use light for this purpose. Some of these exploit interference effects to achieve technological advantages, such as amplification effects, or simplified measurement devices. However, all of these schemes require phase stability to be useful. Here we show theoretically and experimentally that this drawback can be lifted by utilizing two-photon interference, which is known to be less sensitive to phase fluctuations. Our results show that non-classical interference can provide a path towards robust interferometric sensing, allowing for increased metrological precision in the presence of phase noise.

ANALYSIS OF GEOLOGICAL MATERIALS BY ICP-AES WITH CALIBRATION IN CONCENTRATION RATIO

A method of calibration in relative concentrations (concentration ratio) previously used only in analysis of non-ferrous and ferrous metals was first implemented when performing silicate analysis of geological materials using atomic emission spectrometry with inductively coupled plasma (AES-ICP). Prior to apply the Concentration Calibration Ratio to analysis of geological materials it is necessary to consider and address the following problems: some of the components are not determined by ICP-AES, matrix elements may be present in different oxidation states. Sample preparation of ores and geological materials was carried out in autoclaves heated at 180°C using HotBlock 200 system. A mixture HCl/HNO3/HF was used at the first step and then added with a 4% H3BO3 solution. The repeatability and intermediate precision of determination when using Concentration Ratio Calibration, calibration without internal standard and Calibration with In as internal standard are compared for determination of SiO2 (content 40 – 75%), Al2O3 (5 – 20%), CaO (0.25 – 15%), MgO (0.1 – 15%), Fe2O3 (0.5 – 15%), Na2O (0.5 – 10%), K2O (0.5 – 5%), P2O5 (0.01 – 0.3%), MnO (0.03 – 0.5%), and TiO2 (0.05 – 2%). The use of Concentration Ratio Calibration provides better metrological characteristics, repeatability and precision in analysis of geological materials compared to other calibration procedures due to elimination of the calibration error of balances and volumetric flasks from total error of analysis; measuring the large intensities of the base element; and better accuracy of measuring the intensity ratio compared to absolute intensity measurements.

Compact Distributed Digitizers With Metrological Precision

Prototype distributed digitizers have been developed with the metrological precision of the individual measurement nodes. A master controller aggregates the data of the nodes and performs all computational tasks. A crucial part of the system is the synchronization of the individual nodes at the nanosecond level using white-rabbit technology. Fiber-optic communication is used to reduce interference and to obtain high isolation. When operated on battery power, this allows for special applications such as the measurement of currents in high-voltage lines. First, results show that a phase difference between nodes of a few microradians can be achieved with a resolution of better than $0.1~\mu $ rad.

Super-resolution in diffractive imaging from hemispherical elastic light scattering data.

Angle-resolved hemispherical elastic light scattering techniques have been used to reconstruct the surface profile of two-dimensional photonic crystals with submicron resolution and metrological precision. Iterative algorithms permit subsequent calculation of a surface autocorrelation function with additional numerical approximation of the power spectrum and then yield final reconstruction of the surface shape. The proposed method enables filtering out unwanted scattering background, precluding the convergence of phase-retrieval algorithms. The estimation of higher harmonics in the power spectrum provides the reconstruction of a realistic surface achieving subwavelength resolution.

Achieving metrological precision limits through postselection

Post-selection strategies have been proposed with the aim of amplifying weak signals, which may help to overcome detection thresholds associated with technical noise in high-precision measurements. Here we use an optical setup to experimentally explore two different post-selection protocols for the estimation of a small parameter: a weak-value amplification procedure and an alternative method, that does not provide amplification, but nonetheless is shown to be more robust for the sake of parameter estimation. Each technique leads approximately to the saturation of quantum limits for the estimation precision, expressed by the Cram\'er-Rao bound. For both situations, we show that information on the parameter is obtained jointly from the measuring device and the post-selection statistics.

Quantum computation speedup limits from quantum metrological precision bounds

We propose a scheme for translating metrological precision bounds into lower bounds on query complexity of quantum search algorithms. Within the scheme the link between quadratic performance enhancement in idealized quantum metrological and quantum computing schemes becomes clear. More importantly, we utilize results from the field of quantum metrology on a generic loss of quadratic quantum precision enhancement in presence of decoherence to infer an analogous generic loss of quadratic speed-up in oracle based quantum computing. While most of our reasoning is rigorous, at one of the final steps, we need to make use of an unproven technical conjecture. We hope that we will be able to amend this deficiency in the near future, but we are convinced that even without the conjecture proven our results provide a novel and deep insight into relationship between quantum algorithms and quantum metrology protocols.

Multiply Charged Thorium Crystals for Nuclear Laser Spectroscopy

We have produced laser-cooled crystals of 232Th3+ in a linear rf Paul trap. This is the first time that a multiply charged ion has been laser cooled. Our work opens an avenue for excitation of the nuclear transition in a trapped, cold 229Th3+ ion. Laser excitation of nuclear states would establish a new bridge between atomic and nuclear physics, with the promise of new levels of metrological precision.

Learning from microarray interlaboratory studies: measures of precision for gene expression

BackgroundThe ability to demonstrate the reproducibility of gene expression microarray results is a critical consideration for the use of microarray technology in clinical applications. While studies have asserted that microarray data can be "highly reproducible" under given conditions, there is little ability to quantitatively compare amongst the various metrics and terminology used to characterize and express measurement performance. Use of standardized conceptual tools can greatly facilitate communication among the user, developer, and regulator stakeholders of the microarray community. While shaped by less highly multiplexed systems, measurement science (metrology) is devoted to establishing a coherent and internationally recognized vocabulary and quantitative practice for the characterization of measurement processes.ResultsThe two independent aspects of the metrological concept of "accuracy" are "trueness" (closeness of a measurement to an accepted reference value) and "precision" (the closeness of measurement results to each other). A carefully designed collaborative study enables estimation of a variety of gene expression measurement precision metrics: repeatability, several flavors of intermediate precision, and reproducibility. The three 2004 Expression Analysis Pilot Proficiency Test collaborative studies, each with 13 to 16 participants, provide triplicate microarray measurements on each of two reference RNA pools. Using and modestly extending the consensus ISO 5725 documentary standard, we evaluate the metrological precision figures of merit for individual microarray signal measurement, building from calculations appropriate to single measurement processes, such as technical replicate expression values for individual probes on a microarray, to the estimation and display of precision functions representing all of the probes in a given platform.ConclusionWith only modest extensions, the established metrological framework can be fruitfully used to characterize the measurement performance of microarray and other highly multiplexed systems. Precision functions, summarizing routine precision metrics estimated from appropriately repeated measurements of one or more reference materials as functions of signal level, are demonstrated and merit further development for characterizing measurement platforms, monitoring changes in measurement system performance, and comparing performance among laboratories or analysts.

Use of photoelectron laser phase determination method for attosecond measurements with quantum-mechanical calculations

This paper calculates quantum-mechanically the photoelectron energy spectra excited by attosecond x-rays in the presence of a few-cycle laser. A photoelectron laser phase determination method is used for precise measurements of the pulse natural properties of x-ray intensity and the instantaneous frequency profiles. As a direct procedure without any previous pulse profile assumptions and time-resolved measurements as well as data fitting analysis, this method can be used to improve the time resolutions of attosecond timing and measurements with metrological precision. The measurement range is half of a laser optical cycle.

New stage in the metrological provision for sensors

It is shown that traditional methods of metrological provision for critical sensors do not provide the required level of confidence for measurement results and economic efficiency. The desirability of changing to automatic monitoring of the metrological precision of sensors during operation is substantiated and requirements for the metrological procedures that are necessary are determined.