An October 27, 2025 Polytechnic University of Turin (Politecnico di Torino [PoliTo]) press release announced research into the science of measurement (metrology), Note: Links have been removed,

Tracking electrical resistance is essential to ensure the accuracy and reliability of electrical measurements worldwide. Since 2019, the units of measurement in the International System (SI) are no longer based on standard samples (kilogram, metre, etc.), but are derived from universal constants such as the speed of light. For electrical resistance, reference is therefore made to electrical conductance – which measures the ability of a material to conduct electricity – quantised (G₀) – a combination of Planck’s constant (h) and the elementary charge (e) – typically measured using the quantum Hall effect, a technique that provides accurate and reproducible values but requires expensive cryogenic systems and high-intensity magnetic fields available in only a few national metrology institutes (NMIs).

The study ‘Quantum resistance memristor for International System of Units intrinsically traceable standard’, co-authored by a group of researchers from Politecnico di Torino together with leading European metrology centres and published today in the prestigious journal Nature Nanotechnology, introduces a new standard for the traceability of electrical resistance: memristors, nanometric devices capable of modifying their conductivity in response to external stimuli. This is an innovative discovery: memristors can provide stable resistance values that are intrinsically correlated with the fundamental constants of nature, with the possibility of programming the resistance by modifying the silver nanofilaments that characterise them.

These changes can be adjusted at the atomic level even at room temperature, thus generating quantum leaps – fundamental concepts of quantum mechanics referring to the phenomenon whereby a quantum system passes from one energy level to another in a discontinuous manner, i.e. without passing through intermediate states, as happens with an electron in an atom – discrete, corresponding to G0 (or multiples) that can be measured with conventional reading systems. This approach paves the way for the concept of “NMI-on-a-chip”, i.e. the possibility of integrating the functions of an entire national metrology institute at the microchip level.

In the future, electrical measuring devices such as multimeters – among the most widely used instruments in the industry for measuring electrical quantities – could thus have a memristor as a reference for self-calibration, i.e. to automatically adjust their measurement or operating parameters so as to maintain the accuracy and correctness of results without external human intervention. This will enable the use of simplified calibration procedures in industry and in sectors where the portability of calibrated measurements is a necessity.

“The results obtained and published in the prestigious journal Nature Nanotechnology are the fruit of the European MEMQuD project, where fundamental research by academic institutions such as Politecnico di Torino and the Forschungszentrum Jülich on the phenomenon of “electrochemical polishing” (thanks to which nanofilaments can be “filed” at the atomic level) was coupled with the methodological rigour of the national metrology institutes of Italy, Turkey, Spain, Portugal and Germany”, comment the co-authors of the study Carlo Ricciardi and Fabio Michieletti, respectively professor and post-doctoral researcher at the Department of Applied Science and Technology-DISAT and members of the NaMeS group at Politecnico di Torino.

An October 28, 2025 Universitat Autonoma de Barcelona press release (also on EurekAlert but published November 3, 2025) provides additional insight,

Microchips with a memristor could replace an entire electrical resistance calibration laboratory

An international research collaboration with the involvement of the UAB demonstrates for the first time that memristors, electronic devices at the nanoscale,  can easily calibrate electrical resistance for certain applications without requiring large and complex laboratories working at extreme temperatures and very high magnetic fields. The work, published in Nature Nanotechnology, explores for the first time the metrological applications of these devices in calibration procedures of electronic systems.

Measuring electrical resistance with maximum precision to be used as a standard in metrology requires complex laboratories at temperatures close to the absolute zero and magnetic fields that are more intense than those used in clinical magnetic resonance imaging.

International research under the framework of the European project MEMQuD, which included the involvement of UAB Department of Electronic Engineering professors Enrique Miranda and Jordi Suñé, demonstrates that memristors can provide stable resistance values directly linked to fundamental constants of nature. Thus, they can become a new much simpler standard than current systems for calibrations of this magnitude.

Measurement standards based on constants of nature

Since 2019, all base units of the International System of Units (SI)—including the metre, second, and kilogram—have been based on fundamental natural constants. For example, the kilogram, which was once based on the “prototype kilogram,” is now linked to Planck’s constant h. A metre is defined with respect to the speed of light, and a second by the oscillation of the cesium atom.

Thanks to laser interferometers and atomic clocks, units of length and time can be verified relatively easily worldwide. The situation is quite different for physical quantities such as mass and electrical units. Their metrological traceability is so complex that the measurements are feasible only in a handful of national metrology institutes.

Until now, the quantum Hall effect has served as the standard for electrical resistance. While it provides highly precise and reproducible values, it requires extreme laboratory conditions, i.e. temperatures close to absolute zero and high magnetic fields. The measurements require sophisticated cryogenic systems and strictly controlled facilities.

Memristors as standard resistance measurement systems

Memristors offer a radically different approach. Originally developed as building blocks for novel computing architectures, such as non-volatile memories and neuromorphic circuits emulating computations in the brain, they exhibit a switching behavior that directly follows universal constants.

Functionally, they act as programmable resistors—essentially resistors with memory. This resistance can be changed by applying external voltages or currents. Conductive nanofilaments of individual silver atoms forms inside them. By applying electrical bias, these filaments can be adjusted with atomic precision so that their conductance changes not continuously, but in discrete quantum steps.

“We have confirmed that memristors can reliably generate discrete resistance states that are directly related to universal constants of nature. In 1998, our group already revealed these quantum effects for the first time in the dielectric breakdown of thin insulators. For certain applications, these devices can be used for calibration without the need of complex cooling systems or high magnetic fields”, says UAB professor Enrique Miranda.

A national metrology institute condensed into one microchip

This approach makes it possible to talk about a concept known as “NMI-in-a-chip”: the service of a national metrology institute condensed into a microchip. In the future, this could mean that a measuring device has its resistance reference built-in directly into the chip. Lengthy calibration chains—from measurements in metrology institutes, reference resistors and precision calibrators, to the calibration of end-user devices—would no longer be necessary. Instead of repeatedly sending a multimeter to the calibration laboratory, it could check itself internally, i.e. a built-in calibration standard.

Applications in research and industries

Applications range from simplified calibration procedures in industry to mobile measuring systems and portable standards for research in the field or in space. “We are at the beginning of a paradigm shift—moving away from complex large-scale facilities towards intrinsic, quantum-accurate standards that can be integrated into any chip”, says UAB professor Jordi Suñé.

Quantified electrical conductance

The foundation of this work is the quantized electrical conductance G₀, derived from Planck’s constant h and the elementary charge e. In the experiments, memristors were reproducibly programmed in air at room temperature into stable conductance states of exactly 1·G₀ and 2·G₀, maintained over extended periods of time. Measurements taken at participating research institutes in Italy, Germany, Spain, Turkey, and Portugal revealed a deviation of 3.8 percent for 1·G₀ and 0.6 percent for 2·G₀. The key lies in a process known as “electrochemical polishing”. In this process, unstable atoms are removed from the conducting filament until only a stable quantized conduction channel remains.

The European project MEMQuD, funded by the European Metrology Programme for Innovation and Research (EMPIR) of the EURAMET alliance of metrology organisations, is an international collaboration with the involvement of the UAB, the INRiM (Italy), the Forschungszentrum Jülich, Peter Grünberg Institute (Germany), the Politecnico di Torino (Italy), the IMDEA Nanociencia (Spain), the TUBITAK National Metrology Institute (Turkey), the TOBB University of Economics and Technology (Turkey), the Instituto Português da Qualidade (Portugal), and the Bulgarian Academy of Sciences (Bulgaria).

Here’s a link to and a citation for the paper,

A quantum resistance memristor for an intrinsically traceable International System of Units standard by Gianluca Milano, Xin Zheng, Fabio Michieletti, Giuseppe Leonetti, Gabriel Caballero, Ilker Oztoprak, Luca Boarino, Özgür Bozat, Luca Callegaro, Natascia De Leo, Isabel Godinho, Daniel Granados, Itir Koymen, Mariela Menghini, Enrique Miranda, Luís Ribeiro, Carlo Ricciardi, Jordi Suñe, Vitor Cabral & Ilia Valov. Nature Nanotechnology volume 20, pages 1884–1890 (2025) Published: 27 October 2025 Version of record: 27 October 2025 Issue date: December 2025 DOI: https://doi.org/10.1038/s41565-025-02037-5

This paper is open access.