Electrical metrology has historically relied on precise current comparators, which play a central role in determining accurate current ratios. Conventional devices, however, depend on inductive pickup coils or cryogenic infrastructures such as SQUIDs, imposing limitations on bandwidth, complexity, and operational environments. To address these challenges, we propose a unified comparator architecture based on nitrogen-vacancy (NV) centers in diamond. The system replaces conventional magnetic pickup or flux feedback mechanisms with a solid-state quantum magnetometer that optically detects magnetic flux in the air-gap of a magnetic core. The NV sensor provides sensitivity to both AC and DC magnetic fields, enabling seamless operation across different metrological regimes, and fully compatible with a modern power electronics requirement. The proposed architecture offers key advantages such as complete electrical isolation, compact system, and potential scalability for portable or embedded applications. Modeling and recent advances in NV magnetometry suggest that the required sensitivity is achievable with current technologies. By addressing both AC and DC current measurement requirements in the field of power industries and fundamental electrical standards, this concept paves the way toward a next-generation current ratio standard.

We report a cryogen-free cryogenic current comparator (CCC) system for precision resistance measurements. A helium-gas chamber was developed and installed on the 4 K stage of a cryogen-free dilution refrigerator equipped with a pulse-tube cryocooler. The CCC probe was housed in this chamber and was cooled through helium gas serving as a heat exchange medium. The metrological performance of this helium-gas-cooled CCC was evaluated through precision resistance-ratio measurements and found to be comparable to that obtained under liquid-helium cooling. A quantum Hall resistance (QHR) device was also integrated into the same refrigerator, enabling QHR/100 Ω resistance-ratio measurements. The type-A uncertainty reached the 1 nΩ/Ω level within an averaging time of 100 s, and the resulting resistance-ratio measurements agreed well with conventional liquid-helium-based measurements at the level of a few nΩ/Ω. The system provides this level of measurement performance while consuming less than 1 L of helium gas per thermal cycle.

The evaluation of thermoelectric conversion efficiency remains challenging owing to the lack of internationally standardized measurement protocols. Commonly used techniques — including the heat-flow, guarded-heater, and AC Harman methods — differ fundamentally in their operating principles and sensitivity to heat losses. In this study, we benchmark three module-level efficiency measurement techniques — the heat-flow, guarded-heater, and AC Harman methods — using commercial Bi2Te3-based modules with different module architectures. The conversion efficiencies obtained using the heat-flow and guarded-heater methods showed agreeing central values and similar temperature-dependent trends over the investigated range. In contrast, the efficiency derived using the AC Harman method was systematically lower by approximately 16% to 30%, depending on the module architecture. Steady-state finite-element calculations of heat conduction and radiation indicated that the open thermal boundary condition used in the Harman configuration produces module-architecture-dependent internal temperature distributions and effective temperature differences, consistent with the experimentally observed trend. These results demonstrate that module-level efficiency estimated using the AC Harman method can be affected by nonideal thermal environments and emphasize the necessity of accounting for radiative and substrate-related heat losses. Nevertheless, the AC Harman method remains useful for rapid performance screening, provided that its module- and boundary-condition-dependent systematic bias is appropriately considered. Our results provide a quantitative benchmark for major measurement techniques and support the development of best practices, method-selection guidelines, and future methodological standardization in module-level thermoelectric metrology.

Accurate measurements of alternating current (AC) and direct current (DC) ratios are fundamental to electric power metrology. However, conventional current comparators for AC and DC typically rely on distinct technologies-electromagnetic induction for AC and superconducting quantum interference devices for DC. This technological divide leads to a fragmented and complex traceability system. Bridging this gap is critical for developing unified current standards that meet the demands of temperature power technologies.　In this work, we present a compact, room-temperature AC/DC current comparator that integrates a diamond-based magnetometer using nitrogen-vacancy centers. The device achieves a type-A uncertainty at [Formula: see text] level, while the expanded uncertainty is at [Formula: see text]to [Formula: see text]level, for both AC and DC signals and supports a system bandwidth up to [Formula: see text], without the need for cryogenics. It is comparable to the performance of typical AC comparators, and provides a compact and room-temperature operating platform for further performance improvement. This unified, cryogenics-free solution not only enhances precision and versatility but also expands the applicability of the system to DC resistance bridges in quantum electrical standards.

Ultrastable metal foil 10 k Omega standard resistors are developed. The resistors showed quite stable behavior and the observed long-term resistance drift was around +/- 10 n Omega/Omega in 2 years from just after the fabrication. They showed almost linear temperature characteristics from 18 C-degrees to 28 C-degrees, and the temperature coefficients were less than 15 (n Omega/Omega )/K at around 23 C-degrees. Due to their stress-free structure, the resistance values were quite stable within 5 n Omega/Omega after the abrupt temperature change of about 5 C-degrees. The humidity dependence was within +/- 0.2 (n Omega/Omega )/% at 23 C-degrees, and they also showed stable behavior within +/- 10 n Omega/Omega against the pressure from 700 to 1200 hPa. A vibration test along with an MIL standard, MIL-STD-202, was performed, and a 2.5 k Omega subsection of the 10 k Omega resistor indicated stability within 10 n Omega/Omega after applying vibration for 2 h on each axis (6 h in total).

Quantum Hall Effect (QHE) is the basis of the realisation of the SI unit of electrical resistance, the ohm. Present QHE devices require low temperatures and high magnetic fields to operate. The Quantum Anomalous Hall effect (QAHE) in topological insulators is a good candidate to simplify the realisation of the resistance unit and the development of a ‘quantum electrical metrology toolbox’ for universal adoption of quantum electrical SI standards, beyond just the NMIs. The Joint Research Project QuAHMET — Quantum anomalous Hall effect materials and devices for metrology of the European Partnership on Metrology . European Partnerships are a key implementation tool of the European Commission’s Horizon Europe. The aim of the project is to investigate and implement novel technologies for the development of QAHE devices and measurement systems for metrology, by performing traceable measurement and characterisation of QAHE materials as devices and primary resistance standard candidates. The project is exploring, understanding, and implementing a scientifically grounded methodology for developing metrology grade QAHE devices, by focussing on the improvement of the growth techniques of magnetically doped topological insulator (TI) optimising the material properties for the QAHE, the investigation of electronic, structural, magnetic, and magneto-electronic properties of the samples, and of the limitation conditions of QAHE (expecially temperature and current), by employing also scanning probes and magnetometry techniques at low temperatures. The NMIs involved will be in charge of the development and application of accurate measurement techniques to perform a detailed metrological assessment of the optimised QAHE devices at low-to-zero applied magnetic field. The consortium consists of 14 partners and gathers 7 leading European national metrology institutes (NMIs), a Japanese NMI for metrology, complemented by 6 globally recognized institutes from academia and applied research. The project aims to connect with and impact on NMIs and calibration centers, academia, T&M industry and end users interested in applications, such as spintronics and topological quantum computing and advance the research and progress in the field of TIs. The project started in June 2024 and the poster will report on its advancements and results. The project is open to collaborations and interest from stakeholders. You can connect to the project via its website (sites.google.com/inrim.it/quahmet/home), LinkedIn group (www.linkedin.com/groups/8824119/) and YouTube channel (www.youtube.com/channel/UCaHuyb8YzrjPnLUz7nSiauA). Acknowledgement: The project 23FUN07 QuAHMET has received funding from the European Partnership on Metrology, co-financed from the European Union’s Horizon Europe Research and Innovation Programme and by the Participating States.

Electronic flying qubits offer an interesting alternative to photonic qubits: electrons propagate slower, hence easier to control in real time, and Coulomb interaction enables direct entanglement between different qubits. Although their coherence time is limited, flying electrons in the form of picosecond plasmonic pulses could be competitive in terms of the number of achievable coherent operations. The key challenge in achieving this critical milestone is the development of a new technology capable of injecting 'on-demand' single-electron wavepackets into quantum devices, with temporal durations comparable to or shorter than the device dimensions. Here, we take a significant step towards achieving this regime in a quantum nanoelectronic system by injecting ultrashort single-electron plasmonic pulses into a 14-micrometer-long Mach-Zehnder interferometer. Our results establish that quantum coherence is robust under the on-demand injection of ultrashort plasmonic pulses, as evidenced by the observation of coherent oscillations in the single-electron regime. Building on this, our results demonstrate the existence of a "non-adiabatic" regime that is prominent at high frequencies. This result highlights the potential of flying qubits as a promising alternative to localised qubit architectures, offering advantages such as a reduced hardware footprint, enhanced connectivity, and scalability for quantum information processing.

Recent advancements in circuit quantum electrodynamics have enabled precise manipulation and detection of a single energy quantum in quantum systems. A quantum circuit refrigerator (QCR) is capable of electrically cooling an excited population of quantum systems, such as superconducting resonators and qubits, through photon-assisted tunneling of quasiparticles within a superconductor-insulator-normalmetal junction. In this study, we demonstrate fast QCR in the quantum regime. We perform time-resolved measurement of the QCR-induced cooling of photon number inside a superconducting resonator by harnessing a qubit as a photon detector. From the enhanced photon loss rate of the resonator estimated from the ac Stark shift, the QCR was shown to have a cooling power of approximately 300 aW. Furthermore, even below the single energy quantum, a 100-ns pulse on the QCR can reduce the number of photons inside the resonator below thermal equilibrium. Numerical calculations based on the Lindblad master equation successfully reproduce these experimental results.

Coherent manipulation of plasmon wavepackets in solid-state systems is crucial for advancing nanoscale electronic devices, offering a unique platform for quantum information processing based on propagating quantum bits. Controlling the eigenstate of plasmon wavepackets is essential, as it determines their propagation speed and hence the number of quantum operations that can be performed during their flight time through a quantum system. When plasmon wavepackets are generated by short voltage pulses and transmitted through nanoscale devices, they distribute among multiple electron conduction channels via Coulomb interactions, a phenomenon known as charge fractionalisation. This spreading complicates plasmon manipulation in quantum circuits and makes precise control of the eigenstates of plasmon wavepackets challenging. Using a cavity, we demonstrate the ability to isolate and select electron conduction channels contributing to plasmon excitation, thus enabling precise control of plasmon eigenstates. Specifically, we observe an electron-channel blockade effect, where charge fractionalisation into cavity-confined channels is suppressed due to the plasmon's narrow energy distribution, enabling more stable and predictable plasmonic circuits. This technique provides a versatile tool for designing plasmonic circuits, offering the ability to tailor plasmon speed through local parameters, minimise unwanted plasmon excitation in adjacent circuits, and enable the precise selection of electron-channel plasmon eigenstates in quantum interferometers.

Integration and low power consumption of cryogenic amplifiers, which are essential for reading out quantum qubits, are inevitable issues for scaling up quantum information processing systems. Although cryogenic probers play an important role in this development, measurement solutions using impedance tuners are not available due to the long high frequency wiring for thermal insulation. In this paper we propose a new probe head structure with high thermal insulation. We eliminate metal heat conduction by using electromagnetic coupling between planar resonant circuits. In addition to evaluating the transmission characteristics of the prototype probe head at room temperature, we experimentally assess its thermal stability under conditions with a significant thermal gradient. This technique enables shorter high-frequency lines in cryogenic probers by providing the probe head itself with thermal insulating properties.

This article reports on a numerical simulation using the finite-element method (FEM) on the effects of shielding and guarding electrodes of a vacuum-gap capacitor using coaxial cylindrical electrodes on the capacitance gradient measurements for an electrostatic-force balance apparatus. The electric field of the coaxial cylindrical capacitor with a shielding electrode was computed when the capacitor was open or semi-closed using a grounded-guarding electrode placed around the positive-terminal electrode. The capacitance and unwanted capacitive coefficients between the positive-terminal and grounded electrodes were calculated using the computed electric fields. The FEM results suggested that, under given conditions, there is an optimal overlapping length in the longitudinal direction of the coaxial cylindrical electrodes of the capacitor. This is based on the linearity of the capacitance gradient and parasitic capacitances that resulted in an error in the determination of the capacitance gradient using a three-terminal capacitance bridge in the electrostatic-force balance measurement. The FEM simulations also suggested that the use of a guarding electrode reduced the unwanted parasitic capacitive coefficients between the terminal and shielding electrodes, whereas the guarding electrode had no significant impact on the linearity of the capacitance gradient. Experiments were also conducted to confirm the consistency of the FEM results, which showed good agreement with the measurement uncertainties.

Surface acoustic wave (SAW) technology has been explored in thin-film materials to discover fundamental phenomena and to investigate their physical properties. It is used to excite and manipulate quasiparticles such as phonons or magnons and can dynamically modulate the properties of the materials. In the field, SAWs are typically excited by a continuous wave at a resonant frequency. Recently, generation of a single-cycle SAW pulse has been demonstrated on GaAs substrate. Such a SAW pulse provides a potential to access a single quasiparticle excitation and to investigate its dynamics by time-resolved measurements. On the other hand, to modulate and control the properties of thin-film materials, it is generally required to generate high-intensity SAWs. In this work, we demonstrate the efficient generation of a SAW pulse using a chirp interdigital transducer (IDT) on LiNbO3 substrate. We have fabricated chirp IDT devices with bandwidths from 0.5 GHz to 5.5 GHz. We also confirmed the generation of a SAW pulse with 0.3 ns full width at half maximum by performing time-resolved measurements. The conversion efficiency between input power and SAW on LiNbO3 substrate is approximately 45 times larger than that on GaAs substrate. This enables us to generate a high-intensity SAW pulse, meeting the requirement for the modulation of thin films. Our results will expand the research in the field, such as spintronics and magnonics, and lead to their further advancements.

Emerging technologies demand innovations in metrology: • Agility – to keep pace with a rapidly changing technical landscape; • Ability – to develop novel, perhaps first-ever, measurement capabilities; • Comparability and interoperability – across vendors, in commercial timeframes; • Accelerated delivery – because formal standards may be obsolete by the time they’re published. The same quantum technologies that have revolutionized metrology, such as Josephson junctions that are used to create the world’s most accurate voltage standards and ion traps that are used in time and frequency standards, also underpin emerging new markets in quantum computing, networking and sensing – and these quantum-based products require entirely new approaches for measurement and characterization. The world’s metrology institutes have been at the forefront of the quantum revolution, being both early developers and adopters of quantum technologies for metrology, and are uniquely poised to spearhead the development of metrology for quantum – those measurements and related standards needed by industry to underpin quantum-based products. The metrology community is positioned to create trust in the emerging quantum economy due to its long history of objectivity, neutrality and international collaboration; anticipating industry’s needs to be ready with rigorous measurement capabilities as technologies evolve; and its having formed institutions such as the CIPM, BIPM and IMEKO to support collaborative efforts. The BIPM hosted a workshop in March 2024 which brought together 149 participants from 43 NMIs and designated institutes (DIs) from 39 economies, along with industry representatives, to discuss how best to leverage the expertise of the worlds national metrology institutes (NMIs) and their designated institutes (DIs) to accelerate the development and adoption of quantum technologies through measurements and standards. The workshop supported coordinated development and sharing of measurement “best practices” in support of future standardization, the mission of a new collaborative initiative referred to as NMI-Q. The NMI-Q organizing committee, comprised of representatives of the NMIs of Australia, Canada, Germany, Italy, Japan, the United Kingdom, and the United States, are working on a cooperation framework inspired by the successful VAMAS organization, which conducts coordinated pre-standardization work in material science. NMI-Q has initiated early work in quantum photonics, and expects to expand to a breadth of technical areas, such as measurement and characterization to support multiple quantum computing platforms, quantum networking models, and sensing modalities.

The development of an ultracompact Zener-voltage-standard module intended as a detachable and replaceable dc voltage reference to ensure traceability in measurement instruments is currently in progress. To date, several prototypes of this detachable Zener module have been designed, assembled, and tested. This article presents an evaluation of the output voltage stability of these prototypes under changes in ambient temperature, pressure, humidity, and over time. The latest prototype demonstrates a drift rate, temperature coefficient, pressure coefficient, and humidity coefficient within 1 mu V/V per year, 0.01 ( mu V/V)/degrees C, 0.2 (nV/V)/hPa, and 0.2 mu V/V, respectively.

The operation of superconducting qubits requires a sensitive readout circuit at cryogenic temperatures, driving the demand for cryogenic non reciprocal microwave components such as circulators. However, evaluating these components at low temperatures presents significant challenges for companies and institutions without specialized measurement systems. In the development of such cryogenic non reciprocal components, the temperature dependence of ferrite's magnetic properties is the most critical factor. Therefore, an evaluation technique for accurately assessing these properties at cryogenic temperatures is essential. In this study, we develop a measurement method to characterize low loss ferrite materials over a temperature range of 300 K to 2 K. The use of the circularly polarized resonance mode TE_11n enables the direct estimation of circular complex permeability and the determination of key material parameters, including saturation magnetization and damping constant both essential for assessing the performance of ferrite materials in circulator applications. To validate the reliability of our measurement method, we selected single crystal YIG as the test material, as its magnetic properties at cryogenic temperatures are relatively well known. This demonstration confirms that our method is effective for characterizing various low loss ferrite materials that are potential candidates for compact cryogenic non reciprocal devices.

We have successfully operated a Josephson voltage standard (JVS) with a superconducting shield in a magnetic-field environment. This study involves mounting a NbN-based JVS chip on a custom-made 12 K stage adjacent to the 4 K stage within a dilution refrigerator. A magnetic field, reaching up to 10 T and generated by a superconducting magnet positioned 73 cm below the JVS chip, is initially reduced by a cancellation coil and further minimized by a superconducting shield comprising Nb, Pb, and permalloy. Consequently, clear Shapiro steps were observed under a magnetic field of approximately 10 T. This achievement marks a significant milestone toward facilitating quantum metrology triangle experiments within a single dilution refrigerator and conducting precise voltage measurements under extreme conditions.

This paper presents the lifetime evaluation of the bismuth (Bi) and antimony (Sb) thermocouples assisted by the copper heat shunt in a planar multijunction thermal converter (MJTC) via highly accelerated life testing (HALT). The temperature is selected as the accelerated stress variable. The electrical resistance increment of the thermopile is chosen as the primary signal of failure during HALT. The mean time to failure (MTTF) of the MJTC is calculated at several elevated temperatures using a two-parameter Weibull model. The accumulative failure rate fits well with the Weibull model. The MTTF at rated condition was predicted using the Arrhenius equation. The analysis shows that the MTTF of the modified thermocouple design has a considerably longer lifetime than that of the original one.

Standard approaches to quantum computing require significant overhead to correct for errors. The hardware size for conventional quantum processors in solids often increases linearly with the number of physical qubits, such as for transmon qubits in superconducting circuits or electron spin qubits in quantum dot arrays. While photonic circuits based on flying qubits do not suffer from decoherence or lack of potential scalability, they have encountered significant challenges to overcome photon loss in long delay circuits. Here, we propose an alternative approach that utilizes flying electronic wave packets propagating in solid-state quantum semiconductor circuits. Using a novel time-bin architecture for the electronic wave packets, hardware requirements are drastically reduced because qubits can be created on-demand and manipulated with a common hardware element, unlike the localized approach of wiring each qubit individually. The electronic Coulomb interaction enables reliable coupling and readout of qubits. Improving upon previous devices, we realize electronic interference at the level of a single quantized mode that can be used for manipulation of electronic wavepackets. This important landmark lays the foundation for fault-tolerant quantum computing with a compact and scalable architecture based on electron interferometry in semiconductors.

Recent advancements in circuit quantum electrodynamics have enabled precise manipulation and detection of the single energy quantum in quantum systems. A quantum circuit refrigerator (QCR) is capable of electrically cooling the excited population of quantum systems, such as superconducting resonators and qubits, through photon-assisted tunneling of quasi-particles within a superconductor-insulator-normal metal junction. In this study, we demonstrated instantaneous QCR in the quantum regime. We performed the time-resolved measurement of the QCR-induced cooling of photon number inside the superconducting resonator by harnessing a qubit as a photon detector. From the enhanced photon loss rate of the resonator estimated from the amount of the AC Stark shift, the QCR was shown to have a cooling power of approximately 300 aW. Furthermore, even below the single energy quantum, the QCR can reduce the number of photons inside the resonator with 100 ns pulse from thermal equilibrium. Numerical calculations based on the Lindblad master equation successfully reproduced these experimental results.