March 2, 2020 | Sebastian The Quantum e-leaps project is developing quantum technology for electrical measurements with record-breaking precision A new EU project is developing the most precise measuring device for electric current, a quantum standard, that would be compatible with the quantum standard for voltage. Then they could be placed on the same silicon chip, resulting in an easy-to-use device that could measure all electrical quantities with record precision; the device could also be utilised in the measurement of mass and temperature, for example. The solution is being sought in superconducting nanowires. As of last year, all SI units of measurement have been based on fundamental physical constants. This enables extremely precise measurements in national metrology institutes, but still only seldom outside them. The prototype kilogram over a hundred years old has now been abandoned, for example, but scales implementing the new definition require extremely stable conditions and input from experts. Seconds, in turn, are measured by atomic clocks, with numerous independently functioning and extremely precise versions already existing. In GPS satellites, atomic clocks enable location and map services for mobile phone users. “If it were possible to measure electrical quantities extremely precisely and easily in the same way as seconds, such a method could prove to be very useful in, for example, the development of quantum computers, quantum communications and other quantum technologies. Electricity is also used in the measurement of many other quantities, such as mass and temperature, which means there would be plenty of applications for a precise and easy measurement method. The method does not exist, yet, but we are driving towards one in the four-year Quantum e-leaps project,” states Antti Kemppinen, Senior Scientist, Quantum Systems at VTT, who coordinates the project. Ampere, the unit of electric current, is one of the base units of the SI system, and its value is tied to the elementary electric charge, an unchanging fundamental physical constant. However, because it is difficult to implement a quantum standard for the ampere, it is common to determine it with the help of voltage and resistance. Extremely precise quantum standards, or quantum mechanical measuring devices, are already available for voltage and resistance, but they cannot be put in the same measurement device, let alone on the same silicon chip. The quantum standard for resistance requires a strong magnetic field, which prevents the operation of the quantum standard for voltage. The Quantum e-leaps project attempts to solve this problem by developing a quantum standard for electric current that could be integrated with the quantum standard for voltage; together, they would form a universal quantum standard for electrical quantities. Quantum e-leaps vision. a) An integrated quantum standard converts frequency to quantized voltage and current with precision comparable to atomic clocks and frequency combs. Voltage and current standards enable all electrical standards on a single chip. b) Duality of voltage and current standards, based on Josephson junctions and superconducting (SC) nanowires, respectively. c) Twisted multilayer graphene will enable nanowires with ultimate control of dimensions and superconducting properties, required by the current standard. d) Atomic layer deposition (ALD) of disordered superconductors is another promising route for the nanowire and device development. European top quantum technology research scientists working together A quantum standard for electric current requires quantised electric current, which has been successfully produced by pumping individual electrons, but microscopic quantum effects of this kind are unreliable and cumbersome. Another alternative would be to utilise the macroscopic quantum effects of superconductors, which are already utilised with ease and extreme precision in the quantum standard for voltage. A corresponding quantum standard for electric current is sought by the Quantum e-leaps project with the help of superconducting nanowires. In theory, it is known that the tunnelling of a magnetic flux through a superconducting nanowire causes so-called coherent quantum phase slips, which should cause the quantisation of the electric current. However, this has not been achieved in practice. Quantum e-leaps is the first research project attempting to accomplish the feat through broad European co-operation. The Quantum e-leaps project is part of the EU’s FET Open research programme, which funds ambitious, interdisciplinary and high-risk research projects. Each research team of Quantum e-leaps contributes its own, highest-level competence to the multi-disciplinary international consortium. Project coordinator VTT (Finland) and Leibniz-IPHT (Germany) have a long tradition of creating quantum technologies that work in practical applications, leaning on the basic research carried out by the universities and research institutes. NPL (UK) and VTT are leading national metrology institutes in quantum metrology. Royal Holloway University of London (UK) and Aalto University (Finland) have pioneering expertise on the experiments and theory of coherent quantum phase slips. ETH Zürich University (Switzerland) and University of Regensburg (Germany) provide the project with brand new two-dimensional superconductors such as twisted multilayer graphene and niobium diselenide. Further information: Antti Kemppinen antti.kemppinen@vtt.fi tel. +358 50 410 5522 http://www.e-leaps.eu/ A word version of this press release can be downloaded here.