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PTB supplies primary electrical quantum standards for the BIPM

25.06.2020

The Physikalisch-Technische Bundesanstalt (PTB) and the Bureau International des Poids et Mesures (BIPM, based near Paris) have agreed on a scientific cooperation in the field of metrology of the quantum Hall effect. As part of this cooperation, the PTB is supplying quantum standards to the BIPM for the realization of the unit of electrical resistance, the ohm.

 

 

 

The revised International System of Units (SI) came into force in May 2019 and makes electrical quantum effects particularly important for modern metrology. By defining exact numerical values for the two natural constants Planck's constant h and elementary charge e, the quantized values derived from quantum resistance standards are now exactly known. They are based on the quantum Hall effect and are directly related to the von Klitzing constant RK = h/e2. The realization of the quantum Hall resistance thus provides a primary representation of the ohm.


PTB is one of the few metrology institutes worldwide being able to produce primary quantum standards for electrical resistance. The circuits are based on epitaxially grown semiconductor heterostructures and are manufactured in a clean room centre using molecular beam epitaxy. The quantum Hall effect occurs at low temperatures in a conductive layer just a few nanometres thick. The circuits are evaluated for suitability as quantum resistance standards in PTB laboratories. This is done by high-precision low-temperature measurements using special measurement bridges. If all parameters in the production of the circuits have been adjusted correctly, the quantized resistance value corresponds to the expected target value (given by the von Klitzing constant RK) within a relative deviation of only about one part in a billion.


Over the past 30 years, PTB has delivered quantum Hall standards to other countries in the framework of numerous collaborations with national metrology institutes. The extraordinarily high long-term stability and robustness of the circuits from PTB production has been proven. With the support of BIPM as the highest international metrology institution, PTB makes an important contribution to securing the foundations of metrology and the worldwide harmonization of measurements.

Quantum Hall resistance standard in sample socket

Quantum Hall resistance standard in sample socket

 

 

 

 

Department 2.5 “Semiconductor Physics and Magnetism”