The laboratory realises the unit of electric resistance, the ohm (Ω), by means of the quantum Hall effect and of the exact value of the von Klitzing constant. The Hall resistance of semiconductor devices (GaAs) is measured in the dc regime and transferred to standard resistors, with a potentiometer or a cryogenic current comparator (CCC) working in the 1 Ω-1 MΩ range.
The available instrumentation allows the characterisation of materials and electronic devices in a wide range of temperatures (300 mK - 300 K) and magnetic fields (0 - 16 T). Further current comparator bridges allow for the extension of the resistance scale down to 1 μΩ and the calibration of direct-current current transducers (DCCT).
The national standards of ac electrical resistance, capacitance and inductance are realised with traceability to the quantized Hall resistance, in the acoustic frequency domain (20 Hz - 20 kHz).
The development is focused on the realisation of digital impedance bridges, which combine network simplicity and automation avoiding the loss of measurement accuracy.
The laboratory develops samples for the control of individual charge applied to the fields of quantum metrology of the electrical current and the field of quantum computation.
The research focuses on measurement techniques using cryogenic dilution systems to reduce the effects of thermal fluctuations and on the development of innovative devices for the realisation of quantum currents related to the frequency standard.
The devices developed in our laboratory are based on metallic and superconductive thin film technology and exploit the peculiar properties of quantum interference to control the charge status of mesoscopic islands.
The practical realisation of voltage, current, power and energy in the sinusoidal and time varying regime are performed in this laboratory, with traceability to the fundamental constants through Josephson and quantum Hall effects.
Thermal ac-dc transfer and high-accuracy waveform sampling methods are employed. The available measurement systems are:
- an automatic electromotive force comparator;
- digital phase comparators;
- primary sampling wattmeter and broadband digitisers for power and "power quality" measurements.
The laboratory realises the national standards of:
- impedance (Scattering Parameters)
in the frequency range from 10 MHz to 50 GHz, by means of microcalorimetric systems and vector network analysers. Traceability to the SI is guaranteed by means of the Josephson effect and the practical realisation of the metre.
Measurements are also possible down to the DC regime and up to 110 GHz.