Historically speaking, not much time has passed since Nicola Tesla dazzled audiences with his controlled bursts of lightning and ghostly seeming light effects and a certain Thomas Alva Edison electrified the industrialized world with his inventions. The discovery and technical utilization of electricity took off at the end of the 19th century and conquered more and more conventional technical terrain until, in the late 1940s, the transistor was invented at Bell Labs in New Jersey. The transistor gave electricity its first quantum-mechanical form.
- International units: Today, electric currents and voltages and electrical resistances can be best measured by exploiting quantum-mechanical effects. For many years, national metrology institutes have used quantum effects to disseminate these units, which are named after several pioneers of electricity such as André Marie Ampère, Georg Simon Ohm and Alessandro Volta. The fundamental reorganization of the International System of Units (SI) by means of natural constants means that our entire system of units (with the exception of the candela) is now based on quantum- mechanical principles.
- Practical quantum standards: While, for many years, electrical quantum standards were available only in highly specialized metrological laboratories, such standards are being applied to practical situations with increasing success. For example, at PTB, a programmable “quantum voltmeter” has been commercialized, thus making it available to industry. The Josephson Arbitrary Waveform Synthesizer (JAWS) was developed as a universal tool for generating and measuring arbitrary and spectrally pure alternating voltages.
For many decades, PTB has consistently been among the world’s top addresses in the world of electrical quantum metrology. At PTB, metrologists develop the scientific foundations for extremely high-precision measurements of the electric quantities, specialists manufacture and characterize the hardware components necessary for this purpose in PTB’s own Clean Room Center, and links are forged to industry for practical applications.
For the ohm, the unit of electrical resistance, the freedom of movement of the electrons in a semiconductor is restricted and the resulting abrupt change in the resistance in an applied magnetic field is exploited – this is the so-called quantum Hall effect, for which Klaus von Klitzing received the Nobel Prize in Physics and which was used metrologically at PTB from “the hour of its birth”. For voltages, the Josephson effect of superconductivity is used, for which two electrons always group together to form a couple. Finally, for currents, it is possible at PTB to count the individual electrons carrying the electricity while these electrons, being quantum particles, tunnel through barriers that are normally insurmountable.