| Definition: | macroscopic quantum effect in which, when a voltage U is applied across a Josephson junction, an alternating current of Cooper pairs flows by tunnelling through the junction, generating the emission of electromagnetic radiation having a frequency f proportional to the applied voltage:
f = KjU
where Kj = 2e/h is the Josephson constant, with e being the elementary electric charge and h the Planck constant
NOTE 1 – The alternating-current Josephson effect also manifests itself conversely so that, when a Josephson junction is irradiated by electromagnetic radiation of frequency f, the voltage across it can assume quantized values equal to nf/Kj, where n is a positive integer.
NOTE 2 – The value of the Josephson constant is 483 597,891(12) × 109 Hz V-1 (CODATA, 2006).
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