Superconducting current detecting circuit employing DC flux parametron circuit

Claim 1

A superconducting current detecting circuit comprising: a reference current generation circuit for generating a reference current; and a DC flux parametron circuit for comparing an input current to be detected with said reference current to thereby produce pulse currents in synchronism with an input excitation signal, the number of said pulse currents being varied in accordance with a difference between said input current and said reference current, said pulse currents having positive or negative values depending on the polarity of said difference; wherein said reference current generating circuit includes means for increasing or decreasing said reference current by a quantity corresponding to the number of said pulse currents in response to the polarity of said pulse currents so that said reference current generation circuit produces said reference current which agrees with said input current; and wherein said DC flux parametron circuit is constituted by; an excitation line including a series connection of a first and second inductor to which said input excitation signal is applied, a superconducting loop including a series connection of a third inductor magnetically coupled with said first inductor, a fourth inductor magnetically coupled with said second inductor, and a first and a second Josephson junction, an input line connected with a first connecting point between said third and fourth inductors to which said difference between said input current and said reference current is applied, and a load inductor connected between said first connecting point and a second connecting point between said first and second Josephson junctions, said second connecting point being earthed, and said pulse currents flowing through said load inductor.