New generation of computers foreseen with Josephson devices

Tsutomu Yamashita

S. Takada

L. S. Kuzmin, Alexander S. Sobolev, Claudio D. Gatti +4 more

Axions and axion-like particles appear in well-motivated extensions of the standard model of particle physics and may be the solution to the long-standing puzzle of the dark matter in our Universe. Several new experiments are foreseen in the next decade searching them in a wide range of the parameter space. In the mass region from few to several tens of microelectronvolt, detector sensitivity will be limited by the standard quantum limit of linear amplifiers and a new class of single microwave-photon detector will be needed. We have developed a single photon counter based on the voltage switching of an underdamped Josephson junction that is coupled to a coplanar waveguide. By measuring the switching voltage, we can register single photons at 14 GHz with the rate less than 1 photon per 3000 s.

Sándor Dési

H. Beha, Heinz Jäckel

A new 3-Josephson-junction interferometer is presented as a high-tolerance nonlinear current-injection 2-input AND gate. In Josephson LSI circuits, the tolerances are an important issue. Thus, in our new logic device emphasis has been placed on its static and dynamic tolerance properties. The new HTCID offers considerably better input-signal tolerances than known 2-junction current-injection devices (CID) for identical fabrication tolerance assumptions. The HTCID in this example has a Josephson current ratio of 1:3:1 and a characteristic phase λ = 0.72π. Including circuit parameter variations, this new 3-junction CID allows attractive, high input-signal tolerances of ± 33.3%. Therefore, an almost threefold tolerance improvement over the published 2-junction CID (λ = 0.66π) could be achieved. Trade-off between signal tolerances and device speed is discussed. Computer simulation indicates a worst-case delay of less than 47 ps.

H. H. Zappe