Readily evaluated exact solutions of the sine-Gordon equation are presented for nonlinear standing-wave oscillations on a fixed length of a lossless Josephson transmission line with open-circuit boundary conditions at the ends. Three distinct species of standing waves are described: (i) plasma oscillation, (ii) breather oscillation, and (iii) fluxon oscillation. Fluxon oscillations can absorb power from an external source of bias current; for this case the volt-ampere characteristics relating bias current to average junction have been computed.

A fabrication technique for Nb-Al2O3-Nb Josephson tunnel junctions is described that is an alternative to the trilayer method generally used. At 4.2 K the magnitude of the low-frequency noise in the critical current I0 of four junctions with areas 𝒜 ranging from 7.8 to 115 μm2 was characterized by S1/2I0𝒜1/2/I0 =(14±6)pA μm/μA Hz1/2, where SI0 is the spectral density of the excess noise at 1 Hz. The noise power spectrum of one 3×3 μm2 junction exhibited a Lorentzian feature associated with the emptying and filling of a single trap in the barrier. The low level of noise makes these junctions attractive for use in superconducting quantum interference devices.

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