Noise properties of the Bloch oscillating transistor

We have measured the current noise spectral density of the Bloch oscillating transistor as a function of current gain. We find, as expected from theory and simulations, that the equivalent input noise that shows up in the output is less than the shot noise of the normal-insulating-superconductor tunnel junction (base junction). At the optimal operating point we find a reduced input current noise of 1.0fA/√Hz and a corresponding noise temperature of 0.4 K. The differential current gain at the same point is as large as 30 and the power gain amounts to 35.Peer reviewe

Mesoscopic Josephson junction as a noise detector

Small Josephson junctions are known to be very susceptible to noise. We have utilized this property in developing methods to measure noise as well as environmental resonance modes in mesoscopic systems. We review recent results on tunnel junction systems and show also that higher order moments of shot noise can be addressed with the present method based on the noise-induced modification of incoherent tunneling of Cooper pairs.Peer reviewe

Low Noise Current Amplifier Based on Mesoscopic Josephson Junction

We utilize the band structure of a mesoscopic Josephson junction to construct low noise amplifiers. By taking advantage of the quantum dynamics of a Josephson junction, i.e. the interplay of interlevel transitions and the Coulomb blockade of Cooper pairs, we create transistor-like devices, Bloch oscillating transistors, with considerable current gain and high input impedance. In these transistors, correlated supercurrent of Cooper pairs is controlled by a small base current made of single electrons. Our devices reach current and power gains on the order of 30 and 5, respectively. The noise temperature is estimated to be around 1 Kelvin, but it is realistic to achieve TN < 0.1 Kelvin. These devices provide quantum-electronic building blocks that will be useful in low-noise, intermediate-impedance-level circuit applications at low temperatures.Non Peer reviewe