Pumping properties of the hybrid single-electron transistor in dissipative environment

Pumping characteristics were studied of the hybrid normal-metal/superconductor single-electron transistor embedded in a high-ohmic environment. Two 3 micrometer-long microstrip resistors of CrOx with a sum resistance R=80kOhm were placed adjacent to this hybrid device. Substantial improvement of pumping and reduction of the subgap leakage were observed in the low-MHz range. At higher frequencies 0.1-1GHz, a slowdown of tunneling due to the enhanced damping and electron heating negatively affected the pumping, as compared to the reference bare devices.Comment: 3 pages 4 figure

Parallel pumping of electrons

We present simultaneous operation of ten single-electron turnstiles leading to one order of magnitude increase in current level up to 100 pA. Our analysis of device uniformity and background charge stability implies that the parallelization can be made without compromising the strict requirements of accuracy and current level set by quantum metrology. In addition, we discuss how offset charge instability limits the integration scale of single-electron turnstiles.Comment: 6 pages, 4 figures, 1 tabl

Hybrid single-electron turnstile:towards a quantum standard of electric current

First I discuss various candidates of single-electron current pumps for quantum metrology. Then I focus on the hybrid normal-metal-superconductor turnstile in the form of a one-island single-electron transistor with one gate [1-3]. The device demonstrates robust current plateaus at multiple levels of ef at frequency f. I discuss the various error mechanisms, based on our experiments and theoretical considerations. Ultimately the quantization accuracy is expected to be limited by either two-electron tunneling or by Cooper-pair-electron co-tunneling [4]. We predict that it should be possible to achieve the metrological accuracy of 10−8, while maintaining the quantized current on the level of more than 10 pA, just by one turnstile with realistic parameters using aluminium as a superconductor. Recently we have managed to run ten turnstiles in parallel increasing the current level to above 100 pA [5]. Work on suppressing the harmful sub-gap leakage current is in progress with encouraging experimental results

Development of the SINIS turnstile for the quantum metrological triangle

We develop a quantum current standard based on the hybrid superconductor-insulator-normal-metal- insulator-superconductor (SINIS) structure in turnstile operation. We discuss the properties of the device and the relevant error sources. We also present a preliminary plan how to implement the device in a direct quantum metrological triangle experiment

Radio-frequency transport of single electrons in superconductor-normal- metal tunnel junctions and the quantum metrological triangle

We are developing a single-electron turnstile based on a nanoscale superconductor-insulator-normal-metal-insulator-superconductor (SINIS) structure. The goal is to obtain the frequency to current conversion I = ef with a relative uncertainty <10-8 which would be sufficient for a quantum-based standard of electric current. Finally, the quantum current standard will be compared against the quantum standards of voltage and resistance via Ohm's law in the quantum metrological triangle experiment