11 research outputs found
Two-junction superconductor-normal metal single-electron trap in a combined on-chip RC environment
Dissipative properties of the electromagnetic environment as well as on-chip
RC filtering are shown to suppress random state switchings in the two-junction
superconductor(S) - normal metal(N) electron trap. In our experiments, a local
high-ohmic resistor increased the hold time of the trap by up to two orders of
magnitude. A strong effect of on-chip noise filtering was observed for
different on-chip geometries. The obtained results are promising for
realization of the current standard on the basis of the S-N hybrid turnstile.Comment: 4 pages 3 figures LT2
Single-charge escape processes through a hybrid turnstile in a dissipative environment
We have investigated the static, charge-trapping properties of a hybrid
superconductor---normal metal electron turnstile embedded into a high-ohmic
environment. The device includes a local Cr resistor on one side of the
turnstile, and a superconducting trapping island on the other side. The
electron hold times, t ~ 2-20s, in our two-junction circuit are comparable with
those of typical multi-junction, N >= 4, normal-metal single-electron tunneling
devices. A semi-phenomenological model of the environmental activation of
tunneling is applied for the analysis of the switching statistics. The
experimental results are promising for electrical metrology.Comment: Submitted to New Journal of Physics 201
Towards the observation of phase locked Bloch oscillations in arrays of small Josephson junctions
We have designed an experiment and performed extensive simulations and
preliminary measurements to identify a set of realistic circuit parameters that
should allow the observation of constant-current steps at I=2ef in short arrays
of small Josephson junctions under external AC drive of frequency f.
Observation of these steps demonstrating phase lock of the Bloch oscillations
with the external drive requires a high-impedance environment for the array,
which is provided by on-chip resistors close to the junctions. We show that the
width and shape of the steps crucially depend on the shape of the drive and the
electron temperature in the resistors
Electron Counting Capacitance Standard with an improved five-junction R-pump
The Electron Counting Capacitance Standard currently pursued at PTB aims to
close the Quantum Metrological Triangle with a final precision of a few parts
in 10^7. This paper reports the considerable progress recently achieved with a
new generation of single-electron tunnelling devices. A five-junction R-pump
was operated with a relative charge transfer error of five electrons in 10^7,
and was used to successfully perform single-electron charging of a cryogenic
capacitor. The preliminary result for the single-electron charge quantum has an
uncertainty of less than two parts in 10^6 and is consistent with the value of
the elementary charge.Comment: 16 pages, 9 figures, 1 tabl
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