I am thinking he would be doing dam well to squeek out 100KHz
Thanks for the reminder, Coulombs number is something like
6.245x10^18; below picoamperes you are approaching counting basic
The Radio Frequency Single Electron Transistor (RF-SET) can go
Sorry, all my old links have gone bad and I don't have time to
google for more right now.
OK, got a minute and searched google for:
rf-set transistor bandwidth
Lots of info if you can get down to -459F. Here's an old one:
NEW HAVEN, Conn.- Scientists at Yale University have developed the
world's most sensitive electrometer, a transistor so sensitive it
can count individual electrons as they pass through a circuit. The
detector could be useful not only in developing and testing
miniaturized electronic devices but also as a highly sensitive light
detector in powerful new microscopes and telescopes.
Made from aluminum, the device is about 1,000 times faster than the
best electrometer on record and 1 million times faster than other
single electron transistors, according to a report by Yale applied
physicist Daniel E. Prober in the May 22 issue of the journal
Science. Working with him on the device were Yale postdoctoral
associate Robert J. Schoelkopf; former graduate student Peter
Wahlgren, now in Gteberg, Sweden; and graduate students Alexay A.
Kozhevnikov and Per Delsing.
"Single electron transistors have been around for about a dozen
years, but our laboratory has developed a new type called a Radio
Frequency Single Electron Transistor (RF-SET) that can measure
charges as small as 15-millionths of an electron. It detects an
extremely large bandwidth," said Prober, an expert in
high-temperature superconductivity as well as electron conduction in
metal films, wires and semiconductors.
The goal of many scientists for the last 10 years has been to
develop more precise frequency measurements and to devise current
voltage standards, said Schoelkopf, who began working on the RF-SET
design while a graduate student at California Institute of
Technology. Without that, researchers cannot study and perfect
extremely miniaturized electronic devices and computer chips at the
level where quantum mechanical effects become important.
Currently, the RF-SET works only at temperatures near absolute zero
Kelvin, or about -459 degrees Fahrenheit, thus requiring a large
refrigerator. The Yale scientists are exploring ways to make the
detector work more effectively at higher temperatures.
On the plus side is the device's high operational speed.
Conventional single electron transistor electrometers have been
limited by slow speeds, typically below frequencies of 1 kilohertz
(1,000 cycles per second), Schoelkopf said. The RF-SET can operate
even at frequencies exceeding 100 megahertz (100 million cycles per
second), where the noise due to background charge motion is
completely negligible. In their report, the Yale researchers
describe how improved versions of this device could even approach
the quantum limit, yielding the best electron detectors possible.
Because the device effectively monitors a wide range of photons -
including X-rays, ultraviolet radiation, light, infrared radiation,
and microwaves - the RF-SET design is "the best by many criteria,
very exciting," Prober said. Among the many potential applications
are far-infrared detectors, being considered by the National
Aeronautic and Space Agency (NASA) for use in astronomy, and
high-resolution electron microscopes that can amplify light for the
study of molecular structure in medicine.
Schoelkopf et al. improved the sensitivity to 6.3ue/sqrt[Hz] in
1998, so it has to be much better by now:
The Radio-Frequency Single-Electron Transistor (RF-SET): A Fast and
Schoelkopf et al.
Science 22 May 1998: 1238-1242
Radio-Frequency Single-Electron Transistor as Readout Device for
Qubits: Charge Sensitivity and Backaction
A. Aassime, G. Johansson, G. Wendin, R. J. Schoelkopf, and P.
Received 21 November 2000
We study the radio-frequency single-electron transistor (rf-SET) as
a readout device for charge qubits. We measure the charge
sensitivity of an rf-SET to be 6.3ue/sqrt[Hz] and evaluate the
backaction of the rf-SET on a single Cooper-pair box. This allows us
to compare the needed measurement time with the mixing time of the
qubit imposed by the measurement. We find that the mixing time can
be substantially longer than the measurement time, which would allow
readout of the state of the qubit in a single shot measurement.
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