Measurement Josephson

Summary. We discuss how threshold detectors can be used for a direct measurement of the full counting statistics (FCS) of current fluctuations and how to implement Josephson junctions in this respect. We propose a scheme to characterize the full counting statistics from the current dependence of the escape rate measured. We illustrate the scheme with explicit results for tunnel, diffusive and quasi-ballistic mesoscopic conductors. 

In this paper we address the feasibility of Josephson junction systems for measuring the FCS of a mesoscopic conductor. Our results are as follows. The Josephson junction is a realistic detector, all three factors mentioned are in play. Albeit one can measure FCS provided the width of the barrier 4>o 1. 

To conclude, we proved that Josephson junctions can be used as threshold detectors for non-Gaussian noise produced by coherent conductors. Our theoretical results facilitate a new type of electric noise measurement direct measurement of full counting statistics of the transferred charge. 

The use of the icterus index, as described by Meulengracht, for the assessment of jaundice has fallen into disrepute because of the errors caused by the presence of lipochromes, carotenoids, and other yellow pigments. Josephson (J6) in his survey found that the correlation coefficient between icterus index and serum bilirubin concentration was 0.69 in 360 healthy subjects and 0.84 in 40 jaundiced subjects. In newborn infants however, bilirubin is the only yellow pigment likely to be present and the possibility of determining serum bilirubin concentrations by direct measurement has again been re-examined. Abelson and Boggs (Al) diluted serum from infants with erythroblastosis 1 in 50 and studied the absorption curves. They found that in addition to the bili-... 

J6. Josephson, B., The icterus index as a measure of serum bilirubin concentration. Acta Genet. Statist. Med. 4, 231-235 (1953). 

A comparison between theory and experiment for the fine structure intervals in helium holds the promise of providing a measurement of the fine structure constant a that would provide a significant test of other methods such as the ac Josephson effect the and quantum Hall effect. The latter two differ by 15 parts in 108 and are not in good agreement with each other [59]. 

To compare the theory of ae with experiment, it is necessary to know the value of a, which has been measured in diverse branches of physics. Currently best values of a, with relative standard uncertainty of 1 x 10-7 or less, are those based on the quantum Hall effect [32], the ac Josephson effect [25], the neutron de Broglie wavelength [33], the muonium hyperfine structure [34,35], and an absolute optical frequency measurement of the Cesium >1 line [36] ... 

Thus for a determination of a from a g factor measurement it would be desirable to choose an ion where Z is sufficiently high to get a small uncertainty in a but the influence of higher order QED contributions is not too large. Ca19+ seems to be a good choice. If we assume the same experimental accuracy on that ion as presently obtained in C5+ we would obtain a fractional uncertainty in a of 8 10-8. This is comparable to other present determinations of a from Quantum Hall or Josephson effect. The envisaged improvement in the experimental g factor by one order of magnitude would make the a determination competitive with that extracted from the g factor of the free electron. 

The RF SQUID is based on the AC Josephson effect, uses only one Josephson junction, and is less sensitive than the DC SQUID, but is cheaper and easier to manufacture its SQUID is inductively coupled to a resonant tank circuit. Depending on the external magnetic field, as the SQUID operates in the resistive mode, the effective inductance of the tank circuit changes, thus changing the resonant frequency of the tank circuit. These frequency measurements can be easily done, and thus the losses that appear as the voltage across the load resistor in the circuit are a periodic function of the applied magnetic flux with a period of 0. 

That pairs are at work in the new ceramics has been demonstrated by measurements of what is known as the Josephson effect, named after the physicist Brian D. Jo-sephson, who observed it in 1961 as a graduate student at Cambridge University in England. The Josephson effect,... 

If and when a Josephson junction computer is built, the junction s size and low power dissipation would allow manufacturers to put more guts and gas into their machines. Their cycle times—the time required for a chip to perform one task—would be substantially shortened. Such a computer might, in fact, fill a cube only 2 inches on a side and operate more than fifty times faster than the best that are available today. No mean feat, considering that the world s first all-electronic computer, ENIAC (for Electronic Numerical Integrator and Calculator), covered some 1,500 square feet of floor space at the University of Pennsylvania, where it had its maiden run in 1946, was jam-packed with some twenty thousand vacuum tubes, and weighed in at more than 30 tons. Moreover, its computations were measured in seconds—not a nanosecond, a picosecond (a trillionth of a second), or a femtosecond (a quadrillionth of a second), the measurements computer designers are accustomed to shooting for today. 

This mechanical analog has often proved useful in visualizing the dynamics of Josephson junctions. Sullivan and Zimmerman (1971) actually constructed such a mechanical analog, and measured the average rotation rate of the pendulum as a function of the applied torque this is the analog of the physically important I-V curve (current-voltage curve) for the Josephson junction. 

The Planck constant can be obtained by comparing a watt of mechanical energy measured in SI units to a watt of electrical energj measured in terms of the Josephson constant Kj = 2e/h) and von Klitzing constant (i K = h/e ) in the combination... 

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