Josephson detector

Josephson detector Photoeffect on Cooper pairs in semiconductor within a Josephson junction... 

PL. Richards, The Josephson Junction as a Detector of Microwave and Far-Infrared Radiation... 

Josephson Junctions as Threshold Detectors for Full Counting Statistics... 

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. 

As we explore the interaction of cold-atom systems with microwave and terahertz radiation, we find that they have some unique properties as detectors. A comparison with superconductor-based detectors such as SQUlDs is instractive. Because of the third law of thermodynamics, i.e., a system in a single quantum state has zero entropy, the response of a SQUID is almost free of thermal noise. But an additional properly of SQUIDs is that they exhibit the phenomenon of coherence, i.e., wave interference, which leads to entirely new effects, e.g. the AC and DC Josephson effects. Cold atom clouds share this behavior, as we will discuss below. 

In principle, Josephson junction detectors are useful only for energies corresponding to the single particle energy gap, i.e., wavelengths in the far infrared beyond 100 pm. It is theoretically possible to detect single photons by this means [2.136]. 

A superconducting quantum interference detector formed by two parallel Josephson junctions. 

Much of the interest in superconductor components revolves around the central issue that below a characteristic temperature, Tc, superconductors exhibit zero resistance to the flow of electricity figure 1 A). Above this temperature, the material behaves as a normal metal wherein isolated electrons (or holes) carry the charge with finite resistance. Below Tc, however, the electrons form loosely associated pairs which are responsible for all the superconducting properties. At temperatures close to Tc, only a minute fraction of the conduction electrons form the Cooper pairs (Figure IB). Under such circumstances, superconductivity is easily disrupt by heati light, and magnetic fields. Creation of weakly coupled superconductor structures such as Josephson junctions, serves to further increase the sensitivity of the superconductor components. It is this sensitivity to external stimuli that provides the basis for the preparation of a variety of superconductor-based detectors and devices. 

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