Josephson junctions, first postulated by B. D. Josephson and first made by John Rowell and Philip Anderson, are quantum-mechanical circuit elements of superconducting devices. They are most commonly used in SQUIDs and Rapid Single Flux Quantum integrated circuits. Brian David Josephson (born Cardiff, UK, January 4, 1940) is a British physicist whose discovery of the Josephson effect while a 22_year_old graduate student won him a share (with Leo Esaki and Ivar Giaever) of the 1973 Nobel Prize for Physics. ... Philip Warren Anderson (born December 13, 1923) is an American physicist. ... Fig. ... An electrical network or electrical circuit is an interconnection of electrical elements such as resistors, inductors, capacitors, diodes, switches and transistors. ... A magnet levitating above a high-temperature superconductor (with boiling liquid nitrogen underneath) demonstrates the Meissner effect. ... Suborders Myopsina Oegopsina Squids are the large, diverse group of marine cephalopods popular as food in cuisines as widely separated as Korean and Italian. ... In electronics, rapid single flux quantum (RSFQ) is a digital electronics technology that relies on quantum effects in superconducting materials to switch signals, instead of transistors. ...

A Josephson junction is realized at the interface between two superconducting materials separated by a non-superconducting barrier. Current may flow without resistance within the superconductors, but is hindered at the barrier. However, a supercurrent may tunnel through the barrier, depending on the quantum phase of the superconductors. The amount of supercurrent that may tunnel through the barrier is restricted by the size and substance of the barrier. The maximum value the supercurrent may attain is called the critical current of the Josephson junction, and is an important phenomenological parameter of a junction. This quantity can be affected by temperature and applied magnetic field. Quantum tunneling is the quantum-mechanical effect of transitioning through a classically-forbidden energy state. ... In quantum mechanics a coherent state is a specific kind of quantum state of the quantum harmonic oscillator whose dynamics most closely resemble the oscillating behaviour of a classical harmonic oscillator system. ...

Josephson junctions have two basic electrical properties. The first is that the junctions have an inductive reactance. That is, similarly to inductors, the voltage difference across a junction is related to the time rate of change of the current. The second is that a constant voltage across a junction will produce an oscillating current through the barrier, and vice versa. Thus, Josephson junctions convert a direct-current voltage to an alternating-current current. In the analysis of an alternating-current electrical circuit (for example a RLC series circuit), reactance is the imaginary part of impedance, and is caused by the presence of inductors or capacitors in the circuit. ... An inductor is a passive electrical device that creates a magnetic field when a current (AC or DC) is passed through it. ... Potential difference is a quantity in physics related to the amount of energy that would be required to move an object from one place to another against various types of force. ... In electricity, current refers to electric current, which is the flow of electric charge. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... city lights viewed in a motion blurred exposure. ...

There are two general types of Josephson junctions: overdamped and underdamped. In overdamped junctions, the barrier is conducting (normal metal or superconductor bridge). The effects of the junction's internal electrical resistance will be large compared to its small capacitance. An overdamped junction will quickly reach a unique equilibrium state for any given set of conditions. The barrier of an underdamped junction is an insulator. The effects of the junction's internal resistance will be minimal. Underdamped junctions do not have unique equilibrium states, but are hysteretic. Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and metals are sometimes described as a lattice of positive ions (cations) in a cloud of electrons. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... A capacitor is a device that stores energy in the electric field created between a pair of conductors on which equal but opposite electric charges have been placed. ... Equilibrium or balance is any of a number of related phenomena in the natural and social sciences. ... // Definition An Insulator is a material or object which resists the flow of electric charge. ... Hysteresis is a property of systems (usually physical systems) that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is, systems whose states depend on their immediate history. ...

Linear arrays of Josephson junctions are used to define the voltage standard.

Recently, several scientists have suggested using Josephson junctions to physically create qubits. A quantum bit, or qubit (sometimes qbit) is a unit of quantum information. ...

A Josephson junction can be transformed into a co-called Giaever tunneling junction by the application of a small well defined magnetic field. In such a situation, the new device is called a superconducting tunneling junction (STJ) and is used as a very sensitive photon detector throughout a wide range of the spectrum, from infrared to hard x-ray. Each photon breaks up a number of Cooper pairs which depends on its wavelength. The detector can be operated as a photon-counting spectrometer, with a spectral resolution limited by the shot noise fluctuations in the released charge. The detector has to be cooled to extremely low temperature, typically below 1 Kelvin, to distinguish the signals generated by the detector from the thermal noise. Small arrays of STJs have demonstrated their potential as spectro-photometers and could further be be used in astronomy [1]. They are used for the detection of weak X-ray fluorescence, and could, in principle, be used as infrared imaging devices. Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... BCS theory successfully explains conventional superconductivity, the ability of certain metals at low temperatures to conduct electricity without resistance. ... The wavelength is the distance between repeating units of a wave pattern. ... Shot noise consists of random fluctuations of the electric current in an electrical conductor, which are caused by the fact that the current is carried by discrete charges (electrons). ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... Johnson-Nyquist noise (sometimes thermal noise, Johnson noise or Nyquist noise) is the noise generated by the equilibrium fluctuations of the electric current inside an electrical conductor, which happens without any applied voltage, due to the random thermal motion of the charge carriers (the electrons). ... Astrology: the study of the positions of the celestial objects relative to the Earth and how these positions affect happenings on the lives of cultures, nations and the natural environment. ... Image of a small dog taken in mid-infrared (thermal) light (false color) A thermographic camera, sometimes called a FLIR (forward looking infrared), or an infrared camera less specifically, is a device that forms an image using infrared radiation, similar to a common camera that forms an image using visible...