In quantum optics, an optical phase space is a phase space in which all quantum states of an optical system are described.
 Each point in the optical phase space corresponds to a unique state of an "optical system".
 For any such system, a plot of the "quadratures" against each other, possibly as functions of time, is called a phase diagram.
 If the quadratures are functions of time then the optical phase diagram can show the evolution of a quantum optical system with time.
Alexei Alexeyevich Abrikosov (Russian: Алексе́й Алексе́евич Абрико́сов ; 25 June 1928 – 29 March 2017) was a Soviet, Russian and American theoretical physicist whose main contributions are in the field of condensed matter physics.
 He was awarded the Nobel Prize in Physics in 2003.
In physics, a quantum vortex represents a quantized flux circulation of some physical quantity.
 In most cases quantum vortices are a type of topological defect exhibited in superfluids and superconductors.
 The existence of quantum vortices was predicted by Lars Onsager in 1947 in connection with superfluid helium.
 Onsager also pointed out that quantum vortices describe the circulation of superfluid and conjectured that their excitations are responsible for superfluid phase transitions.
 These ideas of Onsager were further developed by Richard Feynman in 1955 and in 1957 were applied to describe the magnetic phase diagram of type-II superconductors by Alexei Alexeyevich Abrikosov.
 In 1935 Fritz London published a very closely related work on magnetic flux quantization in superconductors.
 London's fluxoid can also be viewed as a quantum vortex.
Pinning force is a force acting on a pinned object from a pinning center.
 In solid state physics, this most often refers to the vortex pinning, the pinning of the magnetic vortices (magnetic flux quanta, Abrikosov vortices) by different kinds of the defects in a type II superconductor.
 Important quantities are the "individual" maximal pinning force, which defines the depinning of a single vortex, and an "average" pinning force, which defines the depinning of the correlated vortex structures and can be associated with the critical current density (the maximal density of non-dissipative current).
 The interaction of the correlated vortex lattice with system of pinning centers forms the magnetic phase diagram of the vortex matter in superconductors.
 This phase diagram is especially rich for high temperature superconductors (HTSC) where the thermo-activation processes are essential.
CALPHAD stands for "CALculation of PHAse Diagrams".
 An equilibrium phase diagram is usually a diagram with axes for temperature and composition of a chemical system.
 It shows the regions where substances or solutions (i.e. phases) are stable and regions where two or more of them coexist.
 Phase diagrams are a very powerful tool for predicting the state of a system under different conditions and were initially a graphical method to rationalize experimental information on states of equilibrium.
 The CALPHAD approach is based on the fact that a phase diagram is a manifestation of the equilibrium thermodynamic properties of the system, which are the sum of the properties of the individual phases.
 It is thus possible to calculate a phase diagram by first assessing the thermodynamic properties of all the phases in a system.
Type-1.5 superconductors are multicomponent superconductors characterized by two or more coherence lengths, at least one of which is shorter than the magnetic field penetration length formula_1, and at least one of which is longer.
 This is in contrast to singe-component superconductors, where there is only one coherence length formula_2 and the superconductor is necessarily either type 1 (formula_3) or type 2 (formula_4) (often a coherence length is defined with extra formula_5 factor, with such a definition the corresponding inequalities are formula_6 and formula_7).
 When placed in magnetic field, type-1.5 superconductors should form quantum vortices: magnetic-flux-carrying excitations.
 They allow magnetic field to pass through superconductors due to a vortex-like circulation of superconducting particles (electronic pairs).
 In type-1.5 superconductors these vortices have long-range attractive, short-range repulsive interaction.
 As a consequence a type-1.5 superconductor in a magnetic field can form a phase separation into domains with expelled magnetic field and clusters of quantum vortices which are bound together by attractive intervortex forces.
 The domains of the Meissner state retain the two-component superconductivity, while in the vortex clusters one of the superconducting components is suppressed.
 Thus such materials should allow coexistence of various properties of type-I and type-II superconductors.
Congruent melting occurs during melting of a compound when the composition of the liquid that forms is the same as the composition of the solid.
 It can be contrasted with incongruent melting.
 This generally happens in two-component systems.
 To take a general case, let A and B be the two components and AB a stable solid compound formed by their chemical combination.
 If we draw a phase diagram for the system, we notice that there are three solid phases, namely A, B and compound AB.
 Accordingly, there will be three fusion or freezing point curves AC, BE and CDE for the three solid phases.
 In the phase diagram, we can notice that the top point D of the phase diagram is the congruent melting point of the compound AB because the solid and liquid phases now have the same composition.
 Evidently, at this temperature, the two-component system has become a one-component system because both solid and liquid phases contains only the compound AB.
In superconductivity, a type-II superconductor is characterized by the formation of magnetic vortices in an applied magnetic field.
 This occurs above a certain critical field strength "H".
 The vortex density increases with increasing field strength.
 At a higher critical field "H", superconductivity is destroyed.
 Type-II superconductors do not exhibit a complete Meissner effect.
In superconductivity, an Abrikosov vortex is a vortex of supercurrent in a type-II superconductor theoretically predicted by Alexei Abrikosov in 1957.
 The supercurrent circulates around the normal (i.e. non-superconducting) core of the vortex.
 The core has a size formula_1 — the superconducting coherence length (parameter of a Ginzburg-Landau theory).
 The supercurrents decay on the distance about formula_2 (London penetration depth) from the core.
 Note that in type-II superconductors formula_3.
 The circulating supercurrents induce magnetic fields with the total flux equal to a single flux quantum formula_4.
 Therefore, an Abrikosov vortex is often called a fluxon.
Ernst Helmut Brandt was German theoretical physicist working on the Abrikosov vortex lattice in type-II superconductors, particularly with the ideal lattice, its nonlocal elastic response, lattice defects, pinning, and geometrical effects in the electromagnetic response of superconductors.

Question: When was the  Soviet, Russian and American theoretical physicist died who describe the magnetic phase diagram of type-II superconductors of Onsager?
Answer: 29 March 2017