Wave-Function Collapse in Quantum Mechanics  

In General > s.a. classical limit of quantum theory.
* Idea: When a quantum measurement is performed, and a certain eigenvalue of the corresponding operator observed, the wave function "suddenly" turns into a corresponding eigenvector; a.k.a. quantum-state reduction; Wigner suggested that conscious observation causes collapse.
* "Reality": Is this a physical process, or is it just related to our knowledge and description of the system? The results on non-local correlations in moving frames make it more difficult to consider the projection postulate as a compact description of real collapses of the wave function.
> Related topics: see collapse as a dynamical process [including state recovery]; decoherence; locality and localization; measurement; quantum experiments.
> Online resources: see SEP page.

And Relativity, Covariant Form > s.a. causality violations.
* Status: Some relativistic models entail excitation of nuclear states which exceeds that of experiment.
* And causality: Despite some claims, it is well known that the process of wave packet reduction cannot be used for superluminal communication.
* Hellwig-Kraus reduction: The wave function is collapsed along the boundary of the past of the measurement.
@ General references: Aharonov & Albert PRD(81) [non-local measurements without violating causality]; Mielnik FP(90) [collapse cannot be consistently introduced]; Pearle in(90), in(92); Finkelstein PLA(00) [projection]; Ghirardi qp/00; Srikanth qp/01, Gambini & Porto PLA(02)qp/01, NJP(03) [covariant]; Zbinden et al PRA(01) [non-local correlations in moving frames]; Myrvold SHPMP(02) [compatible]; Socolovsky NCB(03); Byun FP(04); Jadczyk AIP(06)qp; Blood a1004 [relativistic consistency]; Wen a1008 [and path integrals]; da Silva et al IJMPB(13)-a1012 [observer independence]; Lin AP(12)-a1104 [atom + quantum field model]; Bedingham et al JSP(14)-a1111; Ohanian a1703 [past-light cone collapse]; Myrvold PRA(17)-a1709 [need for non-standard degrees of freedom].
@ For quantum field theory: Bedingham JPA(07), FP(11) [stochastic model].
@ Relativistic GRW mechanism: Tumulka JSP(06)qp/04, AIP(06)qp, FP(07)qp/06; Conway & Kochen FP(06) [not possible], FP(07)qp [reply to comments].

* Spontaneous collapse models: They add a non-linear noise term to the Schrödinger equation and extract definite measurement outcomes either from the wave function (mass density ontology) or the noise itself (flash ontology); They can be Markovian or non-Markovian.
@ Models: Bussey PLA(93) [phonon model]; Assing & Hilbert a1405 [damped, driven]; Ho et al NJP(16)-a1504 [classically driven mechanical oscillator].
@ Spontaneous collapse models: Berg hp/96 [phenomenological]; Diósi a1710-ch [intro]; Tilloy & Wiseman a2105 [recast as Bohmian theories].
@ Stochastic: Diósi JPA(88); Jibu et al PLA(90); Brody & Hughston JMP(02) [as simulation], JPA(06)qp/05 [quantum noise], JMP(05) [finite-time]; Brusheim-Johansson & Hansson qp/06 [chaotic].
@ Lattice, numerical: Dowker & Henson JSP(04)qp/02; Dowker & Herbauts CQG(04)qp, FPL(05)qp/04 [causal, 1+1 null lattice]; Bassi & Ippoliti PRA(04)qp/03 [2-level system]; Gao PRS(13)-a1304 [discrete energy-conserving model].
@ Tests of collapse models: Bahrami et al PRL(14) [non-interferometric]; Adler & Vinante PRA(18)-a1801 [bulk heating effects]; Chelvaniththilan a2010.

References > s.a. axioms [projection postulate]; many-worlds interpretation; quantum information (transfer).
@ I: news pw(07)aug [for light, step-by-step].
@ General: Bussey PLA(84); Home & Whitaker PLA(86), comment Hnizdo PLA(87); Pearle in(86); Damnjanović PLA(88) [as phase transition]; Home & Whitaker PLA(88); Krips BJPS(88); Van Kampen PhyA(88); Ballentine FP(90) [projection postulate], PRA(91) [criticism of some thories]; Gottfried in(90); Namiki et al PLA(94); Fioroni & Immirzi gq/94; Kadomtsev & Kadomtsev SPU(96) [rev]; Ozawa AP(97)qp, qp/97-conf, FdP(98)qp/97 [operational]; Nakhmanson qp/02 [local-realistic]; Zurek PRA(07)qp/07 [information transfer and origin of quantum jumps]; Socolovsky a0806 [geometrical point of view]; Omnès a0911 [derivation of reduction], FP(11)-a1105 [and decoherence]; Hegerfeldt & Sala Mayato PRA(12)-a1111 [Lüders vs von Neumann reduction]; 't Hooft a1112; Hájíček a1311; Singh CS-a1810 [non-technical rev].
@ Not needed, not physical: Fox AJP(83)jan [joint probability operators]; Keller AJP(90)aug [and probabilities]; Zeh PLA(93); Griffiths PRA(02) [resolving paradoxes]; Schlosshauer AP(06)qp/05 [evidence]; Blood a0808 [difficulties of collapse view]; Wechsler a1002 [the other branches don't disappear]; Stoica QSMF(17)-a1607; > s.a. interpretations [statistical].
@ Unitarity: Zurek PRA(13)-a1212 [and repeatability of measurements]; Moldoveanu a1305 [unitary realization].
@ And consciousness: Thaheld BioSys(05)qp; Acacio de Barros & Oas a1609; Okon & Sebastián Syn-a1801 [consciousness-based model]; Kent a2009; Chalmers & McQueen a2105-in [with theory of consciousness and quantum collapse dynamics].
@ Conceptual: Landsberg & Home AJP(87)mar [and the statistical interpretation]; Svetlichny a1104 [and the subjective world]; Cowan & Tumulka BJPS(16)-a1307 [epistemology]; Srikanth a2008 [operational reality, signaling and locality]; Castellani a2011 [as collapse of histories rather than collapse of states]; Wechsler JQIS-a2102 [critical discussion of interpretations]; > s.a. Individuality.
@ And measurement: Gambini qp/98; Gangat PRA(13)-a1303 [observing controlled quantum state collapse]; Bera & Bera a1910 [quantum measurement without collapse]; > s.a. types of measurement [continuous].
@ Related topics: Clarke IJTP(73) [quantum theory with smooth collapse]; Scully et al PRP(78) [Stern-Gerlach example]; Pearle FP(82) [and the gambler problem]; Cini & Lévy-Leblond ed-90 [no reduction]; Gisin PLA(91) [entangled states and non-locality]; Diósi cm/94 [permanent]; Suarez PLA(98)qp [simultaneity]; Isham IJTP(06)qp/05, IJTP(06) [topos perspective]; Yun a1310 [collapse without external observer]; Samarin a1507 [non-mechanical nature of collapse]; > s.a. observers [without observers].

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