Quantum Zeno Effect  

In General > s.a. measurements and types of measurements.
* Idea: (Also called watchdog effect) A continuously–or almost–watched particle (unstable system) never decays, because the state keeps collapsing back to the original state upon observation.
* Quantum Zeno dynamics: The time evolution within the projected "quantum Zeno subspace" defined by the measurement.
@ News, reviews: Maddox Nat(83)nov, Pool Sci(89)nov; Itano qp/06-in [rev, and experiment].
@ General references: Misra & Sudarshan JMP(77), Peres AJP(80)nov [proposal]; Kraus FP(81) [continuous observation]; Bunge & Kálnay NCB(83); Joos PRD(84); Damnjanovic PLA(90), PLA(90); Petrosky et al PLA(90); Home & Whitaker JPA(92), PLA(93); Spiller PLA(94); Nakazato et al PLA(95), PLA(96)qp; Pascazio FP(97) [origin]; Schulman FP(97), PRA(98); Pati & Lawande PRA(98)qp, qp/98/PRL; Toschek & Wunderlich EPJD(01)qp/00; Wallace PRA(01) [computer model]; Gustafson qp/02 [history]; Atmanspacher et al JPA(03) [Z+aZ, nsc's]; Hotta & Morikawa qp/04 [external observers]; Ruseckas & Kaulakys PRA(04) [Zeno + anti-Zeno, general expression]; Koshino & Shimizu PRP(05) [general measurements]; Wallden JPA(07)-a0704 [decoherent histories approach]; Zheng et al PRL(08) [without rotating-wave approximation]; Bagis a0906.
@ Real / finite-time measurements: Ruseckas PLA(01)qp/02; Ruseckas & Kaulakys PRA(01); Egusquiza & Garay PRA(03) [real clocks].
@ Indirect measurements: Koshino & Shimizu PRA(03) [with finite errors]; Makris & Lambropoulos PRA(04)qp; Hotta & Morikawa PRA(04), criticism Wallentowitz & Toschek PRA(05), reply Ozawa qp/06.
@ Other special cases: Peres & Ron PRA(90) [partial]; Hradil et al PLA(98) [infinitely frequent]; Delgado et al PRA(06)qp [distant detector].
@ Dynamical approach: Blanchard & Jadczyk PLA(93) [model from piecewise deterministic dynamics]; Pascazio & Namiki PRA(94); Facchi et al PLA(00)qp, PRL(01)qp/00, PRA(02)qp/01; Koshino PRA(05) [vs conventional formalism].
@ Quantum Zeno dynamics: Facchi et al a0710; Facchi & Pascazio JPA(08)-a0903 [rev]; Facchi & Ligabò a0911.
@ Related topics: Kitano PRA(97) [and adiabatic change]; Mancini & Bonifacio PRA(01) [from competing decoherence]; Schmidt JPA(02)mp [and von Neumann algebras], in(03)mp; > s.a. decoherence; experiments; phase.

Examples and Applications > s.a. constrained systems; entanglement; Friedrichs Model.
@ Examples: Mihokova et al PRA(97) [atoms]; Elattari & Gurvitz PRL(00)qp/99 [e and quantum dot]; Balzer et al OC(00)qp/01, Wunderlich et al ZN(01)qp [ions]; Luís PRA(03) [2-level system]; Schmidt JPA(03)mp/02 [in quantum statistical mechanics]; Koshino & Shimizu PRL(04) [exponentially decaying systems]; Dhar et al qp/05 [super-Zeno]; Maniscalco et al PRL(06) [Brownian motion]; Modi & Shaji PLA(07) [unstable system with two bound states]; Bernu et al PRL(08) [with light in a cavity].
@ In quantum field theory: Alvarez-Estrada & Sánchez-Gómez PLA(99)qp/98 [absence]; Bar IJTP(03)qp/01; Facchi & Pascazio in(03)qp/02; Rossi et al PRA(08)-a0710 [cavity QED].
@ Applications, effects: Yuasa et al JPSJ(03)qp/04, JMO(04)qp [state purification]; De Liberato PRA(07)-a0705 [decay rate of a metastable but non-decaying system]; Monras & Romero-Isart a0801 [and information control in spin chains]; Rossi et al PLA(09)-a0907 [and semiclassical evolution]; > s.a. hadrons [inhibition of proton decay].

Variations
* Anti-Zeno effect: A perpetual observation leads to an immediate disappearance of an unstable system.
* Spatial Zeno effect: The repetition of the same experiment over the time axis is replaced by simultaneous performances of the same experiment in a number of identical independent nonoverlapping regions of space.
@ Anti-Zeno effect: Kaulakys & Gontis PRA(97); Lewenstein & Rzazewski qp/99; Balachandran & Roy PRL(00)qp/99, IJMPA(02)qp/01; Prezhdo PRL(00) [in chemistry]; Diósi qp/01; Kofman & Kurizki qp/01/ZNA; Exner JPA(05)qp [sufficient conditions].
@ Spatial Zeno effect: Bar & Horwitz IJTP(01); Kouznetsov & Oberst OR(05) [and reflection of waves].
@ Removal of Zeno effect: Kullock & Svaiter PLA(08) [vacuum fluctuations of coupled field].


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