Editing Quantum Zeno effect (section)

==Experiments and discussion==
Experimentally, strong suppression of the evolution of a quantum system due to environmental coupling has been observed in a number of microscopic systems.

In 1989, [[David J. Wineland]] and his group at [[NIST]]<ref name="u0">
{{cite journal
 |last1       = Itano
 |first1      = W.
 |last2       = Heinzen
 |first2      = D.
 |last3       = Bollinger
 |first3      = J.
 |last4       = Wineland
 |first4      = D.
 |year        = 1990
 |title       = Quantum Zeno effect
 |url         = http://www.boulder.nist.gov/timefreq/general/pdf/858.pdf
 |journal     = [[Physical Review A]]
 |volume      = 41
 |issue       = 5
 |pages       = 2295–2300
 |bibcode     = 1990PhRvA..41.2295I
 |doi         = 10.1103/PhysRevA.41.2295
 |pmid = 9903355
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20040720153510/http://www.boulder.nist.gov/timefreq/general/pdf/858.pdf
 |archive-date = 2004-07-20
}}</ref> observed the quantum Zeno effect for a two-level atomic system that was interrogated during its evolution. Approximately 5,000 {{chem2|auto=1|^{9}Be+}} ions were stored in a cylindrical [[Penning trap]] and [[laser cooling|laser-cooled]] to below 250&nbsp;mK. A resonant [[radio frequency|RF]] pulse was applied, which, if applied alone, would cause the entire [[Ground state|ground-state]] population to migrate into an [[excited state]]. After the pulse was applied, the ions were monitored for photons emitted due to relaxation. The ion trap was then regularly "measured" by applying a sequence of [[ultraviolet]] pulses during the RF pulse. As expected, the ultraviolet pulses suppressed the evolution of the system into the excited state. The results were in good agreement with theoretical models.

In 2001, [[Mark G. Raizen]] and his group at the [[University of Texas at Austin]] observed the quantum Zeno effect for an unstable quantum system,<ref name=Raizen>
{{cite journal
 |last1=Fischer |first1=M.
 |last2=Gutiérrez-Medina |first2=B.
 |last3=Raizen |first3=M.
 |year=2001
 |title=Observation of the Quantum Zeno and Anti-Zeno Effects in an Unstable System
 |journal=[[Physical Review Letters]]
 |volume=87 |issue=4 |pages=040402
 |arxiv=quant-ph/0104035
 |bibcode=2001PhRvL..87d0402F
 |doi=10.1103/PhysRevLett.87.040402 |pmid=11461604
|s2cid=11178428
 }}</ref> as originally proposed by Sudarshan and Misra.<ref name=Sudarshan/> They also observed an anti-Zeno effect. Ultracold sodium atoms were trapped in an accelerating [[optical lattice]], and the loss due to tunneling was measured. The evolution was interrupted by reducing the acceleration, thereby stopping [[quantum tunneling]]. The group observed suppression or enhancement of the decay rate, depending on the regime of measurement.

In 2015, Mukund Vengalattore and his group at [[Cornell University]] demonstrated a quantum Zeno effect as the modulation of the rate of quantum tunnelling in an ultracold lattice gas by the intensity of light used to image the atoms.<ref name="PatilChakram2015">{{cite journal |last1=Patil |first1=Y.&nbsp;S. |last2=Chakram |first2=S. |last3=Vengalattore |first3=M. |title=Measurement-Induced Localization of an Ultracold Lattice Gas |journal=Physical Review Letters |volume=115 |issue=14 |pages=140402 |year=2015 |issn=0031-9007 |doi=10.1103/PhysRevLett.115.140402 |pmid=26551797 |bibcode=2015PhRvL.115n0402P |arxiv=1411.2678}}</ref>

In 2024, Björn Annby-Andersson and his colleagues from Lund University in their experiment with a system of two quantum dots with one electron сame to the conclusion that "As the measurement strength is further increased, the Zeno effect prohibits interdot tunneling. A Zeno-like effect is also observed for weak measurements, where measurement errors lead to fluctuations in the on-site energies, dephasing the system." https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.6.043216

The quantum Zeno effect is used in commercial [[atomic magnetometer]]s and proposed to be part of birds' magnetic compass sensory mechanism ([[magnetoreception]]).<ref>
{{cite journal
 |last1=Kominis |first1=I. K.
 |year=2009
 |journal = Phys. Rev. E
 |volume = 80
 |pages = 056115
 |title=Quantum Zeno effect explains magnetic-sensitive radical-ion-pair reactions
 |issue=5
 |doi=10.1103/PhysRevE.80.056115
|pmid=20365051
 |arxiv=0806.0739
 |bibcode=2009PhRvE..80e6115K
 |s2cid=9848948
 }}</ref>

It is still an open question how closely one can approach the limit of an infinite number of interrogations due to the Heisenberg uncertainty involved in shorter measurement times. It has been shown, however, that measurements performed at a finite frequency can yield arbitrarily strong Zeno effects.<ref>{{cite journal |last1=Layden |first1=D. |last2=Martin-Martinez |first2=E. |last3=Kempf |first3=A. |title=Perfect Zeno-like effect through imperfect measurements at a finite frequency |journal=Physical Review A |date=2015 |volume=91 |issue=2 |page=022106 |doi=10.1103/PhysRevA.91.022106 |arxiv = 1410.3826 |bibcode = 2015PhRvA..91b2106L|s2cid=119628035 }}</ref> In 2006, Streed ''et al.'' at MIT observed the dependence of the Zeno effect on measurement pulse characteristics.<ref name=Streed>
{{cite journal
 |last1=Streed |first1=E.
 |last2=Mun |first2=J.
 |last3=Boyd |first3=M.
 |last4=Campbell |first4=G.
 |last5=Medley |first5=P.
 |last6=Ketterle |first6=W.
 |last7=Pritchard |first7=D.
 |year=2006
 |title=Continuous and Pulsed Quantum Zeno Effect
 |journal=[[Physical Review Letters]]
 |volume=97 |issue=26 |pages=260402
 |arxiv=cond-mat/0606430
 |bibcode=2006PhRvL..97z0402S
 |doi=10.1103/PhysRevLett.97.260402
 |pmid=17280408
 |s2cid=2414199
 }}</ref>

The interpretation of experiments in terms of the "Zeno effect" helps describe the origin of a phenomenon.
Nevertheless, such an interpretation does not bring any principally new features not described with the [[Schrödinger equation]] of the quantum system.<ref name=Petrosky1>
{{cite journal
 |last1=Petrosky |first1=T.
 |last2=Tasaki |first2=S.
 |last3=Prigogine |first3=I.
 |year=1990
 |title=Quantum zeno effect
 |journal=[[Physics Letters A]]
 |volume=151 |issue=3–4 |pages=109
 |bibcode=1990PhLA..151..109P
 |doi=10.1016/0375-9601(90)90173-L
}}</ref><ref name=Petrosky2>
{{cite journal
 |last1=Petrosky |first1=T.
 |last2=Tasaki |first2=S.
 |last3=Prigogine |first3=I.
 |year=1991
 |title=Quantum Zeno effect
 |journal=[[Physica A]]
 |volume=170 |issue=2 |pages=306
 |bibcode=1991PhyA..170..306P
 |doi=10.1016/0378-4371(91)90048-H
}}</ref>

Even more, the detailed description of experiments with the "Zeno effect", especially at the limit of high frequency of measurements (high efficiency of suppression of transition, or high reflectivity of a [[ridged mirror]]) usually do not behave as expected for an idealized measurement.<ref name="nanoscope" />

It was shown that the quantum Zeno effect persists in the many-worlds and relative-states interpretations of quantum mechanics.<ref name="dhome">
{{cite journal
 |last1=Home |first1=D.
 |last2=Whitaker |first2=M. A. B.
 |year=1987
 |title=The many-worlds and relative states interpretations of quantum mechanics, and the quantum Zeno paradox
 |journal=[[Journal of Physics A]]
 |volume=20 |issue=11 |pages=3339–3345
 |bibcode=1987JPhA...20.3339H
 |doi=10.1088/0305-4470/20/11/036
}}</ref>