Physical Review Letters

Quantum Zeno Effect Induced by Collisions

B. Nagels, L.J.F. Hermans, P. L. Chapovsky

Published Oct 27, 1997• 79 citations

Abstract

It is proven experimentally that the ortho-para conversion of the nuclear spin isomers of ${}^{13}{\mathrm{CH}}_{3}\mathrm{F}$ molecules can be slowed down by increasing the gas pressure. The observed ``freezing'' of the molecular quantum states can be considered as an example of the quantum Zeno effect induced by collisions.

DOI: 10.1103/physrevlett.79.3097

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Physical Review Letters

Quantum Zeno Effect Induced by Collisions

B. Nagels, L.J.F. Hermans, P. L. Chapovsky

Published Oct 27, 1997• 79 citations

Publisher

Abstract

It is proven experimentally that the ortho-para conversion of the nuclear spin isomers of

{}^{13}{\mathrm{CH}}_{3}\mathrm{F}

molecules can be slowed down by increasing the gas pressure. The observed ``freezing'' of the molecular quantum states can be considered as an example of the quantum Zeno effect induced by collisions.

DOI: 10.1103/physrevlett.79.3097

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Domenico Bruno, Paolo Facchi A, Savino Longo +3 more

arXiv:quant-ph/0206143The Journal of Physical Chemistry AOct 29, 20092 citations

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Yuichiro Matsuzaki, Hirotaka Tanaka

arXiv:1209.3136Journal of the Physical Society of JapanDec 15, 20151 citation

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arXiv:1508.04560Scientific ReportsDec 1, 201516 citations

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Gerard J Milburn, M. J. Gagen

We present a scheme for experimentally observing the quantum Zeno effect using the quantum-nondemolition measurement recently proposed by Brune et al. [Phys. Rev. Lett. 65, 976 (1990)]. The Zeno effect refers to the freezing of the (unitary) free dynamics of a system by rapid measurements. We generalize the Zeno effect to be any change in the survival probability of an initial state induced by very rapid measurements, when such measurements are the dominant source of fluctuations in the system. We derive a master equation for the evolution of a cavity mode when the photon number is monitored by this method. This equation describes a phase-diffusion process. We propose that this measurement scheme be used to monitor the exchange of a single photon between the cavity and a single Rydberg atom. We show that for very rapid monitoring the free oscillation of the atomic inversion is disrupted and the atom can be trapped close to the initial excited state. This is the quantum Zeno effect.We present a scheme for experimentally observing the quantum Zeno effect using the quantum-nondemolition measurement recently proposed by Brune et al. [Phys. Rev. Lett. 65, 976 (1990)]. The Zeno effect refers to the freezing of the (unitary) free dynamics of a system by rapid measurements. We generalize the Zeno effect to be any change in the survival probability of an initial state induced by very rapid measurements, when such measurements are the dominant source of fluctuations in the system. We derive a master equation for the evolution of a cavity mode when the photon number is monitored by this method. This equation describes a phase-diffusion process. We propose that this measurement scheme be used to monitor the exchange of a single photon between the cavity and a single Rydberg atom. We show that for very rapid monitoring the free oscillation of the atomic inversion is disrupted and the atom can be trapped close to the initial excited state. This is the quantum Zeno effect.

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Ortho-para separation of molecules using optical orientation of atoms in hyperfine Zeeman states

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Richard Claude Thompson, José Luis Hernández‐Pozos, J. T. Höffges +2 more

The quantum Zeno effect is the slowing down of the rate of a quantum mechanical transition by the frequent application of measurements to the system. Following the original suggestion of an experiment to test this in trapped ions, Itano et al. performed an experiment in 1990. This was followed by several detailed theoretical treatments of the problem, making new predictions and giving a better understanding of what was happening. Also since then, suggestions for new types of experiment to test the quantum Zeno effect have been made. At Imperial College we are currently setting up an experiment to study the quantum Zeno effect on a single ion, incorporating some of these new ideas. Details of this experiment are discussed in the paper.The quantum Zeno effect is the slowing down of the rate of a quantum mechanical transition by the frequent application of measurements to the system. Following the original suggestion of an experiment to test this in trapped ions, Itano et al. performed an experiment in 1990. This was followed by several detailed theoretical treatments of the problem, making new predictions and giving a better understanding of what was happening. Also since then, suggestions for new types of experiment to test the quantum Zeno effect have been made. At Imperial College we are currently setting up an experiment to study the quantum Zeno effect on a single ion, incorporating some of these new ideas. Details of this experiment are discussed in the paper.

AIP conference proceedingsJan 1, 19990 citations

It is proven experimentally that the ortho-para conversion of the nuclear spin isomers of

{}^{13}{\mathrm{CH}}_{3}\mathrm{F}

Ortho-para separations of

{}^{7}{\mathrm{Li}}_{2}

and

{}^{6}{\mathrm{Li}}_{2}

molecules were achieved by using a monochromatic laser beam to align atoms into a single nuclear spin state. This approach is unlike the cryogenic cooling technique, which has been successful only on very light molecules (such as

{\mathrm{H}}_{2}

and

{\mathrm{D}}_{2}

), which have large energy gaps between the lowest rotational states. The atoms were ``pumped into'' a single hyperfine Zeeman state with defined electron and nuclear spin orientations. The well-resolved rotational structures of the lithium molecules, as shown by laser-induced fluorescence spectra, revealed the enrichment of ortho-components over para-components. Using laser radiation with a power density of $\ensuremath{\sim}10{\mathrm{m}\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}$ can increase the amount of ortho-components by a factor of 2 for

{}^{7}{\mathrm{Li}}_{2}

vapor and by a factor of 3 for

{}^{6}{\mathrm{Li}}_{2}

vapor on a time scale of milliseconds. This paper proposes a model to account for the experimental observations. These increases in the concentrations of ortho-components to para-components are explained by a combined effect of (i) a decrease in molecular density due to the electron spin orientation and (ii) a transfer of nuclear spin momenta from oriented atoms to molecules. The exchange reaction, ${\mathrm{Li}}^{\ensuremath{'}}{+\mathrm{L}\mathrm{i}}_{2}{\ensuremath{\rightarrow}\mathrm{Li}}_{3}{\ensuremath{\rightarrow}\mathrm{Li}}^{\ensuremath{'}}\mathrm{L}\mathrm{i}+\mathrm{L}\mathrm{i},$ appears to transfer the spin orientation from atoms to molecules. A substantial number of ortho-para separations can be achieved through multiple exchange collisions. Applications of this technique to other homonuclear diatomic molecules and polyatomic molecules with nuclear exchange symmetry are predicted.