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arXiv:quant-ph/9901060 · Physical Review A

Quantum anti-Zeno effect

Maciej Lewenstein, Kazimierz Rza̧żewski

Published Jan 10, 2000• 76 citations
arXivHTMLPDF

Abstract

We demonstrate that near-threshold decay processes may be accelerated by repeated measurements. Examples include near-threshold photodetachment of an electron from a negative ion, and spontaneous emission in a cavity close to the cutoff frequency or in a photon band-gap material.
DOI
10.1103/physreva.61.022105

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We theoretically investigate the influence of the phonon-mediated coupling on the properties of the laser generated by a single red-detuned quantum dot (QD), where the QD is coherently driven and coupled to a microscopic cavity which can be engineered in a photonic band-gap (PBG) material. In the low-temperature limit, the phonon-mediated coupling is deleterious to the emission of photon into cavity field and the threshold behavior of the laser persists after the inclusion of the phonon-mediated processes. Without being engineered in the PBG material, if the damping rate $\ensuremath{\kappa}$ of the cavity is close to but smaller than the phonon-mediated spontaneous emission rate $\ensuremath{\gamma}$ of the dot, the photon statistics of the cavity field change from super-Poissonian to sub-Poissonian. The nonclassical effect can be achieved due to the phonon-mediated processes induced by the electron-phonon interaction and the off-resonant dot-cavity coupling. The nonclassical effect can be enhanced by the PBG material. When the effect of the thermal phonon is taken into account, the cavity field exhibits the super-Poissonian property. If $\ensuremath{\kappa}$ is much smaller than $\ensuremath{\gamma}$, the phonon-mediated processes can lead to the increase (decrease) of the photons provided that the incoherent pumping rate is lower (higher) than the effective phonon-mediated threshold. But, if $\ensuremath{\kappa}$ is close to or larger than $\ensuremath{\gamma}$, the emission of the photon may dominate the absorption process, strengthening the intensity of the cavity field.
Frequent measurements can modify the decay of an unstable quantum state with respect to the free dynamics given by Fermi's golden rule. In a landmark article [A. G. Kofman and G. Kurizki, Nature (London) 405, 546 (2000)], Kofman and Kurizki concluded that in quantum decay processes, acceleration of the decay by frequent measurements, called the quantum anti-Zeno effect (AZE), appears to be ubiquitous, while its counterpart, the quantum Zeno effect, is unattainable. However, up to now there have been no experimental observations of the AZE for atomic radiative decay (spontaneous emission) in free space. In this work, making use of analytical results available for hydrogenlike atoms, we find that in free space, only non-electric-dipole transitions should present an observable AZE, revealing that this effect is consequently much less ubiquitous than first predicted. We then propose an experimental scheme for AZE observation, involving the electric quadrupole transition between D5/2{D}_{5/2}D5/2​ and S1/2{S}_{1/2}S1/2​ in the alkali-earth ions Ca+{\mathrm{Ca}}^{+}Ca+ and Sr+{\mathrm{Sr}}^{+}Sr+. The proposed protocol is based on the stimulated Raman adiabatic passage technique, which acts like a dephasing quasimeasurement.