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Interaction-free measurements by quantum Zeno stabilization of ultracold atoms.

Peise J, Lücke B, Pezzé L, Deuretzbacher F, Ertmer W, Arlt J, Smerzi A, Santos L, Klempt C - Nat Commun (2015)

Bottom Line: Quantum mechanics predicts that our physical reality is influenced by events that can potentially happen but factually do not occur.Contrary to existing proposals, our IFM does not require single-particle sources and is only weakly affected by losses and decoherence.We demonstrate confidence levels of 90%, well beyond previous optical experiments.

View Article: PubMed Central - PubMed

Affiliation: Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany.

ABSTRACT
Quantum mechanics predicts that our physical reality is influenced by events that can potentially happen but factually do not occur. Interaction-free measurements (IFMs) exploit this counterintuitive influence to detect the presence of an object without requiring any interaction with it. Here we propose and realize an IFM concept based on an unstable many-particle system. In our experiments, we employ an ultracold gas in an unstable spin configuration, which can undergo a rapid decay. The object-realized by a laser beam-prevents this decay because of the indirect quantum Zeno effect and thus, its presence can be detected without interacting with a single atom. Contrary to existing proposals, our IFM does not require single-particle sources and is only weakly affected by losses and decoherence. We demonstrate confidence levels of 90%, well beyond previous optical experiments.

No MeSH data available.


Related in: MedlinePlus

Zeno suppression of quantum phase transition.The number of atoms in the state (1, 1) produced by spin dynamics during 200 ms (open circles) as a function of the effective loss rate Γ. The error bars indicate the statistical uncertainty due to the finite number of measurements. The insets present the spin dynamics resonances as a function of the energy difference q between the input and the output states. The resonances are shown for the unperturbed case and for finite effective loss rates Γ=15 s−1 and Γ=59 s−1. The strong suppression of spin dynamics for an increased effective loss rate is well reproduced by a theoretical model without free parameters (grey lines). The error bar presents the standard error of the mean fraction of transferred atoms.
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f2: Zeno suppression of quantum phase transition.The number of atoms in the state (1, 1) produced by spin dynamics during 200 ms (open circles) as a function of the effective loss rate Γ. The error bars indicate the statistical uncertainty due to the finite number of measurements. The insets present the spin dynamics resonances as a function of the energy difference q between the input and the output states. The resonances are shown for the unperturbed case and for finite effective loss rates Γ=15 s−1 and Γ=59 s−1. The strong suppression of spin dynamics for an increased effective loss rate is well reproduced by a theoretical model without free parameters (grey lines). The error bar presents the standard error of the mean fraction of transferred atoms.

Mentions: In our experiments, the absorbing object is implemented by a laser beam, which is resonant with the F=2 hyperfine state2829 (see Fig. 1). In combination with the microwave dressing, this laser beam generates an effective loss rate Γ for the level (1, −1), which can be freely controlled by the laser intensity. Figure 2 shows the effect of this loss on the spin dynamics instability. It demonstrates that the loss rate on the level (1, −1) hinders and finally prevents the generation of atoms in the level (1, 1), although this level is not influenced directly. The experimental data are well reproduced by a master equation describing spin dynamics and the additional loss term (see Methods). Interestingly, our setup is equivalent to the proposal by Luis and Peřina, which was initially devised, but never realized, for optical parametric down-conversion1213. Furthermore, the atoms in (1, −1) can be regarded as a decay product of the atoms decaying from (1, 0) to (1, 1). As the Zeno measurement is performed on a decay product, the measurement is considered to be indirect. In this sense, our results represent the first observation of the quantum Zeno effect with a continuous, indirect, negative-result measurement, which is regarded as the most stringent demonstration by some authors30.


Interaction-free measurements by quantum Zeno stabilization of ultracold atoms.

Peise J, Lücke B, Pezzé L, Deuretzbacher F, Ertmer W, Arlt J, Smerzi A, Santos L, Klempt C - Nat Commun (2015)

Zeno suppression of quantum phase transition.The number of atoms in the state (1, 1) produced by spin dynamics during 200 ms (open circles) as a function of the effective loss rate Γ. The error bars indicate the statistical uncertainty due to the finite number of measurements. The insets present the spin dynamics resonances as a function of the energy difference q between the input and the output states. The resonances are shown for the unperturbed case and for finite effective loss rates Γ=15 s−1 and Γ=59 s−1. The strong suppression of spin dynamics for an increased effective loss rate is well reproduced by a theoretical model without free parameters (grey lines). The error bar presents the standard error of the mean fraction of transferred atoms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4403339&req=5

f2: Zeno suppression of quantum phase transition.The number of atoms in the state (1, 1) produced by spin dynamics during 200 ms (open circles) as a function of the effective loss rate Γ. The error bars indicate the statistical uncertainty due to the finite number of measurements. The insets present the spin dynamics resonances as a function of the energy difference q between the input and the output states. The resonances are shown for the unperturbed case and for finite effective loss rates Γ=15 s−1 and Γ=59 s−1. The strong suppression of spin dynamics for an increased effective loss rate is well reproduced by a theoretical model without free parameters (grey lines). The error bar presents the standard error of the mean fraction of transferred atoms.
Mentions: In our experiments, the absorbing object is implemented by a laser beam, which is resonant with the F=2 hyperfine state2829 (see Fig. 1). In combination with the microwave dressing, this laser beam generates an effective loss rate Γ for the level (1, −1), which can be freely controlled by the laser intensity. Figure 2 shows the effect of this loss on the spin dynamics instability. It demonstrates that the loss rate on the level (1, −1) hinders and finally prevents the generation of atoms in the level (1, 1), although this level is not influenced directly. The experimental data are well reproduced by a master equation describing spin dynamics and the additional loss term (see Methods). Interestingly, our setup is equivalent to the proposal by Luis and Peřina, which was initially devised, but never realized, for optical parametric down-conversion1213. Furthermore, the atoms in (1, −1) can be regarded as a decay product of the atoms decaying from (1, 0) to (1, 1). As the Zeno measurement is performed on a decay product, the measurement is considered to be indirect. In this sense, our results represent the first observation of the quantum Zeno effect with a continuous, indirect, negative-result measurement, which is regarded as the most stringent demonstration by some authors30.

Bottom Line: Quantum mechanics predicts that our physical reality is influenced by events that can potentially happen but factually do not occur.Contrary to existing proposals, our IFM does not require single-particle sources and is only weakly affected by losses and decoherence.We demonstrate confidence levels of 90%, well beyond previous optical experiments.

View Article: PubMed Central - PubMed

Affiliation: Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany.

ABSTRACT
Quantum mechanics predicts that our physical reality is influenced by events that can potentially happen but factually do not occur. Interaction-free measurements (IFMs) exploit this counterintuitive influence to detect the presence of an object without requiring any interaction with it. Here we propose and realize an IFM concept based on an unstable many-particle system. In our experiments, we employ an ultracold gas in an unstable spin configuration, which can undergo a rapid decay. The object-realized by a laser beam-prevents this decay because of the indirect quantum Zeno effect and thus, its presence can be detected without interacting with a single atom. Contrary to existing proposals, our IFM does not require single-particle sources and is only weakly affected by losses and decoherence. We demonstrate confidence levels of 90%, well beyond previous optical experiments.

No MeSH data available.


Related in: MedlinePlus