Quantum mechanics predicts that the decay rate of unstable systems could be effectively modified by the process of the measurement of the survival probability. Depending on the intrinsic properties of the unstable system and the experimental setup for the observation, one could obtain the so called (direct) quantum Zeno and inverse quantum Zeno effects corresponding to a slowing down or a speeding up of the decay, respectively. We argue that the inverse quantum Zeno effect is in principle detectable at a percent level for the neutron decay in experiments with trapped ultracold neutrons. Conversely, this effect is basically undetectable in experiments in which the neutron lifetime is measured by measuring the decays of beams of neutrons. As a test of our claim, we propose a simple qualitative correlation between the number of neutrons in the trap and the neutron lifetime: the larger the number, the faster the decay. Finally we discuss also the presently available measurements of the neutron lifetime and address the issue of the possible discrepancy that has been reported among the results obtained by the different experimental techniques.Quantum mechanics predicts that the decay rate of unstable systems could be effectively modified by the process of the measurement of the survival probability. Depending on the intrinsic properties of the unstable system and the experimental setup for the observation, one could obtain the so called (direct) quantum Zeno and inverse quantum Zeno effects corresponding to a slowing down or a speeding up of the decay, respectively. We argue that the inverse quantum Zeno effect is in principle detectable at a percent level for the neutron decay in experiments with trapped ultracold neutrons. Conversely, this effect is basically undetectable in experiments in which the neutron lifetime is measured by measuring the decays of beams of neutrons. As a test of our claim, we propose a simple qualitative correlation between the number of neutrons in the trap and the neutron lifetime: the larger the number, the faster the decay. Finally we discuss also the presently available measurements of the neutron lifetime and address the issue of the possible discrepancy that has been reported among the results obtained by the different experimental techniques.

arXiv:1906.10024Physical review. D/Physical review. D.Mar 5, 202017 citations

QZE and IZE in a Simple Approach and the Neutron Decay

F. Giacosa

We discuss a simple and analytically solvable measurement model which describes the famous Quantum Zeno Effect (QZE) and Inverse Zeno Effect (IZE), that correspond to the slow down and to the increase of the decay rate caused by measurements (or, more in general, by the interaction of an unstable state with the detector and the environment). Within this model one can understand quite general features of the QZE and IZE: by considering an unstable quantum state, such as an unstable particle, whose decay width as function of energy is $Γ(ω)=g^{2}ω^α,$ then -- under quite general assumptions -- the QZE occurs for $α\in(0,1)$ , while the IZE for $α\in(-\infty,0)\cup(1,\infty).$ This result is valid also for more realistic measurement models than the one described in this work. We then apply these considerations to the decay of the neutron, for which $α=5.$ Hence, the realization of the IZE for the neutron decay (and for the majority of weak decays) is in principle possible. Indeed, trap experiments find a lifetime that is $8.7\pm2.1$ s shorter than beam experiments, suggesting that the IZE could have taken place.We discuss a simple and analytically solvable measurement model which describes the famous Quantum Zeno Effect (QZE) and Inverse Zeno Effect (IZE), that correspond to the slow down and to the increase of the decay rate caused by measurements (or, more in general, by the interaction of an unstable state with the detector and the environment). Within this model one can understand quite general features of the QZE and IZE: by considering an unstable quantum state, such as an unstable particle, whose decay width as function of energy is $Γ(ω)=g^{2}ω^α,$ then -- under quite general assumptions -- the QZE occurs for $α\in(0,1)$, while the IZE for $α\in(-\infty,0)\cup(1,\infty).$ This result is valid also for more realistic measurement models than the one described in this work. We then apply these considerations to the decay of the neutron, for which $α=5.$ Hence, the realization of the IZE for the neutron decay (and for the majority of weak decays) is in principle possible. Indeed, trap experiments find a lifetime that is $8.7\pm2.1$ s shorter than beam experiments, suggesting that the IZE could have taken place.

arXiv:2004.07772Acta Physica Polonica BJan 1, 20201 citation

Γ(ω)=g^{2}ω^α,

then -- under quite general assumptions -- the QZE occurs for

α\in(0,1)

, while the IZE for

α\in(-\infty,0)\cup(1,\infty).

This result is valid also for more realistic measurement models than the one described in this work. We then apply these considerations to the decay of the neutron, for which

α=5.

Hence, the realization of the IZE for the neutron decay (and for the majority of weak decays) is in principle possible. Indeed, trap experiments find a lifetime that is

8.7\pm2.1

s shorter than beam experiments, suggesting that the IZE could have taken place.