The Fastest Possible Rate of Decay of Wave Functions

В.Л. Михеев, V. A. Morozov, Natalia V. Morozova

An attempt of changing the radioactive decay rate of atomic nuclei due to interference of wave functions of the initial nucleus and nuclei identical to radioactive decay products has been made. The first experiments have been performed with 212 Po undergoing α decay with a half-life of 0.3 μs. For 212 Po implanted into natural metallic lead, the increase in the decay rate by ∼0.2%, as compared to the decay rate of 212 Po in nickel, has been registered.

Shunlong Luo, Zhengmin Zhang

Michael Keyl

In this paper we propose a method to estimate the density matrix ρ of a d-level quantum system by measurements on the N-fold system in the joint state ρ⊗N. The scheme is based on covariant observables and representation theory of unitary groups and it extends previous results concerning pure states and the estimation of the spectrum of ρ. We show that it is consistent (i.e. the original input state ρ is recovered with certainty if N → ∞), analyze its large deviation behavior, and calculate explicitly the corresponding rate function which describes the exponential decrease of error probabilities in the limit N → ∞. Finally, we discuss the question whether the proposed scheme provides the fastest possible decay of error probabilities.

Stephen Gamboa‐Eastman

Marvin H. Mittleman

The annihilation rate of Ps is proportional to the square of the wave function at the origin. This can be affected by exposure of the atom to a resonant laser. The result depends upon whether the excited state is an S or a P state and whether it is singlet or triplet. An alteration of the decay rate by as much as a factor of 2 is possible.