Abstract: We explore in a rigorous manner the intuitive connection between the non-Markovianity of the evolution of an open quantum system and the performance of the system as a quantum memory. Using the paradigmatic case of a two-level open quantum system coupled to a bosonic bath, we compute the recovery fidelity, which measures the best possible performance of the system to store a qubit of information. We deduce that this quantity is connected, but not uniquely determined, by the non-Markovianity, for which we adopt the Breuer-Laine-Piilo measure proposed in Breuer et al (2009 Phys. Rev. Lett. 103 210401). We illustrate our findings with explicit calculations for the case of a structured environment.

Abstract: The excited states of unstable O-20 were investigated via.-ray spectroscopy following the O-19(d, p)O-20 reaction at 8 AMeV. By exploiting the Doppler shift attenuation method, the lifetimes of the 2(2)(+) and 3(1)(+) states were firmly established. From the gamma-ray branching and E2/M1 mixing ratios for transitions deexciting the 2(2)(+) and 3(1)(+) states, the B(E2) and B(M1) were determined. Various chiral effective field theory Hamiltonians, describing the nuclear properties beyond ground states, along with a standard USDB interaction, were compared with the experimentally obtained data. Such a comparison for a large set of gamma-ray transition probabilities with the valence space in medium similarity renormalization group ab initio calculations was performed for the first time in a nucleus far from stability. It was shown that the ab initio approaches using chiral effective field theory forces are challenged by detailed high-precision spectroscopic properties of nuclei. The reduced transition probabilities were found to be a very constraining test of the performance of the ab initio models.

Abstract: We present first evidence that the cosine of the CP-violating weak phase 2 beta is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B-0 -> D-(*) h(0) with D -> K-S(0)pi(+)pi(-) decays, where h(0) is an element of {pi(0), eta, omega} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the (sic)(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471 +/- 3) x 10(6) B (B) over bar pairs recorded by the BABAR detector and (772 +/- 11) x 10(6) B (B) over bar pairs recorded by the Belle detector. The results of the measurement are sin 2 beta = 0.80 +/- 0.14 (stat) +/- 0.06 (syst) +/- 0.03 (model) and cos 2 beta = 0.91 +/- 0.22(stat) +/- 0.09 (syst) +/- 0.07(model). The result for the direct measurement of the angle beta of the CKM Unitarity Triangle is beta = [22.5 +/- 4.4 (stat) +/- 1.2 (syst) +/- 0.6(model)]degrees. The measurement assumes no direct CP violation in B-0 -> D-(*) h(0) decays. The quoted model uncertainties are due to the composition of the D-0 -> K-S(0)pi(+)pi(-) decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics e(+)e(-) -> c (c) over bar data sample. CP violation is observed in B-0 -> D-(*) h(0) decays at the level of 5.1 standard deviations. The significance for cos 2 beta > 0 is 3.7 standard deviations. The trigonometric multifold solution pi/2 – beta = (68.1 +/- 0.7)degrees is excluded at the level of 7.3 standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.