Particle mixing and the emergence of classicality: A spontaneous-collapse-model view

Abstract

Spontaneous collapse models aim to resolve the measurement problem in quantum mechanics by considering wave-function collapse as a physical process. We analyze how these models affect a decaying flavor oscillating system whose evolution is governed by a phenomenological non-Hermitian Hamiltonian. In turn, we apply two popular collapse models, the QMUPL and the CSL models, to a neutral meson system. By using the equivalence between the approaches to the time evolution of decaying systems with a non-Hermitian Hamiltonian and a dissipator of the Lindblad form in an enlarged Hilbert space, we show that spontaneous collapse can induce the decay dynamics in both quantum state and master equations. Moreover, we show that the decay property of a flavor oscillating system is intimately connected to the time (a)symmetry of the noise field underlying the collapse mechanism. This (a)symmetry, in turn, is related to the definition of the stochastic integral and can provide a physical intuition behind the Itō/Stratonovich dilemma in stochastic calculus.

On the geometric phase for Majorana and Dirac neutrinos

“…In addition, in [22] it is ignored the fact that not all the possible measures that can be done on a quantum system must include demolition of the quantum state [53][54][55]. The design of a non-demolition measure for neutrinos would be a difficult task to achieve, but if one wants to prove that a quantity cannot be observed, one must consider all the possible ways to realize a measurement.…”

Observability of Spontaneous Collapse in Flavor Oscillations and its Relation to the Cp and Cpt Symmetries

“…Fundamental testability of spontaneous collapse allows for a number of experimental proposals such as X-rays [5][6][7][8][9], spontaneous radiation emission from charged particles [10][11][12][13], cold-atom experiments [14], gravitational waves [15], levitated nanoparticles [16], ma er-wave interferometry [17][18][19][20], and optomechanical setups [21][22][23]. Another example is given by mixed particle systems [24][25][26][27][28][29][30] that reveal phenomena of mixing and avor oscillations. Because of these phenomena the states of a mixed particle which are relevant in experiments are given by superpositions of states with distinct masses and, therefore, are interesting for quantummechanical tests [31][32][33][34][35].…”