## Abstract

The problem of quantum coherence in a symmetric double well potential with a dimensionless damping coefficient α for classical motion is studied within a spin 1/2-boson model. The experimentally measured probability p(t) of refinding a definite initial state after time t is approximately expressed by the transverse spin relaxation function φ{symbol}(t), which is determined from a three-pole approximation, that incorporates both the correct long and short time behaviour. For a bare tunnelsplitting δ small compared to the heat bath cutoff ω_{c} we find, that the oscillating component of φ{symbol}(t) is negligible compared to the relaxational one unless α is of order Δ/ω_{c}. Thus p(t)≃(1+exp(-νt))/2 with a mean tunneling rate ν proportional to {Mathematical expression} for α < 2 and T ≪ {Mathematical expression} and proportional to Δ^{2}/ω_{c}·(T/ω_{c})^{α-1} otherwise. The results apply directly to recent measurements of the dynamics of flux states in a SQUID.

Original language | English |
---|---|

Pages (from-to) | 87-91 |

Number of pages | 5 |

Journal | Zeitschrift für Physik B Condensed Matter |

Volume | 54 |

Issue number | 1 |

DOIs | |

State | Published - Mar 1983 |

Externally published | Yes |