Ph.D Student | Goren Tal |
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Subject | Study of the Dynamics of Quantum Vacuum Using Ramsey Interference |

Department | Department of Physics |

Supervisor | Professor Eric Akkermans |

Full Thesis text |

We have generalized the Ramsey interference effect, a widely used spectroscopic tool in atomic physics, to quantum systems with a continuous frequency/energy spectrum. This generalization provides a method to probe new dynamical features of quantum mesoscopic systems by monitoring the time delay between two identically shaped pulses. By exploring the contrast of the Ramsey interference pattern, we have been able to access various dephasing processes affecting the quantum behavior of quasiparticles in mesoscopic conductors.

We have shown how the Ramsey interference pattern modifies the probability to create electron-hole pairs for the specific case of a tunnel junction as a working example of mesoscopic conductor. We have established a useful connection between this probability and the measurable power spectrum (shot noise).

Those general results have been implemented in the case of the dephasing induced on electron-hole pairs by an ohmic environment. We have found that the crossover between high and low impedances (e.g. between Coulomb blockade regime and Johnson noise) can be described using the corresponding behavior of a quantum Brownian particle, and it can be monitored by means of the time delay between the pulses in the Ramsey experimental setup.

Furthermore, we have implemented the Ramsey interference setup in order to investigate the dynamical amplification of vacuum fluctuations in the Schwinger and the dynamical Casimir effects, thus showing that Ramsey interference is useful to study a wide range of driven quantum systems beyond two-level systems as used in atomic spectroscopy.

Finally, we have found that the Schwinger effect can be understood as a two-level system which can be realized, for instance, by means of a NMR setup. This allows for further investigations of the so far, elusive Schwinger effect.