M.Sc Student | Ofer Firstenberg |
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Subject | Interference of Non-classical Sources |

Department | Department of Physics |

Supervisors | Professor Emeritus Ron Amiram |

Dr. Amit Ben-Kish |

The interference between two independent sources has been a subject of interest for many years. In the last decade, many theoretical works addressed the question of interference between two independent Fock states, both in optical and atomic systems. Experimentally, spatial interference was observed between two Bose condensates though their exact initial state is still in dispute.

In contrast to coherent (classical) states, Fock states do not have a well-defined phase. Therefore, all conventional expectation values for an interference measurement between two Fock states show zero interference. However, in the framework of quantum measurement theories, it has been argued that any single experimental trajectory does exhibit interference. The relative phase is selected randomly, as a consequence of the measurement procedure.

We examine the
general characteristics of a two-source temporal interference system. We
suggest that when employing intensity detectors for interference measurements,
one actually measures the intensity in one or more *composed* modes. These
modes are coupled with each other, and often carry energy oscillations between
them. We investigate a special oscillating “phase state”, which has a
well-defined total number of photons (N), with a number uncertainty of
~√N in the composed mode. We claim that this is the state into which the
system evolves in a Fock state interference experiment. The initial Fock states
have a large number uncertainty in the composed modes (~N) and the intensity
measurement serves to reduce this uncertainty to ~√N.

We propose a new scheme for measuring two-source interference, using cavity QED in an off-resonance regime. This system has several advantages over previously suggested systems, since it employs non-continuous QND (Quantum Non Demolition) measurements of the first kind, while avoiding environmental coupling. The evolution of the “oscillating phase state” with a random phase is demonstrated, and other assumptions of the model are verified quantitatively.