Quantum State Engineering in Cold Caesium Atoms: An entangled tale of non-destructively induced collapse and squeezing of quantum states. – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2010 > Quantum State Engineer...

Quantum State Engineering in Cold Caesium Atoms: An entangled tale of non-destructively induced collapse and squeezing of quantum states.

Quantum mechanics is characterised by several strange features, which include quantum uncertainty, quantum measurements, and entanglement. This thesis involves all three of these. The quantum uncertainty poses a fundamental standard quantum limit (SQL) in applications where quantum systems are used to gauge some quantity. A prime example is that of atomic frequency standards, which with unprecedented precision measure an atomic quantum state. Quantum measurements in the form of Quantum Non-Demolition (QND) measurements can be engineered so as to overcome the SQL by redistributing quantum uncertainty amongst different variables of the system. Such squeezed spin-states rely on inter-atomic correlation, which goes by the name of entanglement.In this work we present a detailed description of how we have implemented a QND measurement with laser pulses in a Mach-Zehnder Interferometer (MZI) and demonstrate that we can engineer a squeezed state in a cold trapped ensemble of Cs atoms. We verify that the squeezing is useful for improving the precision of atomic clocks. Along the way, we also investigate several remarkable features of the interaction, by which atoms and light-particles (photons) exchange phase-shifts.

 After the questioning by the opponents, approximately at 4 pm, a reception will be held in the institute cantine.