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Dr Cristian Bonato

Delft University of Technology, The Netherlands

Tuesday, October 22nd, 2013 at 05:00:00 PM

Conference room Querzoli - LENS - via Nello Carrara 1 - Sesto Fiorentino (Florence)

Published on-line at 05:59:41 PM on Wednesday, October 16th, 2013

Sequential adaptive measurements of a single nuclear spin by

In contrast to classical physics, quantum measurements foster an intriguing interplay between information gain and system disturbance.

In contrast to classical physics, quantum measurements foster an intriguing interplay between information gain and system disturbance. Although the outcome of the measurement is probabilistic, the back-action imparted on the measured system is accurately described by quantum theory, given the measurement outcome. Therefore, quantum measurements can be used to manipulate a quantum system without the need for control fields.

In this talk, I will report on the realization of quantum control using sequential partial measurements with real-time feedback on a nuclear spin qubit in diamond. We control the measurement strength via an ancilla qubit (electron spin of a nitrogen-vacancy center). Using post-selection, controlled wavefunction collapse and quantum weak values exceeding 10 are observed. We then exploit a dynamical-stop quantum non-demolition measurement on the ancilla qubit to enable repetitive measurements without post-selection. By incorporating real-time feedback, we demonstrate measurement-only control of a quantum system. Adaptive measurements are an essential building block for measurement-based quantum computing and enhanced-sensitivity quantum metrology.

For further informations, please contact Dr Mario Agio.