15 June 2012 ICFO in Nature Physics

Groups led by Juan P. Torres and Antonio Acin demonstrate the first experimental measurement from data alone of the dimension of an unknown quantum system. The paper Experimental estimation of the dimension of classical and quantum systems has been published in Nature Physics by ICFO Research fellow Dr. Martin Hendrych, ICFO PhD Student Rodrigo Gallego, Prof. Nicholas Brunner (U. Bristol, UK), Dr. Michal Micuda, (ICFO, U. Palacky, Czech Republic), ICREA Prof. Antonio Acin, leader at ICFO of the Quantum Information group and UPC Prof. Juan P. Torres, leader at ICFO of the Quantum Engineering of Light group.

In order to study a physical system, scientists usually assume that the system has a particular dimension. The theoretical models they use to describe experimental observations rely on such an assumption about the dimensionality of the system under consideration. But… would it be possible to assess the dimension of an unknown system from experimental data alone? The answer is yes. Not only this. It might be even possible to certify the quantum nature of the system from the measured data. The work of Hendrych and co-workers represents one of the first demonstrations of device-independent quantum estimation that aims at characterizing unknown quantum systems without making any assumptions on the measuring device used in the protocol.