Research makes particle entanglement easier to measure

March 2016

Measuring multipartite entanglementA new way to detect entanglement in many-particle quantum states has been developed through research involving the University of Strathclyde.
The protocol, proposed by researchers at Strathclyde, the University of Innsbruck and Technische Universität München, is a simplified approach to detecting certain properties of many-particle entanglement, independently from the size of the system.
The experimental measure of entanglement in many-body quantum systems opens a new observational window in the world of quantum matter. It will enable better understanding of the role of quantum mechanical entanglement in these systems and their exotic emerging properties.
Dr Luca Tagliacozzo, a Chancellor’s Fellow in Strathclyde’s Department of Physics, was a partner in the research. He said: “In quantum theory, interactions among particles create fascinating peculiar correlations that cannot be explained by any means known to the classical world. 
“Entanglement is a consequence of strange probabilistic rules of quantum mechanics and seems to permit a peculiar instantaneous connection between particles over long distances that defies the laws of our macroscopic world, a phenomenon that Einstein referred to as ‘spooky action at a distance.’
“Entanglement is a mysterious concept but there is little doubt that it contributes to provide super-powers to quantum systems. Those systems can be used to obtain more precise measurement devices in the field of quantum metrology, to perform faster computations in the field of quantum computing, and to design devices based on exotic properties, such as zero electrical resistance at relatively high temperature, in the field of quantum materials.
“Developing protocols to detect and quantify entanglement of many-particle quantum states is thus a key challenge for current experiments, since detecting entanglement becomes very difficult when many particles are involved.”
 The researchers showed that using the new detection protocol for entanglement enables easy extraction of information about entanglement in many body systems by using the standard measurements techniques available in the laboratories. For example, in the case of neutral atoms trapped in optical lattices, the protocol can be implemented by performing ordinary laser spectroscopy. The protocol provides a measurement of the Quantum Fisher information, a reliable witness for genuinely multipartite entanglement.
The research has been published in the journal Nature Physics (doi: 10.1038/NPHYS3700). The study was led by Dr Philipp Hauke, and Prof Peter Zoller of Innsbruck’s Institute for Theoretical Physics and also involved Dr Markus Heyl of Technische Universität München.
The Research Excellence Framework 2014, the comprehensive rating of UK universities’ research, ranked Strathclyde’s Physics research first in the UK, with 96% of output assessed as world-leading or internationally excellent.