Antonio Acín – Institut de Ciències Fotòniques (ICFO)

Entanglement is a form of correlations observed among quantum particles that does not have a classical analog. It is also one of the most studied properties of quantum mechanics for its application in quantum information protocols. Detecting its presence in systems with many particles, however, remains experimentally and theoretically challenging. The first barrier is the exponential amount of information required to reconstruct the system’s state. The second is that, even if the quantum state is known, the available methods are computationally too demanding even for systems composed of few particles.

In our work, we introduce a new technique for entanglement detection that provides significant advantages with respect to previous methods. First, it scales efficiently with the number of particles, thus allowing for application to systems composed by up to few tens of particles. Second, it needs only the knowledge of a subset of all possible measurements on the state, therefore being apt for experimental implementation. Moreover, since it is based on the detection of Bell inequality violations, our method is device independent, meaning that it allows one to assess entanglement without assuming any prior knowledge of the prepared state or the measurements performed. We report several examples of its implementation for well-known multipartite states, showing that the introduced technique has a promising range of applications.

We expect our findings will contribute to advancing the field of entanglement detection towards larger systems. In particular, this new approach can supersede the current methods used to detect entanglement in state-of-the-art experiments involving tens of particles.


Baccari F, Cavalcanti D, Wittek P & Acin A 2017, ‘Efficient Device-Independent Entanglement Detection for Multipartite Systems‘, Physical Review X, 7, 2, 021042.