Description
Genuine multipartite entanglement (GME), a special type of quantum correlation involving all parts of a composite system, is one of the central topics of quantum information theory. Detecting and preparing GME are challenging tasks, especially as the number of parts of the system increases.
We present results from three papers investigating the detection and activation of GME in quantum systems with infinite-dimensional Hilbert spaces. We first study the detection of GME from incomplete information about a quantum system. In particular, we develop two types of criteria that use only selected two-mode correlations. The first is a numerical criterion capable of certifying GME from a set of reduced two-mode subsystems that are themselves not entangled [1]. The second is an experimentally friendly criterion for detecting GME using only a limited number of measurements [2]. Both criteria reduce the scaling of the required information or number of measurements with the number of system parts from quadratic to linear, opening a way towards the detection of GME in large systems.
We then turn to the activation of GME. During the preparation or transmission of a multipartite quantum state, entanglement may be weakened, and GME can be lost. In some cases, however, GME can be restored by using multiple copies of the state instead of a single copy. We investigate this phenomenon of multi-copy activation of GME in infinite-dimensional systems and identify conditions under which GME can be activated [3].
References:
[1] Nordgren et al., Phys. Rev. A 106, 062410 (2022).
[2] Leskovjanová and Mišta, Quantum 9, 1837 (2025).
[3] Baksová et al., Quantum 9, 1699 (2025).