[HIGHLIGHTS] The size of quantum entanglement can be estimated. China University of Science and Technology has made important progress in quantum entanglement research.

The size of quantum entanglement can be estimated. China University of Science and Technology has made important progress.

Entanglement is the basic concept of quantum theory and the core resource in quantum information. To date, all entangler witnesses have generally only been used to detect the presence or absence of entanglements and have remained silent on estimates of its size. The research team found that entangled witnesses can be appropriately normalized to a distance that can characterize the difference between experimental data generated by a given quantum state and a separable state.