Securely propagating entanglement at the push of a button

Entanglement, Einstein's "spooky action at a distance," today is THE tool of quantum information science. It is the essential resource for quantum computers and used to transmit quantum information in a future quantum network. But it is highly sensitive. It is therefore an enormous challenge to entangle resting quantum bits (qubits) with flying qubits in the form of photons "at the push of a button."