Entanglement distribution with separable states

01.01.2014, 00:00

Newsletter 7

Quantum measurement is the most counterintuitive phenomenon of the micro-world and this shows up most markedly in connection with entangled states. As a result quantum entanglement is a versatile resource for quantum information processing. An entangled quantum state of a composite quantum system cannot be described as the tensor product of separate quantum states of the subsystems involved (i.e., as an overall separable state). Quantum information protocols typically require the distribution of entanglement among separate parties. This is usually accomplished by direct transmission of entangled systems. In recent work we have demonstrated a protocol for entanglement distribution by a separable (i.e. unentangled) system. In this counterintuitive protocol, entanglement is distributed between two remote parties, Alice and Bob, with the help of communication via a separable auxiliary system C' (i.e., the ancilla state). Nevertheless, the state shared by the participants still contains non-classical correlations between the ancilla and the rest of the system, which are vital for the protocol to function. A third party David owns classical information about the preparation of the state, which he can distribute to enable the participants to recover the entanglement. This quantum protocol highlights the complex hierarchical structure of mixed correlated quantum states and the role that classical information plays in quantum information science. 

Contact: christian.peuntinger(at)mpl.mpg(dot)de
Group: Leuchs Division
Reference: C. Peuntinger et al., Phys. Rev. Lett. 111, 230506 (2013).