Robust photonic entanglement distribution by state-independent encoding onto decoherence-free subspace

Efficient and faithful implementation of quantum information tasks, such as quantum computing, quantum communication and quantum metrology(1-3), requires robust and state-independent decoherence-suppressing measures to protect the quantum information carriers. Here we present an experimental demonstration of a robust distribution scheme in which one photon of an entangled photon pair is successfully encoded into and decoded from a decoherence-free subspace by a state-independent scheme. We achieved a high-fidelity distribution of the entangled state over a fibre communication channel, and also demonstrated that the scheme is robust against fragility of the reference frame. The scheme, thanks to its state-independence, is also applicable to the multipartite case where the photon to be distributed is entangled with many other photons. Such a robust and universal scheme for distributing quantum information in an indeterministic but conclusive manner will constitute an important building block of quantum communication and computing networks.