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 , 2 , 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. Before the practical implementation of quantum information schemes, there is a need to reduce loss, both in terms of photons and the information they carry. A robust scheme now experimentally demonstrated tackles this problem using so-called decoherence-free subspace.