For several decades, scientists have been aware of significant benefits allowing quantum information processing technologies to surpass their classical counterparts. Recent technological development allows these benefits to be tested experimentally and in some cases also implemented in practical devices. So far the majority of experimental quantum networks was limited to peer-to-peer communications between two parties. Practical implementation of quantum communications networks, however, needs to address the problem of scalability to serve large numbers of users. Similarly to classical computer networks, their quantum counterparts would require routing protocols to direct the signal from its source to destination. Devices implementing these routing protocols are called quantum routers and have recently been subject of an intense research. In this paper, we report on experimental implementation of a linear-optical quantum router. Our device allows single-photon polarization-encoded qubits to be routed coherently into two spatial output modes depending on the state of two identical control qubits. The polarization qubit state of the routed photon is maintained during the routing operation. The success probability of our scheme can be increased up to 25% making it the most efficient linear-optical quantum router developed to this date.

Faculty of Physics Adam Mickiewicz University PL 61 614 Poznań Poland

Institute of Physics of Czech Academy of Sciences Joint Laboratory of Optics of Palacký University and Institute of Physics of Academy of Sciences of the Czech Republic 17 listopadu 50A 772 07 Olomouc Czech Republic

RCPTM Joint Laboratory of Optics of Palacký University and Institute of Physics of Czech Academy of Sciences 17 listopadu 12 772 07 Olomouc Czech Republic

Sci Rep. 2020 Jul 7;10(1):11447. doi: 10.1038/s41598-020-68524-y. PubMed

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Supplementary information, 10.1038/s41598-018-31273-0.