title: Robust bidirectional links for photonic quantum networks.
abstract: Optical fibers are widely used as one of the main tools for transmitting not only classical but also quantum information. We propose and report an experimental realization of a promising method for creating robust bidirectional quantum communication links through paired optical polarization-maintaining fibers. Many limitations of existing protocols can be avoided with the proposed method. In particular, the path and polarization degrees of freedom are combined to deterministically create a photonic decoherence-free subspace without the need for any ancillary photon. This method is input state-independent, robust against dephasing noise, postselection-free, and applicable bidirectionally. To rigorously quantify the amount of quantum information transferred, the optical fibers are analyzed with the tools developed in quantum communication theory. These results not only suggest a practical means for protecting quantum information sent through optical quantum networks but also potentially provide a new physical platform for enriching the structure of the quantum communication theory.
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China.; Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Jin-Shi
authors.initials: JS
authors.lastname: Xu
authors.affiliation: Department of Physics, South University of Science and Technology of China, Shenzhen 518055, People's Republic of China.; Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 10084, People's Republic of China.; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Man-Hong
authors.initials: MH
authors.lastname: Yung
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China.; Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Xiao-Ye
authors.initials: XY
authors.lastname: Xu
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China.; Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Jian-Shun
authors.identifier: 0000-0002-2191-8350
authors.initials: JS
authors.lastname: Tang
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China.; Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Chuan-Feng
authors.initials: CF
authors.lastname: Li
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China.; Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Guang-Can
authors.initials: GC
authors.lastname: Guo
mesh_terms: D003142:Communication; D016494:Computer Security; D003198:Computer Simulation; D007257:Information Theory; D008027:Light; D055100:Optical Fibers; D017785:Photons; D011789:Quantum Theory; D012542:Scattering, Radiation
keywords: Bidirectional quantum communication; decoherence-free subspace; polarization-maintaining fiber; quantum capacity
references.citation: Science. 2001 Sep 14;293(5537):2059-63
references.pmid: 11557885
references.citation: Phys Rev Lett. 2004 Nov 26;93(22):220501
references.pmid: 15601072
references.citation: Opt Express. 2008 Nov 10;16(23):19118-26
references.pmid: 19582004
references.citation: Nature. 2001 Jan 4;409(6816):46-52
references.pmid: 11343107
references.citation: Phys Rev Lett. 2005 Jul 22;95(4):040503
references.pmid: 16090789
references.citation: Opt Express. 2005 Nov 14;13(23):9415-21
references.pmid: 19503143
references.citation: Science. 2000 Oct 20;290(5491):498-501
references.pmid: 11039926
references.citation: Phys Rev Lett. 2007 Dec 21;99(25):250503
references.pmid: 18233507
references.citation: Phys Rev Lett. 2004 Aug 20;93(8):080502
references.pmid: 15447165
references.citation: Phys Rev Lett. 2003 Nov 21;91(21):217904
references.pmid: 14683338
references.citation: Phys Rev Lett. 2004 Jun 25;92(25 Pt 1):257901
references.pmid: 15245064
references.citation: Phys Rev Lett. 2004 Mar 12;92(10):107901
references.pmid: 15089244
references.citation: Phys Rev Lett. 2005 Sep 2;95(10):100501
references.pmid: 16196913
references.citation: Nature. 2006 Sep 21;443(7109):316-9
references.pmid: 16988707
references.citation: Phys Rev Lett. 2004 Oct 29;93(18):180502
references.pmid: 15525142
references.citation: Phys Rev A. 1995 Oct;52(4):R2493-R2496
references.pmid: 9912632
references.citation: Phys Rev Lett. 2003 Oct 31;91(18):187903
references.pmid: 14611316
references.citation: Phys Rev Lett. 2006 Apr 21;96(15):150504
references.pmid: 16712139
references.citation: Phys Rev Lett. 2003 Aug 22;91(8):087901
references.pmid: 14525278
references.citation: Science. 2001 Feb 9;291(5506):1013-5
references.pmid: 11232562
references.citation: Phys Rev A. 1996 Oct;54(4):2629-2635
references.pmid: 9913771