Faithful qubit distribution assisted by one additional qubit against   collective noise
  We propose a distribution scheme of polarization states of a single photon over collective-noise channel. By adding one extra photon with a fixed polarization, we can protect the state against collective noise via a parity-check measurement and post-selection. While the scheme succeeds only probabilistically, it is simpler and more flexible than the schemes utilizing decoherence-free subspace. An application to BB84 protocol through collective noise channel, which is robust to the Trojan horse attack, is also given. 
T. Yamamoto, J. Shimamura, S. K. Ozdemir, M. Koashi, N. Imoto