Collisional decoherence during writing and reading quantum states
  Collisions, even though they do not limit the lifetime of quantum information stored in ground state hyperfine coherences, may severely limit the fidelity for quantum memory when they happen during the write and read process. This imposes restrictions on the implementation of quantum processes in thermal vapor cells and their performance as a quantum memory. We study the effect of these collisions in our experiment. 
Stephanie Manz, Thomas Fernholz, Joerg Schmiedmayer, and Jian-Wei Pan