Bipartite subspaces having no bases distinguishable by local operations and classical communication.
It is proved that there exist subspaces of bipartite tensor product spaces that have no orthonormal bases that can be perfectly distinguished by means of local operations and classical communication. A corollary of this fact is that there exist quantum channels having suboptimal classical capacity even when the receiver may communicate classically with a third party that represents the channel's environment.
Watrous
John
J
Institute for Quantum Information Science and Department of Computer Science, University of Calgary, Calgary, Alberta, Canada T2N 1N4. jwatrous@cpsc.ucalgary.ca