Efficient use of quantum resources for the transmission of a reference frame

Phys Rev Lett. 2004 Oct 29;93(18):180503. doi: 10.1103/PhysRevLett.93.180503. Epub 2004 Oct 28.

Abstract

We propose a covariant protocol for transmitting reference frames encoded on N spins, achieving sensitivity N-2 without the need of a preestablished reference frame and without using entanglement between sender and receiver. The protocol exploits the use of equivalent representations that were overlooked in the previous literature.