Displaced photon states as resource for dense coding
Sergey A. Podoshvedov · Physical Review A · 2009
We extend the analysis of dense coding protocol based on displaced photon states. The phase transformations with a displaced qubit allow for someone to transform five states to each other. Each ``particle-carrier'' (displaced qubit) carries an equal number of photons. On the receiving side, it is possible to decode all five outcomes using a linear optical scheme with beam splitters and on-off photodetectors that cannot discriminate different number of detected photons. Summarizing, interacting with only a single displaced qubit, it is possible to transmit two bits of information more. Optimal conditions to guarantee maximal communication rate ${\mathrm{log}}_{2}5$ per ``particle-carrier'' (displaced qubit) and influence of decoherence on the communication rate are considered.