Science http://doi.org/s7r (2014)

It's annoying when a letter is lost in the post. Even if a potentially erratic mail service is replaced with teleportation — as is the case for quantum communication — losing what we wish to send is just as frustrating. And unfortunately, this is what happens when quantum data are stored in and teleported via photons — most of the time they just get lost.

Deterministic data delivery can be achieved by means of unconditional teleportation. However, in contrast with the 143 km record distance for standard teleportation, this has previously only been realized in single-system table-top set-ups. Now, Wolfgang Pfaff and colleagues report the unconditional teleportation of a qubit encoded in nitrogen vacancy (NV) centres between two diamonds separated by over three metres.

The key elements required to make the protocol unconditional — a deterministic Bell measurement at the source and a sufficiently long coherence time of the receiver's qubit register — were achieved thanks to the high controllability of NV centres, once more reaffirming the great potential of diamond impurities for applications in quantum information and communication.