Theoretical Breakthrough For Quantum Cryptography 116
KentuckyFC writes "Quantum cryptography uses the quantum properties of photons to guarantee perfect secrecy. But one of its lesser known limitations is that it only works if Alice and Bob are perfectly aligned so that they can carry out well-defined polarization measurements on the photons as they arrive. Physicists say that Alice and Bob must share the same reference frame. That's OK if Alice and Bob are in their own ground-based labs, but it's a problem in many other applications, such as ground-to-satellite communications or even in chip-to-chip communications, because it's hard to keep chips still over distances of the order of the wavelength of light. Now a group of UK physicists have developed a way of doing quantum cryptography without sharing a reference frame. The trick is to use entangled triplets of photons, so-called qutrits, rather than entangled pairs. This solves the problem by embedding it in an extra abstract dimension, which is independent of space. So, as long as both Alice and Bob know the way in which all these abstract dimensions are related, the third provides a reference against which measurements of the other two can be made. That allows Alice and Bob to make any measurements they need without having to agree ahead of time on a frame of reference. That could be an important advance enabling the widespread use of quantum cryptography."
Re:Engineering (Score:4, Insightful)
What makes you think that theory and engineering are mutually exclusive, with a fine dividing line?
"This solves the problem by embedding it...." (Score:5, Insightful)
"This solves the problem by embedding it in an extra abstract dimension, which is independent of space."
Has it occurred to anyone else how UNBELIEVABLY FRIGGIN' COOL it is that a line like that shows up in an article that is talking about building an actual, physical device?
Re:Engineering (Score:4, Insightful)
Theory is coming up with a hypothetical mechanism for incorporating extra information so that it doesn't require a known reference frame.
Engineering is making a device that actually does it reliably.
As my sibling post said, there's no clear dividing line. But this is definitely on the theory-ish side of it.