Theoretical Breakthrough For Quantum Cryptography

Quantum cryptography only works if Alice and Bob share their relative positions in advance. Now physicists have worked out how to do it without this information.

To read the rest of the article, click here.

Note added by Jack:

Einstein's classical principle of covariance requires the laws of physics to be locally frame independent (i.e. independent of absolute accelerations of locally coincident detectors measuring same process. Local gauge invariance induces compensating local spin 1 vector connection fields for parallel transport of all tensor/spinor fields to keep the laws of physics nonlocally frame independent, i.e. Alice and Bob, arbitrarily separated, can have any local frames (internal and spacetime) they like. The quantum result below is analogous to the above classical idea.

http://www.technologyreview.com/blog/arxiv/24899/

Sunday, March 07, 2010

Theoretical Breakthrough for Quantum Cryptography

"Quantum cryptography only works if Alice and Bob share their relative positions in advance. Now physicists have worked out how to do it without this information.

...

That allows Alice and Bob to make any measurements they need without having to agree ahead of time on a frame of reference. There is one proviso: Alice and Bob cannot move too quickly during the measurements since this changes their relative orientation and a new qutrit will be needed to establish a reference.

That'll be useful for quantum encryption over satellite links, the kind of thing that government agencies and the military might want to do. But there's another, more valuable application.

If quantum encryption is ever to be widely used, it'll need to work between one microchip and another without the need to share a frame of reference in advance. That's always been a problem because the chips inside computers are constantly on the move (relative the the wavelength of light) and because photon polarisations drift as they move through optical fibres, introducing another source of error.

That's why quantum cryptography that is reference frame independent is an enabling technology and so potentially hugely valuable. It means that Laing and co may have made one of the key breakthroughs that will bring quantum cryptography to the masses."

Ref: arxiv.org/abs/1003.1050: Reference Frame Independent Quantum Key Distribution