Qutrits for quantum cryptography?

Physics Today : Quantum cryptography only works if Alice and Bob share their relative positions in advance.Now Anthony Laing from the University of Bristol and associates have figured out a new simple protocol that works for particle dimensions of prime or power-prime.The simplest case in which this works is an entangled pair of qubits , which have been widely used in quantum cryptography experiments .Laing’s protocol can simplify the operation of existing qubit setups and has immediate applications for communication systems such as earth-to-satellite links and the use of integrated photonic waveguides.The paper also details a photonic implementation of the scheme for entangled pairs of three dimensional particles, so-called qutrits .The protocol works because security is guaranteed with a measure of the purity on the entanglement shared by Alice and Bob. This kind of measure is robust in an unknown or slowly varying reference frame, yet would reveal the action of any Eavesdropper, (called Eve in this example), as her measurements would strongly and negatively impact the purity. Interestingly, the varying reference frame has no impact at all on the correlations Alice and Bob use determine their secret key.Crucially, the protocol achieves reference frame independent quantum cryptography without the use of the extra resources which make previous protocols more challenging and in some cases unwieldy. Related links Reference frame independent quantum key distribution Theoretical Breakthrough for Quantum Cryptography MIT Technology Review