Is a 100 per cent foolproof security system possible? The answer seems to be yes, after a group of clever quantum cryptographers working with the Bank of Austria transferred 3,000 euros (HK$28,000) last week using what may be the most unbreakable channel in the history of humankind. What intrigues me is that the physicists made use of two of the most theoretical of principles in physics: the famous Heisenberg's uncertainty principle and quantum entanglement, which most people would regard as being without any possible practical application. The uncertainty principle says that the very act of observing a particle would disturb it. The more recent entanglement discovery finds that two particles, having interacted at some point in their careers, could become 'entangled' so that anything that happens to one particle would immediately affect the other, even if they are separated by millions of kilometres (diehard romantics may find this appealing). The bank physicists this week created a pair of entangled photons, or light particles, to encrypt the money transfer, so that any tinkering, say a cyber-theft, that disturbs one particle would immediately 'alert' the second particle at the other end of the encryption. Since all such break-ins exploit a delay in between the break-in and the security alert, the new quantum system may be regarded as unbreakable, at least in principle. And the transfer of money - can there be anything more practical?