Submission + - Unexpected Problems For Quantum Money (technologyreview.com)
KentuckyFC writes: Various physicists have suggested that it should be possible to exploit the strange properties of quantum mechanics to create a form of quantum money that can never be counterfeited. One of the important features that any practical currency must have is that anybody must be able to determine its veracity. That's a little more tricky for quantum money given that it's easy to destroy quantum properties by measuring them. However, inspiration for solving this problem comes from public key encryption where anybody can encrypt a message using a public key but only those with a different private key can decrypt it. But the various schemes to do this are all thought to be insecure. Today, a team from MIT describe a new way to create quantum money so that nobody can make a copy, not even the bank that issued it. The technique is based on the kind of asymmetric thinking behind public key encryption and also on the difficulty of repeating quantum measurements once they have been made. However, the MIT team finish their paper with a bombshell. They say that while they expect their technique to be secure, they are unable to prove it. They conclude: "Much as we wish it were otherwise, it seems possible that public-key quantum money intrinsically requires a new mathematical leap of faith, just as public-key cryptography required a new leap of faith when it was first introduced in the 1970s."
