First 'Quantum Computer Chips' Demonstrated

holy_calamity writes "The first quantum computer chips have been made by two US groups, New Scientist reports. Both NIST and Yale have demonstrated chips where information was transferred between two superconducting qubits using a 'quantum bus'. The bus is made from a cavity that traps a single microwave photon as a standing wave — the NIST group also managed to use the bus to store data from one qubit for a short time. 'After encoding information in one qubit, they transferred it into the cavity for 10 nanoseconds before transferring it to the other qubit. Yale's chip used qubits around 1-micron square built on silicon, while NIST used larger 10-square-micron qubits on top of sapphire. In both prototypes, the bus between the qubits was between five and seven millimeters long.'"

Comments

Encryption?

[bucky0]

Once quantum computers become mainstream, what will we use for encryption? Are there algorithms that are computable by standard computers but are also unbreakable using quantum computers?

Re:Encryption?

[carleton]

To clarify both sides, unless I've missed something in the last couple of years, AES was designed[1] with the possibility of quantum computing in mind and the solution is to use double the bit length you'd otherwise need (which is the same for at least some elliptic curve-based Public Key algorithms but for different algorithmic reasons). Is this still computable by standard computers? Yes. Does it make it harder to use "strong" crypto in limited hardware, a little. Could there be improved algorithms down the road that push it to the point that it takes the same order of time to decrypt on standard computers algorithms knowing the key as it does to decrypt (break) on quantum computers without knowing the key? Possibly (in the sense that I don't know of any proofs showing limits on efficiency gains etc.).

[1]Designed is probably not the right word, but basically, brute force searching of 128bit symmetric keys is believed to be secure in the sense that using all atoms as non-quantum computers would find it some point after expected heat death of universe. However, quantum computers can (being lazy, start at wikipedia's entry on cryptoanalysis, look for grover algorithm) do a brute force search in quadratic time (so 128bits would take on the order of 2^64 steps which is much more tractable... however, using 256bit AES keys (which would otherwise be overkill for most things) now take on the order of 2^128 steps which again hits that whole heat death thing, unless either a better algorithm comes out or someone comes out with some sort of hyper-quantum-computing idea)

Re:Encryption?

[krog]

If you're referring to the fact that observing the quantum register will destroy its state, you're right. But the part you're not mentioning is that there is a high probability you just observed the right answer. Measure it a few times -- or a few hundred or thousand, hell with it, that part's still O(1) -- and you can poll for the right key.

If you think that trying to crack the key with which a file was encrypted will re-encode the file with a different key, I can't help you there.

Re:Argh!

[Tyler Durden]

If I understand it correctly, a Quantum Computer already is a Beowulf Cluster of possibilities.