How Good Would This Be?

[MartinCarpenter]

They're simply utterly different to current computers in how they work. I wouldn't dream of claiming expert knowledge but instead of doing linear turing machine style stuff you instead set up a single massively entangled state and then to have to carefully manipulate that so that when it collapses to a single thing under observation you're 'magically' left with your desired answer.

Hence why they can solve certain problems - like factorisation and code breaking - enormously faster than traditional things. I'd imagine that there will be quite a few other types of problems where they'll be terrible.

Being studied at Universities of course so I imagine plenty of stuff to read in papers/online. The factorisation algorithm got published a while ago iirc. Must be using simulations I suppose.

Not obviously clear whether or not they'll be very useful for chess

[Michael Farthing]

What I can't see at present is how what you describe is in essence conceptually different from functional based languages such as Forth? This has an initial and final state with a functional specification between. I do realise that you're placing the 'entanglement' in the initial state rather than the 'manipulation'. It seems to me, however, that the problem is only fully specified by both the initial state and the 'manipulation' unless the manipulation is identical for all problems.

However, I'm clearly in deeper than my 5ft 8 (yeah I know, from the arc.... and I still prefer descriptive notation too).

[MartinCarpenter]

Its how everything is worked out inbetween. With a classical computer you check through each state one at a time, in a nice orderly fashion.

The simple explanation of a quantum computer is that you can entangle all of the states you're working on so that any operation you apply affects all of them at once. Sounds great really. The complications start because of what measurement will do that set of entangled states - it collapses.

In practice it seems to be genuinely rather involved - http://en.wikipedia.org/wiki/Quantum_factoring - they're not kidding about it being hard to understand! Also quite a lot of classical computation still involved, just a critical step or two down using quantum circuits.