[cryptography] D-Wave Sells First Quantum Computer

James A. Donald jamesd at echeque.com
Sat May 28 22:05:40 EDT 2011


On 28/05/11 03:37, James A. Donald wrote:
>> What can be said is that the class of problems soluble by a quantum computer
>> is larger than the class of problems soluble by a classical computer.

On 2011-05-29 9:01 AM, David-Sarah Hopwood wrote:
> No, it can't:
>
>   - for idealized quantum and classical computers (with unbounded memory
>     running for unbounded time), those classes are identical.
>
>   - for quantum and classical computers that can be practically built at any
>     point in time, and with a limit on the time to find a solution, it
>     certainly isn't clear that the class of problems soluble by quantum
>     computers will be larger (ever). That depends on how big and fast you
>     can make quantum computers and classical computers.

What can be said is that the class of problems soluble by a quantum 
computer with a polynomially large number of components in polynomial 
time is larger than the class of problems soluble by a classical 
computer with a polynomially large number of components in polynomial time.



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