On 21-09-2019 18:54, Alan Grayson wrote:
On Saturday, September 21, 2019 at 10:43:57 AM UTC-6, smitra wrote:
On 21-09-2019 14:52, Alan Grayson wrote:
On Saturday, September 21, 2019 at 6:40:50 AM UTC-6, John Clark
wrote:
On Sat, Sep 21, 2019 at 8:29 AM Alan Grayson
<agrays...@gmail.com>
wrote:
_> What I don't understand is why a computer programmed to
assume
a superposition, say of two states, represents a system in both
states simultaneously (which I find to be false for reasons
previously stated), would speed up any calculation. Can anyone
answer this question? AG _
Well, if you're right about superposition then a Quantum Computer
can't speed up a calculation, therefore if this rumor turns out
to
be true that would prove you are not right about superposition.
John K Clark
My question is a conceptual one; why would assuming a
superposition
means what I earlier stated, speed up any calulation? AG
Richard Feynman who invented the conceptional idea of a quantum
computer
had answered this question long before quantum algorithms that are
used
today were invented. He simply argued that it the time it takes for
a
classical computation to compute the properties of an interacting
quantum system with N degrees of freedom, increases exponentially as
a
function of N. So, if a classical computer is running a particular
algorithm that can be mathematically shown to be equivalent to
computing
a property of an N part quantum system, then you could just build
that
quantum system and measure that property. One can then consider
doing
that in a more practical way by constructing a universal quantum
computing device.
Saibal
What are you claiming; that a quantum computer isn't really designed
to
calculate anything, but rather simulates some quantum system? It's
still
above my pay grade unfortunately. AG
Once you get to a universal computing device the distinction doesn't
matter. I think David Deutsch was the one who showed how to get to a
universal quantum computer. Note that in the old days before we had
practical classical computers people used to numerically compute the
solution of differential equations by building an electric circuit
involving resistors, coils and condensers put together such that the
voltage or current at some point as a function of time would be
described by the same differential equation as the one they wanted to
solve.
Saibal
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