Re:Fake Physics
by sgt101 on Sunday January 22, 2017 @02:53PM
(#13456988)
I think that the largest simulation of a quantum computer on a super computer is about 40qbits. Therefore quantum supremacy (weak...) is 41 stable qbits. There are numbers of groups out there that are building (working on projects with the funding to complete) machines with 100's of stable qbits now, so my argument is that quantum supremacy of the weak sort is a matter of engineering. I think that quantum computers that factor primes with 100's of digits (like 2048 bit ones) requires 1000's of qbits, say a couple of orders of magnitudes beyond the machines that are currently in train to be built.
The Hooft thing is that there are limits on computation due to the process of the universe and that if a classical computer that was at the plank scale, runs at plankian speed (help help I am using terms I can't understand!!!) and covered the whole of the universe couldn't do it from the beginning of time to heat death... then nor can an arbitrary QC. Shores algorithm does factors in (log n)^3 maybe we'll find that there are physical limits on the scale of QC which hold it below hundreds of millions of qbits where a plankian computer could be synthesised, and/or it may be that such a computer can't run at high clock speeds, and because of this BQP algorithms can't be run on problems that are not allowed in the sense that they somehow solve the universe.
I don't think anyone has any reason to believe this is true in an engineering sense but there is every reason to believe that large QC will be very, very difficult in an engineering sense and I think that the people building one do expect to run into problems of this sort eventually, but at the moment they are delighted to find that they are able to do things at the lower end that will create devices that are going to be transformational for reasoning about some components of the physical universe - for example simulation of the interactions of very large molecules - maybe mapping seconds of a virus interacting with a cell membrane using months of QC ?
The Hooft thing is that there are limits on computation due to the process of the universe and that if a classical computer that was at the plank scale, runs at plankian speed (help help I am using terms I can't understand!!!) and covered the whole of the universe couldn't do it from the beginning of time to heat death... then nor can an arbitrary QC. Shores algorithm does factors in (log n)^3 maybe we'll find that there are physical limits on the scale of QC which hold it below hundreds of millions of qbits where a plankian computer could be synthesised, and/or it may be that such a computer can't run at high clock speeds, and because of this BQP algorithms can't be run on problems that are not allowed in the sense that they somehow solve the universe.
I don't think anyone has any reason to believe this is true in an engineering sense but there is every reason to believe that large QC will be very, very difficult in an engineering sense and I think that the people building one do expect to run into problems of this sort eventually, but at the moment they are delighted to find that they are able to do things at the lower end that will create devices that are going to be transformational for reasoning about some components of the physical universe - for example simulation of the interactions of very large molecules - maybe mapping seconds of a virus interacting with a cell membrane using months of QC ?