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New silicon structure opens the gate to quantum computers

princeton.edu

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Re: New silicon structure opens the gate to quantum computers

#51

Post by frik »

Sniffnoy wrote: post #39
frik wrote: post #29

Earlier quoted context omitted.

Can the idea of quantum computing be simplified/abstracted to say instead of doing binary (0 1) calculations, it do does calculation on arbitrary base? E.g. base 16 (hex) or base 1024? If this is true, it would be easier to code, and compilers could spit out very efficient machine code.

Yes, base has nothing to do with anything, talking about "qubits" is just a convention since computation is usually thought of in terms of bits. The fundamental idea of a quantum computer though has nothing to do with binary in particular. Same as for classical computers. It's not clear to me why you claim this would be related to efficient machine code, though.

Current "digital" microchips use electric "on" (1) and "off" (0) and base 2 (also called binary) mathematics is used.

Someone explained me quantum mechanics that it supports more states, not just on (1) and off (0), that it can have dozens or hundreds of states. Is this correct / state-of-the-art understanding?

I imagine how cool it would be to have more states, not just 0 and 1. A computer running on more states could encode machine code in fewer instructions, so it could calculate more with the same frequency.

So why downvote me? Either explain me where I got something wrong, or skip it in case you know less than me.

Re: New silicon structure opens the gate to quantum computers

#52

Post by skate22 »

tim-- wrote: post #10

My biggest pet peeve about quantum computing is that no one can answer me the question of "what can quantum computing do for me?". The answer I hear is that it helps solve the traveling salesman in record time, and that's all great and everything, but how will quantum computing be able to do things such as decrease the time it takes to train a RNN, or look up data in a database?

So the NSA can break RSA in the USA. sorry, got carried away there for a second..

Re: New silicon structure opens the gate to quantum computers

#53

Post by snarfy »

tim-- wrote: post #10

My biggest pet peeve about quantum computing is that no one can answer me the question of "what can quantum computing do for me?". The answer I hear is that it helps solve the traveling salesman in record time, and that's all great and everything, but how will quantum computing be able to do things such as decrease the time it takes to train a RNN, or look up data in a database?

I liked this explanation using playing cards -

https://www.youtube.com/watch?v=1X4OZYVwyO8&t=4m38s

Re: New silicon structure opens the gate to quantum computers

#54

Post by jamesrcole »

tim-- wrote: post #10

My biggest pet peeve about quantum computing is that no one can answer me the question of "what can quantum computing do for me?". The answer I hear is that it helps solve the traveling salesman in record time, and that's all great and everything, but how will quantum computing be able to do things such as decrease the time it takes to train a RNN, or look up data in a database?

The work on quantum computing is basic research. You can't expect to be able to predict the actual real-world impact of basic research while it's still being developed.

Quantum mechanics is a good example. It's had massive, real-world impact, but nobody could have predicted that.

The details need to be fleshed out, and people then need to explore things with it, play around, do further research on top of it.

Re: New silicon structure opens the gate to quantum computers

#55

Post by naasking »

tim-- wrote: post #10

My biggest pet peeve about quantum computing is that no one can answer me the question of "what can quantum computing do for me?". The answer I hear is that it helps solve the traveling salesman in record time, and that's all great and everything, but how will quantum computing be able to do things such as decrease the time it takes to train a RNN, or look up data in a database?

> The answer I hear is that it helps solve the traveling salesman in record time, and that's all great and everything, but how will quantum computing be able to do things such as decrease the time it takes to train a RNN, or look up data in a database?

"Quantum computers can search arbitrarily large databases by a single query" [1]. That's Grover's algorithm from 1997, one of the pinnacle results that got people excited about quantum computing. If you haven't come across it before, then you must not have read too much about quantum computing!

[1] https://arxiv.org/pdf/quant-ph/9706005.pdf

Re: New silicon structure opens the gate to quantum computers

#56

Post by jcoffland »

visarga wrote: post #45
jcoffland wrote: post #36

Earlier quoted context omitted.

The traveling salesman problem is NP-complete and therefore not known to be solvable in less time on a quantum computer. https://cstheory.stackexchange.com/questions/31084/travellin...

> The traveling salesman problem is NP-complete and therefore not known to be solvable in less time on a quantum computer. That's only a problem if you need the exact solution. If you're OK with 99.9% quality, approximate solutions are much cheaper. So the question is, is it necessary to invest into that 1%?

That has nothing to do with quantum vs. classical.

Re: New silicon structure opens the gate to quantum computers

#57

Post by jcoffland »

Beltiras wrote: post #43
jcoffland wrote: post #35

Earlier quoted context omitted.

Shor’s algorithm can factorize integers on a quantum computer asymptoticly faster than on a classical computer but the algorithm requires at least a 128 qubit quantum computer to factor a 128 bit number and thereby break something like 128 bit RSA encryption. No one yet has, or is publicly admitting to having, a reliable 128 qubit device. In some cases, error correction can be achieved simply by running the algorithm…

Error correction is immaterial for the factoring case. You multiply the factors and if you do not get the original number you know you have to run it again.

In Schor's algorithm, the quantum computer finds the period p of B mod N were N is the number you are trying to factor and B is a random number less than N. The quantum computer may find p with imperfect accuracy. Running the algorithm repeatedly can improve the accuracy of p. You can also try other numbers close to p. Both are examples of error correcting a quantum algorithm.

Re: New silicon structure opens the gate to quantum computers

#58

Post by Sniffnoy »

frik wrote: post #51
Sniffnoy wrote: post #39

Earlier quoted context omitted.

Yes, base has nothing to do with anything, talking about "qubits" is just a convention since computation is usually thought of in terms of bits. The fundamental idea of a quantum computer though has nothing to do with binary in particular. Same as for classical computers. It's not clear to me why you claim this would be related to efficient machine code, though.

Current "digital" microchips use electric "on" (1) and "off" (0) and base 2 (also called binary) mathematics is used. Someone explained me quantum mechanics that it supports more states, not just on (1) and off (0), that it can have dozens or hundreds of states. Is this correct / state-of-the-art understanding? I imagine how cool it would be to have more states, not just 0 and 1. A computer running on more states cou…

> Someone explained me quantum mechanics that it supports more states, not just on (1) and off (0), that it can have dozens or hundreds of states. Is this correct / state-of-the-art understanding?

No, that's not really correct. Being able to put states in superposition is very different from having more classical states.

> I imagine how cool it would be to have more states, not just 0 and 1. A computer running on more states could encode machine code in fewer instructions, so it could calculate more with the same frequency.

That doesn't really make any sense. A cycle is still a cycle. How many instructions you can encode with a given length doesn't tell you anything about how fast they execute.

Even going with an extremely charitable reading, I don't think there's any way anything that you're talking about could lead to anything better than a constant-factor speedup (and not a large one). The point of quantum computing isn't to get mere constant-factor speedups. Such a thing would be insignificant in comparison to what quantum computers can actually do.

Re: New silicon structure opens the gate to quantum computers

#59

Post by visarga »

jcoffland wrote: post #56
visarga wrote: post #45

Earlier quoted context omitted.

> The traveling salesman problem is NP-complete and therefore not known to be solvable in less time on a quantum computer. That's only a problem if you need the exact solution. If you're OK with 99.9% quality, approximate solutions are much cheaper. So the question is, is it necessary to invest into that 1%?

That has nothing to do with quantum vs. classical.

Approximate solutions have to do with solving problems with limited resources and scaling up. Quantum computers will be fast at solving certain types of problems, while approximate solutions are fast at solving practical problems.
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