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'Unprecedented' discovery could propel quantum computers to reality

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Re: 'Unprecedented' discovery could propel quantum computers to reality

#21

Post by timsally »

tux1968 wrote: post #6

"For qubits, they can hold a value of “1” or “0” as well as both values at the same time. Described as superposition,"... Am a bit frustrated reading that same description for years and still having no clue what it really means. Both values at the same time... huh? What is the physical property that is existing in two states at once? And how does that feature translate into speedier computation? Is it so hard to unde…

Michael Nielsen has a series of Khan Academy style videos called Quantum computing for the determined: http://michaelnielsen.org/blog/quantum-computing-for-the-det.... Nielsen co-wrote the textbook on quantum computing and has made significant contributions to the field.

Re: 'Unprecedented' discovery could propel quantum computers to reality

#22

Post by vasco »

If you can store values for a given time frame with such time frame higher than the delay of the circuit, why don't we just build a latch and extend the time frame indefinitely? Or are these diamonds only settable once, and then you have to build another one?

Re: 'Unprecedented' discovery could propel quantum computers to reality

#23

Post by caf »

Difwif wrote: post #16

We always hear about the ramifications a quantum computer would have if used to crack enterprise level security. Does there exist encryption that would be troublesome even for a quantum computer to crack or are we just SOL if one of these falls into the wrong hands?

I believe that quantum computers only give a square root speedup for bruteforcing symmetric encryption algorithms, so we'd just have to double the key length of those.

Asymmetric algorithms based on the hardness of factoring or calculating discrete logarithms are broken, though.

Re: 'Unprecedented' discovery could propel quantum computers to reality

#24

Post by redwood »

Difwif wrote: post #16

We always hear about the ramifications a quantum computer would have if used to crack enterprise level security. Does there exist encryption that would be troublesome even for a quantum computer to crack or are we just SOL if one of these falls into the wrong hands?

Quantum communication is unbreakable right?

Re: 'Unprecedented' discovery could propel quantum computers to reality

#25

Post by batista »

tux1968 wrote: post #6

"For qubits, they can hold a value of “1” or “0” as well as both values at the same time. Described as superposition,"... Am a bit frustrated reading that same description for years and still having no clue what it really means. Both values at the same time... huh? What is the physical property that is existing in two states at once? And how does that feature translate into speedier computation? Is it so hard to unde…

>Am a bit frustrated reading that same description for years and still having no clue what it really means. Both values at the same time... huh? What is the physical property that is existing in two states at once?

Ever heard of this quantum mechanics thing?

Re: 'Unprecedented' discovery could propel quantum computers to reality

#26

Post by adrianN »

saulrh wrote: post #17
adrianN wrote: post #10

Earlier quoted context omitted.

Think of a qbit as a 2D vector. You can express it as a (1,0)+b (0,1), where (1,0) is the "1" state and (0,1) is the "0" state. In quantum mechanics a and b are complex numbers. When you measure the qbit the quantum state by magic collapses to (1,0) with probability a^2 or to (0,1) with probability b^2. The power of quantum computers come from the fact that transformations or your qbits act on the superpositioned sta…

This explanation is missing a little bit of background. A classical computer's state is represented by a single number - the concatenation of all of the classical bits in its memory. The transition function in a classical computer takes a state and moves it into another state - a simple mapping. A quantum computer's state is a 2D vector of unit length. Transitions are actually rotations on this vector. Observing the…

A k-qbit computer's state is actually a unit vector in 2^k dimensional complex space. This exponential blowup makes it difficult to simulate quantum computers on classical systems.

Re: 'Unprecedented' discovery could propel quantum computers to reality

#27

Post by loceng »

This I believe is how certain aspects of the mind exists, information being temporarily stored and interactive with other systems. Theoretically then systems of the brain/mind should be able to be duplicated. This would allow for managing of large amounts of information, at very high speed, with no-heat generation. The only heat generated would be through the support systems / foundation - I suppose much like how the brain functions as a foundation for the mind.

A brain made out of a diamond? Indiana Jones anyone?

Re: 'Unprecedented' discovery could propel quantum computers to reality

#28

Post by freehunter »

batista wrote: post #25
tux1968 wrote: post #6

"For qubits, they can hold a value of “1” or “0” as well as both values at the same time. Described as superposition,"... Am a bit frustrated reading that same description for years and still having no clue what it really means. Both values at the same time... huh? What is the physical property that is existing in two states at once? And how does that feature translate into speedier computation? Is it so hard to unde…

> Am a bit frustrated reading that same description for years and still having no clue what it really means. Both values at the same time... huh? What is the physical property that is existing in two states at once? Ever heard of this quantum mechanics thing?

You act like quantum mechanics is an easy thing to understand.

Re: 'Unprecedented' discovery could propel quantum computers to reality

#29

Post by carols10cents »

tux1968 wrote: post #6

"For qubits, they can hold a value of “1” or “0” as well as both values at the same time. Described as superposition,"... Am a bit frustrated reading that same description for years and still having no clue what it really means. Both values at the same time... huh? What is the physical property that is existing in two states at once? And how does that feature translate into speedier computation? Is it so hard to unde…

Programming the Universe by Seth Lloyd really helped me to understand this stuff. http://www.amazon.com/Programming-Universe-Quantum-Computer-...

Re: 'Unprecedented' discovery could propel quantum computers to reality

#30

Post by freehunter »

tete wrote: post #13

Can someone maybe describe the details of "could propel" and what exactly "reality" mean? I've always been told "when quantum computers become reality you can forget about everything you learned on computer science". For me reality would be that one can use it in production, even if it's a complete niche. In other words is it "we got a step closer" or "we potentially solved our only (major) problem"?

Quantum computers are used in production, as you say in a complete niche. Lockheed Martin bought a quantum computer (and associated research & development) from D-Wave for use in their "most complex computations". [1]

There's no further notice of what Lockheed has done with it, but at least there's one quantum computer in private hands designed to do production work.

[1] http://www.marketwire.com/press-release/d-wave-systems-sells...

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