Quantum computing infeasibility due to quantum tomography?

[Joy Christian]

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Happy Birthday, Richard Feynman --- father of the idea of a "quantum computer." I wish you were still around.

[thray]

The bottom line is that we still don't understand probability as a mathematical theory. We sample a slice of wave many times, expecting to reduce the probability distributions to a certain numerical result that is manageable. This "sift and search" technology assumes linear time -- such that preserves the probability of ordered results.

From the article:

" ... a qubit state is not a one or a zero but is a probability to produce a one or a zero on measurement, and this probability evolves in time. I can take two qubits that are set identically and then measure them some time later. After repeating this many times, I should find that the probability distributions are the same. That's the theory; in practice, they experience slightly different environments, so at some point later in time, one will have slightly changed relative to the other in an unpredictable way.

"So, in addition to a bit-flip error, you can also have a phase-flip error, which is an error in the relationship between two bits rather than an error in the value of one particular bit."

Conventional quantum computing tries to circumvent this problem by building in enough redundancy to assure superpositions of the wave function on measurement remain intact. Yet one finds this redundancy quickly grows to infinity.

Two necessary requirements:

1) a framework that tames infinities locally -- the framework that Joy Christian supplies.

And

2) a theory of time reversibility that brings non-linear time into a useful, linear, domain -- the theory of timelike-correlated parameters due to Karl Hess and Walter Philipp. My interpretation of Philipp's mathematics is that only a pairwise state guarantees an unambiguous initial condition for a continuous measurement function. That is, pairwise correlations (Joy's framework) exist in both past and future states as a result of initial condition, and not quantum entanglement. A computable function is then as Joy describes it: "limit of products = product of limits." A departure from digital information processing, substituting the calculus of continuous functions, is the essence of a pairwise correlation.

Karl Hess communicated to me privately: "Sometimes things take a while, but they are caught in an awful trap. After trying to do quantum computation with entangled pairs for another 10 years, some one will be smart enough to find a way to put a stop to the nonsense."

Indeed.

Tom

[Joy Christian]

Karl Hess communicated to me privately: "Sometimes things take a while, but they are caught in an awful trap. After trying to do quantum computation with entangled pairs for another 10 years, someone will be smart enough to find a way to put a stop to the nonsense."

Professor Hess is absolutely right, of course, Tom.

But how many billions would have been spent on the fantasy by then? And how many fraudsters like Aaronson and Gill would have benefited from it (if only indirectly)?

[thray]

Karl Hess communicated to me privately: "Sometimes things take a while, but they are caught in an awful trap. After trying to do quantum computation with entangled pairs for another 10 years, someone will be smart enough to find a way to put a stop to the nonsense."

Professor Hess is absolutely right, of course, Tom.

But how many billions would have been spent on the fantasy by then? And how many fraudsters like Aaronson and Gill would have benefited from it (if only indirectly)?

Joy, no doubt. They have a wealth of momentum and funds; they are poor in ideas. Whose side would you rather be on?

[Joy Christian]

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The following is a critique of Europe’s quantum community’s Quantum Manifesto contributed to the launch of a Billion Euros quantum technologies flagship initiative:

Abstract:

The claims made in a manifesto resulting in the European quantum technologies flagship initiative in quantum technology are critically reviewed.

Paper: https://arxiv.org/abs/1605.08569

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[FrediFizzx]

The latest hype seems to be this,

"A Schrödinger cat living in two boxes"
http://science.sciencemag.org/content/352/6289/1087
http://arxiv.org/abs/1601.05505

But easy to see in Sect. M that they use the same trickery as usual to show a "violation" of Bell-CHSH. Man, there is going to be a lot of really disappointed people when they finally wake up!

[Joy Christian]

The latest hype seems to be this,

"A Schrödinger cat living in two boxes"
http://science.sciencemag.org/content/352/6289/1087
http://arxiv.org/abs/1601.05505

But easy to see in Sect. M that they use the same trickery as usual to show a "violation" of Bell-CHSH. Man, there is going to be a lot of really disappointed people when they finally wake up!

Sad indeed.

But they are unlikely to wake up any time soon.

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[Joy Christian]

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Yet another pessimistic (or rather realistic) view on "quantum computers" by one of the "experts": http://www.ams.org/publications/journal ... i-p508.pdf

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[Gordon Watson]

But easy to see in Sect. M that they use the same trickery as usual to show a "violation" of Bell-CHSH. Man, there is going to be a lot of really disappointed people when they finally wake up!

Fred, I'm not sure what you are getting at here. I'd welcome some elaboration, especially re this: "they use the same trickery as usual to show a "violation" of Bell-CHSH." Doesn't QM theory and practice violate Bell-CHSH? Thanks.

[Joy Christian]

Fred, I'm not sure what you are getting at here. I'd welcome some elaboration, especially re this: "they use the same trickery as usual to show a "violation" of Bell-CHSH." Doesn't QM theory and practice violate Bell-CHSH? Thanks.

Gordon,

Nothing can violate a mathematical inequality. It is insane even to suggest that something can "violate" a mathematical inequality.

So, no. Neither quantum mechanics nor any experiment violates Bell-CHSH inequality. How can they?

It seems that in this forum only Michel, Fred, and I understand this.

To be sure, quantum mechanics makes a different prediction (as does my local model) for the Bell-CHSH string of expectation values; namely, CHSH < 2\/2 (not 2).

But that is not the same thing as claiming that quantum mechanics "violates" CHSH < 2. It simply means that CHSH < 2 is just wrong.

I will let Fred elaborate on the trickery of how experimentalists switch to CHSH < 4 in practice. Although Michel has explained this dozens of times in this forum.

Joy

[FrediFizzx]

I will let Fred elaborate on the trickery of how experimentalists switch to CHSH < 4 in practice. Although Michel has explained this dozens of times in this forum.

Let me qualify that an inequality of Bell's type is mathematically impossible to violate. That is just the trickery; they shift to a different inequality where the bound is 4 for CHSH. In Bell-CHSH, the expectation terms are dependent on elements in each other so you have a bound of 2. For QM and the experiments, the expectation terms are independent thus by simple mathematical inspection one can have,

+1 -(-1) +1 +1 = 4

[Gordon Watson]

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Re CHSH: I have moved my discussion with Joy and Fred (and maybe others) to a new thread, "CHSH - the facts!"
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[Joy Christian]

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The trouble with quantum computing: https://eandt.theiet.org/content/articl ... computing/

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[Joy Christian]

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The trouble with quantum computing: https://eandt.theiet.org/content/articl ... computing/

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By the way "quantum supremacist" is the most appropriate term for the promoters of "quantum supremacy" such as Scott Aaronson (as discussed in the above article).

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[Joy Christian]

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17 Years Of Major Startups Financing Quantum Computing In One Timeline: https://www.cbinsights.com/blog/quantum ... -timeline/.

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[jreed]

It might interest you to look at the article that appeared on page B4 of the Wall Street Journal, Monday May 8. The title is "A Quantum Leap for Computers Looms". In it the author describes an experiment done with travel paths of 10,000 taxis in downtown Beijing using the D-Wave quantum computer. Here's what's in the article:

"After six months and several attempts, Dr. Hoffmann and his team in March came up with an algorithm for the computer that optimized the routes for each taxi within a fraction of a second. A normal computer would have taken about 45 minutes to complete the same task, he said."

[Joy Christian]

It might interest you to look at the article that appeared on page B4 of the Wall Street Journal, Monday May 8. The title is "A Quantum Leap for Computers Looms". In it the author describes an experiment done with travel paths of 10,000 taxis in downtown Beijing using the D-Wave quantum computer. Here's what's in the article:

"After six months and several attempts, Dr. Hoffmann and his team in March came up with an algorithm for the computer that optimized the routes for each taxi within a fraction of a second. A normal computer would have taken about 45 minutes to complete the same task, he said."

Wake me up when you actually have your "Perpetual Computing Machine" in your hand, or as a laptop on your desk, commercially viable, and demonstrably exhibiting "exponential speedup."

I do hope you know what "exponential speedup" means --- it means dividing by zero, not by 1/(45 x 60000).

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[Joy Christian]

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Google Plans to Demonstrate the Supremacy of Quantum Computing by the End of 2017: http://spectrum.ieee.org/computing/hard ... -computing.

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[minkwe]

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Google Plans to Demonstrate the Supremacy of Quantum Computing by the End of 2017: http://spectrum.ieee.org/computing/hard ... -computing.

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So that hasn't been demonstrated yet? I wonder why? What about D-wave, and ilk?

I'll believe it when I see one.

[Joy Christian]

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Google Plans to Demonstrate the Supremacy of Quantum Computing by the End of 2017: http://spectrum.ieee.org/computing/hard ... -computing.

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So that hasn't been demonstrated yet? I wonder why? What about D-wave, and ilk?

I'll believe it when I see one.

Google is equally capable of making a fraudulent claim like the ones that IBM and D-Wave have been making. It is all about money and PR. But PR can backfire.

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