# Counterfactual computation

• posted

My attention was drawn (by George, thanks!) to Kwiat's web page below:

I found a paragraph about "Counterfactual Computation" in there, near the end. I cite: "... one can perform a measurement on a quantum computer and obtain information about the solution to a problem without the computer actually running". It's not even a first-of-April article and they even managed to get it published in Nature.

I suppose that if it doesn't need to be run, it doesn't need to exist at all. Their funding money can be cut, too.

Jeroen Belleman

• posted

On a sunny day (Fri, 24 May 2019 11:41:40 +0200) it happened Jeroen Belleman wrote in :

It is not the only weird statement I have come across about 'quantum'.

Well as long as we 'photon', 'spooky action at a distance', 'more or less dead cats', and have supper and positions, OK I have stated in an other group that it feels to me like a big hoax.

Unbreakable encryptions, sometimes I wonder.. maybe it is me not understanding something basic, but in my not so humble opinion things went already wrong with the Copenhagen conference. Copenhagen Interpretation.

I have given this joke several times, regarding the math working out, this was in 2013: QM is and always will be mathematical probabilities. It has nothing to do with reality.

Three scientist, after working on QED for years, where admitted to the mad house. One day, after years of treatment, doctor decided to test if they were ready to be let lose in society again. He called them into his office, asked a few simple questions: He asked the first one: "How much is 3 + 5?" "August" answered the first one. The doctor replied, "Wrong, you have to stay a bit longer."

Then he asked the second one: "How much is 15 + 4?" "January" was the reply. "Wrong", doctor said, "You have to stay a bit longer too."

Finally he asked the last one: "How much is 4 x 7?" "28" the third one replied. "Correct", the doctor said, "You are cured, you can leave.".

While guiding the third one out of the gate of the madhouse, doctor had some doubts. "How did you arrive at that number 28 he asked?"

"Simple", answered the third one, "I multiplied August with January".

And there, but for fortune, go today's scientists.

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Now maybe it is not so bad, but I do not see a kwantuum computah in the local shop. Almost like the 100% better battery system that is invented every few weeks, x^n would now have NY powered from a battery the size of a sugar cube.

OTOH If you knew how that QM computah works, and IF you know the errors, then you can say without running it what the problem is!

Neural nets we are, are funny things, and if QM holds true I am sure nature is already using it.

From an other perspective, every electron in the know universe is feeling the effect of every other electron, that is how radio works for example. It is all about resonances, and what is working? Maybe that kwantuum computah could be exited by merely thinking about it (neurons jiggle electrons too). But I still would like one for sale in the shop to play with...

eeeehhh

• posted

I'm not sure, but if you really cared you might write and ask. I barely understand any of this stuff.. (non-linear optics and fancy x-tals.)

George H.

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According to the great mathematician, philosopher and all around cool guy, Douglas Adams, the hard part is knowing the problem. They had the answer 4

2 very early on and I believe it took another 2.5 books to arrive at the qu estion which seemed to have been corrupted by a few of the electrons in the Universe not staying where they were expected to.
```--
Rick C.

- Get 5,000 miles of free Supercharging ```
• posted

Hi Jan, entangled photons and Bell's inequality is now a table top experiment... in a bunch of student labs. I went down to Kiko Galvez's lab last summer and spent 3 days at a workshop. (A great time!)

(There's a lot there.. but down the page you can find articles about doing the measurements with a 405 nm laser pointer as the photon source.)

Playing with correlated photons (as opposed to correlated and entangled) was very interesting. At the end of the lab we measured Bell's inequality, (with entangled photons) and found a 'correlation' of 0.65.. (Ideally we'd get 0.707.. but errors.) Where a classical theory predicts 0.5 at best.

To be honest I don't really understand the theory and need to think about it more. My 'best' understanding is the last graph in this section,

This,

George H.

• posted

I don't care enough, maybe. The usual answer is 'shut up and calculate', and indeed that works. What I have an issue with is the unnecessary mysticism surrounding it all.

But I don't think we need to go through that again.

Can we think of an electronic circuit that does the equivalent of what a BBO crystal does to light?

Jeroen Belleman

• posted

Tunnel diodes are cool. Electrons can't overcome the potential barrier, so they just appear on the other side.

I miss tunnel diodes.

```--
John Larkin         Highland Technology, Inc

lunatic fringe electronics```
• posted

I'd agree, to a point. Classical physics works fine for light, except for its interaction with matter. I'd like to see a classical derivation of h.

The argument with the cats seems to deny that all quantum effects are only detectable by statistics.

Jeroen Belleman

• posted

On a sunny day (Fri, 24 May 2019 08:03:39 -0700) it happened John Larkin wrote in :

I have seen those on ebay some years ago, I did get some unijuntions from there, 2N4246.

Electrons, what do they look like? and other goofy paper today:

But what they actually show is just a probability distribution of a point charge? if you ask me.

• posted

On a sunny day (Fri, 24 May 2019 07:31:33 -0700 (PDT)) it happened George Herold wrote in :

I see it is way, If I have a pair of shoes, and sent one of the pair to you, you open the parcel and see a left one, then you INSTANTLY know I have the right one. WOW timeless spooky action really .. I have known about Alain Aspect's experiment back in the eighties I think it was, we discussed that here a lot.

But I also know about epicycles, a theory, mathematical model, that gave the right answer based on a wrong assumption, that is where the joke came from... When it was found the planets actually orbited the sun, things all of the sudden became a lot simpler and could be understood by more then the then few 'experts'.. We need to look for a simple explanation, hidden variables failed too IIRC.

At the Copenhagen Conference their was also De Broglie's proposition for example.

• posted

Yeah I can't really help that. Conceptually, it's not all that different than doing double slit interference 'one photon at a time'. Which is still kinda 'mysterious' to me.

Hmm, parametric down conversion.. we've talked about that. (non-linear capacitors) But the problem is that we don't have 'single photon detectors' at radio frequencies.

George H.

• posted

You can still get 3V zeners. :^) GH

• posted

Yeah, I don't spend much time thinking about different interpretations of QM. (They all give the same answer in the end, so pick the one that works for you.) I read somewhere that Griffiths 'interpretation' was more appealing to some.

George H.

• posted

On a sunny day (Fri, 24 May 2019 09:51:07 -0700 (PDT)) it happened George Herold wrote in :

Interesting. Where my alarm goes of is in the sentence: ... and the relation of physical science and Christian theology. Was not PI proposed to be 4? Oh well... Maybe in Trump University.. ooops, sorry John L.

I just read it, and it seems a logical, top-down view of the state of affairs.

?

I just showed this link in an other posting, to me it shows confusion about what an electron 'looks like':

• posted

Hmm here's the original

I think the author your piece is confused. They appear to have measured the 'orbital' geometry of the electron wave function... which is nice but not really new. (AFAIK)

George H.

• posted

On a sunny day (Fri, 24 May 2019 11:52:36 -0700 (PDT)) it happened George Herold wrote in :

Agreed, nothing to do with geometry of an electron, just probabiliy of orbits.

OK!

• posted

Do they tunnel or something?

```--
John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  ```
• posted

On a sunny day (Fri, 24 May 2019 12:08:26 -0700) it happened John Larkin wrote in :

I was thinking it would not be that hard to make a mechanical construction that only passes balls dropped from a given height. No mysteries needed.

?
• posted

Whether an atom bomb detonates or not is a matter of quantum statistics, which makes it a fairly macro event. Some got un/lucky that way and didn't go off.

```--
John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  ```
• posted

Yeah, well that's the story I heard. Low voltage zeners are heavy doped and you get tunneling with reverse bias.

GH

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