Counterfactual computation

[Jeroen Belleman]

pcdhobbs@gmail.com wrote:

There are a couple of interesting quirks for the wavefunction
though. The probability envelope for a photon (or particle)
in transit must be exactly zero for all regions ahead of its
starting point+ct which means that a symmetric Gaussian
distribution just will not do.

That is causality. An effect cannot occur where the wave that
carries it hasn't reached yet.

Interestingly that isn't quite true. I recall from my long-ago
relativistic quantum class that solutions to the Dirac equation
don't go identically to zero outside the light cone, but do decay
exponentially there.

Otherwise you can't satisfy the patching condition at the light
cone boundary.

Cheers

Phil Hobbs

A physically possible wave-like influence doesn't start and stop
instantly either, so that makes good sense.

Jeroen Belleman

 

[John Larkin]

On Mon, 27 May 2019 22:21:04 +1000, Chris Jones
<lugnut808@spam.yahoo.com> wrote:

On 25/05/2019 01:03, John Larkin wrote:
On Fri, 24 May 2019 10:15:36 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Fri, 24 May 2019 11:41:40 +0200) it happened Jeroen Belleman
jeroen@nospam.please> wrote in <qc8e8j$b2t$1@gioia.aioe.org>:

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

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources

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

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:
quote
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.
end quote
----

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...


disclaimer
eeeehhh
end disclaimer

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

I miss tunnel diodes.

Meh. I think they are the reason why none of my Tek 475s will trigger
properly any more, so I'm not so fond of them.

TDs seemed to be reliable. But if you can verify that a scope has a
bad TD, I have a modest collection of them and could donate a few.

They are easy to test. All you need is a function generator and a
working scope, and maybe a resistor.


--

John Larkin Highland Technology, Inc trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Chris Jones]

On 28/05/2019 00:46, John Larkin wrote:

On Mon, 27 May 2019 22:21:04 +1000, Chris Jones
lugnut808@spam.yahoo.com> wrote:

On 25/05/2019 01:03, John Larkin wrote:
On Fri, 24 May 2019 10:15:36 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Fri, 24 May 2019 11:41:40 +0200) it happened Jeroen Belleman
jeroen@nospam.please> wrote in <qc8e8j$b2t$1@gioia.aioe.org>:

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

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources

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

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:
quote
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.
end quote
----

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...


disclaimer
eeeehhh
end disclaimer

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

I miss tunnel diodes.

Meh. I think they are the reason why none of my Tek 475s will trigger
properly any more, so I'm not so fond of them.

TDs seemed to be reliable. But if you can verify that a scope has a
bad TD, I have a modest collection of them and could donate a few.

They are easy to test. All you need is a function generator and a
working scope, and maybe a resistor.

Thank you very much for the kind offer, but unfortunately (?) I have too
much other stuff to do at the moment (better paying but less fun), so
diagnosing the 475s will have to wait. Anyway thank you.

Chris

 

[George Herold]

On Sunday, May 26, 2019 at 2:44:59 PM UTC-4, Jeroen Belleman wrote:

On 2019-05-26 10:39, Martin Brown wrote:
On 24/05/2019 17:23, George Herold wrote:
On Friday, May 24, 2019 at 11:00:31 AM UTC-4, Jeroen Belleman wrote:
George Herold wrote:
On Friday, May 24, 2019 at 5:41:46 AM UTC-4, Jeroen Belleman wrote:
My attention was drawn (by George, thanks!) to Kwiat's web
page below:

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources


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'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.)

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.

I don't think the mysticism is entirely unjustified. It is decidedly
hard to interpret how Bell's inequality holds without some difficulty.
I would find it unacceptable to have non-local variables with FTL
communication as a get out of jail free card for "explaining" QM.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Original_Bell's_inequality

When we have a more complete theory it may be obvious how entanglement
actually works in detail, but at the moment it looks a bit worryingly
like Newton's classical gravity acting at a distance with infinte speed.

Entanglement means that some aggregate property of an EM signal is
conserved across conversions. The LO and IF in a super-heterodyne
receiver are entangled, because you can reconstruct the original
RF by mixing them together again. This is precisely what Zeilinger
did with light in his article "Imaging with undetected photons".

This?
https://arxiv.org/ftp/arxiv/papers/1401/1401.4318.pdf

I skimmed it... (I'm not much of a non-linear optics type.)
But I think those are correlated down converted 'photons'.
And not entangled. All entangled photons are correlated,
most correlated photons are not entangled. (I think that is right.)

Making entangled photons is hard.. And the only 'cool' experiment
I know of to do with them is the Bell inequality measurement...
Which is not that showy... no nice pictures. So they don't
get reported much.

George H.

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.

In a handwaving sort of way you can visualise it as the particle
exploring all possible paths available to it. This happens to result in
the path of shortest time being the central white light fringe and path
differences of a few wavelengths having peaks of probability too.

Particles don't follow multiple paths at once. Waves do. Photons aren't
particles, they are quantized interactions between matter and EM waves.
There is no such thing as a discrete photon in transit. There will never
be a pea-shooter for single photons at determined instants.


The problem is that you cannot know which slot your photon went through
if you want to see the interference pattern.


That's not a problem. Interference is a fundamental property of waves.

Jeroen Belleman

 

[John Larkin]

On Tue, 28 May 2019 22:38:02 +1000, Chris Jones
<lugnut808@spam.yahoo.com> wrote:

On 28/05/2019 00:46, John Larkin wrote:
On Mon, 27 May 2019 22:21:04 +1000, Chris Jones
lugnut808@spam.yahoo.com> wrote:

On 25/05/2019 01:03, John Larkin wrote:
On Fri, 24 May 2019 10:15:36 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Fri, 24 May 2019 11:41:40 +0200) it happened Jeroen Belleman
jeroen@nospam.please> wrote in <qc8e8j$b2t$1@gioia.aioe.org>:

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

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources

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

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:
quote
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.
end quote
----

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...


disclaimer
eeeehhh
end disclaimer

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

I miss tunnel diodes.

Meh. I think they are the reason why none of my Tek 475s will trigger
properly any more, so I'm not so fond of them.

TDs seemed to be reliable. But if you can verify that a scope has a
bad TD, I have a modest collection of them and could donate a few.

They are easy to test. All you need is a function generator and a
working scope, and maybe a resistor.

Thank you very much for the kind offer, but unfortunately (?) I have too
much other stuff to do at the moment (better paying but less fun), so
diagnosing the 475s will have to wait. Anyway thank you.

Chris

I have a collection of beautiful Tek 547s and a zillion plugins that I
planned to restore some day. If I'm eternally too busy to do that, I
guess that's OK too.


--

John Larkin Highland Technology, Inc trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[George Herold]

On Tuesday, May 28, 2019 at 10:52:12 AM UTC-4, Jeroen Belleman wrote:

George Herold wrote:
On Sunday, May 26, 2019 at 2:44:59 PM UTC-4, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:

[Snip!]

When we have a more complete theory it may be obvious how entanglement
actually works in detail, but at the moment it looks a bit worryingly
like Newton's classical gravity acting at a distance with infinte speed.
Entanglement means that some aggregate property of an EM signal is
conserved across conversions. The LO and IF in a super-heterodyne
receiver are entangled, because you can reconstruct the original
RF by mixing them together again. This is precisely what Zeilinger
did with light in his article "Imaging with undetected photons".

This?
https://arxiv.org/ftp/arxiv/papers/1401/1401.4318.pdf

I skimmed it... (I'm not much of a non-linear optics type.)
But I think those are correlated down converted 'photons'.
And not entangled. All entangled photons are correlated,
most correlated photons are not entangled. (I think that is right.)

Mmh. I think I agree, except that I think in terms of
waves and signals, not photons.

An entangled pair carries some complementary information,
so that if you measure one, you can foretell the result
of the identical measurement on the other, but neither
alone will give a definite result.


Making entangled photons is hard.. And the only 'cool' experiment
I know of to do with them is the Bell inequality measurement...
Which is not that showy... no nice pictures. So they don't
get reported much.

George H.

I should see if I can come up with an RF signal processing
equivalent of such an experiment. Hold on...

Grin, no worries I'm pretty sure that EM radiation behaves the same
regardless of frequency. It's a matter of what detectors you have.

In the 'visible' photons are entangled in their polarization.
I'm trying to think of an RF source where the polarization
is unknown.. or can have any value.

George H.

Jeroen Belleman

 

[Jeroen Belleman]

George Herold wrote:

On Sunday, May 26, 2019 at 2:44:59 PM UTC-4, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:

[Snip!]

When we have a more complete theory it may be obvious how entanglement
actually works in detail, but at the moment it looks a bit worryingly
like Newton's classical gravity acting at a distance with infinte speed.
Entanglement means that some aggregate property of an EM signal is
conserved across conversions. The LO and IF in a super-heterodyne
receiver are entangled, because you can reconstruct the original
RF by mixing them together again. This is precisely what Zeilinger
did with light in his article "Imaging with undetected photons".

This?
https://arxiv.org/ftp/arxiv/papers/1401/1401.4318.pdf

I skimmed it... (I'm not much of a non-linear optics type.)
But I think those are correlated down converted 'photons'.
And not entangled. All entangled photons are correlated,
most correlated photons are not entangled. (I think that is right.)

Mmh. I think I agree, except that I think in terms of
waves and signals, not photons.

An entangled pair carries some complementary information,
so that if you measure one, you can foretell the result
of the identical measurement on the other, but neither
alone will give a definite result.

Making entangled photons is hard.. And the only 'cool' experiment
I know of to do with them is the Bell inequality measurement...
Which is not that showy... no nice pictures. So they don't
get reported much.

George H.

I should see if I can come up with an RF signal processing
equivalent of such an experiment. Hold on...

Jeroen Belleman

 

[Phil Hobbs]

On 5/24/19 11:15 AM, Jeroen Belleman wrote:

Jan Panteltje wrote:
On a sunny day (Fri, 24 May 2019 11:41:40 +0200) it happened
Jeroen Belleman <jeroen@nospam.please> wrote in
qc8e8j$b2t$1@gioia.aioe.org>:

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

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources



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

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.
[...]

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.

ISTR that Planck had a good try at that around 1900.

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

A single scintillation is detectable, but it's only statistically
_predictable_. The cat thing IIRC is an argument that you could have a
macroscopic object in a mixed quantum state--QM doesn't apply merely on
the atomic scale.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 5/26/19 4:39 AM, Martin Brown wrote:

On 24/05/2019 17:23, George Herold wrote:
On Friday, May 24, 2019 at 11:00:31 AM UTC-4, Jeroen Belleman wrote:
George Herold wrote:
On Friday, May 24, 2019 at 5:41:46 AM UTC-4, Jeroen Belleman wrote:
My attention was drawn (by George, thanks!) to Kwiat's web
page below:

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources


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'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.)

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.

I don't think the mysticism is entirely unjustified. It is decidedly
hard to interpret how Bell's inequality holds without some difficulty.
I would find it unacceptable to have non-local variables with FTL
communication as a get out of jail free card for "explaining" QM.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Original_Bell's_inequality

When we have a more complete theory it may be obvious how entanglement
actually works in detail, but at the moment it looks a bit worryingly
like Newton's classical gravity acting at a distance with infinte speed.

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.

In a handwaving sort of way you can visualise it as the particle
exploring all possible paths available to it. This happens to result in
the path of shortest time being the central white light fringe and path
differences of a few wavelengths having peaks of probability too.

The problem is that you cannot know which slot your photon went through
if you want to see the interference pattern.

Thinking of a photon as an elementary excitation rather than a wavy
billiard ball renders that a whole lot less mysterious, I think. You
get to use Maxwell's equations, and compute the probability density of
detection events vs. position.

It's the interaction of light with matter that's really mysterious.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 5/27/19 8:38 AM, Jeroen Belleman wrote:

Martin Brown wrote:
On 26/05/2019 19:44, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:
On 24/05/2019 17:23, George Herold wrote:
On Friday, May 24, 2019 at 11:00:31 AM UTC-4, Jeroen
Belleman wrote:
George Herold wrote:
On Friday, May 24, 2019 at 5:41:46 AM UTC-4, Jeroen
Belleman wrote:
My attention was drawn (by George, thanks!) to Kwiat's
web page below:

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources





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'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.)

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.

I don't think the mysticism is entirely unjustified. It is
decidedly hard to interpret how Bell's inequality holds
without some difficulty. I would find it unacceptable to have
non-local variables with FTL communication as a get out of
jail free card for "explaining" QM.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Original_Bell's_inequality




When we have a more complete theory it may be obvious how
entanglement actually works in detail, but at the moment it
looks a bit worryingly like Newton's classical gravity acting
at a distance with infinte speed.

Entanglement means that some aggregate property of an EM signal
is conserved across conversions. The LO and IF in a
super-heterodyne receiver are entangled, because you can
reconstruct the original RF by mixing them together again. This
is precisely what Zeilinger did with light in his article
"Imaging with undetected photons".


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.

In a handwaving sort of way you can visualise it as the
particle exploring all possible paths available to it. This
happens to result in the path of shortest time being the
central white light fringe and path differences of a few
wavelengths having peaks of probability too.

Particles don't follow multiple paths at once. Waves do. Photons
aren't particles, they are quantized interactions between matter
and EM waves. There is no such thing as a discrete photon in
transit. There will never be a pea-shooter for single photons at
determined instants.

Yes there is. And it has been done many times. With a suitably
dense filter and a monochromatic source you can do Young's slit
experiment so that there is never more than one photon in the
apparatus at a time. It became a lot easier to demonstrate once
Boksenberg's Image Photon Counting System became available which
does what it says on the tin. It has even been done in real time
at one of the RI Christmas Lectures.

This is completely beside the point. Of course you can attenuate
a light source so that the time between detections exceeds the
light-speed delay of the apparatus. Detection events will still
be random with a Poisson distribution. This behaviour can be
perfectly explained by a semi-classical model, where the probability
of detection depends on the power density of the incident wave.
No particle-like photons needed.

The impossible photon pea-shooter I was referring to was to
fire photons at a *regular* predictable rate. *That* is never
going to happen.

Not sure. You can make a reasonably regularly-spaced sequence of
quantum transitions via coulomb blockade. If you picked the right
transition, and arranged the geometry so that only one EM mode was
coupled to it, you might be able to do that.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Jeroen Belleman]

On 2019-05-28 19:46, Phil Hobbs wrote:

On 5/27/19 8:38 AM, Jeroen Belleman wrote:
Martin Brown wrote:
On 26/05/2019 19:44, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:
On 24/05/2019 17:23, George Herold wrote:
On Friday, May 24, 2019 at 11:00:31 AM UTC-4, Jeroen
Belleman wrote:
George Herold wrote:
On Friday, May 24, 2019 at 5:41:46 AM UTC-4, Jeroen
Belleman wrote:
My attention was drawn (by George, thanks!) to Kwiat's
web page below:

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources





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'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.)

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.

I don't think the mysticism is entirely unjustified. It is
decidedly hard to interpret how Bell's inequality holds
without some difficulty. I would find it unacceptable to have
non-local variables with FTL communication as a get out of
jail free card for "explaining" QM.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Original_Bell's_inequality




When we have a more complete theory it may be obvious how
entanglement actually works in detail, but at the moment it
looks a bit worryingly like Newton's classical gravity acting
at a distance with infinte speed.

Entanglement means that some aggregate property of an EM signal
is conserved across conversions. The LO and IF in a
super-heterodyne receiver are entangled, because you can
reconstruct the original RF by mixing them together again. This
is precisely what Zeilinger did with light in his article
"Imaging with undetected photons".


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.

In a handwaving sort of way you can visualise it as the
particle exploring all possible paths available to it. This
happens to result in the path of shortest time being the
central white light fringe and path differences of a few
wavelengths having peaks of probability too.

Particles don't follow multiple paths at once. Waves do. Photons
aren't particles, they are quantized interactions between matter
and EM waves. There is no such thing as a discrete photon in
transit. There will never be a pea-shooter for single photons at
determined instants.

Yes there is. And it has been done many times. With a suitably
dense filter and a monochromatic source you can do Young's slit
experiment so that there is never more than one photon in the
apparatus at a time. It became a lot easier to demonstrate once
Boksenberg's Image Photon Counting System became available which
does what it says on the tin. It has even been done in real time
at one of the RI Christmas Lectures.

This is completely beside the point. Of course you can attenuate
a light source so that the time between detections exceeds the
light-speed delay of the apparatus. Detection events will still
be random with a Poisson distribution. This behaviour can be
perfectly explained by a semi-classical model, where the probability
of detection depends on the power density of the incident wave.
No particle-like photons needed.

The impossible photon pea-shooter I was referring to was to
fire photons at a *regular* predictable rate. *That* is never
going to happen.

Not sure. You can make a reasonably regularly-spaced sequence of
quantum transitions via coulomb blockade. If you picked the right
transition, and arranged the geometry so that only one EM mode was
coupled to it, you might be able to do that.

Cheers

Phil Hobbs

That may end up with a device that shoots electron peas on demand,
but I'll admit I'm wrong only if someone manages to shoot photons
with it. Such a device would finally bring a definite answer to whether
it's either the field that is quantized, or rather just its interaction
with matter.

Jeroen Belleman

 

[Jeroen Belleman]

On 2019-05-28 17:17, George Herold wrote:

On Tuesday, May 28, 2019 at 10:52:12 AM UTC-4, Jeroen Belleman wrote:
George Herold wrote:
On Sunday, May 26, 2019 at 2:44:59 PM UTC-4, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:

[Snip!]

When we have a more complete theory it may be obvious how entanglement
actually works in detail, but at the moment it looks a bit worryingly
like Newton's classical gravity acting at a distance with infinte speed.
Entanglement means that some aggregate property of an EM signal is
conserved across conversions. The LO and IF in a super-heterodyne
receiver are entangled, because you can reconstruct the original
RF by mixing them together again. This is precisely what Zeilinger
did with light in his article "Imaging with undetected photons".

This?
https://arxiv.org/ftp/arxiv/papers/1401/1401.4318.pdf

I skimmed it... (I'm not much of a non-linear optics type.)
But I think those are correlated down converted 'photons'.
And not entangled. All entangled photons are correlated,
most correlated photons are not entangled. (I think that is right.)

Mmh. I think I agree, except that I think in terms of
waves and signals, not photons.

An entangled pair carries some complementary information,
so that if you measure one, you can foretell the result
of the identical measurement on the other, but neither
alone will give a definite result.


Making entangled photons is hard.. And the only 'cool' experiment
I know of to do with them is the Bell inequality measurement...
Which is not that showy... no nice pictures. So they don't
get reported much.

George H.

I should see if I can come up with an RF signal processing
equivalent of such an experiment. Hold on...
Grin, no worries I'm pretty sure that EM radiation behaves the same
regardless of frequency. It's a matter of what detectors you have.

In the 'visible' photons are entangled in their polarization.
I'm trying to think of an RF source where the polarization
is unknown.. or can have any value.

I would use the phase in lieu of the polarization.

Jeroen Belleman

 

[Jeroen Belleman]

On 2019-05-28 19:40, Phil Hobbs wrote:

On 5/24/19 11:15 AM, Jeroen Belleman wrote:
Jan Panteltje wrote:
On a sunny day (Fri, 24 May 2019 11:41:40 +0200) it happened
Jeroen Belleman <jeroen@nospam.please> wrote in
qc8e8j$b2t$1@gioia.aioe.org>:

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

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources



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

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.
[...]

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.

ISTR that Planck had a good try at that around 1900.


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

A single scintillation is detectable, but it's only statistically
_predictable_. The cat thing IIRC is an argument that you could have a
macroscopic object in a mixed quantum state--QM doesn't apply merely on
the atomic scale.

Cheers

Phil Hobbs

Even if the cat's lot is determined by some quantum event, it's
silly to pretend that its state is a superposition of all possible
states. That may be a mathematically convenient way of treating
the problem, but in practice you'll always have one outcome per
event. This so-called superposition is really just the admission of
our ignorance regarding the cat's fate. To pretend anything else
would be mysticism.

The probability distribution will become evident only after having
sacrificed a lot of cats.

Jeroen Belleman

 

[Phil Hobbs]

On 5/28/19 2:57 PM, Jeroen Belleman wrote:

On 2019-05-28 19:40, Phil Hobbs wrote:
On 5/24/19 11:15 AM, Jeroen Belleman wrote:
Jan Panteltje wrote:
On a sunny day (Fri, 24 May 2019 11:41:40 +0200) it happened
Jeroen Belleman <jeroen@nospam.please> wrote in
qc8e8j$b2t$1@gioia.aioe.org>:

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

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources




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

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.
[...]

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.

ISTR that Planck had a good try at that around 1900.


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

A single scintillation is detectable, but it's only statistically
_predictable_.  The cat thing IIRC is an argument that you could have a
macroscopic object in a mixed quantum state--QM doesn't apply merely on
the atomic scale.

Cheers

Phil Hobbs


Even if the cat's lot is determined by some quantum event, it's
silly to pretend that its state is a superposition of all possible
states.

Nobody AFAIK was expecting Schroedinger's cat to be a practical
experiment any more than Einstein's relativistic elevator.

That may be a mathematically convenient way of treating
the problem, but in practice you'll always have one outcome per
event.

Once it's known. That's sort of the point of the exercise.

This so-called superposition is really just the admission of
our ignorance regarding the cat's fate. To pretend anything else
would be mysticism.

That's an *a priori* assumption. I'm sort of a mystic myself, but not
about physics.

The probability distribution will become evident only after having
sacrificed a lot of cats.

Well, virtual cats. Keeping the mixed state intact would probably
involve cooling the cat down to some nanokelvins, which might bias the
results a bit.

Cheers

Phil Hobbs



--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 5/28/19 3:18 PM, Jeroen Belleman wrote:

On 2019-05-28 19:46, Phil Hobbs wrote:
On 5/27/19 8:38 AM, Jeroen Belleman wrote:
Martin Brown wrote:
On 26/05/2019 19:44, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:
On 24/05/2019 17:23, George Herold wrote:
On Friday, May 24, 2019 at 11:00:31 AM UTC-4, Jeroen
Belleman wrote:
George Herold wrote:
On Friday, May 24, 2019 at 5:41:46 AM UTC-4, Jeroen
Belleman wrote:
My attention was drawn (by George, thanks!) to Kwiat's
web page below:

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources






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'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.)

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.

I don't think the mysticism is entirely unjustified. It is
decidedly hard to interpret how Bell's inequality holds
without some difficulty. I would find it unacceptable to have
non-local variables with FTL communication as a get out of
jail free card for "explaining" QM.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Original_Bell's_inequality





When we have a more complete theory it may be obvious how
entanglement actually works in detail, but at the moment it
looks a bit worryingly like Newton's classical gravity acting
at a distance with infinte speed.

Entanglement means that some aggregate property of an EM signal
is conserved across conversions. The LO and IF in a
super-heterodyne receiver are entangled, because you can
reconstruct the original RF by mixing them together again. This
is precisely what Zeilinger did with light in his article
"Imaging with undetected photons".


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.

In a handwaving sort of way you can visualise it as the
particle exploring all possible paths available to it. This
happens to result in the path of shortest time being the
central white light fringe and path differences of a few
wavelengths having peaks of probability too.

Particles don't follow multiple paths at once. Waves do. Photons
aren't particles, they are quantized interactions between matter
and EM waves. There is no such thing as a discrete photon in
transit. There will never be a pea-shooter for single photons at
determined instants.

Yes there is. And it has been done many times. With a suitably
dense filter and a monochromatic source you can do Young's slit
experiment so that there is never more than one photon in the
apparatus at a time. It became a lot easier to demonstrate once
Boksenberg's Image Photon Counting System became available which
does what it says on the tin. It has even been done in real time
at one of the RI Christmas Lectures.

This is completely beside the point. Of course you can attenuate
a light source so that the time between detections exceeds the
light-speed delay of the apparatus. Detection events will still
be random with a Poisson distribution. This behaviour can be
perfectly explained by a semi-classical model, where the probability
of detection depends on the power density of the incident wave.
No particle-like photons needed.

The impossible photon pea-shooter I was referring to was to
fire photons at a *regular* predictable rate. *That* is never
going to happen.

Not sure.  You can make a reasonably regularly-spaced sequence of
quantum transitions via coulomb blockade.  If you picked the right
transition, and arranged the geometry so that only one EM mode was
coupled to it, you might be able to do that.

Cheers

Phil Hobbs



That may end up with a device that shoots electron peas on demand,
but I'll admit I'm wrong only if someone manages to shoot photons
with it. Such a device would finally bring a definite answer to whether
it's either the field that is quantized, or rather just its interaction
with matter.

Jeroen Belleman

I'm with you there.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[George Herold]

On Tuesday, May 28, 2019 at 8:00:36 PM UTC-4, Phil Hobbs wrote:

On 5/28/19 3:18 PM, Jeroen Belleman wrote:
On 2019-05-28 19:46, Phil Hobbs wrote:
On 5/27/19 8:38 AM, Jeroen Belleman wrote:
Martin Brown wrote:
On 26/05/2019 19:44, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:
On 24/05/2019 17:23, George Herold wrote:
On Friday, May 24, 2019 at 11:00:31 AM UTC-4, Jeroen
Belleman wrote:
George Herold wrote:
On Friday, May 24, 2019 at 5:41:46 AM UTC-4, Jeroen
Belleman wrote:
My attention was drawn (by George, thanks!) to Kwiat's
web page below:

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources






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'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.)

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.

I don't think the mysticism is entirely unjustified. It is
decidedly hard to interpret how Bell's inequality holds
without some difficulty. I would find it unacceptable to have
non-local variables with FTL communication as a get out of
jail free card for "explaining" QM.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Original_Bell's_inequality





When we have a more complete theory it may be obvious how
entanglement actually works in detail, but at the moment it
looks a bit worryingly like Newton's classical gravity acting
at a distance with infinte speed.

Entanglement means that some aggregate property of an EM signal
is conserved across conversions. The LO and IF in a
super-heterodyne receiver are entangled, because you can
reconstruct the original RF by mixing them together again. This
is precisely what Zeilinger did with light in his article
"Imaging with undetected photons".


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.

In a handwaving sort of way you can visualise it as the
particle exploring all possible paths available to it. This
happens to result in the path of shortest time being the
central white light fringe and path differences of a few
wavelengths having peaks of probability too.

Particles don't follow multiple paths at once. Waves do. Photons
aren't particles, they are quantized interactions between matter
and EM waves. There is no such thing as a discrete photon in
transit. There will never be a pea-shooter for single photons at
determined instants.

Yes there is. And it has been done many times. With a suitably
dense filter and a monochromatic source you can do Young's slit
experiment so that there is never more than one photon in the
apparatus at a time. It became a lot easier to demonstrate once
Boksenberg's Image Photon Counting System became available which
does what it says on the tin. It has even been done in real time
at one of the RI Christmas Lectures.

This is completely beside the point. Of course you can attenuate
a light source so that the time between detections exceeds the
light-speed delay of the apparatus. Detection events will still
be random with a Poisson distribution. This behaviour can be
perfectly explained by a semi-classical model, where the probability
of detection depends on the power density of the incident wave.
No particle-like photons needed.

The impossible photon pea-shooter I was referring to was to
fire photons at a *regular* predictable rate. *That* is never
going to happen.

Not sure.  You can make a reasonably regularly-spaced sequence of
quantum transitions via coulomb blockade.  If you picked the right
transition, and arranged the geometry so that only one EM mode was
coupled to it, you might be able to do that.

Cheers

Phil Hobbs



That may end up with a device that shoots electron peas on demand,
but I'll admit I'm wrong only if someone manages to shoot photons
with it. Such a device would finally bring a definite answer to whether
it's either the field that is quantized, or rather just its interaction
with matter.

Jeroen Belleman


I'm with you there.

Hmm, Let's say you're allowed some device with only probabilities.
So you push a button and one out of X times you get a photon.
If X was ten would that be a photon gun? (I'm thinking of single
atom/defect sources, some blast of laser light and a confocal microscope to
focus on one. X is the fraction of 2*pi steradians I can catch...
1/10th is probably too greedy.) Photons are created at 'atoms' and
destroyed/ detected at others. I don't see how having a single photon
gun is any different than a single photon detector.
(except the gun is harder technically. :^)

George H.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Tue, 28 May 2019 20:00:31 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 5/28/19 3:18 PM, Jeroen Belleman wrote:
On 2019-05-28 19:46, Phil Hobbs wrote:
On 5/27/19 8:38 AM, Jeroen Belleman wrote:
Martin Brown wrote:
On 26/05/2019 19:44, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:
On 24/05/2019 17:23, George Herold wrote:
On Friday, May 24, 2019 at 11:00:31 AM UTC-4, Jeroen
Belleman wrote:
George Herold wrote:
On Friday, May 24, 2019 at 5:41:46 AM UTC-4, Jeroen
Belleman wrote:
My attention was drawn (by George, thanks!) to Kwiat's
web page below:

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources






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'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.)

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.

I don't think the mysticism is entirely unjustified. It is
decidedly hard to interpret how Bell's inequality holds
without some difficulty. I would find it unacceptable to have
non-local variables with FTL communication as a get out of
jail free card for "explaining" QM.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Original_Bell's_inequality





When we have a more complete theory it may be obvious how
entanglement actually works in detail, but at the moment it
looks a bit worryingly like Newton's classical gravity acting
at a distance with infinte speed.

Entanglement means that some aggregate property of an EM signal
is conserved across conversions. The LO and IF in a
super-heterodyne receiver are entangled, because you can
reconstruct the original RF by mixing them together again. This
is precisely what Zeilinger did with light in his article
"Imaging with undetected photons".


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.

In a handwaving sort of way you can visualise it as the
particle exploring all possible paths available to it. This
happens to result in the path of shortest time being the
central white light fringe and path differences of a few
wavelengths having peaks of probability too.

Particles don't follow multiple paths at once. Waves do. Photons
aren't particles, they are quantized interactions between matter
and EM waves. There is no such thing as a discrete photon in
transit. There will never be a pea-shooter for single photons at
determined instants.

Yes there is. And it has been done many times. With a suitably
dense filter and a monochromatic source you can do Young's slit
experiment so that there is never more than one photon in the
apparatus at a time. It became a lot easier to demonstrate once
Boksenberg's Image Photon Counting System became available which
does what it says on the tin. It has even been done in real time
at one of the RI Christmas Lectures.

This is completely beside the point. Of course you can attenuate
a light source so that the time between detections exceeds the
light-speed delay of the apparatus. Detection events will still
be random with a Poisson distribution. This behaviour can be
perfectly explained by a semi-classical model, where the probability
of detection depends on the power density of the incident wave.
No particle-like photons needed.

The impossible photon pea-shooter I was referring to was to
fire photons at a *regular* predictable rate. *That* is never
going to happen.

Not sure.  You can make a reasonably regularly-spaced sequence of
quantum transitions via coulomb blockade.  If you picked the right
transition, and arranged the geometry so that only one EM mode was
coupled to it, you might be able to do that.

Cheers

Phil Hobbs



That may end up with a device that shoots electron peas on demand,
but I'll admit I'm wrong only if someone manages to shoot photons
with it. Such a device would finally bring a definite answer to whether
it's either the field that is quantized, or rather just its interaction
with matter.

Jeroen Belleman


I'm with you there.

Cheers

Phil Hobbs

Is there a classical explanation for the behavior of a half-silvered
mirror, a beam splitter? It can't split a photon.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Clifford Heath]

On 29/5/19 1:31 pm, John Larkin wrote:

On Tue, 28 May 2019 20:00:31 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 5/28/19 3:18 PM, Jeroen Belleman wrote:
On 2019-05-28 19:46, Phil Hobbs wrote:
On 5/27/19 8:38 AM, Jeroen Belleman wrote:
Martin Brown wrote:
On 26/05/2019 19:44, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:
On 24/05/2019 17:23, George Herold wrote:
On Friday, May 24, 2019 at 11:00:31 AM UTC-4, Jeroen
Belleman wrote:
George Herold wrote:
On Friday, May 24, 2019 at 5:41:46 AM UTC-4, Jeroen
Belleman wrote:
My attention was drawn (by George, thanks!) to Kwiat's
web page below:

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources






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'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.)

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.

I don't think the mysticism is entirely unjustified. It is
decidedly hard to interpret how Bell's inequality holds
without some difficulty. I would find it unacceptable to have
non-local variables with FTL communication as a get out of
jail free card for "explaining" QM.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Original_Bell's_inequality





When we have a more complete theory it may be obvious how
entanglement actually works in detail, but at the moment it
looks a bit worryingly like Newton's classical gravity acting
at a distance with infinte speed.

Entanglement means that some aggregate property of an EM signal
is conserved across conversions. The LO and IF in a
super-heterodyne receiver are entangled, because you can
reconstruct the original RF by mixing them together again. This
is precisely what Zeilinger did with light in his article
"Imaging with undetected photons".


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.

In a handwaving sort of way you can visualise it as the
particle exploring all possible paths available to it. This
happens to result in the path of shortest time being the
central white light fringe and path differences of a few
wavelengths having peaks of probability too.

Particles don't follow multiple paths at once. Waves do. Photons
aren't particles, they are quantized interactions between matter
and EM waves. There is no such thing as a discrete photon in
transit. There will never be a pea-shooter for single photons at
determined instants.

Yes there is. And it has been done many times. With a suitably
dense filter and a monochromatic source you can do Young's slit
experiment so that there is never more than one photon in the
apparatus at a time. It became a lot easier to demonstrate once
Boksenberg's Image Photon Counting System became available which
does what it says on the tin. It has even been done in real time
at one of the RI Christmas Lectures.

This is completely beside the point. Of course you can attenuate
a light source so that the time between detections exceeds the
light-speed delay of the apparatus. Detection events will still
be random with a Poisson distribution. This behaviour can be
perfectly explained by a semi-classical model, where the probability
of detection depends on the power density of the incident wave.
No particle-like photons needed.

The impossible photon pea-shooter I was referring to was to
fire photons at a *regular* predictable rate. *That* is never
going to happen.

Not sure.  You can make a reasonably regularly-spaced sequence of
quantum transitions via coulomb blockade.  If you picked the right
transition, and arranged the geometry so that only one EM mode was
coupled to it, you might be able to do that.

Cheers

Phil Hobbs



That may end up with a device that shoots electron peas on demand,
but I'll admit I'm wrong only if someone manages to shoot photons
with it. Such a device would finally bring a definite answer to whether
it's either the field that is quantized, or rather just its interaction
with matter.

Jeroen Belleman


I'm with you there.

Cheers

Phil Hobbs

Is there a classical explanation for the behavior of a half-silvered
mirror, a beam splitter? It can't split a photon.

It can, it does, and you can recombine them to get interference fringes.
That's kinda the point of wave-particle duality.

Clifford Heath.

 

[John Larkin]

On Wed, 29 May 2019 14:54:15 +1000, Clifford Heath
<no.spam@please.net> wrote:

On 29/5/19 1:31 pm, John Larkin wrote:
On Tue, 28 May 2019 20:00:31 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 5/28/19 3:18 PM, Jeroen Belleman wrote:
On 2019-05-28 19:46, Phil Hobbs wrote:
On 5/27/19 8:38 AM, Jeroen Belleman wrote:
Martin Brown wrote:
On 26/05/2019 19:44, Jeroen Belleman wrote:
On 2019-05-26 10:39, Martin Brown wrote:
On 24/05/2019 17:23, George Herold wrote:
On Friday, May 24, 2019 at 11:00:31 AM UTC-4, Jeroen
Belleman wrote:
George Herold wrote:
On Friday, May 24, 2019 at 5:41:46 AM UTC-4, Jeroen
Belleman wrote:
My attention was drawn (by George, thanks!) to Kwiat's
web page below:

http://research.physics.illinois.edu/QI/Photonics/research/#single-photon-sources






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'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.)

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.

I don't think the mysticism is entirely unjustified. It is
decidedly hard to interpret how Bell's inequality holds
without some difficulty. I would find it unacceptable to have
non-local variables with FTL communication as a get out of
jail free card for "explaining" QM.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Original_Bell's_inequality





When we have a more complete theory it may be obvious how
entanglement actually works in detail, but at the moment it
looks a bit worryingly like Newton's classical gravity acting
at a distance with infinte speed.

Entanglement means that some aggregate property of an EM signal
is conserved across conversions. The LO and IF in a
super-heterodyne receiver are entangled, because you can
reconstruct the original RF by mixing them together again. This
is precisely what Zeilinger did with light in his article
"Imaging with undetected photons".


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.

In a handwaving sort of way you can visualise it as the
particle exploring all possible paths available to it. This
happens to result in the path of shortest time being the
central white light fringe and path differences of a few
wavelengths having peaks of probability too.

Particles don't follow multiple paths at once. Waves do. Photons
aren't particles, they are quantized interactions between matter
and EM waves. There is no such thing as a discrete photon in
transit. There will never be a pea-shooter for single photons at
determined instants.

Yes there is. And it has been done many times. With a suitably
dense filter and a monochromatic source you can do Young's slit
experiment so that there is never more than one photon in the
apparatus at a time. It became a lot easier to demonstrate once
Boksenberg's Image Photon Counting System became available which
does what it says on the tin. It has even been done in real time
at one of the RI Christmas Lectures.

This is completely beside the point. Of course you can attenuate
a light source so that the time between detections exceeds the
light-speed delay of the apparatus. Detection events will still
be random with a Poisson distribution. This behaviour can be
perfectly explained by a semi-classical model, where the probability
of detection depends on the power density of the incident wave.
No particle-like photons needed.

The impossible photon pea-shooter I was referring to was to
fire photons at a *regular* predictable rate. *That* is never
going to happen.

Not sure.  You can make a reasonably regularly-spaced sequence of
quantum transitions via coulomb blockade.  If you picked the right
transition, and arranged the geometry so that only one EM mode was
coupled to it, you might be able to do that.

Cheers

Phil Hobbs



That may end up with a device that shoots electron peas on demand,
but I'll admit I'm wrong only if someone manages to shoot photons
with it. Such a device would finally bring a definite answer to whether
it's either the field that is quantized, or rather just its interaction
with matter.

Jeroen Belleman


I'm with you there.

Cheers

Phil Hobbs

Is there a classical explanation for the behavior of a half-silvered
mirror, a beam splitter? It can't split a photon.

It can, it does, and you can recombine them to get interference fringes.
That's kinda the point of wave-particle duality.

Clifford Heath.

If you use two single-photon detectors after the splitter, you'll see
that each photon goes one way or the other. That's not very classical.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Jeroen Belleman]

John Larkin wrote:

[Snip!]

Is there a classical explanation for the behavior of a half-silvered
mirror, a beam splitter? It can't split a photon.

Don't you have that backwards? It's the QM interpretation that
requires it to split a photon to take multiple paths.

In the classical view it splits a wave, which is nothing
mysterious. The problem is that you can detect the wave
only by its effect on matter, which is quantized and
probabilistic.

Come to think of it, I've become so accustomed to the
existence of EM fields and waves that I hardly pause
at the mystery of their existence and propagation in a
perfect vacuum.

Jeroen Belleman