View Full Version : Afshar's experiment
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\n\nSee New Scientist 24 july 04 pp30\n\nA simple double slit diffraction setup (but circular holes not slits)\nexperiment.\n\nA lens focusses the holes with a detector at the focal point for each\nslit.\n\nLocation of (double slit/hole interference) minima identified.\n\nSimple single hole diffraction pattern seen by each detector as\nexpected, one for each hole.\n\nWires are now placed at the position of the minima.\n\nNo effect on the pattern seen by the detectors.\n\nBlank off one hole, diffraction pattern due to wires now seen.\n\nConclusion: a diffraction pattern is produced although we know which\nhole the photons went through.\n\nHe claims this contradicts Bohr\'s \'principle of complementarity\'.\n\nHe is proposing to do a \'one quantum\' version next.\n\n--\nOz\nThis post is worth absolutely nothing and is probably fallacious.\n\nBTOPENWORLD address about to cease. DEMON address no longer in use.\n>>Use oz@farmeroz.port995.com<<\nozacoohdb@despammed.com still functions.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>See New Scientist 24 july 04 pp30
A simple double slit diffraction setup (but circular holes not slits)
experiment.
A lens focusses the holes with a detector at the focal point for each
slit.
Location of (double slit/hole interference) minima identified.
Simple single hole diffraction pattern seen by each detector as
expected, one for each hole.
Wires are now placed at the position of the minima.
No effect on the pattern seen by the detectors.
Blank off one hole, diffraction pattern due to wires now seen.
Conclusion: a diffraction pattern is produced although we know which
hole the photons went through.
He claims this contradicts Bohr's 'principle of complementarity'.
He is proposing to do a 'one quantum' version next.
--
Oz
This post is worth absolutely nothing and is probably fallacious.
BTOPENWORLD address about to cease. DEMON address no longer in use.
>>Use oz@farmeroz.port995.com<<
ozacoohdb@despammed.com still functions.
Caroline Thompson
Jul26-04, 03:41 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\n"Oz" <oz@farmeroz.port995.com> wrote in message\nnews:eGDoZTHHokABFw9w@farmeroz.port995.co m...\n> See New Scientist 24 july 04 pp30\n\nBut we still have no full report in a journal! The experiment achieved a\nlot of publicity at the end of April through John Cramer\'s talk:\nhttp://faculty.washington.edu/jcramer/talks.html\n\nThe New Scientist article tells us rather more than the talk but still not\nenough. Is a full paper out yet?\n\nCaroline\n\nCaroline H Thompson\n\nch.thompson1@virgin.net\nhttp://freespace.virgin.net/ch.thompson1/\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Oz" <oz@farmeroz.port995.com> wrote in message
news:eGDoZTHHokABFw9w@farmeroz.port995.com...
> See New Scientist 24 july 04 pp30
But we still have no full report in a journal! The experiment achieved a
lot of publicity at the end of April through John Cramer's talk:
http://faculty.washington.edu/jcramer/talks.html
The New Scientist article tells us rather more than the talk but still not
enough. Is a full paper out yet?
Caroline
Caroline H Thompson
ch.thompson1@virgin.net
http://freespace.virgin.net/ch.thompson1/
Big Bird
Jul26-04, 01:31 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nOz <oz@farmeroz.port995.com> wrote in message news:<eGDoZTHHokABFw9w@farmeroz.port995.com>...\n> See New Scientist 24 july 04 pp30\n>\n> A simple double slit diffraction setup (but circular holes not slits)\n> experiment.\n>\n[...]\n\nA short quote from\nhttp://groups.google.com/groups?selm=apchvf%24som%241%40glue.ucr.edu&output=gplain\n\n"Of course New Scientist specializes in wild and soon-forgotten\nclaims. It\'s getting to the point where the main reason to read\nthis magazine is to know what not to believe. That\'s sad, because\nit wasn\'t always this way. They still have some good articles!\nBut "caveat emptor" is the order of the day here."\n\n\n\n\n--\n#!/usr/bin/tclsh\nset map {a . b @ c com d gui e http f pen g serve h ven}\nputs "My real e-mail address is [string map \\$map shbfdnageac]"\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Oz <oz@farmeroz.port995.com> wrote in message news:<eGDoZTHHokABFw9w@farmeroz.port995.com>...
> See New Scientist 24 july 04 pp30
>
> A simple double slit diffraction setup (but circular holes not slits)
> experiment.
>
[...]
A short quote from
http://groups.google.com/groups?selm=apchvf%24som%241%40glue.ucr.edu&output=gplain
"Of course New Scientist specializes in wild and soon-forgotten
claims. It's getting to the point where the main reason to read
this magazine is to know what not to believe. That's sad, because
it wasn't always this way. They still have some good articles!
But "caveat emptor" is the order of the day here."
--
#!/usr/bin/tclsh
set map {a . b @ c com d gui e http f pen g serve h ven}
puts "My real e-mail address is [string map $map shbfdnageac]"
Caroline Thompson
Jul27-04, 12:50 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\n"Big Bird" <condor@biosys.net> wrote in message\nnews:df160b8f.0407261004.598f1248@posting .google.com...\n> Oz <oz@farmeroz.port995.com> wrote in message\nnews:<eGDoZTHHokABFw9w@farmeroz.port995.c om>...\n> > See New Scientist 24 july 04 pp30\n> >\n> > A simple double slit diffraction setup (but circular holes not slits)\n> > experiment.\n> >\n> [...]\n>\n> A short quote from\n>\nhttp://groups.google.com/groups?selm=apchvf%24som%241%40glue.ucr.edu&output=gplain\n>\n> "Of course New Scientist specializes in wild and soon-forgotten\n> claims. It\'s getting to the point where the main reason to read\n> this magazine is to know what not to believe. That\'s sad, because\n> it wasn\'t always this way. They still have some good articles!\n> But "caveat emptor" is the order of the day here."\n\nAgreed, New Scientist goes in for wild claims, especially when it\'s anything\nto do with quantum theory or cosmology, but perhaps you should have pointed\nout that Baez was talking here about the tetraneutron, not Afshar\'s\nexperiment. The latter may well be interesting. We don\'t know. I wrote\nagain to Afshar yesterday and he informed me that his paper is under review.\nBut might he not in any event be right in saying that the experiment is best\nexplained by wave theory, not photons? It clearly involves interference and\ndiffraction effects.\n\nCaroline\n\nCaroline H Thompson\n\nch.thompson1@virgin.net\nhttp://freespace.virgin.net/ch.thompson1/\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Big Bird" <condor@biosys.net> wrote in message
news:df160b8f.0407261004.598f1248@posting.google.c om...
> Oz <oz@farmeroz.port995.com> wrote in message
news:<eGDoZTHHokABFw9w@farmeroz.port995.com>...
> > See New Scientist 24 july 04 pp30
> >
> > A simple double slit diffraction setup (but circular holes not slits)
> > experiment.
> >
> [...]
>
> A short quote from
>
http://groups.google.com/groups?selm=apchvf%24som%241%40glue.ucr.edu&output=gplain
>
> "Of course New Scientist specializes in wild and soon-forgotten
> claims. It's getting to the point where the main reason to read
> this magazine is to know what not to believe. That's sad, because
> it wasn't always this way. They still have some good articles!
> But "caveat emptor" is the order of the day here."
Agreed, New Scientist goes in for wild claims, especially when it's anything
to do with quantum theory or cosmology, but perhaps you should have pointed
out that Baez was talking here about the tetraneutron, not Afshar's
experiment. The latter may well be interesting. We don't know. I wrote
again to Afshar yesterday and he informed me that his paper is under review.
But might he not in any event be right in saying that the experiment is best
explained by wave theory, not photons? It clearly involves interference and
diffraction effects.
Caroline
Caroline H Thompson
ch.thompson1@virgin.net
http://freespace.virgin.net/ch.thompson1/
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\nOz wrote:\n> A simple double slit diffraction setup (but circular holes not slits)\n> experiment.\n\nYour description of the experiment below leaves out some points I\nthink. I had to google around for a scan of the experimental setup from\nNew Scientist to understand what it was about (I\'ll fill in some holes\nbelow - no pun intended :)). While googling I picked up the point from\nanother poster in this thread that the experiment was a bit\nsensationally handled by both some other physicists claiming alternate\nQM interpretations and the magazine itself.\n\n> A lens focusses the holes with a detector at the focal point for each\n> slit.\n\nClarification: there is a single lens, with two detectors displaced\nalong the image plane so that each detector sees each hole in the\nscreen. The detectors seem to be cameras, not photo multiplicators from\nthe new scientist image, although this probably has no effect on the\noutcome.\n\nThe lens is placed so that the wall with the holes is at the first\nfocal distance and the plane with the detectors are at the second focal\ndistance.\n\n> Location of (double slit/hole interference) minima identified.\n>\n> Simple single hole diffraction pattern seen by each detector as\n> expected, one for each hole.\n>\n> Wires are now placed at the position of the minima.\n\nThis needs to be clarified as well. The wires are placed perpendicular\nto the line adjoining the detectors, *just in front of the lens*, in\nsuch a way as to block as little light as possible on the image plane,\nin effect placing them in the interference patterns minimas.\n\nImportantly, the interference pattern and wires exist in the field\n*between the holes and the lens*.\n\nThe detectors see a diffraction pattern from each hole but also measure\nthe total illumination.\n\n> No effect on the pattern seen by the detectors.\n\nThe effect on the illumination at the detectors is below the\nexperiments threshold, at least.\n\n> Blank off one hole, diffraction pattern due to wires now seen.\n\nIn essence, a reduction of intensity stemming from light blocked by the\nwires since they are not in the interference patterns "valleys"\nanymore. I think I read a figure of a 6% reduction somewhere consistent\nwith a wire-width to inter-wire distance ratio of 6%.\n\n> Conclusion: a diffraction pattern is produced although we know which\n> hole the photons went through.\n\nI think the authors claim is that the *interference* effect exists even\nif which-way information is available.\n\nNow I haven\'t done any calculations or read the New Scientist article\nexcept looking at the lab setup graphics, but if I would hazard a quick\nguess, it would be that it will turn out that even if the wires are\nplaced in the interference fields valleys, the finite width of the\nwires will diffract just enough photons to erase the which-way\ninformation that was gained by focusing the detectors at the holes in\nthe wall through the lens.\n\nConsider the limiting case with wires placed with their centres in the\ninterference fields valleys as before, but expand their width so much\nthat they almost touch each other. What you have now is yet another\nwall with a bunch of slits in! Obviously, almost all which-way\ninformation is lost after the wavefronts pass these almost\ninfinitesimal slits since they will diffract the photons equally no\nmatter from which hole in the *first* wall they originated, so any\ndetector placed after this obstacle will be like running a new\nmultiple-slit interference setup (although with the lens now severely\ndefocusing the too-closely placed new slits). And since the which-way\ninformation from the first wall is erased, interference is free to\nhappen between the first and the second wall. After the secondary wall\nthe detectors can pick up which-way information causing them to behave\nas if there was little subsequent interference.\n\nConversely, the other limiting case is with no wires (or secondary\nwall) present. Then all which-way information is present and again the\ndetectors behave as if there was no interference.\n\nThe experiment shows a case in between these limits and the effect I\nguessed at above could (and should, according to traditional QM) turn\nout to always cancel any attempt to find both 100% interference and\n100% which-way information. This would be better showed with some\ncalculations of course...\n\n/Bjorn\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Oz wrote:
> A simple double slit diffraction setup (but circular holes not slits)
> experiment.
Your description of the experiment below leaves out some points I
think. I had to google around for a scan of the experimental setup from
New Scientist to understand what it was about (I'll fill in some holes
below - no pun intended :)). While googling I picked up the point from
another poster in this thread that the experiment was a bit
sensationally handled by both some other physicists claiming alternate
QM interpretations and the magazine itself.
> A lens focusses the holes with a detector at the focal point for each
> slit.
Clarification: there is a single lens, with two detectors displaced
along the image plane so that each detector sees each hole in the
screen. The detectors seem to be cameras, not photo multiplicators from
the new scientist image, although this probably has no effect on the
outcome.
The lens is placed so that the wall with the holes is at the first
focal distance and the plane with the detectors are at the second focal
distance.
> Location of (double slit/hole interference) minima identified.
>
> Simple single hole diffraction pattern seen by each detector as
> expected, one for each hole.
>
> Wires are now placed at the position of the minima.
This needs to be clarified as well. The wires are placed perpendicular
to the line adjoining the detectors, *just in front of the lens*, in
such a way as to block as little light as possible on the image plane,
in effect placing them in the interference patterns minimas.
Importantly, the interference pattern and wires exist in the field
*between the holes and the lens*.
The detectors see a diffraction pattern from each hole but also measure
the total illumination.
> No effect on the pattern seen by the detectors.
The effect on the illumination at the detectors is below the
experiments threshold, at least.
> Blank off one hole, diffraction pattern due to wires now seen.
In essence, a reduction of intensity stemming from light blocked by the
wires since they are not in the interference patterns "valleys"
anymore. I think I read a figure of a 6% reduction somewhere consistent
with a wire-width to inter-wire distance ratio of 6%.
> Conclusion: a diffraction pattern is produced although we know which
> hole the photons went through.
I think the authors claim is that the *interference* effect exists even
if which-way information is available.
Now I haven't done any calculations or read the New Scientist article
except looking at the lab setup graphics, but if I would hazard a quick
guess, it would be that it will turn out that even if the wires are
placed in the interference fields valleys, the finite width of the
wires will diffract just enough photons to erase the which-way
information that was gained by focusing the detectors at the holes in
the wall through the lens.
Consider the limiting case with wires placed with their centres in the
interference fields valleys as before, but expand their width so much
that they almost touch each other. What you have now is yet another
wall with a bunch of slits in! Obviously, almost all which-way
information is lost after the wavefronts pass these almost
infinitesimal slits since they will diffract the photons equally no
matter from which hole in the *first* wall they originated, so any
detector placed after this obstacle will be like running a new
multiple-slit interference setup (although with the lens now severely
defocusing the too-closely placed new slits). And since the which-way
information from the first wall is erased, interference is free to
happen between the first and the second wall. After the secondary wall
the detectors can pick up which-way information causing them to behave
as if there was little subsequent interference.
Conversely, the other limiting case is with no wires (or secondary
wall) present. Then all which-way information is present and again the
detectors behave as if there was no interference.
The experiment shows a case in between these limits and the effect I
guessed at above could (and should, according to traditional QM) turn
out to always cancel any attempt to find both 100% interference and
100% which-way information. This would be better showed with some
calculations of course...
/Bjorn
pseudospin
Jul28-04, 12:30 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\n\nOz <oz@farmeroz.port995.com> wrote in message news:<eGDoZTHHokABFw9w@farmeroz.port995.com>...\n> See New Scientist 24 july 04 pp30\n>\n> A simple double slit diffraction setup (but circular holes not slits)\n> experiment.\n>\n....\n\n\nIt would be interesting if this reopened then whole Bohr-Einstein\ndebate about quantum mechanics but it won\'t. There is a trivial error\nin Afshar\'s argument.\n\nFor his refutation of the Copenhagen Interpretation to be valid he\nneeds to able to ascertain through which slit a photon passes.\n\nIn his set-up without the wires in place there are two pinholes and\ntwo detectors. You can cover up one of the pinholes and see where the\nlight goes. All of the light from the open pinhole ends up at one of\nthe detectors, and none at the other. This situation is reversed when\nyou open the other pinhole and close the first. Afshar concludes from\nthis that when both pinholes are open all the light at one of the\ndetectors came only from it\'s associated pinhole, and all the light at\nthe other detector comes from the other pinhole. This is obviously\ntrue, right?\n\nEr no, unfortunately. Afshar is thinking too classically. With both\npinholes open the photons from each pinhole interfere with each other\nand you can no longer tell which bit of quantum mechanical amplitude\ncame from where. In a very real sense, when a photon is detected it\ncan be said to have originated from both pinholes.\n\nAfshar, and by proxy a lot of other people (including new scientist\nand several physicists), have exposed their ignorance of basic quantum\nmechanics.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Oz <oz@farmeroz.port995.com> wrote in message news:<eGDoZTHHokABFw9w@farmeroz.port995.com>...
> See New Scientist 24 july 04 pp30
>
> A simple double slit diffraction setup (but circular holes not slits)
> experiment.
>
....
It would be interesting if this reopened then whole Bohr-Einstein
debate about quantum mechanics but it won't. There is a trivial error
in Afshar's argument.
For his refutation of the Copenhagen Interpretation to be valid he
needs to able to ascertain through which slit a photon passes.
In his set-up without the wires in place there are two pinholes and
two detectors. You can cover up one of the pinholes and see where the
light goes. All of the light from the open pinhole ends up at one of
the detectors, and none at the other. This situation is reversed when
you open the other pinhole and close the first. Afshar concludes from
this that when both pinholes are open all the light at one of the
detectors came only from it's associated pinhole, and all the light at
the other detector comes from the other pinhole. This is obviously
true, right?
Er no, unfortunately. Afshar is thinking too classically. With both
pinholes open the photons from each pinhole interfere with each other
and you can no longer tell which bit of quantum mechanical amplitude
came from where. In a very real sense, when a photon is detected it
can be said to have originated from both pinholes.
Afshar, and by proxy a lot of other people (including new scientist
and several physicists), have exposed their ignorance of basic quantum
mechanics.
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\npseudospin <mrh@thsun1.ph.bham.ac.uk> writes\n\n>Er no, unfortunately. Afshar is thinking too classically. With both\n>pinholes open the photons from each pinhole interfere with each other\n>and you can no longer tell which bit of quantum mechanical amplitude\n>came from where.\n\nOh, that\'s a neat argument.\n\n>In a very real sense, when a photon is detected it\n>can be said to have originated from both pinholes.\n\nThat\'s good, very good.\n\nNow what if we did the same experiment using two lasers, throttled down\nso \'only one photon is in the apparatus at any one time\'.\n\nWould you expect the same result?\nI would.\n\n>Afshar, and by proxy a lot of other people (including new scientist\n>and several physicists), have exposed their ignorance of basic quantum\n>mechanics.\n\nI don\'t think that\'s the real point. I think the real point is that\noptics gives a clear and simple description and using occham\'s razor is\nthe one to be preferred. Personally I have no doubt that QM\n(particulate) will give the same results, it ought to - its been honed\nto match experiment very well.\n\n--\nOz\nThis post is worth absolutely nothing and is probably fallacious.\n\nBTOPENWORLD address about to cease. DEMON address no longer in use.\n>>Use oz@farmeroz.port995.com<<\nozacoohdb@despammed.com still functions.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>pseudospin <mrh@thsun1.ph.bham.ac.uk> writes
>Er no, unfortunately. Afshar is thinking too classically. With both
>pinholes open the photons from each pinhole interfere with each other
>and you can no longer tell which bit of quantum mechanical amplitude
>came from where.
Oh, that's a neat argument.
>In a very real sense, when a photon is detected it
>can be said to have originated from both pinholes.
That's good, very good.
Now what if we did the same experiment using two lasers, throttled down
so 'only one photon is in the apparatus at any one time'.
Would you expect the same result?
I would.
>Afshar, and by proxy a lot of other people (including new scientist
>and several physicists), have exposed their ignorance of basic quantum
>mechanics.
I don't think that's the real point. I think the real point is that
optics gives a clear and simple description and using occham's razor is
the one to be preferred. Personally I have no doubt that QM
(particulate) will give the same results, it ought to - its been honed
to match experiment very well.
--
Oz
This post is worth absolutely nothing and is probably fallacious.
BTOPENWORLD address about to cease. DEMON address no longer in use.
>>Use oz@farmeroz.port995.com<<
ozacoohdb@despammed.com still functions.
chronon
Jul29-04, 11:24 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n"BW" <bjorn@sparta.lu.se> wrote in message news:<ce46n0\\$r5d@odah37.prod.google.com>...\n> Now I haven\'t done any calculations or read the New Scientist article\n> except looking at the lab setup graphics, but if I would hazard a quick\n> guess, it would be that it will turn out that even if the wires are\n> placed in the interference fields valleys, the finite width of the\n> wires will diffract just enough photons to erase the which-way\n> information that was gained by focusing the detectors at the holes in\n> the wall through the lens.\n>\n\nThe conclusion seems to be that this is wholly a wave phenomenon, so\nnot only does it not upset quantum interpretations, it doesn\'t really\nshow any quantum effects. So this should mean that the experiment\ncould also be done with water waves - now there\'s a nice science fair\nproject.\n\nStephen Lee\nwww.chronon.org\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"BW" <bjorn@sparta.lu.se> wrote in message news:<ce46n0$r5d@odah37.prod.google.com>...
> Now I haven't done any calculations or read the New Scientist article
> except looking at the lab setup graphics, but if I would hazard a quick
> guess, it would be that it will turn out that even if the wires are
> placed in the interference fields valleys, the finite width of the
> wires will diffract just enough photons to erase the which-way
> information that was gained by focusing the detectors at the holes in
> the wall through the lens.
>
The conclusion seems to be that this is wholly a wave phenomenon, so
not only does it not upset quantum interpretations, it doesn't really
show any quantum effects. So this should mean that the experiment
could also be done with water waves - now there's a nice science fair
project.
Stephen Lee
www.chronon.org
pseudospin
Jul29-04, 12:18 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n> Now what if we did the same experiment using two lasers, throttled down\n> so \'only one photon is in the apparatus at any one time\'.\n>\n> Would you expect the same result?\n\nI\'m not sure what you mean. If you intend to have the light from the\ntwo lasers going through different pinholes (I.e. laser 1 light only\ngoes through pinhole 1, laser 2 only though pinhole 2) and then reduce\nit down to one photon at a time, I would expect to see the equivalent\nresult as when you just close one of the pinholes.\n\nIf you mean to have the two lasers firing a single photon each through\nthe two pinholes at the same time then I would expect to see the same\nas the single laser experiment.\n\n\n>\n> >Afshar, and by proxy a lot of other people (including new scientist\n> >and several physicists), have exposed their ignorance of basic quantum\n> >mechanics.\n>\n> I don\'t think that\'s the real point. I think the real point is that\n> optics gives a clear and simple description and using occham\'s razor is\n> the one to be preferred. Personally I have no doubt that QM\n> (particulate) will give the same results, it ought to - its been honed\n> to match experiment very well.\n\nOk, you are saying that the way to do QM is to treat everything as\nwaves until the moment that a measurement takes place. If you do this\nyou wont go wrong as this is precisely the Copenhagen interpretation.\n\nIn Afshar\'s experiment the light from the two pinholes is wavelike, it\nundergoes wavelike interference at the lens (in fact this interfernce\noccurs at every point between the pinholes and the detection screens)\nand is eventually detected at one of the detectors. Only on detection\ndoes the wavefunction collapse. Afshar seems to think that on\ndetection the whole history of the particle collapses down to some\nclassical trajectory.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Now what if we did the same experiment using two lasers, throttled down
> so 'only one photon is in the apparatus at any one time'.
>
> Would you expect the same result?
I'm not sure what you mean. If you intend to have the light from the
two lasers going through different pinholes (I.e. laser 1 light only
goes through pinhole 1, laser 2 only though pinhole 2) and then reduce
it down to one photon at a time, I would expect to see the equivalent
result as when you just close one of the pinholes.
If you mean to have the two lasers firing a single photon each through
the two pinholes at the same time then I would expect to see the same
as the single laser experiment.
>
> >Afshar, and by proxy a lot of other people (including new scientist
> >and several physicists), have exposed their ignorance of basic quantum
> >mechanics.
>
> I don't think that's the real point. I think the real point is that
> optics gives a clear and simple description and using occham's razor is
> the one to be preferred. Personally I have no doubt that QM
> (particulate) will give the same results, it ought to - its been honed
> to match experiment very well.
Ok, you are saying that the way to do QM is to treat everything as
waves until the moment that a measurement takes place. If you do this
you wont go wrong as this is precisely the Copenhagen interpretation.
In Afshar's experiment the light from the two pinholes is wavelike, it
undergoes wavelike interference at the lens (in fact this interfernce
occurs at every point between the pinholes and the detection screens)
and is eventually detected at one of the detectors. Only on detection
does the wavefunction collapse. Afshar seems to think that on
detection the whole history of the particle collapses down to some
classical trajectory.
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\npseudospin <mrh@thsun1.ph.bham.ac.uk> writes\n>\n>> Now what if we did the same experiment using two lasers, throttled down\n>> so \'only one photon is in the apparatus at any one time\'.\n>>\n>> Would you expect the same result?\n>\n>I\'m not sure what you mean. If you intend to have the light from the\n>two lasers going through different pinholes (I.e. laser 1 light only\n>goes through pinhole 1, laser 2 only though pinhole 2)\n\nCorrect.\n\n>and then reduce\n>it down to one photon at a time, I would expect to see the equivalent\n>result as when you just close one of the pinholes.\n\nI\'ve lost the reference, but it was posted here about a year ago.\nNo, you do indeed get interference.\n\n>>\n>> >Afshar, and by proxy a lot of other people (including new scientist\n>> >and several physicists), have exposed their ignorance of basic quantum\n>> >mechanics.\n>>\n>> I don\'t think that\'s the real point. I think the real point is that\n>> optics gives a clear and simple description and using occham\'s razor is\n>> the one to be preferred. Personally I have no doubt that QM\n>> (particulate) will give the same results, it ought to - its been honed\n>> to match experiment very well.\n>\n>Ok, you are saying that the way to do QM is to treat everything as\n>waves until the moment that a measurement takes place. If you do this\n>you wont go wrong as this is precisely the Copenhagen interpretation.\n\nActually I don\'t quite think this. Currently I believe all particles are\nwaves, massive ones being something related to solitons.\n\nBut if you are going to have to produce numeric results, then I strongly\nsuspect that particulate QM is the easiest way to get the answer in many\ncases. I suspect the two are equivalent apart from these conceptual\ndetails.\n\n>In Afshar\'s experiment the light from the two pinholes is wavelike, it\n>undergoes wavelike interference at the lens (in fact this interfernce\n>occurs at every point between the pinholes and the detection screens)\n>and is eventually detected at one of the detectors. Only on detection\n>does the wavefunction collapse. Afshar seems to think that on\n>detection the whole history of the particle collapses down to some\n>classical trajectory.\n\nI doubt that from the article as he says its best explained optically.\nLight is a wave in optics and so has no particle-like qualities.\n\n--\nOz\nThis post is worth absolutely nothing and is probably fallacious.\n\nBTOPENWORLD address about to cease. DEMON address no longer in use.\n>>Use oz@farmeroz.port995.com<<\nozacoohdb@despammed.com still functions.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>pseudospin <mrh@thsun1.ph.bham.ac.uk> writes
>
>> Now what if we did the same experiment using two lasers, throttled down
>> so 'only one photon is in the apparatus at any one time'.
>>
>> Would you expect the same result?
>
>I'm not sure what you mean. If you intend to have the light from the
>two lasers going through different pinholes (I.e. laser 1 light only
>goes through pinhole 1, laser 2 only though pinhole 2)
Correct.
>and then reduce
>it down to one photon at a time, I would expect to see the equivalent
>result as when you just close one of the pinholes.
I've lost the reference, but it was posted here about a year ago.
No, you do indeed get interference.
>>
>> >Afshar, and by proxy a lot of other people (including new scientist
>> >and several physicists), have exposed their ignorance of basic quantum
>> >mechanics.
>>
>> I don't think that's the real point. I think the real point is that
>> optics gives a clear and simple description and using occham's razor is
>> the one to be preferred. Personally I have no doubt that QM
>> (particulate) will give the same results, it ought to - its been honed
>> to match experiment very well.
>
>Ok, you are saying that the way to do QM is to treat everything as
>waves until the moment that a measurement takes place. If you do this
>you wont go wrong as this is precisely the Copenhagen interpretation.
Actually I don't quite think this. Currently I believe all particles are
waves, massive ones being something related to solitons.
But if you are going to have to produce numeric results, then I strongly
suspect that particulate QM is the easiest way to get the answer in many
cases. I suspect the two are equivalent apart from these conceptual
details.
>In Afshar's experiment the light from the two pinholes is wavelike, it
>undergoes wavelike interference at the lens (in fact this interfernce
>occurs at every point between the pinholes and the detection screens)
>and is eventually detected at one of the detectors. Only on detection
>does the wavefunction collapse. Afshar seems to think that on
>detection the whole history of the particle collapses down to some
>classical trajectory.
I doubt that from the article as he says its best explained optically.
Light is a wave in optics and so has no particle-like qualities.
--
Oz
This post is worth absolutely nothing and is probably fallacious.
BTOPENWORLD address about to cease. DEMON address no longer in use.
>>Use oz@farmeroz.port995.com<<
ozacoohdb@despammed.com still functions.
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n"Oz"\n\n> >I\'m not sure what you mean. If you intend to have the light from the\n> >two lasers going through different pinholes (I.e. laser 1 light only\n> >goes through pinhole 1, laser 2 only though pinhole 2)\n> >and then reduce it down to one photon at a time, I would expect to see\n> >the equivalent result as when you just close one of the pinholes.\n\n> I\'ve lost the reference, but it was posted here about a year ago.\n> No, you do indeed get interference.\n\nIn terms of photons the condition for interference\nis that the two paths lead to the same cell of phase space,\nso that the path of each photon is intrinsically indeterminate\n(\'welcher weg\'). Of course, if you close one slit and then\nthe other (and the first re-opens) the shutter (random or not\nrandom) must be switched in a time which is less than the\nuncertainty in the time arrival of the photon.\n\n-L. Janossy, and K. Nagy, [Annalen der Physik, 17, (1956),\n115-121].\n-Leonard Mandel [J. Opt. Soc. Amer., 49, (1959), 931]\n-R.M. Sillitto and Catherine Wykes [Physics Letters, 39-A-4,\n(1972), 333] who performed the Janossy and Nagy experiment and found\na marvelous interference when just one photon was present in their\ninterferometer, at a time, and when their electro-optic\n(not random) shutter was switched several times during the\ntime-travel of each photon.\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Oz"
> >I'm not sure what you mean. If you intend to have the light from the
> >two lasers going through different pinholes (I.e. laser 1 light only
> >goes through pinhole 1, laser 2 only though pinhole 2)
> >and then reduce it down to one photon at a time, I would expect to see
> >the equivalent result as when you just close one of the pinholes.
> I've lost the reference, but it was posted here about a year ago.
> No, you do indeed get interference.
In terms of photons the condition for interference
is that the two paths lead to the same cell of phase space,
so that the path of each photon is intrinsically indeterminate
('welcher weg'). Of course, if you close one slit and then
the other (and the first re-opens) the shutter (random or not
random) must be switched in a time which is less than the
uncertainty in the time arrival of the photon.
-L. Janossy, and K. Nagy, [Annalen der Physik, 17, (1956),
115-121].
-Leonard Mandel [J. Opt. Soc. Amer., 49, (1959), 931]
-R.M. Sillitto and Catherine Wykes [Physics Letters, 39-A-4,
(1972), 333] who performed the Janossy and Nagy experiment and found
a marvelous interference when just one photon was present in their
interferometer, at a time, and when their electro-optic
(not random) shutter was switched several times during the
time-travel of each photon.
Franz Heymann
Jul31-04, 09:15 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n"Oz" <oz@farmeroz.port995.com> wrote in message\nnews:1G1i5GCUWVCBFw5O@farmeroz.port995.co m...\n>\n> pseudospin <mrh@thsun1.ph.bham.ac.uk> writes\n> >\n> >> Now what if we did the same experiment using two lasers,\nthrottled down\n> >> so \'only one photon is in the apparatus at any one time\'.\n> >>\n> >> Would you expect the same result?\n> >\n> >I\'m not sure what you mean. If you intend to have the light from\nthe\n> >two lasers going through different pinholes (I.e. laser 1 light\nonly\n> >goes through pinhole 1, laser 2 only though pinhole 2)\n>\n> Correct.\n>\n> >and then reduce\n> >it down to one photon at a time, I would expect to see the\nequivalent\n> >result as when you just close one of the pinholes.\n>\n> I\'ve lost the reference, but it was posted here about a year ago.\n> No, you do indeed get interference.\n\nTwo "identical" laser beams have a coherence time of onlt about a\nsecond or so, sothat whatever interference patterns you get from the\ntwo beams will fluctuate randomly with a charcteristic time comparable\nto the coherence times of the lasers.\n\nFranz\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Oz" <oz@farmeroz.port995.com> wrote in message
news:1G1i5GCUWVCBFw5O@farmeroz.port995.com...
>
> pseudospin <mrh@thsun1.ph.bham.ac.uk> writes
> >
> >> Now what if we did the same experiment using two lasers,
throttled down
> >> so 'only one photon is in the apparatus at any one time'.
> >>
> >> Would you expect the same result?
> >
> >I'm not sure what you mean. If you intend to have the light from
the
> >two lasers going through different pinholes (I.e. laser 1 light
only
> >goes through pinhole 1, laser 2 only though pinhole 2)
>
> Correct.
>
> >and then reduce
> >it down to one photon at a time, I would expect to see the
equivalent
> >result as when you just close one of the pinholes.
>
> I've lost the reference, but it was posted here about a year ago.
> No, you do indeed get interference.
Two "identical" laser beams have a coherence time of onlt about a
second or so, sothat whatever interference patterns you get from the
two beams will fluctuate randomly with a charcteristic time comparable
to the coherence times of the lasers.
Franz
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\nFranz Heymann <notfranz.heymann@btopenworld.com> writes\n\n>Two "identical" laser beams have a coherence time of onlt about a\n>second or so, sothat whatever interference patterns you get from the\n>two beams will fluctuate randomly with a charcteristic time comparable\n>to the coherence times of the lasers.\n\nYou would have too look up the reference and then get details of the\nactual experiment, but the results given on spr were as I reported.\n\nI imagine if both lasers were of particularly high stability, the\ncoherence time could well be rather more than two seconds.\n\nI have no idea how the \'spacing\' of the photons was arrived at. Naively\none imagines that if the power in each beam was W and the energy of the\nphotons was E then the number of photons/sec would be taken to be W/E.\n\nIf the \'flight time\' between the slits and the detector was t_d, then we\nwould be looking for W/E<<t_d.\n\nHmm. I guess if \'the apparatus\' were 0.1m long, we would have\n\nt_d ~ 3x10^(-10) sec.\n\nSo if one aimed for a photon \'in the apparatus\' from one source for\n1/1000 of the time one would have over 1M photons in each 2sec interval.\n\nSounds pretty doable to me....\n\n--\nOz\nThis post is worth absolutely nothing and is probably fallacious.\n\nBTOPENWORLD address about to cease. DEMON address no longer in use.\n>>Use oz@farmeroz.port995.com<<\nozacoohdb@despammed.com still functions.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Franz Heymann <notfranz.heymann@btopenworld.com> writes
>Two "identical" laser beams have a coherence time of onlt about a
>second or so, sothat whatever interference patterns you get from the
>two beams will fluctuate randomly with a charcteristic time comparable
>to the coherence times of the lasers.
You would have too look up the reference and then get details of the
actual experiment, but the results given on spr were as I reported.
I imagine if both lasers were of particularly high stability, the
coherence time could well be rather more than two seconds.
I have no idea how the 'spacing' of the photons was arrived at. Naively
one imagines that if the power in each beam was W and the energy of the
photons was E then the number of photons/sec would be taken to be W/E.
If the 'flight time' between the slits and the detector was t_d, then we
would be looking for W/E<<t_d.
Hmm. I guess if 'the apparatus' were .1m long, we would have
t_d ~ 3x10^(-10) sec.
So if one aimed for a photon 'in the apparatus' from one source for
1/1000 of the time one would have over 1M photons in each 2sec interval.
Sounds pretty doable to me....
--
Oz
This post is worth absolutely nothing and is probably fallacious.
BTOPENWORLD address about to cease. DEMON address no longer in use.
>>Use oz@farmeroz.port995.com<<
ozacoohdb@despammed.com still functions.
Greg Egan
Aug12-04, 08:30 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nIn article <1G1i5GCUWVCBFw5O@farmeroz.port995.com>, Oz\n<oz@farmeroz.port995.com> wrote:\n\n[snip]\n\n> Actually I don\'t quite think this. Currently I believe all particles are\n> waves, massive ones being something related to solitons.\n>\n> But if you are going to have to produce numeric results, then I strongly\n> suspect that particulate QM is the easiest way to get the answer in many\n> cases. I suspect the two are equivalent apart from these conceptual\n> details.\n\nWhy do you believe you need to invoke solitons in QM? Solitons keep\ntheir shape as they propagate. Particles in QM do no such thing.\n\nYou get "particle-like" behaviour in QM by having a wave function that is\nspatially narrow: i.e. a blip or a pulse when you draw the graph of\namplitude against a spatial coordinate. But in general, such blips will\nspread out over time, e.g. an electron in free space, if you start out\nwith a wavefunction that is a small square pulse, will rapidly become\ndelocalised. There are exceptions: a harmonic oscillator potential,\nV(x)=kx^2, will allow a correctly-shaped Gaussian wave packet to\noscillate back and forth without changing shape, but the generic\nsituation is that the wave function *will* change shape over time. An\nelectron is not a soliton.\n\nNaive sources like New Scientist burble on endlessly about mysterious\nwave/particle duality, but this duality is really about as mysterious as\nthe fact that 4 is equal to 1+1+1+1 as well as 2+2. You can write *any*\nwave function as a sum of localised blips. You just put a blip at each\npoint with the same amplitude as the wave at that point. You can also\nwrite *the same* wave function as a sum of sinusoidal oscillations; you\njust do a Fourier analysis. Both of these mathematical sums are correct\nat the same time.\n\nWhere the controversy comes in is what happens when you perform an action\nwhich would cause some macroscopic detector to show result 1 if the wave\nfunction was a blip at x_1 and result 2 if the wave function was a blip\nat x_2, and in fact it is a sum that includes both of those blips.\n\nBut whatever you believe about the measurement process, any theory that\ndoesn\'t allow blips in an electron\'s wave function to rapidly become\nnon-localised -- i.e. to behave in a very non-solitonic way -- will\ndirectly contradict experimental results.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>In article <1G1i5GCUWVCBFw5O@farmeroz.port995.com>, Oz
<oz@farmeroz.port995.com> wrote:
[snip]
> Actually I don't quite think this. Currently I believe all particles are
> waves, massive ones being something related to solitons.
>
> But if you are going to have to produce numeric results, then I strongly
> suspect that particulate QM is the easiest way to get the answer in many
> cases. I suspect the two are equivalent apart from these conceptual
> details.
Why do you believe you need to invoke solitons in QM? Solitons keep
their shape as they propagate. Particles in QM do no such thing.
You get "particle-like" behaviour in QM by having a wave function that is
spatially narrow: i.e. a blip or a pulse when you draw the graph of
amplitude against a spatial coordinate. But in general, such blips will
spread out over time, e.g. an electron in free space, if you start out
with a wavefunction that is a small square pulse, will rapidly become
delocalised. There are exceptions: a harmonic oscillator potential,
V(x)=kx^2, will allow a correctly-shaped Gaussian wave packet to
oscillate back and forth without changing shape, but the generic
situation is that the wave function *will* change shape over time. An
electron is not a soliton.
Naive sources like New Scientist burble on endlessly about mysterious
wave/particle duality, but this duality is really about as mysterious as
the fact that 4 is equal to 1+1+1+1 as well as 2+2. You can write *any*
wave function as a sum of localised blips. You just put a blip at each
point with the same amplitude as the wave at that point. You can also
write *the same* wave function as a sum of sinusoidal oscillations; you
just do a Fourier analysis. Both of these mathematical sums are correct
at the same time.
Where the controversy comes in is what happens when you perform an action
which would cause some macroscopic detector to show result 1 if the wave
function was a blip at x_1 and result 2 if the wave function was a blip
at x_2, and in fact it is a sum that includes both of those blips.
But whatever you believe about the measurement process, any theory that
doesn't allow blips in an electron's wave function to rapidly become
non-localised -- i.e. to behave in a very non-solitonic way -- will
directly contradict experimental results.
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\nGreg Egan <gregegan@netspace.zebra.net.au> writes\n>\n>In article <1G1i5GCUWVCBFw5O@farmeroz.port995.com>, Oz\n><oz@farmeroz.port995.com> wrote:\n>\n>[snip]\n>\n>> Actually I don\'t quite think this. Currently I believe all particles are\n>> waves, massive ones being something related to solitons.\n>>\n>> But if you are going to have to produce numeric results, then I strongly\n>> suspect that particulate QM is the easiest way to get the answer in many\n>> cases. I suspect the two are equivalent apart from these conceptual\n>> details.\n>\n>Why do you believe you need to invoke solitons in QM? Solitons keep\n>their shape as they propagate. Particles in QM do no such thing.\n\nYes. Well, no. As far as I can glean from the threads mostly populated\nby Mr Essell the solitons that emulate schroedinger do in fact disperse.\nI imagine they disperse whilst still maintaining their soliton-ness. As\nhas been pointed out current soliton formulations do not allow for the\nmerging or interaction of solitons, but that doesn\'t mean that species\nthat do in spaces that allow it, cannot exist.\n\nI imagine that a soliton in a box would match precisely with a particle\nin a box. I see an electron as a soliton in a box, although the box is\nin fact another soliton (in another dimension so to speak). Of course I\nam far too ignorant to be precise, or even vague, but I increasingly see\nsomething like a balance between an electric field trying to disperse\nand a mass field trying to collapse. The soliton is in both of these\n(electric dominating space and mass dominating time), collapsing in time\nbut simultaneously expanding in space. Given the difference in strength\nbetween the two forces I would expect the electric force to dominate,\nthat is the electron would be large spatially compared to its mass (time\nextent). This is about what we see, the electron is \'sort of atom sized\'\n(consider orbitals) but has very small mass. In contrast a proton is\nsmaller because the higher mass dominates the electric field.\n\nPlease note that I am NOT saying the electron is a BH or indeed anything\nlike that. I\'m saying that its collapsing in the time dimension whilst\nexpanding in the electric dimension and the whole thing is oscillating\nbetween the two in a soliton-like manner. Whether this will require\nmodification to maxwell and/or GR at small scales I don\'t know, but I\nwouldn\'t be at all surprised.\n\n>You get "particle-like" behaviour in QM by having a wave function that is\n>spatially narrow: i.e. a blip or a pulse when you draw the graph of\n>amplitude against a spatial coordinate. But in general, such blips will\n>spread out over time, e.g. an electron in free space, if you start out\n>with a wavefunction that is a small square pulse, will rapidly become\n>delocalised.\n\nYes. That is close to the soliton behaviour mentioned by essel.\nElectrons are \'quite well localised\', that is they disperse only a\nlittle, electron beams are often rather precise. Compare that with the\n\'infinitely dispersing\' photon.\n\n>There are exceptions: a harmonic oscillator potential,\n>V(x)=kx^2, will allow a correctly-shaped Gaussian wave packet to\n>oscillate back and forth without changing shape, but the generic\n>situation is that the wave function *will* change shape over time. An\n>electron is not a soliton.\n\nThe problem is that electrons are elementary particles and also waves.\nThat said I haven\'t come across any other possible description of a wave\nthat gives this discreteness, that is generates waves that are identical\nand quantised. I can, however, readily imagine a non-linear universe\nwhere the very laws of spacetime (and any other forces) allow a small\nand specific number of tightly defined solitons and no other persistent\nentities. This sort of universe would have properties for these solitons\nthat match well with what we see.\n\n>Naive sources like New Scientist burble on endlessly about mysterious\n>wave/particle duality, but this duality is really about as mysterious as\n>the fact that 4 is equal to 1+1+1+1 as well as 2+2. You can write *any*\n>wave function as a sum of localised blips. You just put a blip at each\n>point with the same amplitude as the wave at that point. You can also\n>write *the same* wave function as a sum of sinusoidal oscillations; you\n>just do a Fourier analysis. Both of these mathematical sums are correct\n>at the same time.\n\nAbsolutely, I agree, I have no problem with this.\nExcept we NEVER see a pointlike particle and virtual particles seem\ngenerally to be accepted as useful figments of a complex integration.\n\nWe see wavelike particles all around us, though.\n\n>Where the controversy comes in is what happens when you perform an action\n>which would cause some macroscopic detector to show result 1 if the wave\n>function was a blip at x_1 and result 2 if the wave function was a blip\n>at x_2, and in fact it is a sum that includes both of those blips.\n>\n>But whatever you believe about the measurement process, any theory that\n>doesn\'t allow blips in an electron\'s wave function to rapidly become\n>non-localised -- i.e. to behave in a very non-solitonic way -- will\n>directly contradict experimental results.\n\nI am still awaiting an experiment that shows this and is not amenable to\nthe (handwavy - I am an ignorant) mechanism I currently hold as a good\ndescription.\n\n--\nOz\nThis post is worth absolutely nothing and is probably fallacious.\n\nBTOPENWORLD address about to cease. DEMON address no longer in use.\n>>Use oz@farmeroz.port995.com<<\nozacoohdb@despammed.com still functions.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Greg Egan <gregegan@netspace.zebra.net.au> writes
>
>In article <1G1i5GCUWVCBFw5O@farmeroz.port995.com>, Oz
><oz@farmeroz.port995.com> wrote:
>
>[snip]
>
>> Actually I don't quite think this. Currently I believe all particles are
>> waves, massive ones being something related to solitons.
>>
>> But if you are going to have to produce numeric results, then I strongly
>> suspect that particulate QM is the easiest way to get the answer in many
>> cases. I suspect the two are equivalent apart from these conceptual
>> details.
>
>Why do you believe you need to invoke solitons in QM? Solitons keep
>their shape as they propagate. Particles in QM do no such thing.
Yes. Well, no. As far as I can glean from the threads mostly populated
by Mr Essell the solitons that emulate schroedinger do in fact disperse.
I imagine they disperse whilst still maintaining their soliton-ness. As
has been pointed out current soliton formulations do not allow for the
merging or interaction of solitons, but that doesn't mean that species
that do in spaces that allow it, cannot exist.
I imagine that a soliton in a box would match precisely with a particle
in a box. I see an electron as a soliton in a box, although the box is
in fact another soliton (in another dimension so to speak). Of course I
am far too ignorant to be precise, or even vague, but I increasingly see
something like a balance between an electric field trying to disperse
and a mass field trying to collapse. The soliton is in both of these
(electric dominating space and mass dominating time), collapsing in time
but simultaneously expanding in space. Given the difference in strength
between the two forces I would expect the electric force to dominate,
that is the electron would be large spatially compared to its mass (time
extent). This is about what we see, the electron is 'sort of atom sized'
(consider orbitals) but has very small mass. In contrast a proton is
smaller because the higher mass dominates the electric field.
Please note that I am NOT saying the electron is a BH or indeed anything
like that. I'm saying that its collapsing in the time dimension whilst
expanding in the electric dimension and the whole thing is oscillating
between the two in a soliton-like manner. Whether this will require
modification to maxwell and/or GR at small scales I don't know, but I
wouldn't be at all surprised.
>You get "particle-like" behaviour in QM by having a wave function that is
>spatially narrow: i.e. a blip or a pulse when you draw the graph of
>amplitude against a spatial coordinate. But in general, such blips will
>spread out over time, e.g. an electron in free space, if you start out
>with a wavefunction that is a small square pulse, will rapidly become
>delocalised.
Yes. That is close to the soliton behaviour mentioned by essel.
Electrons are 'quite well localised', that is they disperse only a
little, electron beams are often rather precise. Compare that with the
'infinitely dispersing' photon.
>There are exceptions: a harmonic oscillator potential,
>V(x)=kx^2, will allow a correctly-shaped Gaussian wave packet to
>oscillate back and forth without changing shape, but the generic
>situation is that the wave function *will* change shape over time. An
>electron is not a soliton.
The problem is that electrons are elementary particles and also waves.
That said I haven't come across any other possible description of a wave
that gives this discreteness, that is generates waves that are identical
and quantised. I can, however, readily imagine a non-linear universe
where the very laws of spacetime (and any other forces) allow a small
and specific number of tightly defined solitons and no other persistent
entities. This sort of universe would have properties for these solitons
that match well with what we see.
>Naive sources like New Scientist burble on endlessly about mysterious
>wave/particle duality, but this duality is really about as mysterious as
>the fact that 4 is equal to 1+1+1+1 as well as 2+2. You can write *any*
>wave function as a sum of localised blips. You just put a blip at each
>point with the same amplitude as the wave at that point. You can also
>write *the same* wave function as a sum of sinusoidal oscillations; you
>just do a Fourier analysis. Both of these mathematical sums are correct
>at the same time.
Absolutely, I agree, I have no problem with this.
Except we NEVER see a pointlike particle and virtual particles seem
generally to be accepted as useful figments of a complex integration.
We see wavelike particles all around us, though.
>Where the controversy comes in is what happens when you perform an action
>which would cause some macroscopic detector to show result 1 if the wave
>function was a blip at x_1 and result 2 if the wave function was a blip
>at x_2, and in fact it is a sum that includes both of those blips.
>
>But whatever you believe about the measurement process, any theory that
>doesn't allow blips in an electron's wave function to rapidly become
>non-localised -- i.e. to behave in a very non-solitonic way -- will
>directly contradict experimental results.
I am still awaiting an experiment that shows this and is not amenable to
the (handwavy - I am an ignorant) mechanism I currently hold as a good
description.
--
Oz
This post is worth absolutely nothing and is probably fallacious.
BTOPENWORLD address about to cease. DEMON address no longer in use.
>>Use oz@farmeroz.port995.com<<
ozacoohdb@despammed.com still functions.
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