Caroline Thompson
Nov3-04, 10:06 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:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:net@nospam.com> wrote in\nmessage news:VEfgd.22437\\$SW3.3788@fed1read01...\n> "TomGee" <lvlus@hotmail.com> wrote in message\n>> "Ken Kubos" <kubos@execpc.com> wrote in message\n>> news:<10o1rd9ppnl2e92@corp.supernews.com>...\n\nRe Press Release:\n>>> http://www.physorg.com/news1755.html\n>>>\n>>> Photons Under Control\n>>> October 28, 2004\n>>>\n>>> Building block created for quantum-computing, secure communication and\n>>> quantum Internet\n\nFull ref to paper:\nMatthias Keller, Birgit Lange, Kazuhiro Hayasaka, Wolfgang Lange & Herbert\nWalther, "Continuous generation of single photons with controlled waveform\nin an ion-trap cavity system", Nature 431, 1085, 28 October 2004\n\nUnfortunately I can\'t readily get hold of a copy, since the claims sound\ninteresting.\n\n>> Thanks, Ken, for the information you posted. Do you have an opinion as\n>> to the wavelength of a single photon?\n\nThe emitted "photons" are all supposed to have wavelength 866 nm, according\nto the Press Release.\n\nPerhaps what you mean is the pulse duration? From the graphs this seems to\nbe about 2 ns for a "photon" with a single peak to its profile, about 4 ns\nfor a double-peaked one.\n\nBut the fascinating question is whether or not what they are seeing is in\nfact consistent with the accepted ideas of what a "photon" is! They say\nthat the double-peaked time spectrum represents observations on *single\nphotons*. These are obtained by varying the pump profile in a similar\npattern. How can what we are seeing be anything other than a purely wave\neffect, especially in view of the fact that the emission only occurs when\nthe ion is in a resonant state between two mirrors?\n\nA resonance cannot happen instantaneously! I have not checked but would in\nany event be happy to bet that, if they were to allow some light to escape\nthrough the other mirror of the pair, they could detect a simultaneous\n"photon" there! In other words, they are not producing "single photons" but\ncomplete wave systems. [Equally, I wonder if, with the use of detectors\nwith dead times of less than 2 ns, they could detect each double-peaked\n"photon", if not all "photons", more than once.]\n\nOK, so clearly my notion of the modern idea of what a "photon" is must be\nwrong! I\'m assuming it means the indivisible little fellow that cannot be\nsplit, as per the Copenhagen interpretation of quantum theory. But if it is\nan extended pulse (which I have always believed -- see for example\nhttp://arxiv.org/abs/quant-ph/9711044) and *can* be split (or detected twice\nif only we have sufficiently short dead times in our detectors), why cling\nto the term "single photon"? Why not just say "accurately controlled light\npulse"?\n\n> It was an excited calcium atom. It has a few hundred associated\n> characteristic energy levels, each of which could mathematically be\n> back-calculated to a wavelength. It wouldn\'t *mean* anything, however.\n\nWhy not? The dimensions of the cavity are presumably carefully chosen so\nthat an exact number of wavelengths span the trap. The wavelength is surely\na very meaningful quantity.\n\nCheers\nCaroline\n\nCaroline H Thompson\n\nch.thompson1@virgin.net\nhttp://freespace.virgin.net/ch.thompson1/\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>"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:net@nospam.com> wrote in
message news:VEfgd.22437$SW3.3788@fed1read01...
> "TomGee" <lvlus@hotmail.com> wrote in message
>> "Ken Kubos" <kubos@execpc.com> wrote in message
>> news:<10o1rd9ppnl2e92@corp.supernews.com>...
Re Press Release:
>>> http://www.physorg.com/news1755.html
>>>
>>> Photons Under Control
>>> October 28, 2004
>>>
>>> Building block created for quantum-computing, secure communication and
>>> quantum Internet
Full ref to paper:
Matthias Keller, Birgit Lange, Kazuhiro Hayasaka, Wolfgang Lange & Herbert
Walther, "Continuous generation of single photons with controlled waveform
in an ion-trap cavity system", Nature 431, 1085, 28 October 2004
Unfortunately I can't readily get hold of a copy, since the claims sound
interesting.
>> Thanks, Ken, for the information you posted. Do you have an opinion as
>> to the wavelength of a single photon?
The emitted "photons" are all supposed to have wavelength 866 nm, according
to the Press Release.
Perhaps what you mean is the pulse duration? From the graphs this seems to
be about 2 ns for a "photon" with a single peak to its profile, about 4 ns
for a double-peaked one.
But the fascinating question is whether or not what they are seeing is in
fact consistent with the accepted ideas of what a "photon" is! They say
that the double-peaked time spectrum represents observations on *single
photons*. These are obtained by varying the pump profile in a similar
pattern. How can what we are seeing be anything other than a purely wave
effect, especially in view of the fact that the emission only occurs when
the ion is in a resonant state between two mirrors?
A resonance cannot happen instantaneously! I have not checked but would in
any event be happy to bet that, if they were to allow some light to escape
through the other mirror of the pair, they could detect a simultaneous
"photon" there! In other words, they are not producing "single photons" but
complete wave systems. [Equally, I wonder if, with the use of detectors
with dead times of less than 2 ns, they could detect each double-peaked
"photon", if not all "photons", more than once.]
OK, so clearly my notion of the modern idea of what a "photon" is must be
wrong! I'm assuming it means the indivisible little fellow that cannot be
split, as per the Copenhagen interpretation of quantum theory. But if it is
an extended pulse (which I have always believed -- see for example
http://arxiv.org/abs/http://www.arxiv.org/abs/quant-ph/9711044) and *can* be split (or detected twice
if only we have sufficiently short dead times in our detectors), why cling
to the term "single photon"? Why not just say "accurately controlled light
pulse"?
> It was an excited calcium atom. It has a few hundred associated
> characteristic energy levels, each of which could mathematically be
> back-calculated to a wavelength. It wouldn't *mean* anything, however.
Why not? The dimensions of the cavity are presumably carefully chosen so
that an exact number of wavelengths span the trap. The wavelength is surely
a very meaningful quantity.
Cheers
Caroline
Caroline H Thompson
ch.thompson1@virgin.net
http://freespace.virgin.net/ch.thompson1/
message news:VEfgd.22437$SW3.3788@fed1read01...
> "TomGee" <lvlus@hotmail.com> wrote in message
>> "Ken Kubos" <kubos@execpc.com> wrote in message
>> news:<10o1rd9ppnl2e92@corp.supernews.com>...
Re Press Release:
>>> http://www.physorg.com/news1755.html
>>>
>>> Photons Under Control
>>> October 28, 2004
>>>
>>> Building block created for quantum-computing, secure communication and
>>> quantum Internet
Full ref to paper:
Matthias Keller, Birgit Lange, Kazuhiro Hayasaka, Wolfgang Lange & Herbert
Walther, "Continuous generation of single photons with controlled waveform
in an ion-trap cavity system", Nature 431, 1085, 28 October 2004
Unfortunately I can't readily get hold of a copy, since the claims sound
interesting.
>> Thanks, Ken, for the information you posted. Do you have an opinion as
>> to the wavelength of a single photon?
The emitted "photons" are all supposed to have wavelength 866 nm, according
to the Press Release.
Perhaps what you mean is the pulse duration? From the graphs this seems to
be about 2 ns for a "photon" with a single peak to its profile, about 4 ns
for a double-peaked one.
But the fascinating question is whether or not what they are seeing is in
fact consistent with the accepted ideas of what a "photon" is! They say
that the double-peaked time spectrum represents observations on *single
photons*. These are obtained by varying the pump profile in a similar
pattern. How can what we are seeing be anything other than a purely wave
effect, especially in view of the fact that the emission only occurs when
the ion is in a resonant state between two mirrors?
A resonance cannot happen instantaneously! I have not checked but would in
any event be happy to bet that, if they were to allow some light to escape
through the other mirror of the pair, they could detect a simultaneous
"photon" there! In other words, they are not producing "single photons" but
complete wave systems. [Equally, I wonder if, with the use of detectors
with dead times of less than 2 ns, they could detect each double-peaked
"photon", if not all "photons", more than once.]
OK, so clearly my notion of the modern idea of what a "photon" is must be
wrong! I'm assuming it means the indivisible little fellow that cannot be
split, as per the Copenhagen interpretation of quantum theory. But if it is
an extended pulse (which I have always believed -- see for example
http://arxiv.org/abs/http://www.arxiv.org/abs/quant-ph/9711044) and *can* be split (or detected twice
if only we have sufficiently short dead times in our detectors), why cling
to the term "single photon"? Why not just say "accurately controlled light
pulse"?
> It was an excited calcium atom. It has a few hundred associated
> characteristic energy levels, each of which could mathematically be
> back-calculated to a wavelength. It wouldn't *mean* anything, however.
Why not? The dimensions of the cavity are presumably carefully chosen so
that an exact number of wavelengths span the trap. The wavelength is surely
a very meaningful quantity.
Cheers
Caroline
Caroline H Thompson
ch.thompson1@virgin.net
http://freespace.virgin.net/ch.thompson1/