Arnold Neumaier
Jun27-04, 05:57 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\nA collapse challenge\n____________________\n\nJune 20, 2004\n\nArnold Neumaier\n\n\nA single photon is prepared in a superposition of two beams.\nA photosensitive screen blocks one of the two beams but has a big hole\nwhere the other beam can pass without significant interference.\nAt twice the distance of the first screen, a second photosensitive\nscreen without hole is placed.\n\nThe experimental observation is that the photon is observed at exactly\none of the two screens, at the position where the corresponding beam\nends.\n\nThe challenge is to build from first principles and your preferred\ninterpretation a complete, observer-free, quantum model of this\nexperiment (photon, two screens, and an environment),\ntogether with a formal analysis that completely explains the\nexperimental result.\n\n\nComments.\n\n1. The experimental result has the natural interpretation that the\nphoton was either stopped by the first screen,\nor passed that screen successfully. This property is essential for the\nanalysis of any quantum experiment which uses screens with holes to\ncreate or select beams of particles. Thus reproducing this experiment\ncorrectly is a basic requirement for any theoretical model claiming\nto provide complete foundations for quantum mechanics.\n\n2. Clearly, the experimental result is something completely objective,\nabout which all observers agree. Thus the analysis is not permitted to\nhave any dependence on hypothetical observers.\n\n3. Memory, records, etc. are permitted only if they are modelled as\nquantum objects, too, and the properties assumed about them (such as\npermanence or copyability) are derived from first principles, too.\n\n4. Position, momentum, and time are required to be modelled explicitly;\napart from that, appropriate simplifications are permitted.\nFor example, it is ok to treat the photon as a scalar particle,\nand to restrict to a single space dimension.\n\n5. Unitary dynamics demands that the system photon+screen1+screen2,\ncharacterized, say, by basis states of the form\n|photon number, first screen count, second screen count>\n(after tracing out all other degrees of freedom),\nevolves from a pure initial state |1,0,0> into a superposition\nof |0,1,0> and |0,0,1>, while agreement with experiment demands that\nthe final state is either |0,1,0> or |0,0,1>.\nThis disagreement is the measurement problem in its most basic form.\n\n\nThe web page http://www.mat.univie.ac.at/~neum/collapse.html\ncurrently contains a copy of the challenge, and an analysis of the\nchallenge for the Copenhagen interpretation. I plan to update the\nweb page as more information about the challenge becomes available.\n\n\nArnold Neumaier\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>A collapse challenge
__{__________________}
June 20, 2004
Arnold Neumaier
A single photon is prepared in a superposition of two beams.
A photosensitive screen blocks one of the two beams but has a big hole
where the other beam can pass without significant interference.
At twice the distance of the first screen, a second photosensitive
screen without hole is placed.
The experimental observation is that the photon is observed at exactly
one of the two screens, at the position where the corresponding beam
ends.
The challenge is to build from first principles and your preferred
interpretation a complete, observer-free, quantum model of this
experiment (photon, two screens, and an environment),
together with a formal analysis that completely explains the
experimental result.
Comments.
1. The experimental result has the natural interpretation that the
photon was either stopped by the first screen,
or passed that screen successfully. This property is essential for the
analysis of any quantum experiment which uses screens with holes to
create or select beams of particles. Thus reproducing this experiment
correctly is a basic requirement for any theoretical model claiming
to provide complete foundations for quantum mechanics.
2. Clearly, the experimental result is something completely objective,
about which all observers agree. Thus the analysis is not permitted to
have any dependence on hypothetical observers.
3. Memory, records, etc. are permitted only if they are modelled as
quantum objects, too, and the properties assumed about them (such as
permanence or copyability) are derived from first principles, too.
4. Position, momentum, and time are required to be modelled explicitly;
apart from that, appropriate simplifications are permitted.
For example, it is ok to treat the photon as a scalar particle,
and to restrict to a single space dimension.
5. Unitary dynamics demands that the system photon+screen1+screen2,
characterized, say, by basis states of the form
|photon number, first screen count, second screen count>
(after tracing out all other degrees of freedom),
evolves from a pure initial state |1,0,0> into a superposition
of |0,1,0> and |0,0,1>, while agreement with experiment demands that
the final state is either |0,1,0> or |0,0,1>.
This disagreement is the measurement problem in its most basic form.
The web page http://www.mat.univie.ac.at/~neum/collapse.html
currently contains a copy of the challenge, and an analysis of the
challenge for the Copenhagen interpretation. I plan to update the
web page as more information about the challenge becomes available.
Arnold Neumaier
__{__________________}
June 20, 2004
Arnold Neumaier
A single photon is prepared in a superposition of two beams.
A photosensitive screen blocks one of the two beams but has a big hole
where the other beam can pass without significant interference.
At twice the distance of the first screen, a second photosensitive
screen without hole is placed.
The experimental observation is that the photon is observed at exactly
one of the two screens, at the position where the corresponding beam
ends.
The challenge is to build from first principles and your preferred
interpretation a complete, observer-free, quantum model of this
experiment (photon, two screens, and an environment),
together with a formal analysis that completely explains the
experimental result.
Comments.
1. The experimental result has the natural interpretation that the
photon was either stopped by the first screen,
or passed that screen successfully. This property is essential for the
analysis of any quantum experiment which uses screens with holes to
create or select beams of particles. Thus reproducing this experiment
correctly is a basic requirement for any theoretical model claiming
to provide complete foundations for quantum mechanics.
2. Clearly, the experimental result is something completely objective,
about which all observers agree. Thus the analysis is not permitted to
have any dependence on hypothetical observers.
3. Memory, records, etc. are permitted only if they are modelled as
quantum objects, too, and the properties assumed about them (such as
permanence or copyability) are derived from first principles, too.
4. Position, momentum, and time are required to be modelled explicitly;
apart from that, appropriate simplifications are permitted.
For example, it is ok to treat the photon as a scalar particle,
and to restrict to a single space dimension.
5. Unitary dynamics demands that the system photon+screen1+screen2,
characterized, say, by basis states of the form
|photon number, first screen count, second screen count>
(after tracing out all other degrees of freedom),
evolves from a pure initial state |1,0,0> into a superposition
of |0,1,0> and |0,0,1>, while agreement with experiment demands that
the final state is either |0,1,0> or |0,0,1>.
This disagreement is the measurement problem in its most basic form.
The web page http://www.mat.univie.ac.at/~neum/collapse.html
currently contains a copy of the challenge, and an analysis of the
challenge for the Copenhagen interpretation. I plan to update the
web page as more information about the challenge becomes available.
Arnold Neumaier