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View Full Version : Quantum Nondemolition Teleportation


Success_Machine
Apr7-04, 09:13 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resize=yes,status=no,wi dth=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>I recently learned that the state of an entangled particle can be\nmeasured without changing or destroying it, i.e. without using a\ndetector that converts the particle to electrical signals as a means\nof detection. I have a few questions:\n\n1. Does this mean that Shannon\'s Law no longer applies, since a single\nphoton can be used multiple times to communicate a bit of information?\nWhat is the new law governing maximum bitrate per channel ?\n\n2. Since quantum states can be communicated without a line-of-sight,\ndoes this mean that we can dispense with giant high-accuracy targeting\nmirrors for laser communication? Wouldn\'t the information simply find\nit\'s way to the detector in some spooky fashion, without need to point\nan antenna in its direction?\n\n3. Does communication by quantum non-demolition teleportation imply\nthat energy is being transmitted? For example, could I generate\nelectricity in a lab, use it to alternate the states of entangled\nparticles, and thereby supply power to a similarly connected device at\na great distance without a line-of-sight? For example, could I supply\npower to a spacecraft from a ground station without any conventional\ntransmitter?\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">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>I recently learned that the state of an entangled particle can be
measured without changing or destroying it, i.e. without using a
detector that converts the particle to electrical signals as a means
of detection. I have a few questions:

1. Does this mean that Shannon's Law no longer applies, since a single
photon can be used multiple times to communicate a bit of information?
What is the new law governing maximum bitrate per channel ?

2. Since quantum states can be communicated without a line-of-sight,
does this mean that we can dispense with giant high-accuracy targeting
mirrors for laser communication? Wouldn't the information simply find
it's way to the detector in some spooky fashion, without need to point
an antenna in its direction?

3. Does communication by quantum non-demolition teleportation imply
that energy is being transmitted? For example, could I generate
electricity in a lab, use it to alternate the states of entangled
particles, and thereby supply power to a similarly connected device at
a great distance without a line-of-sight? For example, could I supply
power to a spacecraft from a ground station without any conventional
transmitter?

Aaron Denney
Apr7-04, 03:13 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>Let me caveat these comments with "I\'m familiar with quantum\nnondemolition measurements, and quantum teleportation, but not of any\nresults beyond the naive combination."\n\n\nOn 2004-04-06, Success_Machine &lt;womplex_oo1@yahoo.com&gt; wrote:\n&gt; I recently learned that the state of an entangled particle can be\n&gt; measured without changing or destroying it, i.e. without using a\n&gt; detector that converts the particle to electrical signals as a means\n&gt; of detection. I have a few questions:\n&gt;\n&gt; 1. Does this mean that Shannon\'s Law no longer applies, since a single\n&gt; photon can be used multiple times to communicate a bit of information?\n\nNo. A single photon certainly can\'t be used multiple times. Imposing new\ninformation on the other EPR pair breaks the entanglement.\n\nQuantum nondemolition in essence just lets your measurement not further\ndisturb the state after the initial state reduction.\n\nShannon\'s law talks about how many distinguishable states can\nbe sent. This has no effect.\n\n&gt; What is the new law governing maximum bitrate per channel ?\n\nSame old, same old.\n\n&gt; 2. Since quantum states can be communicated without a line-of-sight,\n&gt; does this mean that we can dispense with giant high-accuracy targeting\n&gt; mirrors for laser communication? Wouldn\'t the information simply find\n&gt; it\'s way to the detector in some spooky fashion, without need to point\n&gt; an antenna in its direction?\n\nHuh? You still need to transport something to transport information, and\nthat something can\'t be altered too much along the way.\n\n&gt; 3. Does communication by quantum non-demolition teleportation imply\n&gt; that energy is being transmitted? For example, could I generate\n&gt; electricity in a lab, use it to alternate the states of entangled\n&gt; particles, and thereby supply power to a similarly connected device at\n&gt; a great distance without a line-of-sight? For example, could I supply\n&gt; power to a spacecraft from a ground station without any conventional\n&gt; transmitter?\n\nNo, no, and no.\n\n--\nAaron Denney\n-&gt;&lt;-\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">&nbsp;&nbsp;View this Usenet post in original ASCII form </a></div><P></jabberwocky>Let me caveat these comments with "I'm familiar with quantum
nondemolition measurements, and quantum teleportation, but not of any
results beyond the naive combination."


On 2004-04-06, Success_Machine <womplex_oo1@yahoo.com> wrote:
> I recently learned that the state of an entangled particle can be
> measured without changing or destroying it, i.e. without using a
> detector that converts the particle to electrical signals as a means
> of detection. I have a few questions:
>
> 1. Does this mean that Shannon's Law no longer applies, since a single
> photon can be used multiple times to communicate a bit of information?

No. A single photon certainly can't be used multiple times. Imposing new
information on the other EPR pair breaks the entanglement.

Quantum nondemolition in essence just lets your measurement not further
disturb the state after the initial state reduction.

Shannon's law talks about how many distinguishable states can
be sent. This has no effect.

> What is the new law governing maximum bitrate per channel ?

Same old, same old.

> 2. Since quantum states can be communicated without a line-of-sight,
> does this mean that we can dispense with giant high-accuracy targeting
> mirrors for laser communication? Wouldn't the information simply find
> it's way to the detector in some spooky fashion, without need to point
> an antenna in its direction?

Huh? You still need to transport something to transport information, and
that something can't be altered too much along the way.

> 3. Does communication by quantum non-demolition teleportation imply
> that energy is being transmitted? For example, could I generate
> electricity in a lab, use it to alternate the states of entangled
> particles, and thereby supply power to a similarly connected device at
> a great distance without a line-of-sight? For example, could I supply
> power to a spacecraft from a ground station without any conventional
> transmitter?

No, no, and no.

--
Aaron Denney
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