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Q: "Magic splitter crystals" used for quantum entanglement ( No Answer,   5 Comments )
Question  
Subject: "Magic splitter crystals" used for quantum entanglement
Category: Science > Physics
Asked by: puma99-ga
List Price: $5.00
Posted: 19 Aug 2004 10:28 PDT
Expires: 18 Sep 2004 10:28 PDT
Question ID: 389992
I'd like to do experiments at home, rather like the quantum
teleportation of photons that has been in the news recently. These all
involve photons that are quantumly entangled.

Generally (I think), this seems to involve starting with one photon
and shining it into some object out of which come two entagled
photons.

My question is what is this substance/gadget that will create
entangled photons for me? I'm calling it a "magic splitter crystal" -
but what is it really? And is it something that I could get and
experiment with at home?
Answer  
There is no answer at this time.

Comments  
Subject: Re: "Magic splitter crystals" used for quantum entanglement
From: pinkfreud-ga on 19 Aug 2004 10:32 PDT
 
According to this article, a barium borate crystal was used in the experiment:

http://physicsweb.org/article/news/5/8/20/1
Subject: Re: "Magic splitter crystals" used for quantum entanglement
From: pinkfreud-ga on 19 Aug 2004 10:34 PDT
 
This appears to be the type of crystal:

http://www.photonics.com/XQ/ASP/url.readprod/prodID.609/QX/readprod.htm
Subject: Re: "Magic splitter crystals" used for quantum entanglement
From: keithadler-ga on 19 Aug 2004 16:50 PDT
 
From my recollection, I remember that a calcium flouride atom heated
just right sends off two entangled photos that have correlated states.
 This was the "old school method" for doing this and probably you
could do just that.  Now, how you determine the states ... well that's
a little harder I imagine.

As far as "doing this at home" ... from all the recent news on this
the conditions to perform the experiment are rather rigid.  However, I
did read the other day that someone did something similar in much more
loose conditions.  They used a laser and a barium borate crystal.

http://www.sciam.com/article.cfm?chanID=sa003&articleID=000637AF-BD3C-1123-A74383414B7F4945

and

http://www.globaltechnoscan.com/12Sep-18Sep01/entangled_particles.htm

Note that creating entangled pairs is a hit and miss effort as it
doesn't always work.  Even with highly modern equipment only 1 pair in
a large number of misses becomes entangled.  A good book on this that
I read recently was:

http://www.amazon.com/exec/obidos/tg/detail/-/1568582323/qid=1092959154/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/104-5730925-2791910?v=glance&s=books&n=507846

This book will cover off the origins of the experiments that led to
the validation of Quantum Mechanics and the disproving of the EPR
paper led by Einstein.  Perhaps you can trace back to the early 1950's
work mentioned in this book that laid the ground for creating
entangled pairs.  Perhaps that lab environment is easy to create at
home.

Let me know if you get this going ... sounds like a great hobby.  All
this is well beyond my personal understanding of Physics, but
nonetheless it's captivated me recently.
Subject: Re: "Magic splitter crystals" used for quantum entanglement
From: puma99-ga on 19 Aug 2004 23:49 PDT
 
Thanks...! I'll get the book you gave the link for, keithadler...
Subject: Re: "Magic splitter crystals" used for quantum entanglement
From: queltar-ga on 23 Aug 2004 05:03 PDT
 
The process happening in these "magic crystals" is called SPDC,
sponteneous parametric down conversion. There are many different types
of crytals such as BBO(barium borate), LBO(Lithium borate),
PPLN(periodically poled lithiu, niobade) etc. The choice of crystal
depends on the wavelenghts you want and whether you want typeI or
typeII SPDC. this should help you find the right manufacturers

About doing it @home, it are very difficult and expensive experiments....

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