[Marxism] quantum information: putting certainty in the bank

[Louis Proyect <lnp3@xxxxxxxxx>]

(Les, for some reason this bounced.)

The Subject line is the title of a review of a paper published last week on
the topic of quantum information theory. its an interesting title for a
couple reasons.

classical information theory was developed in the late 1940's, by Shannon

  
<http://www.ieee.org/organizations/history_center/legacies/shannon.html>http://www.ieee.org/organizations/history_center/legacies/shannon.html

(his major paper was done while at AT&T's Bell Labs) and others, in part as
a means to analyze the capacity of information transmission schemes to
handle data flows:

   
<http://en.wikipedia.org/wiki/Information_theory>http://en.wikipedia.org/wiki/Information_theory

by introducing statistical concepts like uncertainty and entropy, insight
was gained into transmission processes based on classical physical grounds.
Schumacher (based on von Neumann's quantum entropy)  among others extended
this work into the quantum realm, but these  results were thought to be
highly unsatisfactory for several reasons, e.g.,

     
<http://prola.aps.org/abstract/PRA/v63/i2/e022113>http://prola.aps.org/abstract/PRA/v63/i2/e022113
,

one of the chief complaints being that quantum systems would admit negative
uncertainty. what the hell could that mean???

which brings us back to the current paper under review. it's authors were
able to construct an analysis which makes sense of negative uncertainty
(the review article calls this "more than certain") in terms of a quantum
condition called entanglement (i've written briefly on this, check the
archives, or google is your friend). from the review:

n practice, if the receiver is more than certain, the sender doesn't need
to transmit any qubits at all for the receiver to be able to decipher the
message. So the receiver can put some certainty in the bank for a rainy
day, in the form of extra entanglement with the sender that could be used
to reduce the receiver's uncertainty about future messages. Entanglement is
such a strong form of correlation that it can actually be used to send
qubits from the sender to the receiver using a procedure known as quantum
teleportation[6]. On the accounting ledger, therefore, having stored
entanglement is almost as good as being able to communicate.


since classical systems do not exhibit entanglement (that's a long story in
itself), we have another example of how contemporary quantum theory can be
seen to oppose the notion that quantum mechanics is all about uncertainty
and unknowability -- interesting reason #1.

interesting reason #2 is the "bank" is the review's title. a sizable
fraction of current work in quantum information theory relates to quantum
cryptography, currently the prayer of financial systems worldwide for
providing bullet-proof security to financial transactions. this relates in
part to quantum uncertainty, in that any attempt to sniff out quantum
transmission of information MUST of necessity alter the state of that
information, and being a detectable alteration, means no one can eavesdrop
un-noticed on said transactions. if you still believe quantum mechanics is
in error, your future in financial thievery looks bright.


i am certainly,
les schaffer



p.s. an interesting article on info theory and creationism:

  
<http://home.mira.net/~reynella/debate/informat.htm>http://home.mira.net/~reynella/debate/informat.htm


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