Entangled photons secure money transfer

[R. A. Hettinga]

Further entanglement of the hype-meter with its peg...

Cheers,
RAH
-------

<http://www.newscientist.com/news/print.jsp?id=ns99994914>
 

 New Scientist

Entangled photons secure money transfer

 

17:10 22 April 04

 

NewScientist.com news service

 

An electronic money transaction has been carried out in at a bank in
Austria using entangled photons to create an unbreakable communications
code.

Although commercial quantum cryptography products already exist, none of
these use entangled photons to guarantee secure communications.

The link was used to transfer money between Vienna City Hall and Bank
Austria Creditanstalt on Wednesday. The cryptographic system was developed
by Anton Zeilinger and colleagues from the University of Vienna and the
Austrian company ARC Seibersdorf Research.

Entangled photons obey the strange principles of quantum physics, whereby
disturbing the state of one will instantly disturb the other, no matter how
much distance there is in between them.

The pairs of entangled photons used were generated by firing a laser
through a crystal to effectively split single photons into two. One photon
from each entangled pair was then sent from the bank to the city hall via
optic fibre.


Key creation


When these photons arrived at their destination, their state of
polarisation was observed. This provided both ends of the link with the
same data, either a one or a zero. In this way, it is possible to build a
cryptographic key with which to secure the full financial transaction.

 Quantum entanglement ensures the security of communications because any
attempt to intercept the photons in transit to determine the key would be
immediately obvious to those monitoring the state of the other photons in
each pair.

 And because the resulting key is random it can be used to provide
completely secure link even over an unprotected communications channel,
provided a new key is used each time.

This system can be guaranteed secure. By contrast, most existing
non-quantum cryptographic systems rely on extremely time-consuming
mathematical problems to create a code that are impractical - but not
impossible - to break.

"If you are talking about large sums of money, people are interested,"
Zeilinger told New Scientist. He adds that the system should not be much
more expensive to implement than current technology.


Sewer link


The photon-encrypted money transfer saw the Mayor of Vienna transfer a
3000-Euro donation into an account belonging to the University of Vienna
team. The two buildings are just 500 metres away from one another, but
fibre optics had to be fed through 1.5 kilometres of sewage system to make
the link.

Zeilinger says in principle it should be possible to extend this link to 20
kilometres. Beyond this distance it becomes difficult to transmit single
photons reliably.

In June 2003 the same team at the University of Vienna transmitted
entangled photons through free space across the river Danube.

The commercial quantum cryptographic devices that exist already, made by
companies like ID Quantique and MagiQ, use different principles to create a
secure key. They also use weak light pulses instead of individual photons.

 Because these pulses must be sufficiently weak to guarantee security, more
sensitive detectors are required, says Tim Spiller, a quantum
communications researcher at Hewlett-Packard's research laboratory in
Bristol, UK. He notes that using pairs of entangled photons would make it
easier to guarantee absolute secrecy.


-- 
-----------------
R. A. Hettinga <mailto: rah at ibuc.com>
The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
44 Farquhar Street, Boston, MA 02131 USA
"... however it may deserve respect for its usefulness and antiquity,
[predicting the end of the world] has not been found agreeable to
experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'