1. Quantum Encryption Cryptography’s Holy Grail by Samantha Matthews

2. Conventional Encryption  Data transmission is asynchronous.  Data are sent in groups of photons and translated by the receiving computer.  The encryption key is sent embedded in the data stream and can be intercepted in transit without either party’s knowledge.

3. Quantum Encryption  Data transmission is synchronous.  Data are sent in weak pulses of photons.  The physical behavior of the particles themselves gives the receiver the encryption key.  If a third party interrupts the data stream, the encryption key is rendered useless and both parties are alerted.  The encryption key isn’t in the message, it is the message.

4. Why Quantum Encryption Works  Subatomic particles can exist in multiple states until something interacts with them and changes those states.  Heisenberg’s Uncertainty Principle  p  x  1/2*h/2   p  x  1/2*h/2  We can know the location or linear momentum of a particle, but not both. We can know the location or linear momentum of a particle, but not both.  Think of Schrödinger's cat, a quantum mechanical outgrowth of this principle.

5. Why Quantum Encryption Works, Part 2  It makes use of quantum entanglement, the interdependency of the physical states of quantum particles.  Changing the state of one particle (through observation) changes the state of other particles around it.

6. How Quantum Encryption Works on the Sender’s End  A laser separates individual photons and sends them to an instrument called a modulator.  The modulator sends the photons to other network nodes via fiber-optic cable.  The photons are encoded by sending them at different time intervals. Chip Elliot, an engineer for BBN Technologies, next to a quantum cryptograph.

7. How Quantum Encryption Works on the Receiver’s End  The receiver accepts the photons and examines their modulation. If it matches the original one, the encryption key is saved and used to decode data sent over the network through conventional methods, such as the Internet. Martin Jasper of Boston University examines a single photon detector module.

8. Why Quantum Encryption Is Needed  Many researchers are currently trying to develop quantum computers, which are believed to be capable of exponentially greater computing power than today’s supercomputers.  If quantum computers become a reality before quantum encryption does, modern encryption methods could become obsolete.

9. Applications of Quantum Encryption  Governmental and intelligence operations  Financial and business transactions  Personal encryption (files, e-mail)  Many things no one’s thought of yet

10. More Information  I found these websites useful.  http://www.cs.caltech.edu/~westside/quantum- intro.html http://www.cs.caltech.edu/~westside/quantum- intro.html http://www.cs.caltech.edu/~westside/quantum- intro.html  http://www.qubit.org/library/intros/crypt.html http://www.qubit.org/library/intros/crypt.html  http://www.upscale.utoronto.ca/GeneralInterest/Harriso n/QuantTeleport/QuantTeleport.html http://www.upscale.utoronto.ca/GeneralInterest/Harriso n/QuantTeleport/QuantTeleport.html http://www.upscale.utoronto.ca/GeneralInterest/Harriso n/QuantTeleport/QuantTeleport.html  I found very useful an article from the Oct. 4, 2004 St. Louis Post-Dispatch; a somewhat earlier version can be found at http://www.nashuatelegraph.com/apps/pbcs.dll/article? AID=/20040926/BUSINESS01/209260303 http://www.nashuatelegraph.com/apps/pbcs.dll/article? AID=/20040926/BUSINESS01/209260303 http://www.nashuatelegraph.com/apps/pbcs.dll/article? AID=/20040926/BUSINESS01/209260303