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Quantum Physics Meets Computer Science

Euclidean

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When quantum physics deals with the smallest of small particles, and computer science deals with elaborate algorithms and problem solving, you might wonder why these two sciences would ever cross paths, but research since the 1980s has spawned a new science from these two already elaborate fields: quantum computing.

In quantum computing, rather than using ones and zeros to represent data, the unique quantum state of electrons is used to encode information. This principle is particularly useful in one of computer science's sub-disciplines: cryptography. Cryptography is the study of encrypting and decrypting secret messages and other information. It in itself is a dense field of study because of all the tricks hackers have devised to crack security systems and steal valuable information. Quantum computing though, promises to take cryptography to a whole new level.

In traditional cryptographic systems, messages are encoded and decoded using a special key known only to the sender and receiver, but in quantum computing, the individual and unique spins of electrons are known only to the sender and receiver. What is the advantage? Well, if a hacker, for instance, decides to listen in on the conversation, the spins of the electrons will change, and the sender and receiver will know to stop communicating.

How does this happen? How can a electron's spin change just by the mere act of observing it? Remember that we see things because photons enter our eyes. Sensors are designed to observe electrons or other atomic and subatomic particles using photons just like the human eye. Recall, though, that a photon is a bundle of energy. Thus, whenever a photon strikes an electron, it gives the electron enough energy to change the electron's trajectory. Thus, the mere act of observing an electron changes the electron's motion. This conundrum is the reason for The Uncertainty Principle in quantum physics, which says that the more you know about the momentum of a particle, the less you know about its position, and the more you know about its position, the less you know about its momentum.

This powerful feature - knowing exactly when someone eavesdrops on a conversation - makes quantum encryption virtually unbreakable. Of course, quantum cryptography relies on waves being sent between the sender and receiver, and sometimes it can be difficult to get a clear signal, making quantum cryptography somewhat unreliable at the moment, but with advances in technology, and an evolution in wireless communication, we may one day live in a world where messages are sent safely to their destinations and we will no longer have to worry about hackers intercepting sensitive information.

You can read more about a recent study in quantum cryptography here:

http://www.sciencenews.org/view/generic/id/349318/description/News_in_Brief_Quantum_cryptography_takes_flight



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