Online services have many techniques in place to protect the credit card numbers and other personal information that you send to them. To protect your information, they scramble, or encrypt, your data. When the encrypted information arrives at their site, they unscramble, or decode, information by using a key, and mathematical instructions. Anyone who tries to intercept the encrypted information will get a meaningless string of numbers.
For bank transactions, a key usually contains a very large number, sometimes hundreds of digits long. And the only way to break the key is to find the two unique numbers that, when multiplied together, create that big number. Currently, even the world's fastest supercomputers would take months to break up these numbers. But someday computers may catch up and break these codes. That's where quantum encryption comes in.
Quantum encryption protects data in another way. In quantum cryptography, data is still encoded and a key is still needed to decode it. But it has another safeguard. The information is sent as a stream of photons, or particles of light. Anyone who tries to intercept the information has to detect some of the photons. But according to a law of quantum physics, known as the Heisenberg uncertainty principle, detecting the photons will cause an irreversible change in them, and this change will be instantly detected by sender and receiver. They can then stop the transmission well before the eavesdropper gets enough information to decode the message. Since the dawn of quantum physics, Heisenberg's uncertainly principle has told us that we can't ever gain complete information on any object in nature -- and now it is being used to protect our privacy for important transactions.