China successfully launched the world's first quantum satellite from the Jiuquan Satellite Launch Center in northwestern Gobi Desert at 1:40 am on Tuesday. [Photo/Xinhua]

Spooky & entangled

Quantum physics is the study of the basic building blocks of the world at a scale smaller than atoms. These tiny particles behave in a way that could overturn assumptions of how the world works.

One of the strange properties of quantum physics is that a tiny particle acts as if it's simultaneously in two locations -- a phenomenon known as "superposition." The noted interpretation is the thought experiment of Schrodinger's cat -- a scenario that presents a cat that may be simultaneously both alive and dead.

If that doesn't sound strange enough, quantum physics has another phenomenon which is so confounded that Albert Einstein described as "spooky action at a distance" in 1948.

Scientists found that when two entangled particles are separated, one particle can somehow affect the action of the far-off twin at a speed faster than light.

Scientists liken it to two pieces of paper that are distant from each other: if you write on one, the other immediately shows your writing.

In the quantum entanglement theory, this bizarre connection can happen even when the two particles are separated by the galaxy.

By harnessing quantum entanglement, the quantum key technology is used in quantum communications, ruling out the possibility of wiretapping and perfectly securing the communication.

A quantum key is formed by a string of random numbers generated between two communicating users to encode information. Once intercepted or measured, the quantum state of the key will change, and the information being intercepted will self-destruct.

According to Pan, scientists also plan to test quantum key distribution between QUESS and ground stations in Austria. Italy, Germany and Canada, as they have expressed willingness to cooperate with China in future development of quantum satellite constellations, said Pan.