QUANTUM CRYPTOGRAPHY

Quantum cryptography uses physics to generate a key that realises on the properties of light, in particular, photons. A photon is a tiny particle of light that is too small to be seen individually. All light is made up of photons; not only visible light, but also radio waves, television broadcast, x-rays, ultraviolet and so on. The difference between all of these applications is the wavelength of the radiation involved.
       
Photons have no mass and travel at the speed of light. They have another property known as polarisation which, through quantum mechanics enables a secret key to be sent from the sender to the receiver. This key can then be used to decrypt an encoded message sent over a public channel such as the internet.

The particular quantum properties of photons mean that if an eavesdropper looks at the secret key, a change occurs to the particles of light being observed. The receiver would then know that something had changed and that their communications might be compromised.

So the main advantage of quantum cryptography over conventional cryptography is the 

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