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Quantum cryptography

How quantum technologies enable uncrackably secure communication.

Enter quantum computers

Large quantum computers will be able to crack most existing (classical) encryption mechanisms.

The first factorization performed on a quantum computer in the year 2001.

Mathematically secure: Quantum cryptography

Quantum cryptography is mathematically secure because the laws of nature prohibit eavesdropping on a quantum encrypted message.

The BB84 quantum cryptography algorithm

The goal of cryptography: Two parties share a key, whereas eavesdroppers are left out of the game.
One way to implement the first two steps of the algorithm: Alice prepares single photons and sends them to Bob. The photons are prepared in either one of four states, right or left circularly polarized light or horizontal/vertical linearly polarized light.
The third step: Bob makes a public facebook post explicitly stating the randomly chosen basis he measured the qubits in. Alice checks her feed and sees Bob’s post. She’s like ‘whoa Bob, shit’s getting real’. She makes a public post announcing whether she had prepared them in the same basis or not. By the way, this can all happen publicly because the information about the measurement basis is useless without the measurement results.
An example for BB84: Alice prepares 10 qubits in a random basis (1) and sends them to Bob. Bob measures in a random basis gettting some results (2), afterwards they both broadcast their basis and discuss them, trashing the qubits which were measured in the wrong basis by Bob (3). On half the qubits which are okay, they also discuss the results of the measurement. If they get matching results, they accept the measurement outcomes of the qubits they are left with as their key, in this case the qubits 2, 5 and 10.

The base of quantum security: quantum information can not be copied!

Unlike classical information, quantum information can not be cloned.

Quantum cryptography is already used today

The state of Geneva already uses Quantum Key Distribution for 10 years in its elections.

Quantum technologies are on the rise

Trying to make sense of quantum physics with the help of green tea.