Quantum cryptography

Quantum tips and techniques provide far more secure methodologies for various cryptographic tasks facilitating quantum information theory. Under current commercial communication systems, it is primarily government bodies and a few high-end security companies that are interested in quantum cryptographic techniques. A few firms have started providing networking solutions formulated on quantum mechanics—for example, Swiss Quantum, MagiQ, etc.

One of the most fundamental aspects of any cryptographic system is the key distribution between sender and receiver. Quantum Key Distribution (QKD) is one of the most well established aspects of cryptography, governed by the laws of physics. In our quantum channel, the sender is Alice and the receiver is Bob. Now, as we have seen earlier, qubits follow the ‘no-cloning’ principle. So, if any eavesdropper tries to grasp the state of the qubit (i.e., polarisation) during the secret key exchange between Alice and Bob, the victim qubit is destroyed (either its polarisation, spin or both) and, hence, the eavesdropper is unable to decode the qubit. Bob gets a qubit with a failed checksum (a protocol to check data integrity) and asks Alice for retransmission. Thus, the only overhead is the retransmission of the victim qubit by Alice.

In 1984, Charles Bennett and Gilles Brassarad (BB84) formulated a protocol for quantum key distribution. It assumes a quantum channel for key distribution and classical channel