Compare and contrast different Quantum Key Distribution (QKD) protocols, such as BB84 and E91.

Quantum Key Distribution (QKD) protocols are at the forefront of secure communication, leveraging the principles of quantum mechanics to create unbreakable encryption keys. Two prominent QKD protocols, BB84 (Bennett-Brassard 1984) and E91 (Ekert 1991), differ in their approaches while achieving the same goal of secure key distribution. Below, I'll compare and contrast these two QKD protocols: BB84 Protocol: 1. Basis of Security: - BB84 relies on the principle of quantum indeterminacy. It uses the properties of quantum bits (qubits) to detect any eavesdropping attempts during key distribution. 2. Encoding and Measurement: - Alice, the sender, randomly encodes each qubit in one of two bases (rectilinear or diagonal). She transmits the qubits to Bob. - Bob randomly chooses one of the two bases to measure each received qubit. - If Bob chooses the correct basis (matching Alice's), he will obtain the correct measurement result. Otherwise, he has a 50% chance of measuring incorrectly. 3. Key Distillation: - Alice and Bob publicly compare which bases ....