BB84 Quantum Key Distribution (QKD) | Unconditionally Secure Keys
Quick Technical Answer:
BB84 is the pioneering Quantum Key Distribution (QKD) protocol devised by Bennett and Brassard in 1984. It uses conjugate measurement bases (+ and ×) and the no-cloning theorem to generate provably secure cryptographic keys immune to computational attacks.
Formula / Unitary:
\text{Bases: } \mathcal{Z} = \{|0\rangle, |1\rangle\}, \quad \mathcal{X} = \{|+\rangle, |-\rangle\}, \quad \text{QBER} > 11\% \implies \text{Abort}
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Frequently Asked Questions
How does BB84 detect an eavesdropper?
According to quantum mechanics, measuring a quantum state collapses it. If an eavesdropper (Eve) intercepts qubits in the wrong basis, she introduces errors into Alice and Bob's key, triggering an identifiable Quantum Bit Error Rate (QBER).