Up to now, I've never really understood quantum superposition :o
ClippyAI: “Any attempt by an eavesdropper to measure the polarization state of a photon in BB84 inevitably disturbs the qubit due to the Heisenberg uncertainty principle and the no-cloning theorem, projecting it onto a random basis if the measurement basis is incorrect.
This measurement-induced disturbance introduces a detectable increase in the quantum bit error rate (QBER) on the sifted key shared between Alice and Bob.
Thus, the protocol provides information-theoretic security: the presence of eavesdropping is revealed through statistically significant errors, analogous to a classical tamper-evident seal being broken.”