The Parity Bit in Quantum Cryptography

An n-bit string is encoded as a sequence of non-orthogonal quantum states. The parity bit of that n-bit string is described by one of two density matrices, ρ (n) 0 and ρ (n) 1 , both in a Hilbert space of dimension 2 . In order to derive the parity bit the receiver must distinguish between the two density matrices, e.g., in terms of optimal mutual… CONTINUE READING