Abstract
We consider two quantum cryptographic schemes relying on encoding the key into qudits, i.e., quantum states in a -dimensional Hilbert space. The first cryptosystem uses two mutually unbiased bases (thereby extending the BB84 scheme), while the second exploits all available such bases (extending the six-state protocol for qubits). We derive the information gained by a potential eavesdropper applying a cloning-based individual attack, along with an upper bound on the error rate that ensures unconditional security against coherent attacks.
- Received 26 July 2001
DOI:https://doi.org/10.1103/PhysRevLett.88.127902
©2002 American Physical Society