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Security of Quantum Key Distribution Using d -Level Systems

2002; American Physical Society; Volume: 88; Issue: 12 Linguagem: Inglês

10.1103/physrevlett.88.127902

1092-0145

Nicolas J. Cerf, Mohamed Bourennane, Anders Karlsson, Nicolas Gisin,

Quantum Mechanics and Applications

We consider two quantum cryptographic schemes relying on encoding the key into qudits, i.e., quantum states in a $d$-dimensional Hilbert space. The first cryptosystem uses two mutually unbiased bases (thereby extending the BB84 scheme), while the second exploits all $d+1$ 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.