Quantum Algorithms Database
Six-State Quantum Key Distribution Protocol
An extension of BB84-style quantum key distribution using six measurement states instead of four, improving security against certain eavesdropping strategies.
Year
1998 (Bruss)
Inventor(s)
Dagmar Bruss
Speedup Type
No Speedup Claimed
Difficulty
★★★☆☆
The Problem
Establishing a shared secret key between two parties with even stronger security guarantees against intercept-and-resend eavesdropping attacks than the original BB84 protocol.
How It Works
Adds a third measurement basis to the standard BB84 setup, increasing the chance that any eavesdropping attempt is detected, at the cost of a higher fraction of discarded key bits.
Real-World Impact
One of several BB84 variants used in research and some commercial QKD systems, illustrating the ongoing refinement of quantum cryptography protocols beyond the original 1984 proposal.