Quantum Algorithms Database
E91 Quantum Key Distribution
A quantum key distribution protocol based on entangled particle pairs and Bell inequality tests rather than single-photon polarization.
Year
1991
Inventor(s)
Artur Ekert
Speedup Type
No Speedup Claimed
Difficulty
★★★☆☆
The Problem
Establishing a shared secret key with security based directly on the foundational properties of quantum entanglement.
How It Works
Distributes entangled particle pairs to both parties; measuring them in different bases and checking for Bell inequality violations both generates the key and detects eavesdropping.
Real-World Impact
Connects practical cryptography directly to the foundational tests of quantum mechanics (Bell's theorem), and underlies some modern device-independent QKD schemes.