Quantum-locked key distribution at nearly the classical capacity rate

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Information Theory

Background:

• Quantum data locking enables strong encryption, violating classical one-time pad security by using minimal keys for extensive data.
• A significant gap exists between two quantum cryptography security measures: Holevo information and accessible information.

Purpose of the Study:

• To establish accessible information as a practical security criterion in quantum cryptography.
• To introduce a novel quantum key generation protocol for memoryless qudit channels.

Main Methods:

• Investigating the role of eavesdropper quantum memory coherence time.
• Developing a secret key generation protocol for qudit channels.

Main Results:

• Accessible information becomes a sensible security criterion when eavesdropper memory coherence time is bounded.
• A new protocol achieves high secret key generation rates in symmetric qudit channels (e.g., erasure, depolarizing).

Conclusions:

• The findings bridge theoretical security gaps in quantum cryptography.
• The protocol offers efficient secret key generation, approaching classical capacity limits under specific conditions.