High-Rate Field Demonstration of Large-Alphabet Quantum Key Distribution
MASSACHUSETTS INST OF TECH LEXINGTON LEXINGTON United States
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Quantum key distribution QKD enables secure symmetric key exchange for information-theoretically secure communication via one-time-pad encryption. QKD also enables frequent re-keying of symmetric block ciphers. A goal for QKD in both settings is to increase the secret-key generation rate. In metro-scale links, the detectors limit the rates attainable by single-photon-based QKD schemes the long reset time compared to the detection timing jitter of even advanced single-photon detector technologies caps the maximum secret-key rate for binary-encoded systems below what the optical channel could support. For a given detector technology, this cap can be raised by encoding photons in high-dimensional basis states qudits instead of qubits, so that each detected photon yields more information than would be possible under binary encoding 3. Here, we demonstrate a record QKD rate for three different channel losses using a new prepare-and-measure high-speed, large-alphabet QKD protocol, including the firstfield demonstration of large-alphabet QKD.
- Quantum Theory and Relativity