Hannover 2016 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 62: Quantum Information: Quantum Computing and Communication III
Q 62.6: Talk
Friday, March 4, 2016, 12:15–12:30, e214
Large-Alphabet Time-Frequency Quantum Key Distribution — •Jasper Rödiger1,2, Nicolas Perlot1, Matthias Leifgen2, Robert Elschner1, Roberto Mottola2, Oliver Benson2, and Ronald Freund1 — 1Fraunhofer Heinrich-Hertz Institut, Berlin, Germany — 2Nanooptik AG, Humboldt-Universität zu Berlin, Berlin, Germany
We investigate a quantum key distribution (QKD) scheme, referred to as time-frequency (TF-) QKD, based on the time-frequency uncertainty relation. It is a BB84-like QKD protocol with the two bases being modulations in time and frequency, namely the pulse position modulation (PPM) and frequency shift keying (FSK). Assuming one photon per pulse, measuring in one of the bases increases the measurement uncertainty in the other and thus destroys most information encoded there, similar to BB84.
TF-QKD is mostly compatible to classical communication technologies. Since PPM is a well-established coding technique in free-space communication and polarization is free for duplexing, TF-QKD is very well suited for free-space communication. In addition it is possible to use a large alphabet, thus to send a high number of bits per photon.
With a proof-of-principle experiment, using two symbols per basis, it was possible to distribute a key with a sifted key rate of 12 kbit/s. More symbols per basis and a higher key-rate are the subjects of current investigation. Numerical simulations identified optimal pulse relations and showed that a larger alphabet increases the secret key rate.