Erlangen 2022 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 28: Quantum Information (Quantum Communication) I

Q 28.4: Talk

Wednesday, March 16, 2022, 11:15–11:30, Q-H12

Temporal mode decoding with a multi-output quantum pulse gate — •Laura Serino, Jano Gil-Lopez, Werner Ridder, Raimund Ricken, Christof Eigner, Benjamin Brecht, and Christine Silberhorn — Paderborn University, Department of Physics, Integrated Quantum Optics, Institute for Photonic Quantum Systems (PhoQS), Warburgerstr. 100, D-33098 Paderborn, Germany

Quantum key distribution (QKD) is a secure communication method that allows two parties to encrypt a message through a random secret key encoded in the degrees of freedom of photons. Notably, high-dimensional (HD) QKD is characterized by a higher level of security and efficiency with respect to its binary counterpart, and temporal modes (TMs) represent a convenient encoding basis.

In this work, we demonstrate a multi-output quantum pulse gate (mQPG), a device based on dispersion-engineered sum-frequency generation in periodically poled lithium niobate waveguides which can serve as a receiver for HD QKD. The mQPG allows one to project an input state at the same time onto all the elements of a HD TM basis and map the result of each projection onto a distinct output frequency.

To achieve multi-channel operation, the poling structure is engineered to generate multiple phase-matching peaks. Appropriate shaping of the pump spectrum maps each TM to one phase-matching peak and hence output frequency. A time-of-flight measurement achieves frequency-demultiplexing of the output beam, mapping the input TM to the arrival time of the photon. As proof of principle, we show a five-dimensional detector tomography obtained with this method.