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Q: Fachverband Quantenoptik und Photonik
Q 41: Poster: Quantum Optics and Photonics II
Q 41.2: Poster
Mittwoch, 13. März 2019, 16:15–18:15, S Fobau Physik
Estimating the Unpredictability in a Quantum Random Number Generator — •Johannes Seiler1, Thomas Strohm2, and Wolfgang P. Schleich1 — 1Institut für Quantenphysik and Center for Integrated Quantum Science and Technology (IQST), Universität Ulm — 2Robert Bosch GmbH
For random number generators, unpredictability, i.e. the condition that the random numbers are neither predictable by any model, nor an attacker can obtain enough information in order to predict them, often plays an important role, e.g. when they are used in secure communication protocols. Due to the physical nature of the generation process and the inherent indeterminism of quantum theory, a quantum random number generator (QNRG) offers at least theoretically the possibility to create such unpredictable random numbers. Unfortunately, real life implementations of QRNGs usually suffer from imperfections that open the door for an attacker to get at least partial information about the generated numbers. We discuss the unpredictability of a realistic QRNG by exploiting an elementary two-qubit scheme, modeling the random number generator and its environment. We show that the unpredictability crucially depends on the entanglement of these qubits. Based on a fully quantum mechanical calculation we provide an upper bound for the information accessible to an attacker, when the user knows the density matrix of his subsystem, independent of any further restrictions. Moreover, for certain restrictions on the attacker’s measurement, we propose a procedure on how to reduce this upper bound.