Group Seminar at LMU: Enhancing Quantum Key Distribution with single-photon sources based on semiconductor quantum dots
Tim Hebenstreit,University of Jena
Group Seminar at LMU and zoom
Monday, April 24th, 09:00am (MEZ)
B84 with quantum dot sources in LA excitation
The field of Quantum Technologies is a research area which is largely emerging in recent years. There is a wealth of promising real-world applications – one of them being Quantum Key Distribution (QKD). The first QKD scheme by Bennett and Brassard from 1984 is still a primitive and test bed for QKD experiments.  Recent theoretical work from Bozzio et al. has shown that quantum dot sources (QDS) in longitudinal phonon-assisted (LA) excitation can outperform Poisson-distributed sources (PDS) such as attenuated lasers that are usually used.  Within this work we plan to test the BB84 protocol with such quantum dot sources in LA excitation to demonstrate the improved distance scaling with respect to PDS.  Figure 1 shows the setup built to carry out the demonstration. Alice is operating the QDS and sends the single-photons to Bob. She encodes information in the polarization basis using a quarter- and a half-wave plate (QWP, HWP). The quantum channel between Alice and Bob is simulated using a variable optical attenuator (VOA). Bob on the receiving side operates a polarimeter which can measure the polarization of the photon sent by Alice. For the detection of the single-photons he uses high efficient (>90 %) superconducting nanowire single-photon detectors (SNSPD). We expect to demonstrate that QDS are able to outperform PDS in terms of secret key rate when the collection efficiency η from the QDS is above a threshold of 34 %.  This would allow for a better distance-scaling of QKD.
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