Dr. Christoph Marquardt Profile

Dr. Christoph Marquardt

at Max-Planck-Institut fur die Physik des Lichts

SPIE Involvement:

Author

Proceedings Article | 1 August 2021 Presentation + Paper

Goals and feasibility of the deep space quantum link

Luca Mazzarella, Makan Mohageg, Dmitry Strekalov, Aileen Zhai, Ulf Israelsson, Andrey Matsko, Nan Yu, Charis Anastopoulos, Bradley Carpenter, Jason Gallicchio, Bei-Lok Hu, Thomas Jennewein, Paul Kwiat, Shih-Yuin Lin, Alexander Ling, Christoph Marquardt, Matthias Meister, Brian Moffat, Raymond Newell, Albert Roura, Christian Schubert, Giuseppe Vallone, Paolo Villoresi, Lisa Wörner

Proceedings Volume 11835, 118350J (2021) https://doi.org/10.1117/12.2593986

KEYWORDS: Quantum physics, Teleportation, General relativity, Quantum optics, Quantum mechanics, Photons, Satellites, Particles, Quantum communications, Physics

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Proceedings Article | 7 October 2019 Paper

Stratospheric QKD: feasibility analysis and free-space optics system concept

Florian Moll, Thierry Botter, Christoph Marquardt, David Pusey, Amita Shrestha, Andrew Reeves, Kevin Jaksch, Kevin Gunthner, Oemer Bayraktar, Christian Mueller-Hirschkorn, Alberto Diago Gallardo, Dionisio Diaz Gonzalez, Wenjamin Rosenfeld, Peter Freiwang, Gerd Leuchs, Harald Weinfurter

Proceedings Volume 11167, 111670H (2019) https://doi.org/10.1117/12.2539076

KEYWORDS: Quantum key distribution, Free space optics, Telescopes, Adaptive optics, Electronics, Receivers, Atmospheric particles, Polarization, Atmospheric modeling, Telecommunications

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Quantum key distribution (QKD) is one of the most mature quantum technologies and can provide quantum-safe security in future communication networks. Since QKD in fiber is limited to a range of few hundred kilometers, one approach to bridge continental scale distances may be the use of high altitude pseudo satellites (HAPS) as mobile trusted nodes in the stratosphere. In parallel, free-space laser communication for high rate data transmission has been a subject of research and development for several decades and its commercialization is progressing rapidly. Important synergies exist between classical free-space communication and QKD systems since the quantum states are often implemented using the same degrees of freedom such as polarization or field amplitude and phase. These synergies can be used to benefit from the progress in classical free-space laser communication in QKD applications. In this paper, the use case of QKD in a stratospheric environment is described wherein HAPS may serve as relay station of secret keys and encrypted data. The mission scenario and HAPS capabilities are analyzed to derive special requirements on the stratospheric laser terminal, the link geometry and the ground segment with respect to a feasibility demonstration. To obtain a flexible and compatible system, discrete variable and continuous variable QKD protocols are considered to be implemented side by side in the HAPS payload. Depending on the system parameters, it can be beneficial to use the one or the other kind of protocol. Thus, a direct comparison of both in one and the same system is of scientific interest. Each of the protocols has particular requirements on coupling efficiency and implementation. Link budget calculations are performed to analyze possible distances, key rates and data transmission rates for the different schemes. In case of the QKD system, the mean coupling efficiency is of main interest, i.e. signal fluctuations arising from atmospheric turbulence must be taken into account in the security proof, but the buffered key generation relaxes real-time requirements. This is different to classical communications, where the corresponding fading loss must be assessed. A system architecture is presented that comprises the optical aircraft terminal, the optical ground terminal and the most important subsystems that enable implementation of the considered QKD protocols. The aircraft terminal is interfaced with the dedicated quantum transmitter module (Alice) and the ground station with the dedicated quantum receiver module (Bob). The optical interfaces are SMF couplings which put high requirements on the receiving optics, in particular the need for wave-front correction with adaptive optics. The findings of the system study are reviewed and necessary next steps pointed out.

Proceedings Article | 25 September 2017 Open Access

Quantum measurements of signals from the Alphasat TDP1 laser communication terminal

D. Elser, K. Günthner, I. Khan, B. Stiller, Ö Bayraktar, C. Müller, K. Saucke, D. Tröndle, F. Heine, S. Seel, P. Greulich, H. Zech, B. Gütlich, I. Richter, S. Philipp-May, Ch. Marquardt, G. Leuchs

Proceedings Volume 10562, 105623O (2017) https://doi.org/10.1117/12.2296184

KEYWORDS: Quantum key distribution, Quantum communications, Satellites, Laser communications, Astronomical imaging, Quantum cryptography, Satellite communications, Networks, Quantum optics, Adaptive optics

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Proceedings Article | 24 February 2017 Presentation + Paper

Laser based bi-directional Gbit ground links with the Tesat transportable adaptive optical ground station

Frank Heine, Karen Saucke, Daniel Troendle, Matthias Motzigemba, Hermann Bischl, Dominique Elser, Christoph Marquardt, Hennes Henninger, Rolf Meyer, Ines Richter, Zoran Sodnik

Proceedings Volume 10096, 100960Y (2017) https://doi.org/10.1117/12.2252826

KEYWORDS: Quantum key distribution, Telecommunications, Space operations, Atmospheric optics, Adaptive optics, Optical communications, Data communications, Relays, Satellites, Clocks, Receivers

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Proceedings Article | 7 December 2016 Presentation

Proof-of-principle test of coherent-state continuous variable quantum key distribution through turbulent atmosphere (Conference Presentation)

Ivan Derkach, Christian Peuntinger, László Ruppert, Bettina Heim, Kevin Gunthner, Vladyslav Usenko, Dominique Elser, Christoph Marquardt, Radim Filip, Gerd Leuchs

Proceedings Volume 9996, 999605 (2016) https://doi.org/10.1117/12.2242107

KEYWORDS: Quantum key distribution, Transmittance, Modulation, Information security, Computer security, Data modeling, Quantum information theory, Quantum information, Quantum physics, Fiber optics

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Continuous-variable quantum key distribution is a practical application of quantum information theory that is aimed at generation of secret cryptographic key between two remote trusted parties and that uses multi-photon quantum states as carriers of key bits. Remote parties share the secret key via a quantum channel, that presumably is under control of of an eavesdropper, and which properties must be taken into account in the security analysis. Well-studied fiber-optical quantum channels commonly possess stable transmittance and low noise levels, while free-space channels represent a simpler, less demanding and more flexible alternative, but suffer from atmospheric effects such as turbulence that in particular causes a non-uniform transmittance distribution referred to as fading. Nonetheless free-space channels, providing an unobstructed line-of-sight, are more apt for short, mid-range and potentially long-range (using satellites) communication and will play an important role in the future development and implementation of QKD networks. It was previously theoretically shown that coherent-state CV QKD should be in principle possible to implement over a free-space fading channel, but strong transmittance fluctuations result in the significant modulation-dependent channel excess noise. In this regime the post-selection of highly transmitting sub-channels may be needed, which can even restore the security of the protocol in the strongly turbulent channels. We now report the first proof-of-principle experimental test of coherent state CV QKD protocol using different levels Gaussian modulation over a mid-range (1.6-kilometer long) free-space atmospheric quantum channel. The transmittance of the link was characterized using intensity measurements for the reference but channel estimation using the modulated coherent states was also studied. We consider security against Gaussian collective attacks, that were shown to be optimal against CV QKD protocols . We assumed a general entangling cloner collective attack (modeled using data obtained from the state measurement results on both trusted sides of the protocol), that allows to purify the noise added in the quantum channel . Our security analysis of coherent-state protocol also took into account the effect of imperfect channel estimation, limited post-processing efficiency and finite data ensemble size on the performance of the protocol. In this regime we observe the positive key rate even without the need of applying post-selection. We show the positive improvement of the key rate with increase of the modulation variance, still remaining low enough to tolerate the transmittance fluctuations. The obtained results show that coherent-state CV QKD protocol that uses real free-space atmospheric channel can withstand negative influence of transmittance fluctuations, limited post-processing efficiency, imperfect channel estimation and other finite-size effects, and be successfully implemented. Our result paves the way to the full-scale implementation of the CV QKD in real free-space channels at mid-range distances.

Conference Committee Involvement (1)

Third International Conference on Optical Angular Momentum

4 August 2015 | New York, United States

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