Composable free-space continuous-variable quantum key distribution using discrete modulation

• URL: http://arxiv.org/abs/2410.12915v1
• Date: Wed, 16 Oct 2024 18:02:53 GMT
• Title: Composable free-space continuous-variable quantum key distribution using discrete modulation
• Authors: Kevin Jaksch, Thomas Dirmeier, Yannick Weiser, Stefan Richter, Ömer Bayraktar, Bastian Hacker, Conrad Rösler, Imran Khan, Stefan Petscharning, Thomas Grafenauer, Michael Hentschel, Bernhard Ömer, Christoph Pacher, Florian Kanitschar, Twesh Upadhyaya, Jie Lin, Norbert Lütkenhaus, Gerd Leuchs, Christoph Marquardt,
• Abstract summary: Continuous-variable (CV) quantum key distribution (QKD) allows for quantum secure communication. We present a CV QKD system using discrete modulation that is especially designed for urban atmospheric channels. This will allow to expand CV QKD networks beyond the existing fiber backbone.
• Score: 3.864405940022529
• License:
• Abstract: Continuous-variable (CV) quantum key distribution (QKD) allows for quantum secure communication with the benefit of being close to existing classical coherent communication. In recent years, CV QKD protocols using a discrete number of displaced coherent states have been studied intensively, as the modulation can be directly implemented with real devices with a finite digital resolution. However, the experimental demonstrations until now only calculated key rates in the asymptotic regime. To be used in cryptographic applications, a QKD system has to generate keys with composable security in the finite-size regime. In this paper, we present a CV QKD system using discrete modulation that is especially designed for urban atmospheric channels. For this, we use polarization encoding to cope with the turbulent but non-birefringent atmosphere. This will allow to expand CV QKD networks beyond the existing fiber backbone. In a first laboratory demonstration, we implemented a novel type of security proof allowing to calculate composable finite-size key rates against i.i.d. collective attacks without any Gaussian assumptions. We applied the full QKD protocol including a QRNG, error correction and privacy amplification to extract secret keys. In particular, we studied the impact of frame errors on the actual key generation.

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