Quantum 2025 – wissenschaftliches Programm
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MON: Monday Contributed Sessions
MON 1: QIP Implementations: Photons I
MON 1.5: Vortrag
Montag, 8. September 2025, 15:15–15:30, ZHG001
Phase stabilization of high-bandwidth squeezed and entangled states over 1km distributed optical fiber — •Sophie Verclas1, Benedict Tohermes1, and Roman Schnabel2 — 1Institut für Quantenphysik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg — 2Institut für Quantenphysik & Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg
Quantum Key Distribution (QKD) is a technology for secure communication between two parties, using the principles of quantum mechanics. Our continuous-variable QKD experiment implements a fiber-based scheme, connecting two laboratories in two separated buildings (building A and B). We set up an EPR entanglement source in building A, consisting of two squeeze lasers and overlapped their outputs at a 50/50 beamsplitter to generate two-mode squeezed states. They are shared between A and B via a 1km optical fiber. In both buildings, the states are measured with self built balanced homodyne detectors. Due to the entanglement, the results are random but also correlated and can be used to generate a secret key. Attacks on the channel and on devices in building B reduce the entanglement strength and can thus be quantified. A major challenge in this setup is the phase stabilization and synchronization between the two buildings. Here, I will introduce the experiment, discuss the problem of phase noise and our approach to a control scheme for its compensation. As a first result, I will show measurements for the phase lock of distributed squeezed states, which is an important first step towards stabilized entanglement.
Keywords: Quantum key distribution; Quantum noise lock; Squeezed light; Fiber link; Phase stabilization