arXiv subjects

Poul Kristensen

Publications and source records attributed to Poul Kristensen.

2 recordsLinked to original sources

arXiv2019

Orbital angular momentum states enabling fiber-based high-dimensional quantum communication

Quantum networks are the ultimate target in quantum communication, where many connected users can share information carried by quantum systems. The keystones of such structures are the reliable generation, transmission and manipulation of quantum states. Two-dimensional quantum states, qubits, are steadily adopted as information units. However, high-dimensional quantum states, qudits, constitute a richer resource for future quantum networks, exceeding the limitations imposed by the ubiquitous qubits. The generation and manipulation of such $D$-level systems have been improved over the last ten years, but their reliable transmission between remote locations remains the main challenge. Here, we show how a recent air-core fiber supporting orbital angular momentum (OAM) modes can be exploited to faithfully transmit $D$-dimensional states. Four OAM quantum states and their superpositions are created, propagated in a 1.2 km long fiber and detected with high fidelities. In addition, three quantum key distribution (QKD) protocols are implemented as concrete applications to assert the practicality of our results. This experiment enhances the distribution of high-dimensional quantum states, attesting the orbital angular momentum as vessel for the future quantum network.

quant-ph↗

arXiv2018

Discovery of Soliton Self-Mode Conversion in Multimode Optical Fibers

Nonlinear optical wave propagation manifests in a multitude of frequencies generated from quantum-noise, and selecting desired nonlinear products usually requires seeding the medium with extraneous waves, employing spatial or spectral filters, or operation in resonant cavities. This is especially true for multimode systems because of their high density of states. Here we report the discovery of a self-action effect, originating from quantum noise, leading to complete nonlinear optical conversion of an ultrashort soliton pulse between two distinct, spatially coherent eigenmodes that are frequency-separated by one Raman Stokes shift. That systematic nonlinear spatial reconfiguration occurs in fibers with mode counts exceeding 10,000, which are often deemed to be chaotic, points to the fundamental role of intermodal group velocity dispersion in the selection rules for multimode nonlinear optics. We demonstrate wideband spectral translations of ~70% of the carrier frequency, and the generation of record, Megawatt peak-power pulses in the biologically crucial 1300-nm spectral window, directly out of a flexible optical fiber. More generally, this novel nonlinear coupling mechanism may be applied to fibers or on-chip waveguides, and facilitate, power-scalable spatially coherent, ultrashort pulse generation from the visible to the mid-IR.

physics.optics↗