Time-entanglement is a promising resource for the implementation of quantum communications over standard fiber networks. In particular, photonic qudits can enhance the performance of quantum communication, including quantum key distribution, in terms of noise robustness, quantum information content, distance reach, as well as security and secret key rates. However, time-entangled photonic qudits are not ready yet to be fully exploited for quantum communications in fiber networks that are fully compatible with standard telecommunication architecture. Here, we demonstrate the implementation of telecommunication-compatible quantum communications based on picosecond-spaced time-entangled qudits. To this end, we make use of an integrated photonic chip comprising a cascade of programmable interferometers and a spiral waveguide. We use entangled qudits to implement high-speed quantum key distribution, chip-to-chip entanglement distribution, and quantum state propagation over 60 km of standard fiber. Our results show the potential of time-entangled qudits for high-speed quantum communications in telecommunication-compatible architecture.
Quantum technologies harness nonclassical features of particles, here, photons, to develop novel, efficient, and precise devices for information processing applications. Superposition, entanglement, as well as the coherent manipulation of quantum states are at the heart of the second quantum revolution (quantum 2.0) which targets the development of secure cryptographic systems, complex computation protocols, and more. Emerging quantum architectures rely on the realistic implementation of photonic schemes which are scalable, resource-efficient, and compatible with CMOS technologies as well as fiber networks. This work demonstrates current schemes utilized for time-/frequency-bin entanglement generation and processing by leveraging existing telecommunications and integrated photonics infrastructures.
We review our work on implementing integrated QFC sources based on microring resonators for on-chip generation of two- and multi-photon time-bin entangled states, d-level frequency-entangled photon pairs, and multipartite d-level cluster states. We also present our recent progress on telecom-compatible, scalable, time-entangled two-photon qubits using on-chip Mach-Zehnder interferometers (MZI) in combination with spiral waveguides. Both approaches are highly cost-effective, efficient, and practical, since we coherently manipulate the time and frequency modes through standard fiber-linked components that are compatible with off-the-shelf telecommunications infrastructures. Our work paves the way for robust sources and processors of complex photon states for future quantum technologies.
In this contribution we report on a novel approach for pump and stokes pulse generation in extremely compact all-fiber
systems using parametric frequency conversion (four-wave-mixing) in photonic-crystal fibers. Representing a
completely alignment-free approach, the all-fiber ytterbium-based short-pulse laser system provides intrinsically
synchronized tunable two-color picosecond pulses emitted from a single fiber end. The system was designed to address
important CH-stretch vibrational resonances. Strong CARS signals are generated and proved by spectroscopic
experiments, tuning the laser over the resonance of toluene at 3050cm-1. Furthermore the whole laser setup with a
footprint of only 30x30cm2 is mounted on a home-built laser-scanning-microscope and CARS imaging capabilities are
verified. The compact turn-key system represents a significant advance for CARS microscopy to enter real-world, in
particular bio-medical, applications.
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