Periodically poled lithium niobate waveguides (PPLN/W) are considered to be one of the most useful toolboxes for enabling quantum communication experiments. Thanks to the high optical confinement over longer lengths than in bulk configurations (a few cm in our case), such structures provide highly efficient non-linear interactions, i.e., in parametric downconversion, or sum and difference frequency generation regimes. Within the framework of long-distance quantum communication at telecom wavelengths, PPLN/Ws have therefore been proved to be a key ingredient for building ultrabright sources of time-bin, as well as polarization entangled photons, and for photonic quantum interfaces providing coherent wavelength conversions from telecom to visible wavelength range, and conversely. During the presentation, we will discuss some recent experimental advances regarding polarization entanglement sources and quantum interfaces.
Periodically poled lithium niobate waveguides (PPLN/W) are considered to be one of the most useful toolboxes for enabling quantum communication experiments. Thanks to the high optical confinement over longer lengths than in bulk configurations (a few cm in our case), such structures provide highly efficient non-linear interactions, i.e., in parametric downconversion, or sum and difference frequency generation regimes. Within the framework of long-distance quantum communication at telecom wavelengths, PPLN/Ws have therefore been proved to be a key ingredient for building ultrabright sources of time-bin, as well as polarization entangled photons, and for photonic quantum interfaces providing coherent wavelength conversions from telecom to visible wavelength range, and conversely. During the presentation, we will discuss some recent experimental advances regarding polarization entanglement sources and quantum interfaces.
Periodically poled lithium niobate waveguides (PPLN/W) are considered to be one of the most useful toolboxes for quantum communication experiments. Thanks to the high optical confinement over longer lengths than in bulk configurations (a few cm in our case), such structures provide highly efficient non-linear interactions, both in down- and up-conversion regimes. Within the framework of long-distance quantum communication at telecom wavelengths, PPLN/Ws have therefore been proved to be a key ingredient for building ultra-bright sources of energy-time, time-bin, as well as polarization entangled pairs of photons, up-conversion based detectors for telecom photon detection, photonic quantum interfaces for coherent wavelength conversion, and also for quantum relays in the entanglement swapping configuration.
Periodically poled lithium niobate waveguides (PPLN/W) are nowadays considered to be one of the most useful toolboxes for quantum communication experiments. Thanks to the high optical confinement over longer lengths than in bulk configurations (a few cm in our case), such structures provide highly efficient non-linear interactions, both in down- and up-conversion regimes. Within the framework of long-distance quantum communication at telecom wavelength, PPLN/Ws have therefore been proved to be a key ingredient for building ultra-bright sources of energy-time, time-bin, as well as polarization entangled pairs of photons, up-conversion based detectors for telecom photon detection and photonic quantum interfaces for coherent wavelength conversion, as well as quantum relays in the entanglement swapping configuration. During the presentation, we will discuss some recent experimental advances regarding two quantum relay scenarios employed to extend the maximum achievable distance of quantum communication. Based on picosecond regime operation, the first relies on the entanglement swapping configuration, and the other on single qubit teleportation using a telecom oriented chip dedicated to one-way quantum communication. In the first realization, we demonstrate that the utilization of PPLN/Ws and standard components available from the telecommunications industry, associated with the picosecond operation regime enables reaching near-perfect two-photon interference (or coalescence) while maintaining high effective photon pair rates. Using pairs of photons emitted around 1550 nm and appropriate filtering stages, we obtain the highest coalescence net visibility, i.e., of 99%, ever reported. As coalescence is seen a major step towards entanglement swapping, we believe that our picosecond guided-wave scheme provides an efficient trade-off between CW and femtosecond regimes, and emphasize why it should lead to realistic quantum relay and repeater schemes, namely by offering an reduced-constraint solution to the synchronization issue when two completely independent lasers are employed. We shall focus on our experimental demonstration and detail a comparative study of performance with similar reported experiments. As a second realization, we will give further directions towards the integration of several functions on a single optical chip, such as a photon pair generator and electro-optically controllable couplers. The idea is to realize a telecom-like quantum relay chip on lithium niobate through which teleportation of single qubits can be done so as to provide the necessary relay function in a compact, stable, efficient, and user-friendly fashion. We will discuss preliminary results obtained with this device for fully fiber-based one-way quantum communication systems. We will conclude by emphasizing the large potential of what we call "guided-wave quantum communication" developed in our laboratory.
The quantum nature of light at the single photon level allows for unique applications that classical physics neither predicts nor describes. Most notably, appropriate conditions may cause the states of photons with indistinguishable properties to become entangled, enabling novel approaches to quantum computation, secure communications, and metrology. \n \nAny operational quantum information network transporting entangled-photon states must establish a high-fidelity link between its distant nodes despite the inherent fragility of entangled states. However, the lack of a universal operating wavelength for all optical devices makes this a substantial challenge. Telecommunication fibers, entangled photon pair sources, quantum optical memories, and quantum repeaters all function in disparate spectral windows dictated by the properties of the materials used to fabricate them. Quantum frequency conversion (QFC), the single-photon limit of nonlinear parametric sum and difference frequency generation in optics, offers a bridge between spectral regions with full preservation of quantum state character, including entanglement. \n \nPeriodically poled optical waveguides in ferroelectric crystals are versatile tools in nonlinear optics. Confining the nonlinear interaction to a waveguide greatly enhances its efficiency compared to bulk optics. Periodic poling, the process of periodically inverting the domains of a ferroelectric medium using a strong electric field, enables a variety of quasi-phase matching configurations to engineer a desired nonlinear interaction. \n \nThis work concentrates on the design, development, fabrication, and characterization of a titanium-diffused periodically poled lithium niobate (Ti:PPLN) waveguide device. This device is designed to execute single-step quantum frequency conversion from 369.5nm to 1550nm in order to facilitate a quantum state transfer between standard fiber telecommunication wavelengths and an atomic quantum memory system employing trapped ytterbium ions. \n \nThe creation of phase matching conditions for such an extreme distance in frequency demands precise control of high magnitude electric fields on the single-micron scale. As the first demonstration of its kind in Ti:PPLN, the development of these devices included novel improvements to existing fabrication methods, improving the state-of-the-art of precision, quality, and yield for poling of ferroelectric crystals.
We report the realization of a fiber-coupled polarization entangled photon-pair source at 1310 nm based on a birefringent titanium in-diffused waveguide integrated into periodically poled lithium niobate. By making use of a dedicated and high-performance setup, we characterized the quantum properties of the pairs by measuring two-photon interference in both Hong–Ou–Mandel and standard Bell inequality configurations. For the two sets of measurements we obtained interference net visibilities reaching nearly 100%, which represent important and competitive results compared to those for the similar waveguide-based configurations already reported. These results prove the relevance of our approach as an enabling technology for long-distance quantum communication.
We describe the design and application of domain-engineered, periodically poled lithium niobate (PPLN) for use to produce entangled photons and for other tools in quantum information and communications. By specially designing and controlling the PPLN poling pattern, multiple nonlinear optical processes can be simultaneously phasematched. This capability can be used to generate polarization-entangled photon pairs through type-II spontaneous parametric downconversion. The single PPLN crystal is designed to produce both the |HV〉 and |VH〉 states where the downconverted photons are distinguishable by wavelengths, which enables generation of post-selection-free, polarization-entangled twin photons. We describe the design and fabrication of the PPLN crystal, and initial experimental results for downconversion of a 775 nm pump to 1532 nm and 1567 nm orthogonally polarized photons. We also discuss other applications of engineered optical frequency conversion for quantum information including the use of dual-wavelength upconversion as a beamsplitter to route or analyze photons.
We report the realization of a fiber coupled polarization entangled photon-pair source at 1310 nm based on a birefringent titanium in-diffused waveguide integrated on periodically poled lithium niobate. By taking advantage of an original setup, we characterized the quantum properties of the pairs by measuring two-photon interference in both Hong-Ou-Mandel and standard Bell inequality configurations. We obtained, for the two sets of measurements, interference net visibilities reaching nearly 100%, which represent the best results ever reported for similar waveguide-based configurations. These results prove the relevance of our approach as an enabling technology for long-distance quantum communication.