Quantum Devices

Future development of quantum communication and information processing (QCIP) will strongly rely on the development of miniaturized and reliable optical components. In our group we approach this goal by harnessing the potential of integrated optics. We develop integrated optical devices and circuits specifically designed for single photon (pair) generation, quantum state manipulation and storage.

The generation of single photons and single photon pairs is a prerequisite for most quantum optical experiments (either for fundamental research or even for practical applications like e.g. quantum key distribution). Therefore, some of our current activities address the development of rugged and efficient photon (pair) sources.

The capability to distribute entanglement to remote locations is a precursor for future quantum systems. Of particular interest are entanglement-based quantum communication systems compatible with existing standard fiber telecom networks. Therefore, the development of telecom compatible, compact and reliable sources of entangled photons is a prerequisite to pave the way for a successful implementation of future quantum information technologies into real world applications. Therefore, some of our current activities address the development of rugged and efficient entangled photon (pair) sources.

Currently, the most prominent ideas in Quantum Information Processing (QIP) rely on the transmission of quantum states in the optical range, thus photons are used as quantum information carriers ('flying qubits'). In many cases, however, the optical frequencies at which quantum information can be generated, stored or processed locally differ substantially from each other and more importantly from the spectral range of optimal transmission in optical fibers. While atoms, ions and other solid state systems used for that purpose have transitions in the UV- and visible range, efficient optical…

In our group, we aim for increasing integration density, complexity and functionalities of devices in PPLN and PPKTP waveguide. As one example, we combined two different photon pair sources in a sequence of periodically poled areas together with a waveguide-based passive directional coupler.

The device (see Figure 1) is capable to generate photonic triplets by cascaded parametric down-conversion [1], which are known to be the fundamental entities for more exotic quantum states like Greenberger-Horne-Zeilinger states and Werner states.

Integrated optical devices in LiNbO3 have been developed since almost 40 years. In the past decades a multitude of devices has been demonstrated. Some of them – in particular electro-optic modulators – have become successful commercial products. Most of the device developments in the past were dedicated for applications in telecommunications. Our vision is to benefit from these experiences and adapt them to the challenging demands required for quantum optical applications.

By developing efficient and specifically tailored PDC sources the potential of integrated quantum devices in LiNbO3 is…