Second-generation quantum technologies can be applied in many areas where they enable the improvement of known technologies and open up fundamentally new possibilities. Examples include: Quantum communication makes it possible to secure communications against future, yet unknown, attacks; the increased performance of quantum computers through parallelization of computations brings the solution of previously intractable problems within reach; quantum simulators make it possible to simulate the behavior of complex quantum systems using other, highly controlled quantum systems. Components of quantum technology such as coherent optical memories promise new neuromorphic computer architectures for artificial intelligence and machine learning.
Our scientific mission at DLR and TU Berlin is to advance second generation quantum information technologies. The research interest of the FITS group focuses on the fundamentals of quantum communication and optical post-digital computing. In the area of quantum communications, we are interested in quantum repeater networks. In the area of post-digital computing, we are exploring optical neural networks for machine learning and photonic quantum computing architectures.
All these applications need single photon sources on the one hand and quantum memories as key components on the other hand. For both, but especially for the latter, there is still a considerable need for research before "real" applications can be realized.
Photonic quantum memories are devices that can store single photons in a quantum coherent manner. They are a so far missing key component for the second quantum revolution and enable a variety of new applications. For example, quantum networks promise demonstrable security in communications and also the possibility of connecting quantum computers and simulators for computation on distributed machines.
In our research, we focus on quantum memories implemented in room-temperature alkali vapor, a robust platform suitable not only for applications on the ground, but also onboard of satellites.
Single photon sources are devices that emit only a single photon at a time. As such, they are a key resource for all photonic quantum technologies. Ideally, a single photon source should (i) emit only one photon at a time, (ii) on demand, (iii) at a high generation rate, and (iv) in a well-defined state in a single spatial, temporal, and spectral mode. Furthermore, and very importantly, (v) different sources should be able to generate identical photons in a reproducible manner. Despite enormous research efforts, such an ideal source does not yet exist.
In our research, we focus on the most advanced single-photon sources available today, namely atom-like solid-state systems, e.g., semiconductor quantum dots and sources based on spontaneous parametric downconversion (SPDC).