The basis of all our quantum-information experiments are single photons. One aim of our research is to develop and build efficient single-photon that generate pure, indistinguishable photons to be used in quantum-information experiments. In those experiments, described below, we use integrate on-chip technology to manipulate the photons. State-of-the-art single-photon detectors facilitate measuring the photons with a high efficiency, a prerequisite for all our experiments.
Secure quantum computing in quantum networks
A focus of our research is quantum cloud computing and the question how distributed quantum computing can be realized in quantum networks. Quantum computers do not only offer speed-ups in data processing, but also allow one to preserve the privacy of a computation. This allows performing delegated computations in quantum networks, where clients can access the resources of a more computationally-powerful quantum server without divulging the content of the requested computation.
Quantum computation and error correction
The implementation of quantum algorithms with practical applications is another focus of our research. For example, quantum computers can solve systems of linear equations exponentially faster than classical computers. As large systems of linear equations appear in almost every scientific discipline, this is one of the most promising applications of a quantum computer. Further, in realistic scenarios for quantum information processing, noise causes errors in the computation. These errors have to be taken into account for any application of quantum information processing. Implementing error correction in experiment is therefore an important building block for quantum computers, especially when run in realistic scenarios.
Quantum simulation and quantum metrology
Besides quantum computing, two key applications of quantum technologies are quantum simulation and quantum metrology. Quantum simulators are easily controllable quantum systems that can mimic complex quantum systems – and thus be used to learn about properties of the complex system. Quantum metrology uses quantum systems to measure certain parameters with a precision not possible to obtain classically.
Verification of quantum technology
The promise of quantum computers that they can solve problems intractable for classical computers opens up new fundamental questions. One of the most important questions in this field today is whether the correctness of quantum computations can be certified by entities that are inherently unable to compute the results themselves. Such verifications are important for future large-scale quantum computations and quantum simulations.