Quantum computing and quantum state storage
Stefan Kröll, Division of Atomic Physics

Our research group work with laser spectroscopic techniques on rare-earth-ion-doped inorganic crystals at cryogenic temperatures to create hardware for quantum computers and quantum memories.

Praseodymium doped yttrium silicate crystal.

These types of crystals are very similar to those used in solid state lasers. Recent technological and experimental progress has allowed an unprecedented capacity of control at the atomic level. This has given rise to an effort to build a quantum computer that would exploit quantum phenomena such as entanglement, up to now not accessible to experiments. Quantum computers hold the promise for solving efficiently some computationally hard problems, like e.g. large integer factorisation or the simulation of quantum systems. More in general the construction of quantum computers offers a structured way of how to learn to control quantum systems. With devices getting smaller quantum effects play an increasingly important role in the basic functioning high technology systems, but not only in the sense of placing fundamental limits, but opening new avenues which have no counterpart in classical physics. At the same time development of quantum hardware also builds directly on nanotechnologies developed for our present day computing and communication devices, and provides new challenges for engineering and control of quantum mechanical systems far beyond what has been achieved today. An interface between quantum information carriers (quantum states of light) and quantum information storage and processors (atoms, ions, solid state) is an integral part of a full-scale quantum information system. In quantum information processing simple classical detection is inadequate for recording into memory, because it destroys the quantum state by adding extra noise to it. Hence quantum interfaces, such as quantum memories has to be developed. We are an experimental group specialising in laser spectroscopy and optics for the construction of hardware for quantum computers and quantum memories as stated above