Jul 12 2013
Rene Gerritsma of Johannes Gutenberg University Mainz (JGU) has been awarded funding from the European Research Council in support of his work on quantum simulations with ultracold atoms and ions. His project on "Hybrid Atom-Ion Quantum Systems" will be funded by a prestigious ERC Starting Grant worth EUR 1.5 million.
The figure schematically shows a Paul trap with four main electrodes, in which a crystal of Yb+ ions is trapped and overlapped with an optically-trapped cloud of lithium ions. Credit: Rene Gerritsma
The central goal of the project is to study the properties of solids by using a quantum simulator based on a hybrid system of cold ions interacting with a degenerate Fermi gas.
More than 30 years ago, Richard Feynman proposed that quantum simulators could be used to study large many-body quantum systems. Feynman realized that it is beyond the ability of existing computer technology to calculate many properties of such systems. For example, just storing the quantum state of a comparably small system of only 50 electrons would already require a computer with an inconceivable amount of RAM capacity. In this case, 250 complex numbers would have to be stored, corresponding to quadrillions of bits. In contrast, Feynman's proposed quantum simulator would be able to cope with the task of investigating the properties of many-body quantum systems such as solids.
Crystalline solids consist of a regular lattice of positively charged atomic cores (ions) surrounded by a Fermi gas of electrons. Important properties of solids, such as their electrical conductivity, are strongly influenced by the interplay between these electrons and the lattice atoms. Lattice vibrations (sound waves) also play a major role including the mediation of the electron-electron interactions thought to be responsible for high-temperature superconductivity. Although some phase transitions that occur in solids, e.g. the transition from a Mott insulator to a superconductor, can be studied using a quantum simulator that employs only ultracold atoms, there is to date no atomic model system that can simulate the effect of real lattice vibrations on electrons.
In his project, Gerritsma plans to use ytterbium ion crystals (simulating the ionic core lattice) and an ultracold gas of lithium atoms (simulating an electronic Fermi gas). By letting the atoms and ions interact in a controlled manner, this model system may provide a deeper insight into the properties of solids and a route towards new quantum simulators of electron-lattice interactions. For the first time, the focus will be on venturing deep into the ultracold regime of atom-ion interactions, where quantum mechanical effects dominate. Tools originally developed for implementing quantum information processing make it possible to employ ions as sensors to probe the properties of the quantum simulator and these tools could even be used to detect individual atoms.
Rene Gerritsma studied Physics at the University of Groningen in the Netherlands and received his doctorate from the University of Amsterdam. He then worked as a postdoctoral researcher at the Institute for Quantum Optics and Quantum Information in Innsbruck, Austria. Since late 2011, he has been a member of the Quantum, Atomic, and Neutron Physics (QUANTUM) group at the Institute of Physics of Johannes Gutenberg University Mainz. The ERC Starting Grant gives him the opportunity to establish his own research group. Gerritsma's experimental research in the QUANTUM work group is supported by his collaboration with theoretical physicist Professor Walter Hoffstetter of the Goethe University in Frankfurt and the Transregional Collaborative Research Center 49 on "Condensed Matter Systems with Variable Many-Body Interactions."