Trapped-Ion Quantum Information and Simulation
Welcome to our group! We use trapped ions for quantum information processing, in particular quantum simulation, and for modern spectroscopy.
Group picture October 2011.
Front row left to right: Timko Dubielzig, Vidyut Kaushal, Malte Niemann, Sebastian Grondkowski.
Back row left to right: Thomas Borchard, Martina Carsjens, Henning Hahn, Christian Ospelkaus.
October 2011: We have produced our first surface-electrode traps in the PTB cleanroom facility. The picture on the right-hand side shows a portion of a surface-electrode trap. In this case, we are using the design of [Nature 476, 181 (2011)] to benchmark our production process. Picture by Martina Carsjens.
Depending on conditions, single trapped ions can be held and observed in Paul traps for minutes to months.
Our trap technology is based on microfabricated surface-electrode traps [see e. g. Seidelin et al., PRL 96, 253003 (2006)]. We produce our surface-electrode traps at PTB in the 'Reinraumzentrum' (clean room facility). These traps are realized using a lithographic process and galvanic deposition of the electrode structures.
Ions as qubits
Atomic Ions are exceptionally well controllable quantum systems. The internal structure of an ion can be used to store quantum information. We will use hyperfine-qubits with energy splittings of a few GHz. Such internal states of trapped ions can exhibt very long coherence times [see e. g. Langer et al., PRL 95, 060502 (2005)]. The qubit states can be measured with fidelities exceeding 99%.
Interactions between ions
When several ions are held in a common trap, they form a so-called Coulomb crystal, where the repulsion between ions is balanced by the restoring force from the trap. Using radiation resonant with the qubit transition and the motional frequencies, this can be used to induce a qubit-state dependent interaction between ions. These interactions can be put to work for deterministic entangling quantum logic gates, for quantum simulation of interacting many-body systems, and for modern spectroscopy.
We investigate laser-less schemes for qantum state manipulation of trapped ions with respect to quantum simulation. Quantum simulation is a field that was started by Richard Feynman in 1982 and is rapidly expanding both theoretically and experimentally.
With trapped ions in regular surface-electrode trap arrays, one hopes to create artificial interacting spin systems which can shed light on the behavior of quantum many-body systems [Schmied et al., PRL 102, 233002 (2009)]. Those can be exponentially hard to simulate even on today's supercomputers. One of our aims is to apply integrated microwave techniques [C. Ospelkaus et al., PRL 101, 090502 (2008); C. Ospelkaus et al., Nature 476, 181 (2011)] to quantum simulation [see also Chiaverini and Lybarger, PRA 77, 022324 (2008)]. This could provide a highly integrated and scalable approach to quantum simulation.
We also investigate quantum state manipulation techniques for modern precision spectroscopy of charged particles which cannot be manipulated in the common, laser-based way. Examples include the proton or charged molecules.
Our group has labs both at Leibniz Universität Hannover and at PTB in Braunschweig. In Hannover, we are setting up a cryogenic ion trap setup for quantum simulation experiments and spectroscopy. Our trap production and characterization effort is concentrated at PTB in Braunschweig.
We acknowledge funding by Leibniz Universität Hannover, PTB and the cluster of excellence QUEST.