Seminar
Tuesday, 04 May, 2010
Group Seminar LMU: Generation of multi-particle entanglement on an atom chip
Tuesday, 04.05.2010 10 a.m. (s.t.) in H107, Fakultät für Physik LMU
Max Riedel, Munich Atom Chip Group, Fakultät für Physik LMU
Entanglement-based technologies, such as quantum information processing, quantum simulations, and quantum metrology, have the potential to revolutionize our way of computing and measuring, and help clarify the puzzling concept of entanglement itself. Ultracold atoms on atom chips are attractive for their implementation, as they provide control over quantum systems in compact, robust, and scalable setups. A severe limitation of atom chips, however, is that techniques to control atomic interactions and thus to generate entanglement have not been experimentally available so far.Here, we present experiments where we generate multi-particle entanglement on an atom chip by controlling elastic collisional interactions with a state-dependent microwave near-field potential. We employ this technique to generate spin-squeezed states of a two-component Bose-Einstein condensate and show that they are useful for quantum metrology. The observed reduction in spin noise combined with the spin coherence imply four-partite entanglement between the condensate atoms and could be used to improve an interferometric measurement by -2.5 dB over the standard quantum limit. Our data show good agreement with a dynamical multi-mode simulation and allow us to reconstruct the Wigner function of the spin-squeezed condensate. The techniques demonstrated here could be directly applied in chip-based atomic clocks which are currently being set up. Furthermore, they constitute the key ingredient for a quantum phase gate previously proposed by our group.