Prof. Dr. Martin Weitz
Our group (previously located in Munich) has expertise in many of the key experimental techniques required for the successfully carrying out quantum logic in optical lattices. This includes experience in the area of laser cooling and trapping of atoms in optical lattices, atom optics and quantum manipulation of atoms.
Past achievements include the development of a novel 'mesoscopic' optical lattice based on the radiation near 10.6 microns emitted by a CO2-laser. Laser cooled rubidium atoms have been trapped by dipole forces in an intense standing wave of this far-detuned radiation. Besides the unusually large lattice constant (5.3 mm) of several times the absorption wavelength of the rubidium D2 line, intriguing properties of this type of lattice also include extremely long coherence times, as the expected average photon scattering time is over 10 minutes. We have imaged the atomic fluorescence emitted from the individual microtraps with an optical microscope. To our knowledge, this represents the first observation of individual sites of an optical lattice with periodicity near half the trapping wavelength. Our initial experiments demonstrate that preparing and reading out of individual qubits should in principle be possible in the CO2-laser optical lattice. We have measured the atomic phase space density of the trapped atoms. Using laser cooling alone, the surprisingly high value of 1/300 is obtained. Further cooling into the ground state is required for quantum logic. In ongoing work, we evaporatively cool the atoms to a phase space density of 1/15, and further progress is expected soon. In addition, novel line narrowing effects were observed when manipulating the cold atoms in the CO2-laser trap using Raman transitions.
An important experimental issue for quantum computation is the process of decoherence. We have realized an experiment in which photons are scattered from one of the paths of a four path (two-qubits) Ramsey interference setup. The experimental scheme can serve as a model system for the study of decoherence in quantum systems, as e.g. quantum logic gates.
Of relevance to the proposed work is also experience in the manipulation of atoms using dark quantum superposition states. Our experience in this area includes the demonstration of the first atom interferometer based on dark states and the realization of the first multiple beam interferometer for atoms, which was realized by projecting atomic wavepackets onto multicomponent dark states.
The Tuebingen group are involved in the QUBITS network of the current QIPC funding round.
Back to Research
Back to Participants