Prof Dieter Jaksch

Abstract:

Quantum optical systems that implement quantum computing tasks concentrating on two-qubit gates are presented. Two schemes, one based on dipole moments of Rydberg atoms and the other base on conditional Coulomb interactions between ions in arrays of micro-traps, are analyzed. These schemes are combined with the features of quantum optics, in particular quantum control and long decoherence times.

Abstract:

We review recent proposals for performing entanglement manipulation via controlled interactions between trapped atoms. State-dependent, time-varying microscopic potentials allow one to obtain with high fidelity a conditional phase shift realizing a universal quantum gate. We discuss possible physical implementations with existing experimental techniques, for example optical lattices and magnetic micro-traps.

Abstract:

We develop a method to entangle neutral atoms using cold controlled collisions. We analyse this method in two particular set-ups: optical lattices and magnetic microtraps. Both offer the possibility of performing certain multi-particle operations in parallel. Using this fact, we show how to implement efficient quantum error correction and schemes for fault-tolerant computing. © 2000 Taylor & Francis Group, LLC.

Abstract:

We theoretically study specific schemes for performing a fundamental two-qubit quantum gate via controlled atomic collisions by switching microscopic potentials. In particular we calculate the fidelity of a gate operation for a configuration where a potential barrier between two atoms is instantaneously removed and restored after a certain time. Possible implementations could be based on microtraps created by magnetic and electric fields, or potentials induced by laser light.

Abstract:

Controlled cold collisions of atoms in optical lattices allow implementation of highly parallel entanglement operation and quantum gates. Applications include quantum computing with efficient quantum error correction. The use of cold controlled collisions of atoms, trapped in the ground state of the lattice wells, a mechanism to introduce dynamic phase shifts depending on the state of the atoms is proposed. In lattices with ordered filling structures, highly parallel entanglement operations could be implemented, corresponding to a novel class of quantum gates. These multi-qubit quantum gates can be employed for efficient quantum error correction. How the parallelism in an optical lattice could be used for quantum computation in general is discussed.