Quantum computation and multiparticle entanglement with trapped atoms and ions

Hartmut Häffner, W. Hänsel, Christian F. Roos +11 more

John Chiaverini

Anders Søndberg Sørensen, Klaus Mølmer

In the ion trap quantum computer, quantum bits are represented by the internal state of the trapped ions, and the collective vibrations of the ions are exploited for the coherent manipulation of the state of several bits. We have developed a method to perform gates on different ions by illuminating the ions with bichromatic light. Our gates are independent of the motional state of the ions and they may be applied to ions in any state or, e.g., thermal mixture of vibrational states. Moreover, our proposal allows the production of multiparticle entangled states even in situations without experimental access to the individual ions in the trap. Maximally entangled states of any number of ions are produced by simply illuminating all ions with the same beams of bichromatic light.

Gongwei Lin, Xu‐Bo Zou, Ming-Yong Ye +2 more

A scheme is presented for realizing a quantum phase gate with three-level atoms, solid-state qubits---often called artificial atoms, or ions that share a quantum data bus such as a single-mode field in the cavity quantum electrodynamics system or a collective vibrational state of trapped ions. In this scheme, the conditional phase shift is tunable and controllable via the total effective interaction time. Furthermore, the method can be used to effectively prepare graph states, which are important resources for quantum computation, quantum error correction, studies of multiparticle entanglement, and fundamental tests of nonlocality and decoherence.

Dahyun Yum, Taeyoung Choi

Klaus Mølmer, Anders Søndberg Sørensen

We propose an efficient method to produce multiparticle entangled states of ions in an ion trap for which a wide range of interesting effects and applications have been suggested. Our preparation scheme exploits the collective vibrational motion of the ions, but it works in such a way that this motion need not be fully controlled in the experiment. The ions may, e.g., be in thermal motion and exchange mechanical energy with a surrounding heat bath without detrimental effects on the internal state preparation. Our scheme does not require access to the individual ions in the trap.