Hannover 2010 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 39: Quantum Information: Atoms and Ions III

Q 39.4: Talk

Wednesday, March 10, 2010, 17:30–17:45, E 214

Combining dressed states and ion traps for coherent qubits — •Nuala Timoney, Ingo Baumgart, and Christof Wunderlich — Fachbereich Physik, Universität Siegen, 57068 Siegen

Coherence time is an important property of a quantum computer. A weakness of an ion trap quantum computer, is its potential dependence on magnetic field sensitive levels. Ambient magnetic field noise is the cause of the shorter coherence times of magnetic field sensitive levels (5 ms) compared to their field insensitive counterparts (500 ms) as observed in ¹⁷¹Yb⁺. A scheme is suggested which is based on using dressed states as qubits, adiabatically turning on the fields before and turning the fields off at the end of the operations.

A three level system of hyperfine states is dressed by microwave photons and prepared in its dark state using STIRAP, Rabi oscillations are observed between the dark and the ground state and a Ramsey time measurement reveals a preliminary coherence time of 6.06 ms. In comparison a simpler two level dressed state scheme, which is based on a magnetic field insensitive transition with a dependence of the transition energy on the Rabi frequency of the dressing field, revealed a preliminary coherence time of 17 ms.

The coherence time measured is presently restricted by technical problems which will be improved in future experiments.