Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan.
Phys Rev Lett. 2012 Feb 10;108(6):060503. doi: 10.1103/PhysRevLett.108.060503.
We propose the generation of entangled states with trapped calcium ions using a combination of an rf dressed state and a spin-dependent force. By using this method, a decoherence-free entangled state of rf qubits can be directly generated, and ideally its fidelity is close to unity. We demonstrate an rf entangled state with a fidelity of 0.68±0.08, which has a coherence time of more than 200 ms by virtue of the fact that it is an eigenstate with energy gaps between adjacent levels. Using the same technique, we also produce a qutrit-qutrit entangled state with a fidelity of 0.77±0.09, which exceeds the threshold value for separability of 2/3.
我们提出了一种使用射频囚禁态和自旋相关力相结合的方法来产生纠缠态。通过这种方法，可以直接产生无退相干的射频量子比特纠缠态，并且理想情况下其保真度接近于 1。我们演示了一个射频纠缠态，其保真度为 0.68±0.08，由于相邻能级之间存在能隙，因此其相干时间超过 200ms。利用相同的技术，我们还产生了一个保真度为 0.77±0.09 的三量子比特纠缠态，超过了可分离性的阈值 2/3。
