NMR Model for studying Decoherence

A. A. Lundin, V. E. Zobov

T. S. Mahesh

愛 岩倉, Masamitsu Bando, Kondo, Yasushi

[Abstract] A quantum computer, that is able to calculate much faster than a conventional one, has been attracting a lot of attentions, recently. The largest obstacle against its realization is a decoherence of a system. We implement a model system with NMR technique of which decoherence can be controlled by varying the concentration of magnetic impurity and apply a dynamical decoupling technique on it. [概要] 量子コンピュータは,通常のコンピュータでは事実上不可能な計算を実行できる可能性を秘めており注目されている. この量子コンピュータの実現を阻む最大の原因は位相緩和である. NMRを用いて磁性不純物濃度を変えることにより位相緩和を制御できるモデルを実装し, さらにそのモデルに対して動的位相緩和抑制を試みた.

愛 岩倉, Yuichiro Matsuzaki, Yasushi Kondo

The largest obstacle to perform quantum information processing is decoherence of a system. In order to overcome this, various techniques, such as dynamical decoupling and quantum Zeno effects, have been proposed and demonstrated. Here, we present an NMR model with which various decoherence suppression techniques can experimentally be evaluated. By changing the conditions in the sample preparation, we can engineer an environment to interact the system that contains the information. Moreover, we can efficiently describe the dynamics by the operator-sum representation due to the simplicity of our model. As concrete examples, we have investigated the performance of dynamical decoupling with several molecules. Our model provides a useful test bench to understand the mechanism of decoherence induced by a noisy environment and to examine various ideas of decoherence suppression techniques.

J. M. Raimond

Yasushi Kondo, Mikio Nakahara, Shogo Tanimura

Liquid-state NMR quantum computer has demonstrated the possibility of quantum computation and supported its development. Using NMR quantum computer techniques, we observed phase decoherence under two kinds of artificial noise fields; one a noise with a long period, and the other with shorter random period. The first one models decoherence in a quantum channel while the second one models transverse relaxation. We demonstrated that the bang-bang control suppresses decoherence in both cases.