Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstrasse 21A, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria.
Department of Physics, University of California, Berkeley, California 94720, USA and Physikalisches Institut, Universität Freiburg, Hermann-Herder-Strasse 3, D-79104 Freiburg, Germany.
Phys Rev Lett. 2013 Sep 6;111(10):100504. doi: 10.1103/PhysRevLett.111.100504. Epub 2013 Sep 5.
Quantum systems in mixed states can be unentangled and yet still nonclassically correlated. These correlations can be quantified by the quantum discord and might provide a resource for quantum information processing tasks. By precisely controlling the interaction of two ionic qubits with their environment, we investigate the capability of noise to generate discord. Firstly, we show that noise acting on only one quantum system can generate discord between two. States generated in this way are restricted in terms of the rank of their correlation matrix. Secondly, we show that classically correlated noise processes are capable of generating a much broader range of discordant states with correlation matrices of any rank. Our results show that noise processes prevalent in many physical systems can automatically generate nonclassical correlations and highlight fundamental differences between discord and entanglement.
混合态量子系统可以是非纠缠的，但仍然是非经典相关的。这些相关性可以通过量子失谐来量化，并且可能为量子信息处理任务提供资源。通过精确控制两个离子量子位与环境的相互作用，我们研究了噪声产生失谐的能力。首先，我们表明，仅作用于一个量子系统的噪声可以在两个量子系统之间产生失谐。以这种方式产生的状态在其相关矩阵的秩方面受到限制。其次，我们表明，经典相关的噪声过程能够产生具有任何秩的相关矩阵的更广泛的失谐状态。我们的结果表明，在许多物理系统中普遍存在的噪声过程可以自动产生非经典相关性，并突出了失谐与纠缠之间的根本区别。
