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Decoherence in crystals of quantum molecular magnets

机译:量子分子磁体晶体的退相干

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摘要

Quantum decoherence is a central concept in physics. Applications such as quantum information processing depend on understanding it; there are even fundamental theories proposed that go beyond quantum mechanics~(1-3), in which the breakdown of quantum theory would appear as an 'intrinsic' decoherence, mimicking the more familiar environmental decoherence processes~4. Such applications cannot be optimized, and such theories cannot be tested, until we have a firm handle on ordinary environmental decoherence processes. Here we show that the theory for insulating electronic spin systems can make accurate and testable predictions for environmental decoherence in molecular-based quantum magnets~5. Experiments on molecular magnets have successfully demonstrated quantum-coherent phenomena~(6-8) but the decoherence processes that ultimately limit such behaviour were not well constrained. For molecular magnets, theory predicts three principal contributions to environmental decoherence: from phonons, from nuclear spins and from intermolecular dipolar interactions. We use high magnetic fields on single crystals of Fe_8 molecular magnets (in which the Fe ions are surrounded by organic ligands) to suppress dipolar and nuclear-spin decoherence. In these high-field experiments, we find that the decoherence time varies strongly as a function of temperature and magnetic field. The theoretical predictions are fully verified experimentally, and there are no other visible decoherence sources. In these high fields, we obtain a maximum decoherence quality-factor of 1.49 × 10~6; our investigation suggests that the environmental decoherence time can be extended up to about 500 microseconds, with a decoherence quality factor of ~6 × 10~7, by optimizing the temperature, magnetic field and nuclear isotopic concentrations.
机译:量子退相干是物理学中的中心概念。诸如量子信息处理之类的应用取决于对它的理解。甚至有超越量子力学的基本理论〜(1-3),其中量子理论的崩溃将表现为“固有”退相干,模仿了更熟悉的环境退相干过程〜4。在我们对普通的环境退相干过程有坚定的了解之前,无法优化此类应用程序,也无法对此类理论进行检验。在这里,我们证明了绝缘电子自旋系统的理论可以对基于分子的量子磁体〜5中的环境退相干做出准确且可测试的预测。在分子磁体上的实验已经成功地证明了量子相干现象〜(6-8),但是最终限制这种行为的退相干过程并没有受到很好的约束。对于分子磁体,理论预测了环境退相干的三个主要贡献:声子,核自旋和分子间偶极相互作用。我们在Fe_8分子磁体(其中Fe离子被有机配体包围)的单晶上使用高磁场来抑制偶极和核自旋退相干。在这些高场实验中,我们发现退相干时间随温度和磁场的变化而变化很大。理论预测已通过实验充分验证,并且没有其他可见的退相干源。在这些高场中,我们获得的最大退相干品质因数为1.49×10〜6。我们的研究表明,通过优化温度,磁场和核同位素浓度,可以将环境退相干时间延长至约500微秒,退相干品质因数约为〜6×10〜7。

著录项

  • 来源
    《Nature》 |2011年第7358期|p.76-79|共4页
  • 作者单位

    Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA,Institute for Terahertz Science and Technology, University of California, Santa Barbara, California 93106,USA,Department of Physics, University of California, Santa Barbara, California 93106, USA;

    Pacific Institute of Theoretical Physics, University of British Columbia, Vancouver, British Columbia V6T 1Z1,Canada,Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada;

    National High Magnetic Field Laboratory, Florida State University,Tallahassee, Florida 32310, USA;

    Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA;

    Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA;

    Pacific Institute of Theoretical Physics, University of British Columbia, Vancouver, British Columbia V6T 1Z1,Canada,Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada;

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