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Optical coherent state discrimination using a closed-loop quantum measurement

机译:使用闭环量子测量的光学相干态判别

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摘要

Quantum mechanics hinders our ability to determine the state of a physical system in two ways: individual measurements provide only partial information about the observed system (because of Heisenberg uncertainty), and measurements are themselves invasive—meaning that little or no refinement is achieved by further observation of an already measured system. Theoretical methods have been developed to maximize the information gained from a quantum measurement while also minimizing disturbance, but laboratory implementation of optimal measurement procedures is often difficult. The standard class of operations considered in quantum information theory tends to rely on superposition-basis and entangled measurements, which require high-fidelity implementation to be effective in the laboratory. Here we demonstrate that real-time quantum feedback can be used in place of a delicate quantum superposition, often called a 'Schrodinger cat state', to implement an optimal quantum measurement for discriminating between optical coherent states. Our procedure actively manipulates the target system during the measurement process, and uses quantum feedback to modify the statistics of an otherwise sub-optimal operator to emulate the optimal cat-state measurement. We verify a long-standing theoretical prediction and demonstrate feedback-mediated quantum measurement at its fundamental quantum limit over a non-trivial region of parameter space.
机译:量子力学以两种方式阻碍了我们确定物理系统状态的能力:单个测量仅提供有关被观测系统的部分信息(由于海森堡不确定性),并且测量本身具有侵入性,这意味着通过进一步的改进几乎或根本无法改善观察已经测量的系统。已经开发了理论方法以最大化从量子测量中获得的信息,同时还最小化干扰,但是在实验室中实施最佳测量程序通常很困难。量子信息理论中考虑的标准操作类别往往依赖于叠加基础和纠缠测量,这需要高保真度的实施才能在实验室中有效。在这里,我们证明了可以使用实时量子反馈代替微妙的量子叠加(通常称为“薛定inger猫状态”)来实现区分光学相干态的最佳量子测量。我们的过程在测量过程中会主动操纵目标系统,并使用量子反馈来修改否则为次优算子的统计信息,以模拟最佳猫态测量。我们验证了一个长期的理论预测,并证明了在参数空间的一个非平凡区域上其基本量子极限下的反馈介导量子测量。

著录项

  • 来源
    《Nature》 |2007年第7137期|774-777|共4页
  • 作者单位

    Quantum Measurement & Control Group, Department of Physics and Astronomy, The University of New Mexico, Albuquerque, New Mexico 87131, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 自然科学总论;
  • 关键词

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