Colangelo G, Martin Ciurana F, Puentes G, Mitchell M W, Sewell R J
ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain.
Departamento de Física, Facultad de Ciencias Exactas y Naturales, Pabellón 1, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
Phys Rev Lett. 2017 Jun 9;118(23):233603. doi: 10.1103/PhysRevLett.118.233603.
We study the generation of planar quantum squeezed (PQS) states by quantum nondemolition (QND) measurement of an ensemble of ^{87}Rb atoms with a Poisson distributed atom number. Precise calibration of the QND measurement allows us to infer the conditional covariance matrix describing the F_{y} and F_{z} components of the PQS states, revealing the dual squeezing characteristic of PQS states. PQS states have been proposed for single-shot phase estimation without prior knowledge of the likely values of the phase. We show that for an arbitrary phase, the generated PQS states can give a metrological advantage of at least 3.1 dB relative to classical states. The PQS state also beats, for most phase angles, single-component-squeezed states generated by QND measurement with the same resources and atom number statistics. Using spin squeezing inequalities, we show that spin-spin entanglement is responsible for the metrological advantage.
我们研究了通过对具有泊松分布原子数的(^{87}Rb)原子系综进行量子非破坏（QND）测量来生成平面量子压缩（PQS）态。QND测量的精确校准使我们能够推断出描述PQS态(F_y)和(F_z)分量的条件协方差矩阵，揭示了PQS态的双重压缩特性。PQS态已被提出用于单次相位估计，而无需事先了解相位的可能值。我们表明，对于任意相位，所生成的PQS态相对于经典态可提供至少3.1 dB的计量优势。在大多数相位角下，PQS态也优于使用相同资源和原子数统计通过QND测量生成的单分量压缩态。利用自旋压缩不等式，我们表明自旋 - 自旋纠缠是计量优势的原因。
