论文标题
超过3 dB
Beating the 3 dB Limit for Intracavity Squeezing and Its Application to Nondemolition Qubit Readout
论文作者
论文摘要
虽然原则上可以任意地挤压传播场，但腔场挤压受到众所周知的3 dB限制，因此应用有限。在这里，我们建议使用完全量子退化的参数放大器（DPA）来击败此挤压极限。具体来说，我们表明，通过{\ it}将两色调驱动到信号模式，泵模式可以{\ it违反直觉}可以由信号模式的光子丢失驱动到挤压稳态中，从原则上讲，{\ \ it {\ IT任意高}高度挤压程度。此外，我们证明，这种腔内挤压可以增加纵向Qubit读数{\ IT指数式}的信噪比，并随着挤压程度而增加。相应地，即使对于适度的参数，也可以实现{\ IT许多数量级}对测量误差的改进。与之形成鲜明对比的是，使用半经典dpa {\}的腔内挤压实际上会增加信噪比，从而提高测量误差。我们的结果扩展了DPA的应用范围，并为现代量子技术开辟了新的机会。
While the squeezing of a propagating field can, in principle, be made arbitrarily strong, the cavity-field squeezing is subject to the well-known 3 dB limit, and thus has limited applications. Here, we propose the use of a fully quantum degenerate parametric amplifier (DPA) to beat this squeezing limit. Specifically, we show that by {\it simply} applying a two-tone driving to the signal mode, the pump mode can, {\it counterintuitively}, be driven by the photon loss of the signal mode into a squeezed steady state with, in principle, an {\it arbitrarily high} degree of squeezing. Furthermore, we demonstrate that this intracavity squeezing can increase the signal-to-noise ratio of longitudinal qubit readout {\it exponentially} with the degree of squeezing. Correspondingly, an improvement of the measurement error by {\it many orders of magnitude} can be achieved even for modest parameters. In stark contrast, using intracavity squeezing of the semiclassical DPA {\it cannot} practically increase the signal-to-noise ratio and thus improve the measurement error. Our results extend the range of applications of DPAs and open up new opportunities for modern quantum technologies.
