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arXiv 1804.01397quant-ph
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强迫对真空辐射的影响

The Effect of Forcing on Vacuum Radiation

Katherine Jones-Smith, Harsh Mathur, Ashton Lowenstein

摘要:

几十年来,真空辐射一直是宇宙学和凝聚态物理理论研究的主题。最近,在实验实现方面也取得了令人印象深刻的进展。在这里,我们研究真空辐射时,场模式参数驱动和经典源。我们发现,在海森堡图像中,模的场算符经历了一个Bogolyubov变换和一个位移,在薛定谔图像中,振子从真空演化到压缩相干态.而Bogolyubov变换是相同的,如果只施加参数驱动,位移是由参数驱动和力。如果在参数驱动之后很好地施加力,则位移与通过单独的力的作用获得的位移相同,并且位移基本上与$t_f$无关,$t_f$是施加力和参数驱动之间的时滞。如果在参数驱动之前施加力,则发现位移作为$t_f$的函数振荡。这种行为可以用量子干涉来理解。对于$t_f$的中间值,观察到丰富多样的行为。振荡可以平稳地关闭或急剧增长,并根据参数驱动和力的强度以及它们被施加的持续时间而减小。当强迫和参数驱动在时间上很好地分离时,位移仅取决于在单个谐振频率处的力的傅立叶分量。然而,对于同时施加力的弱参数驱动,我们表明位移响应于力谱的宽频率范围。我们的研究结果的实验的影响进行了简要讨论。

英文摘要:

Vacuum radiation has been the subject of theoretical study in both cosmology and condensed matter physics for many decades. Recently there has been impressive progress in experimental realizations as well. Here we study vacuum radiation when a field mode is driven both parametrically and by a classical source. We find that in the Heisenberg picture the field operators of the mode undergo a Bogolyubov transformation combined with a displacement, in the Schrödinger picture the oscillator evolves from the vacuum to a squeezed coherent state. Whereas the Bogolyubov transformation is the same as would be obtained if only the parametric drive were applied the displacement is determined by both the parametric drive and the force. If the force is applied well after the parametric drive then the displacement is the same as would be obtained by the action of the force alone and it is essentially independent of $t_f$, the time lag between the application of the force and the parametric drive. If the force is applied well before the parametric drive the displacement is found to oscillate as a function of $t_f$. This behavior can be understood in terms of quantum interference. A rich variety of behavior is observed for intermediate values of $t_f$. The oscillations can turn off smoothly or grow dramatically and decrease depending on strength of the parametric drive and force and the durations for which they are applied. The displacement depends only on the Fourier component of the force at a single resonant frequency when the forcing and the parametric drive are well separated in time. However for a weak parametric drive that is applied at the same time as the force we show that the displacement responds to a broad range of frequencies of the force spectrum. Implications of our findings for experiments are briefly discussed.

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