Squeezed quantum states of graviton and axion in the universe
Squeezed quantum states of graviton and axion in the universe
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DOI：
10.1142/s0218271822500985
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发表时间：
2021-12
影响因子：
2.2
通讯作者：
S. Kanno;J. Soda
中科院分区：
文献类型：
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作者：
S. Kanno;J. Soda
宇宙膨胀期间的粒子产生可以解释为量子态的双模压缩过程。双模压缩态由无限数量的纠缠粒子组成，从而增强了粒子的非经典性。有两种估计挤压程度的方法。一种是采用瞬时真空状态，另一种是采用绝热真空状态。我们利用这两种方法分析研究了引力子和轴子的挤压过程。我们首先考虑膨胀的宇宙学模型，随后瞬时再加热，导致辐射主导的时代。就引力子而言，我们发现两种方法之间的压缩没有质的差异。然而，对于轴子，事实证明，瞬时真空中的挤压随着质量的增加而增加，而绝热真空中的挤压随着质量的增加而减少。然后我们研究了非瞬时再加热对挤压的影响，并表明与瞬时再加热相比，挤压得到增强。我们还说明了压缩态如何增强贝尔不等式的违反以及引力子和轴子的量子噪声。
Particle production during cosmic expansion can be interpreted as a two-mode squeezing process of quantum states. The two-mode squeezed states consist of an infinite number of entangled particles and then enhance the nonclassicality of particles. There are two methods for estimating the degree of squeezing. One is to employ instantaneous vacuum states, and the other is to adopt adiabatic vacuum states. We analytically study the squeezing process of gravitons and axions by using the two methods. We first consider a cosmological model of inflation followed by instantaneous reheating leading to a radiation dominated era. In the case of gravitons, we find no qualitatively difference in the squeezing between the two methods. However, for the axions, it turns out that the squeezing in the instantaneous vacuum increases as the mass increases while the squeezing decreases in the adiabatic vacuum as the mass increases. We then study the effect of non-instantaneous reheating on the the squeezing and show that the squeezing is enhanced compared with the instantaneous reheating. We also illustrate how the squeezed states enhance the violation of Bell inequality and quantum noise of gravitons and axions.