The quantum vacuum plays a central role in physics. Quantum electrodynamics (QED) predicts that the properties of the fermionic quantum vacuum can be probed by extremely large electromagnetic fields. The typical field amplitudes required correspond to the onset of the ‘optical breakdown’ of this vacuum, expected at light intensities >4.7×1029 W/cm2. Approaching this ‘Schwinger limit’ would enable testing of major but still unverified predictions of QED. Yet, the Schwinger limit is seven orders of magnitude above the present record in light intensity achieved by high-power lasers. To close this considerable gap, a promising paradigm consists of reflecting these laser beams off a mirror in relativistic motion, to induce a Doppler effect that compresses the light pulse in time down to the attosecond range and converts it to shorter wavelengths, which can then be focused much more tightly than the initial laser light. However, this faces a major experimental hurdle: how to generate such relativistic mirrors? In this article, we explain how this challenge could nowadays be tackled by using so-called ‘relativistic plasma mirrors’. We argue that approaching the Schwinger limit in the coming years by applying this scheme to the latest generation of petawatt-class lasers is a challenging but realistic objective.

中文翻译：

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从相对论等离子体镜反射拍瓦激光：通往施温格极限的现实路径

量子真空在物理学中起着核心作用。量子电动力学 (QED) 预测，费米子量子真空的特性可以通过极大的电磁场进行探测。所需的典型场幅度对应于该真空的“光学击穿”的开始，预计光强度 >4.7×1029宽/厘米2. 接近这个“施温格极限”将能够测试主要但尚未验证的 QED 预测。然而，施温格极限比目前由高功率激光器实现的光强度记录高出七个数量级。为了缩小这个相当大的差距，一个有前途的范例包括以相对论运动将这些激光束从镜子反射，以引起多普勒效应，将光脉冲及时压缩到阿秒范围并将其转换为更短的波长，然后可以比最初的激光聚焦得更紧密。然而，这面临着一个重大的实验障碍：如何生成这样的相对论镜？在这篇文章中，我们解释了如今如何通过使用所谓的“相对论等离子体镜”来应对这一挑战。