When multiple quantum emitters radiate, their emission rate may be enhanced or suppressed due to collective interference in a process known as super- or subradiance. Such processes are well known to occur also in light emission from free electrons, known as coherent cathodoluminescence. Unlike atomic systems, free electrons have an unbounded energy spectrum, and, thus, all their emission mechanisms rely on electron recoil, in addition to the classical properties of the dielectric medium. To date, all experimental and theoretical studies of super- and subradiance from free electrons assumed only classical correlations between particles. However, dependence on quantum correlations, such as entanglement between free electrons, has not been studied. Recent advances in coherent shaping of free-electron wave functions motivate the investigation of such quantum regimes of super- and subradiance. In this Letter, we show how a pair of coincident path-entangled electrons can demonstrate either super- or subradiant light emission, depending on the two-particle wave function. By choosing different free-electron Bell states, the spectrum and emission pattern of the light can be reshaped, in a manner that cannot be accounted for by a classical mixed state. We show these results for light emission in any optical medium and discuss their generalization to many-body quantum states. Our findings suggest that light emission can be sensitive to the explicit quantum state of the emitting matter wave and possibly serve as a nondestructive measurement scheme for measuring the quantum state of many-body systems.

中文翻译：

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纠缠自由电子的量子干涉引起的超辐射和亚辐射

当多个量子发射器辐射时，由于称为超辐射或亚辐射的过程中的集体干扰，它们的发射率可能会增强或抑制。众所周知，这种过程也发生在自由电子的光发射中，称为相干阴极发光。与原子系统不同，自由电子具有无限的能谱，因此，除了电介质的经典特性外，它们的所有发射机制都依赖于电子反冲。迄今为止，所有关于自由电子超辐射和亚辐射的实验和理论研究都只假设粒子之间存在经典的相关性。然而，尚未研究对量子相关性的依赖，例如自由电子之间的纠缠。自由电子波函数相干成形的最新进展激发了对超辐射和亚辐射的这种量子机制的研究。在这封信中，我们展示了一对重合路径纠缠电子如何展示超辐射或亚辐射光发射，这取决于双粒子波函数。通过选择不同的自由电子贝尔态，可以以经典混合态无法解释的方式重塑光的光谱和发射模式。我们展示了任何光学介质中光发射的这些结果，并讨论了它们对多体量子态的推广。我们的研究结果表明，光发射可能对发射物质波的显式量子态敏感，并可能作为测量多体系统量子态的非破坏性测量方案。