Certifying quantum entanglement is a critical step toward realizing quantum-coherent applications. In this work, we show that entanglement of spins can be unambiguously evidenced in a scanning tunneling microscope with electron spin resonance by exploiting the fact that entangled states undergo a free time evolution with a distinct characteristic time constant that clearly distinguishes it from the time evolution of non-entangled states. By implementing a phase control scheme, the phase of this time evolution can be mapped back onto the population of one entangled spin, which can then be read out reliably using a weakly coupled sensor spin in the junction of the scanning tunneling microscope. We demonstrate through open quantum system simulations with currently available spin coherence times of T₂ ≈ 300 ns, that a signal directly correlated with the degree of entanglement can be measured at temperatures of 100–400 mK accessible in sub-Kelvin scanning tunneling microscopes.

验证量子纠缠是实现量子相干应用的关键一步。在这项工作中，我们证明，通过利用纠缠态经历自由时间演化这一事实，可以在具有电子自旋共振的扫描隧道显微镜中明确证明自旋纠缠，该自由时间演化具有明显的特征时间常数，该特征时间常数将其与非纠缠态。通过实施相位控制方案，可以将这一时间演化的相位映射回一个纠缠自旋的总体，然后可以使用扫描隧道显微镜连接处的弱耦合传感器自旋可靠地读出该总体。我们通过当前可用的自旋相干时间T ₂ ≈ 300 ns 的开放量子系统模拟证明，可以在亚开尔文扫描隧道显微镜可达到的 100–400 mK 温度下测量与纠缠程度直接相关的信号。