Stress-controlled excitonic quantum beats in cuprous oxide

Controlling the quantum coherence of excitons in bulk semiconductors is crucial for developing scalable quantum photonic platforms. Here, we demonstrate active control of excitonic quantum beats in the 1S orthoexciton in cuprous oxide (Cu₂O) via strain engineering. By applying uniaxial bending stress, we induce and precisely tune the fine structure splitting of the 1S orthoexciton. The split states display orthogonal linear polarizations, enabling selective preparation of coherent superpositions. The presence of a quantum beating signal confirms coherent coupling. Our results demonstrate that the beat frequency can be continuously tuned by changing the applied stress, and the beat amplitude can be switched on and off by rotating the detection polarization. These strain-controlled quantum interference effects not only shed light on the fundamental excitonic dynamics but also open avenues for exploiting Cu₂O's unique properties in quantum optics and information processing.