Coherent optical control of single-photon scattering phase in cryogenic rare-earth ion–doped yttrium orthosilicate nanocavities for quantum memory synchronization

This research presents the development and performance analysis of a cryogenic rare-earth-ion–doped yttrium orthosilicate (YSO) nanocavity system for phase-sensitive quantum memory synchronization and coherent optical communication applications. The nanocavity structure was fabricated using focused ion beam milling and photolithography techniques to achieve efficient photon confinement and enhanced light–matter interaction under cryogenic conditions. The experimental results validated stable cavity resonance from 2 K to 4 K and higher optical confinement with the increase of the cavity Q factor from 15 to 60 and the decrease of the cavity resonance linewidth from 10 to 3 GHz. The single-photon excitation experiments showed strong coherent optical coupling between the photons such that an increase in the coupling strength increased the scattering probability of photons from 18% to 90%. Coherent phase modulation was improved by cavity assisted optical interaction, and the Purcell factor was increased from 12 up to 88, depending on the cavity Q factor. The coherence preservation was significantly enhanced, with the coherence lifetime increasing from 18 to 66 when the operating temperature was dropped from 4 K to 1.5 K; the waveguide coupling efficiency was optimized from 35% to 95%, and the synchronization fidelity increased from 50% to 99% during quantum memory operation. The proposed YSO nanocavity platform was capable of stable synchronization, photon storage with high efficiency and potential for good scalability for future integrated quantum photonic communication systems.