Solution-Phase Sample-Averaged Single-Particle Spectroscopy of Quantum Emitters with Femtosecond Resolution

The development of many quantum optical technologies depends on the availability of single quantum emitters with near-perfect coherence. Systematic improvement is limited by a lack of understanding of the microscopic energy flow at the single-emitter level and ultrafast timescales. Here [1] we utilize a combination of fluorescence correlation spectroscopy and ultrafast spectroscopy to capture the sample-averaged dynamics of defects with single-particle sensitivity. We employ this approach to study heterogeneous emitters in two-dimensional hexagonal boron nitride. From milliseconds to nanoseconds, the translational, shelving, rotational and antibunching features are disentangled in time, which quantifies the normalized two-photon emission quantum yield. Leveraging the femtosecond resolution of this technique, we visualize electron–phonon coupling and discover the acceleration of polaronic formation on multi-electron excitation. Corroborated with theory, this translates to the photon fidelity characterization of cascaded emission efficiency and decoherence time. Our work provides a framework for ultrafast spectroscopy in heterogeneous emitters, opening new avenues of extreme-scale characterization for quantum applications.<br/>[1] Jiaojian Shi, Yuejun Shen, Feng Pan, Weiwei Sun, Anudeep Mangu, Cindy Shi, Amy McKeown-Green, Parivash Moradifar, Moungi G. Bawendi, W. E. Moerner, Jennifer A. Dionne, Fang Liu, Aaron M. Lindenberg, Nature Materials 2024.