Direct detection of combined Rabi oscillations and fine-structure quantum beats in a neutral quantum-dot exciton

A commonly observed quantum-interference phenomenon is Rabi oscillations—understood as a ‘quantum beat’ between two dressed states separated by the Rabi splitting (RS) energy in a driven two-level (artificial) atom [1]. It is a signature of quantum coherence fundamental to the manipulation of atomic qubits in quantum information processing, and has been observed in quantum dots (QDs) (see Ref [2] and references therein). Another quantum-beat phenomenon occurs due to interference between the excited states of a V-type atomic system and has also been observed in the transient decay of QD emission from a suddenly excited neutral exciton state X0—an effective V-type system due to fine-structure splitting (FSS). Despite much related theoretical work and the availability of various platforms in which V-type systems could be realised, the observation of Rabi oscillations in resonance fluorescence from a coherently driven three-level V-type system remains a fundamentally interesting open question. In particular, quantum interference involving both RS and FSS has not been demonstrated experimentally. Here, through detection of time-resolved resonance fluorescence from a QD neutral exciton driven in the Rabi regime (Fig. 1), we experimentally demonstrate triple-slit-type quantum interference in a V-type three-level artificial atom [3]. This result is of fundamental interest in the experimental studies of the properties of V-type systems and may pave the way for further insight into their coherence properties. It also suggests QDs as candidates for multi-path-interference experiments for probing foundational concepts in quantum physics [4]. [1] Haroche, S. & Raimond, J.-M. Exploring the Quantum: Atoms, Cavities, and Photons. OUP Oxford, (2006). [2] Dada, A. C., et al. Optica 3, 493–498 (2016). [3] Dada, A. C., et al. arXiv preprint arXiv:1703.02308 (2017). [4] Sinha, U., Couteau, C., Jennewein, T., Laflamme, R., & Weihs, G. Science 329, 418–421 (2010).