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arXiv:2507.05943

Coherent superposition of emitted and resonantly scattered photons from a two-level system in a cavity driven by an even-$π$ pulse

Igor V. Krainov, A. I. Galimov, Yu. M. Serov, Alexey A. Toropov, T. V. Shubina

Published Jul 8, 2025• 0 citations
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Abstract

We examine the nature and quantum satistics of a multiphoton bunch generated under resonant excitation by even-$π$ pulses of a charged quantum dot in a cavity. Experiments with Rabi oscillations in time-resolved photoluminescence, varying pulse duration, and cavity mode detuning show that this multiphoton state is a coherent superposition of emitted photons and resonantly scattered laser photons. The developed model incorporates both resonant scattering and re-excitation mechanisms, allowing us to describe the quantum statistics of the multiphoton state, which is controlled by the coupling between the quantum dot and optical modes in the cavity.

DOI
10.48550/arxiv.2507.05943

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Coherent superposition of emitted and resonantly scattered photons from a two-level system in a cavity driven by an even-πππ pulse
We examine the nature and quantum satistics of a multiphoton bunch generated under resonant excitation by even-πππ pulses of a charged quantum dot in a cavity. Experiments with Rabi oscillations in time-resolved photoluminescence, varying pulse duration, and cavity mode detuning show that this multiphoton state is a coherent superposition of emitted photons and resonantly scattered laser photons. The developed model incorporates both resonant scattering and re-excitation mechanisms, allowing us to describe the quantum statistics of the multiphoton state, which is controlled by the coupling between the quantum dot and optical modes in the cavity.
Strongly coupled quantum dot-cavity systems provide a non-linear configuration of hybridized light-matter states with promising quantum-optical applications. Here, we investigate the coherent interaction between strong laser pulses and quantum dot-cavity polaritons. Resonant excitation of polaritonic states and their interaction with phonons allow us to observe coherent Rabi oscillations and Ramsey fringes. Furthermore, we demonstrate complete coherent control of a quantum dot-photonic crystal cavity based quantum-bit. By controlling the excitation power and phase in a two-pulse excitation scheme we achieve access to the full Bloch sphere. Quantum-optical simulations are in good agreement with our experiments and provide insight into the decoherence mechanisms.
Strongly coupled quantum dot-cavity systems provide a non-linear configuration of hybridized light-matter states with promising quantum-optical applications. Here, we investigate the coherent interaction between strong laser pulses and quantum dot-cavity polaritons. Resonant excitation of polaritonic states and their interaction with phonons allow us to observe coherent Rabi oscillations and Ramsey fringes. Furthermore, we demonstrate complete coherent control of a quantum dot-photonic crystal cavity based quantum-bit. By controlling the excitation power and phase in a two-pulse excitation scheme we achieve access to the full Bloch sphere. Quantum-optical simulations are in good agreement with our experiments and provide insight into the decoherence mechanisms.
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We report on coherent control of the resonantly driven exciton state in a single quantum dot in the strong coupling regime. With picosecond laser pulses, the two-level system undergoes Rabi oscillations and a given coherent superposition of states can be addressed. Using a pair of phase-locked pulses, optical manipulation is achieved during the coherence time of the qu-bit. The dephasing processes are also studied and we show that in typical quantum dots, the coherence time T 2 can be of the same order of magnitude as the effective lifetime of the exciton T 1 (a few hundreds of ps) although not reaching the upper theoretical limit of 2T 1 . We conclude that energy relaxation and pure dephasing processes due to virtual scattering with phonons contribute on an equal footing to the loss of coherence.
We theoretically analyze the temporal dynamics of strongly coupled quantum-dot--cavity system driven by a resonant laser pulse and observe the signature of Rabi oscillation in the time-resolved response of the system (i.e., in the numerically calculated cavity output). We derive simplified linear and nonlinear semiclassical models that approximate well the system's behavior in the limits of high- and low-power driving pulses and describe the role of quantum coherence in the exact dynamics of the system. Finally, we also present time-resolved transmission measurements showing the dynamics of a quantum-dot--cavity system in the presence of a short laser pulse.
We show that resonance fluorescence, i.e., the resonant emission of a coherently driven two-level system, can be realized with a semiconductor quantum dot. The dot is embedded in a planar optical microcavity and excited in a waveguide mode so as to discriminate its emission from residual laser scattering. The transition from the weak to the strong excitation regime is characterized by the emergence of oscillations in the first-order correlation function of the fluorescence, g(tau), as measured by interferometry. The measurements correspond to a Mollow triplet with a Rabi splitting of up to 13.3 microeV. Second-order correlation measurements further confirm nonclassical light emission.