Microscopic theory of indistinguishable single-photon emission from a quantum dot coupled to a cavity: The role of non-Markovian phonon-induced decoherence

We study the fundamental limit on single-photon indistinguishability imposed by decoherence due to phonon interactions in semiconductor quantum dot-cavity quantum electrodynamics systems. Employing an exact diagonalization approach we find large differences compared to standard methods. An important finding is that short-time non-Markovian effects limit the maximal attainable indistinguishability. The results are explained using a polariton picture that yields valuable insight into the phonon-induced dephasing dynamics.

Figure 1

(a) Schematic of a coupled QD-cavity system interacting with longitudinal acoustical phonons and a photonic crystal cavity with an embedded QD. (b) Two-time plane with the time diagonal $\tau =0$ and phonon reservoir correlation time ${\tau }_{\mathrm{corr}}$. The shaded region shows the extent of the short-time regime. (c), (d) Calculated indistinguishability as a function of the QD-cavity coupling strength for light emitted from the QD and the cavity. Parameters: $\Gamma =0.5$ ns${}^{-1}$, $\hslash \kappa =125\mu$eV, $\hslash \Delta =27.78\mu$eV, and $\hslash \gamma =0.85\mu$eV.

Figure 2

(a) Time-dependent dephasing rate from the TCL. (b) Effective phonon density at zero temperature. (c) Phonon population distribution function for $\hslash g=30\mu$eV, $\Gamma =0.5$ ns${}^{-1}$, $\hslash \kappa =125\mu$eV, and $\hslash \Delta =27.78\mu$eV. (d) As (c) with $\hslash g=200\mu$eV.

Figure 3

(a), (b) Indistinguishability as a function of QD-cavity detuning for QD and cavity emission. (c)–(e) Phonon population distribution function for different QD-cavity detuning. For $\Delta =0$ the population has been scaled by a factor of 2. Parameters: $\hslash \Gamma =1\mu$eV, $\hslash \kappa =100\mu$eV, $\hslash g=100\mu$eV, and $\hslash \gamma =1.1\mu$eV.