Spontaneous emission of quantum dot systems in laterally structured microcavities that exhibit photon confinement in all three directions has been studied by time-resolved photoluminescence spectroscopy. For on-resonance conditions, we find that the dot emission rate is increased substantially over that of the unstructured planar cavity. For off-resonance conditions, we are able to suppress the emission rate by an order of magnitude by using cavities with metal coatings, which we attribute to the suppression of leaky optical modes in these structures.

We study a 1D chain of non-interacting bosonic cavities which are subject to nearest-neighbour parametric driving. With a suitable choice of drive phases, this model is strongly analogous to the celebrated Kitaev chain model of a 1D p-wave superconductor. The system exhibits phasedependent chirality: photons propagate and are amplified in a direction that is determined by the phase of the initial drive or excitation. Further, we find a drastic sensitivity to boundary conditions: for a range of parameters, the boundary-less system has only delocalized, dynamically unstable modes, while a finite open chain is described by localized, dynamically stable modes. While our model is described by a Hermitian Hamiltonian, we show that it has a surprising connection to non-Hermitian asymmetric-hopping models. arXiv:1805.12557v1 [cond-mat.mes-hall] 31 May 2018

Quasi-zero-dimensional magnetic polarons in single Cd 0.93 Mn 0.07 Te/Cd 0.6 Mg 0.4 Te quantum dots have been studied by photoluminescence spectroscopy. By comparing the experimental data with model calculations, the energy, the internal magnetic field, and the volume of the magnetic polarons are obtained. Moreover, the magnetic environment of the recombining electron hole pair causes a distinct broadening of the emission line (ϳ4 meV) of one diluted magnetic single quantum dot. The alignment of the Mn-spins in high magnetic fields results in a linewidth narrowing of almost one order of magnitude and the linewidth becomes comparable to that of a nonmagnetic Cd 0.93 Mg 0.07 Te/Cd 0.6 Mg 0.4 Te reference sample. RAPID COMMUNICATIONS R7768PRB 62 A. A. MAKSIMOV et al. RAPID COMMUNICATIONS R7770PRB 62 A. A. MAKSIMOV et al.

Non-Hermitian systems exhibit markedly different phenomena than their conventional Hermitian counterparts. Several such features, such as the non-Hermitian skin effect, are only present in spatially extended systems. Potential applications of these effects in many-mode systems however remains largely unexplored. Here, we study how unique features of non-Hermitian lattice systems can be harnessed to improve Hamiltonian parameter estimation in a fully quantum setting. While the quintessential non-Hermitian skin effect does not provide any distinct advantage, alternate effects yield dramatic enhancements. We show that certain asymmetric non-Hermitian tight-binding models with a $${{\mathbb{Z}}}_{2}$$ Z 2 symmetry yield a pronounced sensing advantage: the quantum Fisher information per photon increases exponentially with system size. We find that these advantages persist in regimes where non-Markovian and non-perturbative effects become important. Our setup is directly compatible with a variety of quantum optical and superconducting circuit platforms, and already yields strong enhancements with as few as three lattice sites.