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The coherence time constitutes one of the most critical parameters that determines whether or not interference is observed in an experiment. For photons, it is traditionally determined by the effective spectral bandwidth of the photon. Here we report on multi-photon interference experiments in which the multi-photon coherence time, defined by the width of the interference signal, depends on the number of interfering photons and on the measurement scheme chosen to detect the particles. A theoretical analysis reveals that all multi-photon interference with more than two particles features this dependence, which can be attributed to higher-order effects in the mutual indistinguishability of the particles. As a striking consequence, a single, well-defined many-particle quantum state can exhibit qualitatively different degrees of interference, depending on the chosen observable. Therefore, optimal sensitivity in many-particle quantum interferometry can only be achieved by choosing a suitable detection scheme.
We propose a new method of resonant enhancement of optical Kerr nonlinearity using multi-level atomic coherence. The enhancement is accompanied by suppression of the other linear and nonlinear susceptibility terms of the medium. We show that the effe
Integrated single-photon detectors open new possibilities for monitoring inside quantum photonic circuits. We present a concept for the in-line measurement of spatially-encoded multi-photon quantum states, while keeping the transmitted ones undisturb
We investigated the depth dependence of coherence times of nitrogen-vacancy (NV) centers through precisely depth controlling by a moderately oxidative at 580{deg}C in air. By successive nanoscale etching, NV centers could be brought close to the diam
We study the effect of the exciton fine-structure splitting on the polarisation-entanglement of photon pairs produced by the biexciton cascade in a single quantum dot. The entanglement is found to persist despite separations between the intermediate
Spins of negatively charged nitrogen-vacancy (NV$^-$) defects in diamond are among the most promising candidates for solid-state qubits. The fabrication of quantum devices containing these spin-carrying defects requires position-controlled introducti