A simple and general strategy for generating frequency-anticorrelated photon pairs

Photon superbunching from a generic tunnel junction

Generating time-correlated photon pairs at the nanoscale is a prerequisite to creating highly integrated optoelectronic circuits that perform quantum computing tasks based on heralded single photons. Here, we demonstrate fulfilling this requirement with a generic tip-surface metal junction. When the junction is luminescing under DC bias, inelastic tunneling events of single electrons produce a stream of visible photons of plasmonic origin whose superbunching index is 17 (improved to a record of 70 by the authors during publication) when measured with a 53-ps instrumental resolution limit. The effect is driven electrically, rather than optically. This discovery has immediate and profound implications for quantum optics and cryptography, notwithstanding its fundamental importance to basic science and its ushering in of heralded photon experiments on the nanometer scale.

High fidelity heralded single-photon source using cavity quantum electrodynamics

Demands for single-photon sources are ubiquitous in quantum information processing as well as in quantum metrology. In many protocols for producing single photons, a cavity-emitter configuration is used. In such cavity quantum electrodynamical systems, the cavity can enforce a well-defined output mode for the photon and enhance its collection efficiency, while the emitter is indispensable for single photon emission. Here we show the two cavity-one two-level emitter configuration can be used to produce exclusively photon pairs, with each photon in a separate mode. Conditioning on detecting a photon in one of the modes, one heralds with high fidelity a single photon in the other mode. Counterintuitively, upon decreasing the coupling of the emitter to one of the modes, the heralding fidelity can further increase.

Dissipation induced by phonon elastic scattering in crystals

We demonstrate that the phonon elastic scattering leads to a dominant dissipation in crystals at low temperature. The two-level systems (TLSs) should be responsible for the elastic scattering, whereas the dissipation induced by static-point defects (SPDs) can not be neglected. One purpose of this work is to show how the energy splitting distribution of the TLS ensemble affects the dissipation. Besides, this article displays the proportion of phonon-TLS elastic scattering to total phonon dissipation. The coupling coefficient of phonon-SPD scattering and the constant P₀ of the TLS distribution are important that we estimate their magnitudes in this paper. Our results is useful to understand the phonon dissipation mechanism, and give some clues to improve the performance of mechanical resonators, apply the desired defects, or reveal the atom configuration in lattice structure of disordered crystals.