Nonlinear down-conversion in a single quantum dot

Abstract

Tailored nanoscale quantum light sources, matching the specific needs of use cases, are crucial building blocks for photonic quantum technologies. Several different approaches to realize solid-state quantum emitters with high performance have been pursued and different concepts for energy tuning have been established. However, the properties of the emitted photons are always defined by the individual quantum emitter and can therefore not be controlled with full flexibility. Here we introduce an all-optical nonlinear method to tailor and control the single photon emission. We demonstrate a laser-controlled down-conversion process from an excited state of a semiconductor quantum three-level system. Based on this concept, we realize energy tuning and polarization control of the single photon emission with a control-laser field. Our results mark an important step towards tailored single photon emission from a photonic quantum system based on quantum optical principles.

Double-Pulse Generation of Indistinguishable Single Photons with Optically Controlled Polarization

“…The weakness of this method is that to get rid of the resonant laser, cross-polarization filtering, which blocks at least 50% of the unpolarized QD emission, has to be used. Various excitation schemes have been explored to solve this problem, for example, by using a pair of dichromatic pulses 0.27 meV detuned from the QD emission, , longitudinal acoustic phonon-assisted excitation with exciton population up to 85%, − optical microcavities with nondegenerate linearly polarized modes, , and stimulated two-photon emission from the biexciton state via a virtual state. , However, an excitation scheme that deterministically generates indistinguishable single photons with a near-unity degree of polarization and large laser-QD detuning is still missing. Combining coherent two-photon excitation (TPE) − with stimulated emission of the biexciton ( XX ) via neutral exciton ( X ) states , (see Figure a) could potentially meet all of the above requirements, but this method has not been employed to generate indistinguishable single photons.…”

On‐Demand Indistinguishable and Entangled Photons Using Tailored Cavity Designs

“…Ideal candidates to generate photons at a desired wavelength are quantum dots (QDs) embedded in semiconductor microcavities. [1,2] These structures enable the generation of polarization controlled, [3,4] highly indistinguishable, single photons, [1] and entangled photon pairs. [5][6][7][8][9] Additionally, the ideal QDcavity system generates only a single set of photons per excitation cycle, [10,11] rendering them excellent quantum emitters for use in optical quantum information processing networks.…”

Using the Autler-Townes and ac Stark effects to optically tune the frequency of indistinguishable single-photons from an on-demand source

“…Additional challenges to implementation of SPSs which have seen recent progress are * cgustin@stanford.edu the desirable criteria of scalability [13][14][15][16], and frequency tuning [17], as QDs are typically grown such that energy levels are stochastic in nature, but many applications require many SPSs with degenerate frequencies. Effective methods for frequency tuning QD SPSs (with a large variance in attainable bandwidth between methods) include electrical tuning [18,19], strain tuning [20][21][22], quantum frequency conversion via optical nonlinearity [23], and multi-photon Raman transition processes utilizing multilevel systems [24][25][26]. This last all-optical tuning process typically involves two sequential laser pulses, and uses the biexciton (two exciton) state, which extends the twolevel structure of the QD to a cascade-type ladder system, and as such is applicable to any ladder system involving three or more energy levels, not just QDs.…”