Wavelength-tunable sources of entangled photons interfaced with atomic vapours

Abstract

The prospect of using the quantum nature of light for secure communication keeps spurring the search and investigation of suitable sources of entangled photons. A single semiconductor quantum dot is one of the most attractive, as it can generate indistinguishable entangled photons deterministically and is compatible with current photonic-integration technologies. However, the lack of control over the energy of the entangled photons is hampering the exploitation of dissimilar quantum dots in protocols requiring the teleportation of quantum entanglement over remote locations. Here we introduce quantum dot-based sources of polarization-entangled photons whose energy can be tuned via three-directional strain engineering without degrading the degree of entanglement of the photon pairs. As a test-bench for quantum communication, we interface quantum dots with clouds of atomic vapours, and we demonstrate slow-entangled photons from a single quantum emitter. These results pave the way towards the implementation of hybrid quantum networks where entanglement is distributed among distant parties using optoelectronic devices.

Strain-inducedg-factor tuning in single InGaAs/GaAs quantum dots

“…As the strain-induced shift in the emission energy is at least a factor of 15 smaller than what has been reported in literature for similar devices [12,17], we expect that the observed effect can be greatly enhanced. Using novel devices an even larger tuning range will be possible [28][29][30]. By optimizing the size, shape, and composition of the dots, we can enhance the valence band contribution and improve even further.…”

Advanced Technologies for Quantum Photonic Devices Based on Epitaxial Quantum Dots

“…In 2016, Trotta et al. experimentally demonstrated their proposal with laser‐machined piezoelectric substrates where they use three independently tunable in‐plane stress fields . Within their approach, there is no requirement on the anisotropic structural axis of a QD.…”

Generating indistinguishable photons from a quantum dot in a noisy environment

“…Two-level QD transitions can generate single photons with a high degree of indistinguishability [1][2][3][4][5][6][7][8][9][10][11][12][13], an ideal resource for implementing future quantum photonic technologies such as boson sampling [14,15] and perhaps ultimately linear optical quantum computing. Multilevel QD systems, including the biexciton → exciton → ground−state cascade and so-called spin−λ systems [16,17] can be used to generate entangled photon pairs [18][19][20][21] and spin-photon entanglement [22][23][24], respectively, which can underpin implementations of quantum repeaters and networks [25]. While a solid-state platform provides benefits for scalability [26], functionality [27,28], and on-chip integration [29][30][31], inherent fluctuations in the semiconductor matrix act as sources of noise [32][33][34][35] that inhomogeneously broaden a QD transition.…”