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arXiv:2004.13725 · Physical Review Research

Dipole-coupled emitters as deterministic entangled photon-pair sources

Derek S. Wang, Tomáš Neuman, Prineha Narang

Published Dec 7, 2020• 11 citations
arXivHTMLPDF

Abstract

Scalable quantum systems require deterministic entangled photon pair sources.Here, we demonstrate a scheme that uses a dipole-coupled emitter pair to deterministically emit polarization-entangled photon pairs.Based on this scheme, we predict spectroscopic signatures and quantify the entanglement with realistic material parameters.In addition, we describe how the Bell state fidelity and efficiency can be optimized by precisely tuning transition frequencies.Finally, we discuss how defect emitters are natural candidates for the proposed scheme, offering numerous advantages including flexible on-chip photonic integration and tunable emission properties via external fields, electromagnetic environments, and defect selection.

DOI
10.1103/physrevresearch.2.043328

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Scalable quantum systems require deterministic entangled photon pair sources.Here, we demonstrate a scheme that uses a dipole-coupled emitter pair to deterministically emit polarization-entangled photon pairs.Based on this scheme, we predict spectroscopic signatures and quantify the entanglement with realistic material parameters.In addition, we describe how the Bell state fidelity and efficiency can be optimized by precisely tuning transition frequencies.Finally, we discuss how defect emitters are natural candidates for the proposed scheme, offering numerous advantages including flexible on-chip photonic integration and tunable emission properties via external fields, electromagnetic environments, and defect selection.
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Entangled photon-pair sources are at the core of quantum applications like quantum key distribution, sensing, and imaging. Operation in space-limited and adverse environments such as in satellite-based and mobile communication requires robust entanglement sources with minimal size and weight requirements. Here, we meet this challenge by realizing a cubic micrometer scale entangled photon-pair source in a 3R-stacked transition metal dichalcogenide crystal. Its crystal symmetry enables the generation of polarization-entangled Bell states without additional components and provides tunability by simple control of the pump polarization. Remarkably, generation rate and state tuning are decoupled, leading to equal generation efficiency and no loss of entanglement. Combining transition metal dichalcogenides with monolithic cavities and integrated photonic circuitry or using quasi-phasematching opens the gate towards ultrasmall and scalable quantum devices.
Solid state quantum emitters with electronic spin properties can be entangled using optical interferometric which-path erasure techniques that rely on identical frequencies and linewidths of the emitters. This promises a powerful, fast and scalable platform for quantum technologies. Using current protocols, a pair of emitters embedded in a waveguide interferometer can be deterministically prepared in a maximally entangled state. However, the amount of entanglement diminishes rapidly with increasing separation of the emission lines and variations in the linewidths of the emitters. Solid state emitters such as quantum dots are subject to intrinsic variations in the fabrication process. Therefore, manufacturing the required number of identical emitters on a chip is not scalable. In this Letter, we present a method that uses readily available pairs of entangled photons to entangle solid state emitters with large transition frequency separations and linewidth variations, circumventing the need to fabricate optically identical emitters. We demonstrate a concurrence of C = 0.95 for typical quantum dots using narrowband photon inputs.
Entangled photon-pair sources are at the core of quantum applications like quantum key distribution, sensing, and imaging. Operation in space-limited and adverse environments such as in satellite-based and mobile communication requires robust entanglement sources with minimal size and weight requirements. Here, we meet this challenge by realizing a cubic micrometer scale entangled photon-pair source in a 3R-stacked transition metal dichalcogenide crystal. Its crystal symmetry enables the generation of polarization-entangled Bell states without additional components and provides tunability by simple control of the pump polarization. Remarkably, generation rate and state tuning are decoupled, leading to equal generation efficiency and no loss of entanglement. Combining transition metal dichalcogenides with monolithic cavities and integrated photonic circuitry or using quasi-phasematching opens the gate towards ultrasmall and scalable quantum devices.
Semiconductor quantum dots (QDs) have emerged as a premier solid-state platform for the deterministic generation of nonclassical light, offering a compelling pathway toward scalable quantum photonic systems. While single-photon emission from QDs has reached a high level of maturity, the realization of high-fidelity entangled photon-pair sources remains an active and rapidly evolving frontier. In this review, we survey the recent progress in QD-based entangled photon sources, highlighting the conceptual evolution from the established biexciton-exciton cascade to the emerging paradigm of spontaneous two-photon emission. We further examine how advances in nanophotonic architectures and coherent control strategies are redefining fundamental performance limits, enabling concurrent improvements in source brightness, coherence, and entanglement fidelity. Finally, we discuss the key physical and technological challenges that must be addressed to bridge the gap between laboratory demonstrations and large-scale deployment. We conclude by outlining the future opportunities for integrating QD-based entangled photon sources into practical quantum communication, computation, and sensing platforms.