Abstract

The generation of on-demand, optimally entangled photon pairs remains one of the most formidable challenges in the quantum optics and quantum information community. Despite the fact that recent developments in this area have opened new doors leading toward the realization of sources exhibiting either high brightness or near-unity entanglement fidelity, the challenges to achieve both together persist. Here, we will provide a historical review on the development of quantum dots (QDs) for entangled photon generation, with a focus on nanowire QDs, and address the latest research performed on nanowire QDs, including measuring entanglement fidelity, light-extraction efficiency, dephasing mechanisms, and the detrimental effects of detection systems on the measured values of entanglement fidelity. Additionally, we will discuss results recently observed pertaining to resonant excitation of a nanowire QD, revealing the potential of such sources to outperform spontaneous parametric down-conversion (SPDC) sources, providing a viable solution to the current challenges in quantum optics and quantum information.

Highlights

  • Entangled photon pairs are one of the key elements for research and in emerging quantum applications with successful results in quantum foundations [1, 2], quantum communication [3–5], and quantum information [6–8]

  • The results reported by Fognini et al [45], in conjunction with the results achieved by resonant two-photon excitation (TPE), equip us with sufficient information to make such a comparison, the ultimate potential of nanowire quantum dots (QDs) in regards to both entanglement fidelity and pair-extraction efficiency, with the values reported for other photonic structures mentioned earlier [26, 32, 33]

  • Based on the results shown by Fognini et al [45] and the improvements gained by performing resonant TPE, we can predict measuring near-unity entanglement fidelity once two important modifications are implemented: the resonant TPE scheme is employed, and the detection system is improved to a fast and low-noise one

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Summary

Introduction

Entangled photon pairs are one of the key elements for research and in emerging quantum applications with successful results in quantum foundations [1, 2], quantum communication [3–5], and quantum information [6–8]. Still none exhibit the promise of quantum dots in realizing an ideal entangled photon source, showing near-unity entanglement fidelity and pair-extraction efficiency Another important feature of QDs affecting the measured entanglement is the finestructure splitting (FSS) of the jXi state, which is caused by the exchange interaction of the electron and hole in the e À h pair, together with geometrical asymmetries of the QD [34, 35]. Off-resonant excitation had been widely used to generate entangled and single photons from QDs in photonic structures This scheme excites charge carriers to energy levels above the bandgap of the host semiconductor, and relaxation of the resulted e À h pairs to the QD’s s-shell, mediated by interactions with phonons, leads to the emission of entangled photons. We will cover the improvements achieved in photon extraction efficiency, reduction of the dephasing processes, suppression of multiphoton emission, and enhancing entanglement fidelity of nanowire QD based entangled photon sources

Nanowire QDs
Bottom-up grown tapered wurtzite nanowire QDs
Optical properties
Entanglement measurements
Dephasing-free entanglement in nanowire QDs
Resonant two-photon excitation
State-of-the-art entangled photon sources
Findings
Conclusion and discussion
Full Text
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