arXiv subjects

Andrea Barbiero

Publications and source records attributed to Andrea Barbiero.

7 recordsLinked to original sources

arXiv2025

Optical spin tomography in a telecom C-band quantum dot

A central challenge for scalable quantum networks is the realization of coherent interfaces between stationary qubits and telecom-band photonic qubits for long-distance entanglement distribution. Semiconductor quantum dots emitting at telecom wavelengths present a promising spin-photon platform, and a precise understanding of the properties of the confined spin is crucial for optimizing its interplay with the photonic qubit. Here, we simultaneously benchmark the electron and hole g-factors and coherence properties of a droplet epitaxy QD, solely from time and polarization resolved photon correlations. These measurements identify the hole as the preferable qubit for spin-photon entanglement in quantum network nodes. We then perform full state tomography of the confined hole ground state to reveal subtle anisotropies in the spin precession, providing essential diagnostics for minimizing phase errors critical for deterministic multiphoton entanglement generation.

quant-ph↗

arXiv2025

An entangled photon source for the telecom C-band based on a semiconductor-confined spin

Multiphoton entangled states are a key resource for quantum networks and measurement-based quantum computation. Scalable protocols for generating such states using solid-state spin-photon interfaces have recently emerged, but practical implementations have so far relied on emitters operating at short wavelengths, incompatible with low-loss fibre transmission. Here, we take a key step towards the generation of telecom wavelength multi-qubit entangled states using an InAs/InP quantum dot. After establishing that all essential criteria for generating cluster states using a ground state spin as the entangler are satisfied, we implement a scalable protocol to entangle the resident spin with sequentially emitted photons directly in the telecom C-band. We demonstrate a two-qubit (spin-photon) entanglement fidelity of $59.5\pm 8.7\%$ and a lower bound of three-qubit (spin-photon-photon) entanglement fidelity of $52.7\pm 11.4\%$. Our results close the performance gap between short-wavelength quantum dot systems and the existing telecom infrastructure, establishing a route towards practical large photonic cluster states for fibre-based quantum network applications.

quant-ph↗

arXiv2025

Purcell enhanced and tunable single-photon emission at telecom wavelengths from InAs quantum dots in circular photonic crystal resonators

Embedding semiconductor quantum dots into bullseye resonators has significantly advanced the development of bright telecom quantum light sources for fiber-based quantum networks. To further improve the device flexibility and stability, the bullseye approach should be combined with a pin diode structure to enable Stark tuning, deterministic charging, and enhanced coherence. In this work, we fabricate and characterize photonic structures incorporating hole gratings that efficiently support charge carrier transport while maintaining excellent optical performance. We report bright, Purcell-enhanced single-photon emission in the telecom C-band under above-band and phonon-assisted excitation. Additionally, we present electrically contacted resonators, demonstrating wide range tuneability of quantum dot transitions in the telecom O-band. These results mark significant steps toward scalable and tunable quantum light sources for real-world quantum photonic applications.

physics.optics↗

arXiv2023

Polarization-selective enhancement of telecom wavelength quantum dot transitions in an elliptical bullseye resonator

Semiconductor quantum dots are promising candidates for the generation of nonclassical light. Coupling a quantum dot to a device capable of providing polarization-selective enhancement of optical transitions is highly beneficial for advanced functionalities such as efficient resonant driving schemes or applications based on optical cyclicity. Here, we demonstrate broadband polarization-selective enhancement by coupling a quantum dot emitting in the telecom O-band to an elliptical bullseye resonator. We report bright single-photon emission with a degree of linear polarization of 96%, Purcell factor of 3.9, and count rates up to 3 MHz. Furthermore, we present a measurement of two-photon interference without any external polarization filtering and demonstrate compatibility with compact Stirling cryocoolers by operating the device at temperatures up to 40 K. These results represent an important step towards practical integration of optimal quantum dot photon sources in deployment-ready setups.

physics.optics↗

arXiv2022

Fine structure splitting analysis of cavity-enhanced telecom-wavelength InAs quantum dots grown on a GaAs(111)A vicinal substrate

The effcient generation of entangled photons at telecom wavelength is crucial for the success of many quantum communication protocols and the development of fiber-based quantum networks. Entangled light can be generated by solid state quantum emitters with naturally low fine structure splitting, such as highly symmetric InAs quantum dots (QDs) grown on (111)-oriented surfaces. Incorporating this kind of QDs into optical cavities is critical to achieve sufficient signal intensitiesfor applications, but has so far shown major complications. In this work we present droplet epitaxy of telecom-wavelength InAs QDs within an optical cavity on a vicinal (2° miscut) GaAs(111)A substrate. We show a remarkable enhancement of the photon extraction efficiency compared to previous reports together with a reduction of the density that facilitates the isolation of single spectral lines. Moreover, we characterise the exciton fine structure splitting and employ numerical simulations under the framework of the empirical pseudopotential and configuration interaction methods to study the impact of the miscut on the optical properties of the QDs. We demonstrate that the presence of miscut steps influences the polarisation of the excitonic states and introduces a preferential orientation in the $C_{3v}$ symmetry of the surface.

quant-ph↗

arXiv2022

High performance single-photon sources at telecom wavelength based on broadband hybrid circular Bragg gratings

Semiconductor quantum dots embedded in hybrid circular Bragg gratings are a promising platform for the efficient generation of nonclassical light. The scalable fabrication of multiple devices with similar performance is highly desirable for their practical use as sources of single and entangled photons, while the ability to operate at telecom wavelength is essential for their integration with the existing fiber infrastructure. In this work we combine the promising properties of broadband hybrid circular Bragg gratings with a membrane-transfer process performed on 3" wafer scale. We develop and study single-photon sources based on InAs/GaAs quantum dots emitting in the telecom O-band, demonstrating bright single-photon emission with Purcell factor > 5 and count rates up to 10 MHz. Furthermore, we address the question of reproducibility by benchmarking the performance of 10 devices covering a wide spectral range of 50 nm within the O-band.

physics.optics↗

arXiv2022

Design study for an efficient semiconductor quantum light source operating in the telecom C-band based on an electrically-driven circular Bragg grating

The development of efficient sources of single photons and entangled photon pairs emitting in the low-loss wavelength region around 1550 nm is crucial for long-distance quantum communication. Moreover, direct fiber coupling and electrical carrier injection are highly desirable for deployment in compact and user-friendly systems integrated with the existing fiber infrastructure. Here we present a detailed design study of circular Bragg gratings etched in InP slabs and operating in the telecom C-band. These devices enable the simultaneous enhancement of the X and XX spectral lines, with collection efficiency in NA=0.65 close to 90% for the wavelength range 1520-1580 nm and Purcell factor up to 15. We also investigate the coupling into single mode fiber, which exceeds 70% in UHNA4. Finally, we propose a modified device design directly compatible with electrical carrier injection, reporting Purcell factors up to 20 and collection efficiency in NA=0.65 close to 70% for the whole telecom C-band.

physics.optics↗