arXiv subjects

Joanna M Zajac

Publications and source records attributed to Joanna M Zajac.

5 recordsLinked to original sources

arXiv2026

Quantum dots for quantum repeaters

This review surveys recent progress in III--V semiconductor quantum dots (QDs) as a platform for quantum repeaters. We start by discussing the state of the art in QD-based non-classical light sources. Specifically, we report on on single-photon and entangled-pair sources operating across near-infrared and telecom wavelengths, with emphasis on the key metrics-multi-photon suppression g2(0), photon indistinguishability, extraction efficiency, and spin coherence time-while discussing frequency conversion, excitation schemes, cavity engineering, remote indistinguishability, and spin coherence. We then examine the two principal repeater architectures. For all-photonic repeaters we review linear cluster- and graph-state generation using QD spins, recent experimental milestones, and the critical role of spin dephasing time. For memory-based repeaters we focus on heterogeneous implementations combining deterministic QD photon sources with room-temperature alkali-vapor memories, providing rate benchmarking against other platforms, discussion of storage protocols, wavelength compatibility, and early demonstrations. Enabling technologies such as cryogenic cooling, on-chip photonic integration, network synchronization and multiplexing are also presented. The review highlights the strength of QD-based architectures and identifies the remaining milestones required for their deployment in practical fiber-based quantum networks.

quant-ph↗

arXiv2024

Efficient broadband antenna for a quantum emitter working at telecommunication wavelengths

Single photons are resources needed for developing quantum networks QN. They distribute quantum information services across commercial optical fiber links and are key ingredient in developing quantum repeaters architectures. Currently, the most robust quantum light sources are Quantum Dots made of III-V materials. They emit highly indistinguishable photons on-demand and with high efficiency. Established devices work at near-infrared wavelengths (NIR) and further research is needed to develop devices working in telecommunication wavelengths O- and S-bands. In this contribution, we propose and model a broadband optical antenna working in O-band. It exhibits high extraction efficiencies with small Purcell enhancement around 2. We also examine far field emission from these structures, ensuring Gaussian mode profile is observed.

physics.optics↗

arXiv2012

Parametric scattering of microcavity polaritons into ghost branches

Polaritons of defined momentum and energy are excited resonantly on the lower polariton branch of a planar semiconductor microcavity in the strong coupling regime, and the spectrally and momentum resolved emission is analyzed. We observe ghost branches from scattering within the lower polariton branch, as well as from scattering to the middle polariton branch, showing the non-linear mixing between different branches. Extending the theoretical treatment of spontaneous parametric luminescence developed in Ciuti et al., Phys. Rev. B 63, 041303 (2001), the eigenmodes of the driven polariton system and its photoluminescence are modeled.

cond-mat.other↗

arXiv2012

Structure and zero-dimensional polariton spectrum of natural defects in GaAs/AlAs microcavities

We present a correlative study of structural and optical properties of natural defects in planar semiconductor microcavities grown by molecular beam epitaxy, which are showing a localized polariton spectrum as reported in Zajac et al., Phys. Rev. B 85, 165309 (2012). The three-dimensional spatial structure of the defects was studied using combined focussed ion beam (FIB) and scanning electron microscopy (SEM). We find that the defects originate from a local increase of a GaAs layer thickness. Modulation heights of up to 140nm for oval defects and 90nm for round defects are found, while the lateral extension is about 2um for oval and 4um for round defects. The GaAs thickness increase is attributed to Ga droplets deposited during growth due to Ga cell spitting. Following the droplet deposition, the thickness modulation expands laterally while reducing its height, yielding oval to round mounds of the interfaces and the surface. With increasing growth temperature, the ellipticity of the mounds is decreasing and their size is increasing. This suggests that the expansion is related to the surface mobility of Ga, which with increasing temperature is increasing and reducing its anisotropy between the [110] and [1-10] crystallographic directions. Comprehensive data consisting of surface profiles of defects measured using differential interference contrast (DIC) microscopy, volume information obtained using FIB/SEM, and characterization of the resulting confined polariton spectrum are presented.

physics.optics↗

arXiv2011

Polariton states bound to defects in GaAs/AlAs planar microcavities

We report on polariton states bound to defects in planar GaAs/AlAs microcavities grown by molecular beam epitaxy. The defect types relevant for the spatial polariton dynamics in these structures are cross-hatch misfit dislocations, and point-like defects extended over several micrometers. We attribute the latter defects to Ga droplets emitted occasionally by the Ga cell during the growth. These defects, also known as oval defects, result in a dome-like local modulation of surface, which is translated into the cavity structure and leads to a lateral modulation of the cavity polariton energy of up to 15\,meV. The resulting spatially localized potential landscape for the in-plane polariton motion creates a series of bound states. These states were characterized by spectrally resolved transmission imaging in real and reciprocal space, and reveal the spatial potential created by the defects. Interestingly, the defect states exhibit long lifetimes in the 10ps range, which we attribute to a spatially smooth confinement potential.

cond-mat.mtrl-sci↗