arXiv subjects

Pasquale Cilibrizzi

Publications and source records attributed to Pasquale Cilibrizzi.

10 recordsLinked to original sources

arXiv2026

Quantum communication networks with defects in silicon carbide

Quantum communication promises unprecedented capabilities enabled by the transmission of quantum states of light. However, current implementations face severe distance limitations due to photon loss. Silicon carbide (SiC) defects have emerged as a promising quantum device platform, offering strong optical transitions, long spin coherence lifetimes and the opportunity for integration with semiconductor devices. Some defects with optical transitions in the telecom range have been identified, allowing to interface with fiber networks without the need for wavelength conversion. These unique properties make SiC an attractive platform for the implementation of quantum nodes for quantum communication networks. We provide an overview of the most prominent defects in SiC and their implementation in spin-photon interfaces. Furthermore, we model an exemplary, memory-enhanced quantum communication protocol in order to extract the parameters required to surpass a direct point-to-point link performance. Based on these insights, we summarize the key steps required towards the deployment of SiC devices in large-scale quantum communication networks.

quant-ph↗

arXiv2025

Scalable registration of single quantum emitters within solid immersion lenses through femtosecond laser writing

The precise registration of solid-state quantum emitters to photonic structures is a major technological challenge for fundamental research (e.g. in cavity quantum electrodynamics) and applications to quantum technology. Standard approaches include the complex multi-step fabrication of photonic structures on pre-existing emitters, both registered within a grid of lithographically-defined markers. Here, we demonstrate a marker-free, femtosecond laser writing technique to generate individual quantum emitters within photonic structures. Characterization of 28 defect centers, laser-written at the centers of pre-existing solid immersion lens structures, showed offsets relative to the photonic structure's center of 260~nm in the x-direction and 60~nm in the y-direction, with standard deviations of $\pm 170$~nm and $\pm 90$~nm, respectively, resulting in an average 4.5 times enhancement of the optical collection efficiency. This method is scalable for developing integrated quantum devices using spin-photon interfaces in silicon carbide and is easily extendable to other materials.

quant-ph↗

arXiv2025

Broadband Fourier transform spectroscopy of quantum emitters photoluminescence with sub-nanosecond temporal resolution

The spectral characterization of quantum emitter luminescence over broad wavelength ranges and fast timescales is important for applications ranging from biophysics to quantum technologies. Here we present the application of time-domain Fourier transform spectroscopy, based on a compact and stable birefringent interferometer coupled to low-dark-count superconducting single-photon detectors, to the study of quantum emitters. We experimentally demonstrate that the system enables spectroscopy of quantum emitters over a broad wavelength interval from the near-infrared to the telecom range, where grating-based spectrometers coupled to InGaAs cameras are typically noisy and inefficient. We further show that the high temporal resolution of single-photon detectors, which can be on the order of tens of picoseconds, enables the monitoring of spin-dependent spectral changes on sub-nanosecond timescales.

quant-ph↗

arXiv2023

Ultra-narrow inhomogeneous spectral distribution of telecom-wavelength vanadium centres in isotopically-enriched silicon carbide

Spin-active quantum emitters have emerged as a leading platform for quantum technologies. However, one of their major limitations is the large spread in optical emission frequencies, which typically extends over tens of GHz. Here, we investigate single V4+ vanadium centres in 4H-SiC, which feature telecom-wavelength emission and a coherent S=1/2 spin state. We perform spectroscopy on single emitters and report the observation of spin-dependent optical transitions, a key requirement for spin-photon interfaces. By engineering the isotopic composition of the SiC matrix, we reduce the inhomogeneous spectral distribution of different emitters down to 100 MHz, significantly smaller than any other single quantum emitter. Additionally, we tailor the dopant concentration to stabilise the telecom-wavelength V4+ charge state, thereby extending its lifetime by at least two orders of magnitude. These results bolster the prospects for single V emitters in SiC as material nodes in scalable telecom quantum networks.

quant-ph↗

arXiv2023

Scalable fabrication of hemispherical solid immersion lenses in silicon carbide through grayscale hard-mask lithography

Grayscale lithography allows the creation of micrometer-scale features with spatially-controlled height in a process that is fully compatible with standard lithography. Here, solid immersion lenses are demonstrated in silicon carbide using a novel fabrication protocol combining grayscale lithography and hard-mask techniques to allow nearly hemispherical lenses of 5 $μ$m radius to be etched into the substrate. The technique is highly scalable and compatible with CMOS technology, and device aspect ratios can be tuned after resist patterning by controlling the chemistry of the subsequent dry etch. These results provide a low-cost, high-throughput and industrially-relevant alternative to focused ion beam milling for the creation of high-aspect-ratio, rounded microstructures.

physics.optics↗

arXiv2023

Self-Induced Valley Bosonic Stimulation of Exciton-Polaritons in a Monolayer Semiconductor

The newly discovered valley degree of freedom in atomically thin two-dimensional transition metal dichalcogenides (TMD) offers a promising platform to explore rich nonlinear physics, such as spinor Bose-Einstein condensate (BEC) and novel valleytronics applications. However, the critical nonlinear effect, such as valley polariton bosonic stimulation, has long remained an unresolved challenge due to the generation of limited polariton ground state densities necessary to induce the stimulated scattering of polaritons in specific valleys. Here, we report the self-induced valley bosonic stimulation of exciton-polaritons via spin-valley locking in a WS2 monolayer microcavity. This is achieved by the resonant injection of valley polaritons at specific energy and wavevector, which allows spin-polarized polaritons to efficiently populate their ground state and induce a valley-dependent bosonic stimulation. As a result, we observe the nonlinear self-amplification of polariton emission from the valley-dependent ground state. Our finding paves the way for the investigation of spin ordering and phase transitions in TMD polariton BEC, offering a promising route for the realization of polariton spin lattices in moiré polariton systems and spin-lasers.

cond-mat.mes-hall↗

arXiv2016

Half-Skyrmion Spin Textures In Polariton Microcavities

We study the polarization dynamics of a spatially expanding polariton condensate under nonresonant linearly polarized optical excitation. The spatially and temporally resolved polariton emission reveals the formation of non-trivial spin textures in the form of a quadruplet polarization pattern both in the linear and circular Stokes parameters, and an octuplet in the diagonal Stokes parameter. The continuous rotation of the polariton pseudospin vector through the condensate due to TE-TM splitting exhibits an ordered pattern of half-skyrmions associated with a half-integer topological number. A theoretical model based on a driven-dissipative Gross-Pitaevskii equation coupled with an exciton reservoir describes the dynamics of the nontrivial spin textures through the optical spin-Hall effect.

physics.optics↗

arXiv2016

Polariton Spin Whirls

We report on the observation of spin whirls in a radially expanding polariton condensate formed under non-resonant optical excitation. Real space imaging of polarization- and time-resolved photoluminescence reveal a spiralling polarization pattern in the plane of the microcavity. Simulations of the spatiotemporal dynamics of a spinor condensate reveal the crucial role of polariton interactions with a spinor exciton reservoir. Harnessing spin dependent interactions between the exciton reservoir and polariton condensates allows for the manipulation of spin currents and the realization of dynamic collective spin effects in solid state systems.

cond-mat.mes-hall↗

arXiv2014

Polariton condensation in a planar microcavity with InGaAs quantum wells

Polariton lattice condensates provide a platform for on chip quantum emulations. Interactions in extended polariton lattices are currently limited by the intrinsic photonic disorder of microcavities. Here, we fabricate a strain compensated planar GaAs/AlAs microcavity with embedded InGaAs quantum wells and report on polariton condensation under non-resonant optical excitation. Evidence of polariton condensation is supported spectroscopically both in reflection and transmission geometry, whilst the observation of a second threshold to photon lasing allows us to conclusively distinguish between the strong- and weak-coupling non-linear regimes.

cond-mat.mes-hall↗

arXiv2012

The Non-linear Optical Spin Hall Effect and Long-Range Spin Transport in Polariton Lasers

We report on the experimental observation of the non-linear analogue of the optical spin Hall effect under highly non-resonant circularly polarized excitation of an exciton polariton condensate in a GaAs/AlGaAs microcavity. Initially circularly polarized polariton condensates propagate over macroscopic distances while the collective condensate spins coherently precess around an effective magnetic field in the sample plane performing up to four complete revolutions.

cond-mat.mes-hall↗