arXiv subjects

C. Antón-Solanas

Publications and source records attributed to C. Antón-Solanas.

7 recordsLinked to original sources

arXiv2026

Spin-polarized lasing in a photonic lattice

We characterize spin-polarized lasing in a two-dimensional photonic lattice fabricated from a GaAs/InGaAs semiconductor microcavity sample. The lattice is defined by a staggered arrangement of rounded rectangular micrometric mesas that laterally confine and couple the optical modes. Polarization-, angle-, and energy-resolved micro-photoluminescence measurements reveal the transition from the strong-coupling regime to photon lasing, accompanied by extended spatial coherence across several lattice unit cells. Under circularly polarized nonresonant excitation, the emitted light acquires a controllable circular polarization whose handedness follows that of the pump. These results establish photonic-lattice VCSELs as a platform for spin-controlled coherent emission in extended optical systems.

physics.optics↗

arXiv2026

Accessing which-path information in the absorption and emission of light by a quantum dot in a Ramsey sequence

We quantify which-path information in the absorption and emission of light by a quantum dot along a Ramsey-like sequence. The quantum dot is excited by two successive classical $π/2$-pulses with tunable relative phase, yielding the spontaneous release of coherent superpositions of zero- and one-photon Fock states into two successive time bins. Along the sequence, the first time bin extracts information on the quantum dot energy state, behaving as a which-path detector for the Ramsey interferometer. The which-path information increases over time, and is accessed through the reduction of contrast of the Ramsey fringes. After the second pulse, the information still present in the first time bin controls the emission of coherent light into the second time bin, which is measurable through the reduction of the contrast of self-homodyne interference fringes in a Mach-Zehnder interferometer. Both measurements are in remarkable agreement with theoretical predictions. Our results quantitatively illustrate how which-path information and more generally quantum correlations impact light-matter energy exchanges in the quantum realm.

quant-ph↗

arXiv2026

Temporal coherence of single photons emitted by hexagonal Boron Nitride defects at room temperature

Color centers in hexagonal boron nitride (hBN) emerge as promising quantum light sources at room temperature, with potential applications in quantum communications, among others. The temporal coherence of emitted photons (i.e. their capacity to interfere and distribute photonic entanglement) is essential for many of these applications. Hence, it is crucial to study and determine the temporal coherence of this emission under different experimental conditions. In this work, we report the coherence time of the single photons emitted by an hBN defect in a nanocrystal at room temperature, measured via Michelson interferometry. The visibility of this interference vanishes when the temporal delay between the interferometer arms is a few hundred femtoseconds, highlighting that the phonon dephasing processes are four orders of magnitude faster than the spontaneous decay time of the emitter. We also analyze the single photon characteristics of the emission via correlation measurements, defect blinking dynamics, and its Debye-Waller factor. Our room temperature results highlight the presence of a strong phonon-electron coupling, suggesting the need to work at cryogenic temperatures to enable quantum photonic applications based on photon interference.

quant-ph↗

arXiv2024

Quantum interferences and gates with emitter-based coherent photon sources

Quantum emitters such as quantum dots, defects in diamond or in silicon have emerged as efficient single photon sources that are progressively exploited in quantum technologies. In 2019, it was shown that the emitted single photon states often include coherence with the vacuum component. Here we investigate how such photon-number coherence alters quantum interference experiments that are routinely implemented both for characterising or exploiting the generated photons. We show that it strongly modifies intensity correlation measurements in a Hong-Ou-Mandel experiment and leads to errors in indistinguishability estimations. It also results in additional entanglement when performing partial measurements. We illustrate the impact on quantum protocols by evidencing modifications in heralding efficiency and fidelity of two-qubit gates.

quant-ph↗

arXiv2022

Photon-number entanglement generated by sequential excitation of a two-level atom

Entanglement and spontaneous emission are fundamental quantum phenomena that drive many applications of quantum physics. During the spontaneous emission of light from an excited two-level atom, the atom briefly becomes entangled with the photonic field. Here, we show that this natural process can be used to produce photon-number entangled states of light distributed in time. By exciting a quantum dot -- an artificial two-level atom -- with two sequential $π$ pulses, we generate a photon-number Bell state. We characterise this state using time-resolved intensity and phase correlation measurements. Furthermore, we theoretically show that applying longer sequences of pulses to a two-level atom can produce a series of multi-temporal mode entangled states with properties intrinsically related to the Fibonacci sequence. Our results on photon-number entanglement can be further exploited to generate new states of quantum light with applications in quantum technologies.

quant-ph↗

arXiv2021

Intrinsic circularly-polarized exciton emission in a twisted van-der-Waals heterostructure

The investigation of excitons in van-der-Waals heterostructures has led to profound insights into the interplay of crystal symmetries and fundamental effects of light-matter coupling. In particular, the polarization selection rules in undistorted, slightly twisted heterostructures of MoSe$_2$/WSe$_2$ were found to be connected with the Moiré superlattice. Here, we report the emergence of a significant degree of circular polarization of excitons in such a hetero-structure upon non-resonant driving with a linearly polarized laser. The effect is present at zero magnetic field, and sensibly reacts on perpendicularly applied magnetic field. The giant magnitude of polarization, which cannot be explained by conventional birefringence or optical activity of the twisted lattice, suggests a kinematic origin arising from an emergent pyromagnetic symmetry in our structure, which we exploit to gain insight into the microscopic processes of our device.

cond-mat.mes-hall↗

arXiv2021

Purcell-enhanced single photon source based on a deterministically placed WSe$_{2}$ monolayer quantum dot in a circular Bragg grating cavity

We demonstrate a deterministic Purcell-enhanced single-photon source realized by integrating an atomically thin WSe$_{2}$ layer with a circular Bragg grating cavity. The cavity significantly enhances the photoluminescence from the atomically thin layer, and supports single-photon generation with $g^{(2)}(0)<0.25$. We observe a consistent increase of the spontaneous emission rate for WSe$_{2}$ emitters located in the center of the Bragg grating cavity. These WSe$_{2}$ emitters are self-aligned and deterministically coupled to such a broadband cavity, configuring a new generation of deterministic single-photon sources, characterized by their simple and low-cost production and intrinsic scalability.

quant-ph↗