BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:6ae8fb44d8552 DTSTART:20261116T090000Z SEQUENCE:0 TRANSP:OPAQUE LOCATION:ICFO Auditorium SUMMARY:ICFO | SUSANA PLASCENCIA OROZCO CLASS:PUBLIC DESCRIPTION:Quantum repeaters play a fundamental role in the development of long-distance quantum network. In most architectures\, their functional c ore is constituted by quantum memories. Although many systems have been in vestigated as potential quantum memory\, no single platform yet satisfies all the requirements simultaneously. Solid-state systems\, particularly cr yogenically cooled rare-earth doped crystals represent one of the most pro mising routes toward efficient\, long-lived and massively multiplexed quan tum memories\, with great prospects for integration. This thesis addresses two main objectives. The first is to extend the spatial multimode capacit y of a rare-earth-doped quantum memory using a praseodymium-doped yttrium orthosilicate Pr^{3+}:Y_2SiO_5 to increase the entanglement generation rat e required for realistic quantum repeater application. The second objectiv e\, carried out in collaboration with Corning\, investigates the spectrosc opic properties of \; erbium-doped-chalcogenides to assess their suita bility as fiber-integrated quantum memory operating at the telecom wavelen gth.\nTo achieve spatial multiplexing in the Pr^{3+}:Y$_2SiO_5 crystal\, w e implement a quantum memory array (QMA) using a pair of acousto-optic def lectors\, creating ten individually controllable spin-wave memory cell fea turing on-demand read-out. By combing the spatial multiplexing of the arra y with the intrinsic temporal multimodality of the atomic frequency comb ( AFC) protocol\, we store and retrieve on-demand up to 250 modes using weak coherent pulses at the single-photon level\, both surpassing the current state-of-the-art for solid-state quantum memory. The high signal-to-noise ratio and low cross-talks enable the storage of heralded single-photons. T o do so\, we use a cavity enhanced spontaneous parametric down conversion source to generate a pair of photons\, with the signal photon stored in th e QMA and the idler at telecommunication wavelength. We demonstrate the vi olation of the Cauchy-Schwarz inequality \; by at least 4.8 standard d eviations in all the memory cells\, demonstrating light-matter quantum cor relations between the QMA and the telecom photon.\nWe further demonstrate the potential use of our system as a random access quantum memory (RAQM) b y storing path and time-bin qubits encoded with weak coherent states in th e quantum memory array\, achieving average fidelities of 95 ±\; 2% a nd 91 ±\; 2%\, respectively. We further load sequentially a time-bin qubit in two different memory cells\, simultaneously store both qubits\, and perform a collective read-out. The high fidelities together with indep endent control pair represent a significant step toward a solid-state RAQM for quantum repeaters and photonic quantum processors.\nFor the fiber-com patible quantum memory\, we study three Er-doped chalcogenide glasses with a different glass network rigidities quantified by the coordination mean number (MCN). We measure their optical coherence time (T_2) through two-pu lse photon echo (TPE) technique and find that the sample with MCN <\;&nb sp\; 2.4 exhibits the shortest T_2\, while the most rigid sample (MNC = 2. 9) suffers from internal stress that also limits the coherence time. The i ntermediate rigidity sample (MNC = 2.69) shows a T_2 close to 1 &mu\;s (co rresponding to a homegeneous linewidth &asymp\; 370 kHz) at 2 K \; and  \; 0.2 T\, which is among the longest coherence times reported for Er -doped glasses under practical cryogenic conditions\, reachable with a sta ndard close-cycle cryostat. However\, the spectral hole burning measuremen ts reveal hole widths around 50 MHz for two best TPE performing samples\, severely restricting the achievable comb finesse and therefore constrainin g the AFC efficiency in these materials.\nMonday November 16\, 10:00 h. IC FO Auditorium \nThesis Director: Prof. Dr. Hugues De Riedmatten DTSTAMP:20261102T210612Z END:VEVENT END:VCALENDAR