Doctoral School

Reading date: 29/05/2026

• MALLA, ADITYA JAGADEESH: COLLOIDAL QUANTUM DOT EMITTERS IN THE SHORTWAVE INFRARED REGION
  
  Author: MALLA, ADITYA JAGADEESH
  Programme: DOCTORAL DEGREE IN PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 16/04/2026
  Reading date: 29/05/2026
  Reading time: 10:00
  Reading place: ICFO Auditorium
  Thesis director: KONSTANTATOS, GERASIMOS
  Thesis abstract: Shortwave infrared (SWIR) light sources are indispensable for applications including advanced imaging, spectroscopy, and sensing; however, their widespread adoption is hindered by the high cost and limited scalability of epitaxial semiconductor technologies such as InGaAs. Colloidal quantum dots (QDs) offer an attractive alternative owing to their high photoluminescence quantum yield, size-tunable emission, large-area processability, and compatibility with low-cost solution-based fabrication. Among various QD-based emitters employing lead sulphide (PbS), this thesis focuses on two complementary technologies: electrically driven quantum-dot light-emitting diodes (QLEDs) and optically pumped downconverters (DCs).The first part of this thesis addresses performance enhancement in QLEDs (emitting at 1380 nm) through systematic device engineering. Charge imbalance is identified as a key factor limiting QLED efficiency and radiance. By optimising the ZnO electron transport layer via controlled annealing-temperature tuning, electron injection was modulated, leading to a maximum external quantum efficiency (EQE) of 20%. Furthermore, the charge balance within the emissive layer was optimised by controlling its thickness, resulting in an increase in maximum radiance from 5 W.sr-1.m-2 to 17.5 W.sr-1.m-2. Building upon this, a dual electron transport layer architecture was implemented to decouple interfacial quality from bulk electron transport, enabling a further enhancement in maximum radiance to 30 W.sr-1.m-2 while maintaining comparable EQE.Light extraction and Joule heating constitute an additional bottleneck in achieving high-performance QLEDs. To overcome substantial optical losses into substrate modes inherent in conventional bottom-emission devices, top-emission QLED (TQLED) architectures were investigated. These offer improved light extraction and allow for the use of opaque, high-thermal-conductivity silicon substrates to manage Joule heating. A high-performance sputtered indium tin oxide (ITO) electrode was developed, exhibiting optical transmission exceeding 85% at 1400 nm and a low sheet resistance of 33 Ω/□. By utilising optimised architecture with integrated ITO optical spacers and a dielectric/metal/dielectric top electrode, a low-Q microcavity was established. This modified the far-field radiation pattern to a forward-directed profile and narrowed the emission linewidth. The synergy between this resonant optical design and superior thermal dissipation enabled a record radiance exceeding 100 W.sr-1.m-2, and allowed for the first demonstration of active see-through SWIR imaging illuminated solely by QLEDs.The second part of the thesis is focused on lead sulphide QD-based DCs. The QD-DCs suffer from performance degradation under high excitation power densities due to the significant heat generation in the process of light absorption. We have developed high-power, stable, and spectrally tunable narrowband and broadband SWIR DCs (1000 nm - 1600 nm). By mixing two different-sized QDs, we exploit Förster resonance energy transfer and photon reabsorption to realise a binary system with a high photoluminescence quantum yield of 35 %. Embedding the QDs in a poly(methyl methacrylate) host mitigates local thermal stress on the QDs, enabling standalone DCs with a high emission power density (EmPD) of 110 mW.cm-2 at 1380 nm. Further optimisation with a spectrally selective distributed Bragg reflector for enhanced light extraction and a sapphire substrate for efficient heat dissipation, we achieved a record EmPD of 385 mW.cm-2 at 1380 nm with optical power conversion efficiency of 10% and operational stability above 230 hours at an EmPD of 190 mW.cm-2. This demonstrates a scalable route to low-cost SWIR light sources, narrowing the performance gap between solution-processed DCs and conventional epitaxial semiconductors.
  

• MOSAHEBFARD, MOHAMMADREZA: Resource Management in Sliced Converged Optical-Wireless 6G Networks: From Strategic Dimensioning to Dynamic Service Provisioning
  
  Author: MOSAHEBFARD, MOHAMMADREZA
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 10/04/2026
  Reading date: 29/05/2026
  Reading time: 11:00
  Reading place: Room C4-021B at the Castelldefels Campus
  Thesis director: VERIKOUKIS, CHRISTOS | VARDAKAS, JOHN
  Thesis abstract: The evolution toward the 6th Generation (6G) networks relies on converged optical-wireless infrastructures and virtualization technologies like Network Functions Virtualization (NFV) to support diverse services through Network Slicing. While enabling flexibility, these paradigms introduce profound complexity in managing shared computational and com-municational resources. This thesis addresses this challenge by identifying a fundamental temporal duality in resource management, spanning the strategic need for agile capacity planning to the operational necessity of real-time service provisioning. This complexity is further aggravated by the presence of various network slices, each with distinct Quality of Service (QoS) requirements. To resolve this dichotomy, distinct methodologies are developed within this PhD thesis.To address the strategic domain, where Mobile Virtual Network Operators (MVNOs) require rapid dimensioning tools for flexible resource leasing, this PhD thesis develops a computationally efficient analytical framework based on one-dimensional Markov chains. Uniquely, this model captures resource occupancy at two levels: physical resources governing Service Function Chain (SFC) instantiation, and virtual resources governing user admission. This stratified modeling avoids state-space explosion while accurately calculating admission ratios, achieving relative errors typically below 2% compared to simulations. The framework is applied to determine the minimum resources required to achieve target admission ratios under varying arrival rates, as well as to identify the necessary capacity to meet different target admission rates under constant traffic loads. This capability enables rapid offline dimensioning to guarantee Quality of Service (QoS) thresholds, offering a scalable alternative to time-consuming simulations and resource-exhaustive optimization approaches.Complementing this, the operational challenge of online SFC Embedding (SFCE) is addressed. Recognizing the NP-hardness of the embedding problem with the objective of jointly minimizing holistic power consumption and blocking probability, HORIZON, a novel holistic heuristic designed to optimize Mobile Virtual Network Operator (MVNO) operational efficiency, is developed. It employs a proactive backward placement strategy coupled with power and latency-aware segmental routing, and integrates comprehensive power models for both servers and Reconfigurable Optical Add-Drop Multiplexers (ROADMs). By enforcing strict inter-slice isolation while maximizing intra-slice efficiency, HORIZON achieves power efficiency within 15% of optimal Integer Linear Programming (ILP) bounds under resource-constrained scenarios. Evaluations across four realistic network topologies demonstrate execution times of 10–18 ms per service request (38–67 times faster than optimal solvers), power savings up to 23.6% compared to state-of-the-art heuristics, and negligible blocking rates, enabling MVNOs to minimize OPerational EXpenditure (OPEX) while strictly adhering to Service Level Agreements (SLAs).
  

• NAVARRO GRANADOS, JORDI: Theoretical and Experimental Study on Cold-Formed Elements for Steel Framing in Seismic Areas
  
  Author: NAVARRO GRANADOS, JORDI
  Programme: DOCTORAL DEGREE IN EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Normal
  Deposit date: 20/03/2026
  Reading date: 29/05/2026
  Reading time: 12:30
  Reading place: ETSEIBUPC, Campus SudAula CapellaAv. Diagonal, 647.08028 Barcelona
  Thesis director: CASAFONT RIBERA, MIQUEL | BOVÉ TOUS, ORIOL
  Thesis abstract: This Thesis presents a theoretical and experimental study on cold-formed elements for seismic-resistant steel framing systems. The focus is on evaluating the feasibility of using low- and mid-rise buildings based on cold-formed steel framing with flat strap bracings as diagonal members, and built-up steel profiles or concrete-filled steel sections as boundary (chord) studs, to resist seismic actions in moderate to high seismicity areas. Three representative prototype residential buildings with five, seven, and ten storeys, located in areas with peak ground accelerations (PGA) of 0.2 g, 0.3 g, and 0.4 g have been considered.This Thesis consists of six chapters; the first is an introduction, the second describes the current state of the art, and the last presents conclusions and future research. Chapters 3, 4, and 5 constitute the main body of this Thesis, and their content is described below.Chapter 3 presents a theoretical investigation into the compressive performance of single Cold-Formed Steel (CFS) members with Cee-shaped cross-sections, as well as various built-up sections (back-to-back, toe-to-toe, nested and a stud pack 4) derived from Cee profiles. The initial assessment of compressive performance is conducted using closed-form hand expressions. These results are subsequently complemented by design based on the Finite Strip Method (FSM) and further refined through simulations employing the Generalised Beam Theory (GBT). Detailed results for the compressive performance of the studied sections, considering a range of parameters including section thicknesses, steel grades, and buckling lengths considered, are also provided. Chapter 4 describes the performed experimental investigation into the compressive performance of steel-only and concrete-filled cold-formed steel built-up sections. The study encompasses the design and preparation of the test specimens, the experimental results, the predicted compressive resistance, and a comparative analysis between the predicted and observed values. Particular attention is given to the increasing of the effective area resulting from concrete infill; which is theoretically and experimentally validated through modifications to existing design approaches. Additionally, Chapter 4 analyses the compressive resistance of two CFS built-up sections filled with concrete -referred to as 4-pack Concrete-Filled Cold-Formed Steel (CF CFS) and 6-pack Concrete-Filled Cold-Formed Steel (CF CFS)-, across a range of concrete strength classes, from C20/25 to C50/60.Chapter 5 develops the design of three representative prototype steel framing buildings, 5-, 7-, and 10-storey, in regions of moderate (PGA 0.2 g) and high seismicity (PGA 0.3 g and 0.4 g) areas, by means of a Finite Element Method software, complemented with hand calculations. The main goal is obtained the internal forces in the most critical members of the buildings (namely the chord studs and the diagonal bracings of the wall panels). As described in detail in Chapter 5, the spectral ordinates, the base shear forces, and their distribution along the height of the buildings have been determined by hand calculations in accordance with the provisions of the second-generation Eurocode, since these provisions are not yet implemented in the FEM software. The results of the seismic analyses for each prototype building and seismicity level are presented, as well as a sizing proposal of the chord studs based on both the internal forces and the compressive performance of the concrete-filled in Chapters 3 and 4.
  

• POPOV, PAVEL PEYCHEV: Quantum simulation of lattice gauge theories with qudit systems
  
  Author: POPOV, PAVEL PEYCHEV
  Programme: DOCTORAL DEGREE IN PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 29/04/2026
  Reading date: 29/05/2026
  Reading time: 10:30
  Reading place: Elements Room i https://teams.microsoft.com/meet/339611996180202?p=2I9fTirIejfsIaqwoW
  Thesis director: LEWENSTEIN, MACIEJ | KASPER, VALENTIN
  Thesis abstract: The spectacular progress in controlling quantum matter has opened new avenues for studying fundamental physics. Various experimental platforms now host hundreds of quantum units, capable of quantum state engineering, Hamiltonian simulation and universal computation, already surpassing what is classically tractable. Remarkably, the versatility of such quantum simulators allows for investigating the physics from very high to very low energy scales. While the long-term goal is to be able to perform fault-tolerant quantum computation, noisy intermediate scale quantum (NISQ) devices are prone to errors and quantum algorithms need to be tailored to the underlying physical platform by exploiting its advantages. In that regard, qudits offer enhanced Hilbert space dimension per information carrier with respect to qubits, allowing for significant reduction of costly entanglement operations. Moreover, the higher-dimensional Hilbert space of qudits natively accommodates complex many-body models, thereby minimizing algorithmic overhead.In this thesis, we investigate the opportunities that qudit devices offer for the quantum simulation of lattice gauge theories. Being extremely successful nonperturbative framework for studying three of the four fundamental interactions--electrodynamics, the weak and the strong force-- lattice gauge theories can be formulated as many-body systems amenable to quantum simulation. This approach overcomes the intrinsic bottlenecks of classical methods, unlocking the ability to explore out-of-equilibrium phenomena and finite-density equilibrium states.The first part of this thesis is dedicated to the development of encoding procedures for lattice gauge theories with Abelian and non-Abelian symmetry on qudit quantum hardware. Building upon advances in the understanding of the structure of the gauge-invariant Hilbert space for specific symmetry groups, we propose scalable qudit implementation of gauge theory models in arbitrary spatial dimensions and devise variational protocols for their equilibrium and out-of-equilibrium simulation. Crucially, our methods apply to gauge theories with dynamical fermionic matter, without the need for nonlocal encodings for the fermions, as they are unitarily removed in the encoding process. In the second part of this thesis, we use quantum-inspired numerical techniques to reveal some of the plethora of physical phenomena simple many-body models with local symmetry host. Using the multi-flavour Schwinger model (quantum electrodynamics in one spatial dimension) as an example, we show how to identify signatures of fractons — gauge field configurations with fractional topological charge. Furthermore, by examining pure gauge theories with non-Abelian dihedral symmetry, we identify the importance of the central subgroup for the spectrum and the dynamics of the many-body model, relating nontrivial fusion rules to lack of confinement and presence of exotic particle excitations. Most importantly, the lattice gauge models for both examples above, due to their simplicity, are amenable to near-term implementation on qudit quantum hardware.Ultimately, this work takes a significant step toward harnessing qudit quantum devices for the simulation of high-energy and condensed-matter systems. By detailing resource-efficient hardware implementations and outlining near-term applications, our findings provide compelling motivation for the continued symbiosis of theoretical design and experimental realization.
  

Reading date: 01/06/2026

• ESPINOZA ZAMBRANO, PAÚL ANDRÉS: Libro del Edificio Electrónico (LdE-e). Una herramienta para impulsar la rehabilitación de edificios residenciales en España
  
  Author: ESPINOZA ZAMBRANO, PAÚL ANDRÉS
  Programme: DOCTORAL DEGREE IN URBAN AND ARCHITECTURAL MANAGEMENT AND VALUATION
  Department: Department of Architectural Technology (TA)
  Mode: Article-based thesis
  Deposit date: 29/04/2026
  Reading date: 01/06/2026
  Reading time: 16:30
  Reading place: ETSAB (Escuela Técnica Superior de Arquitectura de Barcelona) - Planta Baja - Sala de GradosAv. Diagonal, 649-651 - 08028 - Barcelona
  Thesis director: MARMOLEJO DUARTE, CARLOS RAMIRO
  Thesis abstract: The climate emergency and the European Green Deal call for transforming the building sector, a key area in energy consumption and emissions. In Spain, the challenge is greater due to an aging and inefficient residential stock, compounded by the complex management of horizontal property regimes. Despite regulatory progress, energy rehabilitation remains stagnant. This thesis argues that the problem is not solely technical or economic, but a market failure caused by information asymmetry and documentary fragmentation. "Information vortices" prevent the proper valuation of energy efficiency, perpetuating inaction.To address this, the e-Building Logbook (LdE-e) is proposed as an integrated information management model. The model combines two tools from Directive (EU) 2024/1275: the Digital Building Logbook (DBL), as a static technical archive, and the Building Renovation Passport (BRP), as a dynamic roadmap for staged renovations. Its key innovation lies in its technological development using BIM and Blockchain. An architecture is designed to extract data from IFC files to avoid redundancies, alongside a tokenization gateway ensuring data immutability, traceability, and legal validity.The methodology combines qualitative and quantitative phases. First, the model was validated with 21 experts from the sustainable real estate sector, refining its structure, management, and governance —including the proposal of an LdE-e Consortium— and adapting the technology for professional usability.In the quantitative phase, a social perception study was conducted through a survey of 4,041 households across 14 metropolitan areas. Advanced techniques were applied, including Latent Class Analysis (LCA) to profile adoption patterns, and Bayesian-optimised Dense Neural Networks (DNN) to model the complexity of household decision-making.The results reveal two key findings. First, technology is necessary but insufficient: the decisive factor for LdE-e adoption is support through One-Stop Shops (OSS), which transform hesitant users into active adopters. Second, financial stress shapes motivations: households with low energy costs prioritize environmental or lifestyle values, while vulnerable ones act out of economic pragmatism, seeking subsidies and property aesthetic improvements.In conclusion, this thesis provides a robust LdE-e model aligned with European regulations, resolving the information fragmentation in the Spanish market. Its operational viability depends on integration into a socio-technical ecosystem where BIM and Blockchain provide technical security, and One-Stop Shops (OSS) offer the trust and human support needed to mobilize citizens toward decarbonization. The combination of advanced technology and personalized support emerges as the essential formula to overcome current barriers and activate the virtuous circle of energy rehabilitation in Spain's residential stock.