Events 2026

Seminar: TBA

Online seminar

Seminar: TBA

Seminar Room, Serrano 113b

Seminar: The laser stands as one of the most iconic examples of macroscopic coherence, fundamentally reshaping our understanding of light-matter interaction and underpinning key technologies of modern science. Yet lasing action is not exclusive to light: in principle, it can emerge in any bosonic system. The concept of the phonon laser, based on coherent vibrational excitations of mechanical oscillators, has emerged as a new frontier, bridging quantum optics, condensed matter physics, and hybrid quantum technologies. Despite recent progress, current phonon laser realizations remain confined to few-degree-of-freedom systems and typically rely on collective couplings mediated by a common field, limiting both the scalability and spatial control of the phenomenon. Overcoming these constraints is essential for exploring many-body collective regimes, where cooperative phenomena, quantum synchronization, and novel non-equilibrium dynamical phases can arise.
In this talk, I will present a mechanism for generating scalable arrays of individually controllable phonon lasers through Floquet modulation in an Ising-type quantum spin chain [1]. I will show how the interplay between interactions, local control, and dissipation drives a well-defined transition from thermal motion to sustained coherent self-oscillations. Unlike conventional approaches, our architecture removes the need for a global coupling bus, offering a modular, scalable scheme compatible with current hybrid quantum platforms. Notably, the laser array is resilient against resonance mismatches and exhibit complex collective behaviour, including pairwise synchronization and global phase locking. To highlight practical applications, we perform an error-propagation analysis to assess the sensing capabilities of the array. Since our proposal enables scalable and on-demand phonon lasers at arbitrary lattice sites, we believe the obtained results pave the way for advancements in quantum technologies, long-distance synchronization protocols, and quantum-acoustic many-body phenomena.

[1] H. Molinares, G. Romero, V. Montenegro, V. Eremeev​, Scalable phonon-laser arrays with self-organized synchronization, arXiv:2603.29099 (2026) https://doi.org/10.48550/arXiv.2603.29099

Seminar Room, Serrano 113b

Seminar: We implement a gate-tunable transmon (gatemon) qubit based on an InAs nanowire
Josephson junction and identify distinct features in its microwave spectra that provide clear
evidence of ultrastrong light–matter hybridization with a probing resonator [1]. These
signatures include deviations of the measured anticrossing from the predictions of the
Jaynes–Cummings model. Furthermore, we observe photon-number-dependent transitions
whose energies deviate markedly from the JC ladder expected in the strong coupling limit.
We interpret these observations using extended theoretical models that incorporate both
counter-rotating interaction terms and the multilevel, non-conventionally anharmonic
structure of the gatemon. Beyond establishing USC, we achieve time-resolved coherent
control of the gatemon. We extract relaxation and decoherence times that are comparable to
those of gatemons operating outside the USC regime, suggesting that coherence is not
predominantly limited by the enhanced Purcell losses expected in this limit. These results
establish hybrid semiconductor-superconductor circuits as a viable platform for exploring
time-resolved quantum dynamics and new device concepts in the ultrastrong coupling
regime.
[1] I. Casal Iglesias et al., arXiv:2603.19438

Seminar Room, Serrano 121 (CFMAC)

Seminar: Large Fock states are key nonclassical resources for bosonic quantum information, quantum-enhanced metrology, and the exploration of nonclassical dynamics in harmonic oscillators. However, preparing them high success probability remains challenging: deterministic protocols become increasingly control-intensive at large excitation number, while measurement-based strategies are naturally robust but suffer from rapidly decreasing probabilities. In this work, we propose a dispersive circuit-QED protocol that combines Quantum Phase Estimation (QPE) and Quantum Amplitude Amplification (QAA) to overcome this limitation. Starting from a coherent state in a bosonic resonator, QPE maps photon-number information onto a multi-qubit register through photon-number dependent dispersive phases, while QAA coherently amplifies the target register outcome before measurement. In this way, the protocol transforms a weakly heralded measurement scheme into a high-probability preparation method for large Fock states. The approach is compatible with standard superconducting architectures, requires only logarithmic qubit overhead, and exhibits favorable scaling of the amplification cost.

Seminar Room, Serrano 113b

Seminar: I will present experimental studies of one and two photon transitions in an array
of Cs atoms trapped with a lattice of evanescent fields around an optical nanofiber,
a waveguide. The transitions involved in the experiment are 6S1/2, 6P3/2 and 6D5/2.
The single atom absorption is about 0.5% on the 6S1/2 to 6P3/2 transition. We use
the 6S1/2 to 6P3/2 for the one photon excitation with the laser perpendicular to the
nanofiber and observe what couples into the fiber because of the interaction with
the atoms as we change polarization, angle, and detuning. The two 883 nm photon
propagates along the nanofiber and excites the atoms from 6S1/2 to 6D5/2. We
observe two-photon Rabi oscillations while the pulse is on, and then superradiant
decay from the 6D5/2 to 6P3/2 decay at 917 nm with a less pronounced effect on
the 6P3/2 to 6S1/2 transitions at 852 nm.
This work is performed at Shanxi University in Taiyuan China with Yanting Zhao,
Dianqiang Su, Tanbin Wu, and Jian Yuan, in collaboration with Pablo Solano and
Nicolas Vera from Universidad de Concepcion, and Ana Asenjo, Silvia Cardenas,
and Edgar Guardiola from Columbia University.

Seminar Room, Serrano 113b

Seminar: We design a universal framework for fermionic quantum hardware that runs efficient
variational algorithms to simulate generic many-body systems beyond the hardware’s
native interactions. Our analysis shows that one can quantum simulate the ground-state
properties of a broad class of gapless target Hamiltonians of local observables in a
quantum evolution time that grows polynomially with the inverse relative error up to
logarithmic corrections, and offers an exponential speedup over naïve classical
algorithms such as exact diagonalization (ED). We provide numerical evidence and
theoretical argument that this holds for energy density, as well as density-density and
spin-spin correlations in three qualitatively distinct models – the repulsive Hubbard
model; a Hubbard model augmented with nearest-neighbor attractive interactions, which
introduces the phenomenon of pairing; and the Hofstadter-Hubbard model, which
introduces a gauge field and fractional quantum Hall physics. This work demonstrates
the usefulness of current ultracold fermionic quantum platforms for quantum simulating
fermionic many-body systems beyond the models natively implemented in the
hardware.

Online seminar

Seminar: In this talk, I would like to present our results on the interactions of quantum emitters coupled to the boundary of a two-dimensional photonic graphene. While 2D topological lattices typically support propagating edge modes, a zigzag termination in this system hosts a unique set of dispersionless, non-propagating edge modes that form a partial flat band. We show that these light-matter interactions can be effectively described by a dissipative cavity-QED model in which the emitter coherently couples to a localized mode emerging as a superposition of these edge modes. This mode displays an unconventional power-law localization around the qubit yet remains normalizable, with a spatial range that can be precisely tuned by introducing lattice anisotropy. Based on this model, we predict the occurrence of vacuum Rabi oscillations and quantum state transfer between distant emitters along the lattice edge. Finally, we propose a feasible experimental demonstration using superconducting circuit-QED platforms, demonstrating that the predicted phenomena are observable within the coherence times of state-of-the-art transmon qubits

Reference: E. Di Benedetto et al, arXiv:2507.13444 [quant-ph] (2025)

Seminar Room, Serrano 113b

Seminar: Chirality is a fundamental property of nature. Enantiomers exhibit distinct properties in fields such as biomedicine, and achieving their efficient separation and detection remains a challenge of significant interest in physical chemistry. This report focuses on the enantioseparation of gaseous chiral molecules based on the cyclic three-level model, exploring corresponding schemes for different types of molecules. First, it reveals the characteristics of the “phase mismatching” term as a physical resource for spatial separation in asymmetric top chiral molecules. Second, it proposes a double-loop four-level model for symmetric top chiral molecules to achieve Enantiospecific State Transfer (ESST). Finally, for chiral molecules with low asymmetry, a “pump-control” scheme is designed to achieve high-efficiency ESST. These works provide a theoretical reference for the physical separation of chiral molecules under gas-phase conditions.

Seminar Room, Serrano 113b

Seminar: Photons typically interact with their environment only through emission and absorption. In this talk, I will describe a protocol in which microwave photons in superconducting resonators are coupled to an engineered reservoir; instead of removing particles from the system, this reservoir creates non-reciprocal transport between the system’s modes, leading to highly non-trivial dynamics. I will discuss possible applications of this protocol for many-body state preparations and metrology.

Seminar Room, Serrano 113b

Seminar: From a reminder of BB84 and its classical final steps to obtain symetric secure quantum key, to an experiment using an Entablgement Photon Source with coexistance, this talk will contain an overview of the activities undertaken in MadQCI ecosystem.

Seminar Room, Serrano 113b

Seminar: Driven-dissipative many-body systems are typically driven toward nonequilibrium steady states due to the competition between coherent and dissipative dynamics. Exact steady states solutions of these models can offer insight into this competition. Remarkably, there is a class of driven-dissipative models which possess a “hidden” time-reversal symmetry (TRS) and, thus, have exactly solvable steady states, even in the presence of interactions. Many examples of bosonic and spin systems with hidden time-reversal symmetry have been solved; however, it had not been known whether hidden TRS can exist in fermionic systems.

In this talk I will discuss this notion of time-reversal symmetry and its connection exact solutions by way of an example: a boundary driven dissipative spin chain. Then I will discuss how the exact solution technique can be adapted to fermionic systems, and I will present the exact steady state solutions of interacting fermionic model: a 1D lattice of fermions with nearest neighbor p-wave pairing and a global charging energy. The model exhibits a first order phase transition between high- and low-density phases, and its dynamics are shown to be constrained by the hidden TRS, which shows that the symmetry can exist in fermionic systems.

Online seminar

Seminar: Comenzamos el ciclo de seminarios de los departamentos del IEM
para este año 2026 con el del “Departamento de Departamento de
Química y Física Teóricas”. Para ello os invitamos al primer
seminario del ciclo que tendrá lugar en la Sala de Conferencias del
CFMAC (Serrano, 121) el próximo jueves 5 de Marzo a las 12.00h.

Será impartido por el Dr. Juan Ramón Muñoz de Nova que es la reciente
incorporación Ramón y Cajal 2026 en el IEM cuyo
título es: Interdisciplinary Quantum Field Theory: Hawking effect,
Quantum time, Quantum Information in High-Energy Physic.

Seminar Room, Serrano 121 (CFMAC)

Seminar: Quantum networks are the most promising proposal to scale quantum computers in what is known as distributed quantum computation. Superconducting waveguide QED networks have shown to be very effective for distributing quantum information based on the exchange of photons between the nodes of the networks. However, fabrication imperfections of nodes require additional techniques to compensate for the frequency differences, leading to reduced scalability and efficiencies. We present a novel approach to emit and absorb arbitrality detuned photons, allowing for an on-demand and deterministic exchange of quantum information. It leverages the large and good controllability of the light-matter couplings that superconducting circuits provide. Then, we propose a protocol for entanglement distribution between the nodes of the network via emission of fractional photons. Numerical solutions support the feasibility and high-fidelity of both protocols, indicating the new possibilities that detuned single photons bring to quantum networks.

Warning: I wanted to use the seminar as an opportunity to practice for the defence of my bachelor thesis. Since the evaluating professors need not be related to physics, it will be less technical than many of you would like. Nevertheless, you are all invited to come, and after the presentation, I’ll try to answer as best as possible any related questions.

Seminar Room, Serrano 121 (CFMAC)

Seminar: In this talk, I discuss the many-body physics of interacting waveguide QED systems, where photons in a coupled-cavity array are strongly coupled to atomic impurities and interact via local Kerr nonlinearities. After introducing the model and its relevance to nanophotonic crystals, circuit QED lattices, and ultracold atomic systems, I briefly review the striking consequences that additional photon-photon interactions can have on the collective emission dynamics of atomic emitters. I then focus on the ground-state properties of this system, which are governed by the competition between attractive Jaynes-Cummings-mediated binding and intrinsic photon-photon repulsion. This interplay drives the formation of localized few-photon bound states and results in a rich phase diagram featuring Mott-like insulating states as well as superfluid phases characterized by long-range correlations mediated by photons detached from impurity sites.

Online seminar

Seminar: In this talk, I will present flow topology as a practical route to classify dynamical phases in driven dissipative nonlinear systems, distinct from band-topology approaches in Hermitian and non Hermitian periodic settings. The key idea is to extract global information from the semiclassical phase-space flow pattern across all initial conditions, beyond local order parameters.

Using parametrically driven nonlinear resonators as an example, I will introduce a graph-based topological invariant which captures all dynamical phase transitions as drive and detuning are varied, including both local changes, such as local instabilities, and global ones, such as how regions of initial conditions connect to different long-time behaviors. I will show how these predictions are directly confirmed experimentally in a nonlinear electromechanical resonator [1]. I will then show how flow topology also appears in the quantum steady state probability distributions and in asymmetries of their linear responses [2].

Finally, I will extend the framework to limit-cycle phases with persistent oscillations in the steady state. An extension of the graph-invariant above will capture more complex phase transitions, including mergers of limit cycles and the formation of forbidden regions in phase space. In the quantum regime, these flow-topology changes reflect dynamical phase transitions in the transient evolution, even when they are not directly reflected in standard indicators such as the Liouvillian spectral gap [3].

References
[1] Villa et al., Topological classification of driven-dissipative nonlinear systems, Sci. Adv.11, eadt9311 (2025)
[2] Seibold et al., Manifestations of flow topology in a quantum driven-dissipative system, arXiv:2508.16486 (2025).
[3] Gómez and del Pino, Quantum Dynamical Signatures of Topological Flow Transitions in Limit Cycle Phases, arXiv:2512.11747 (2025).

Seminar Room, Serrano 113b

Seminar: I will present our recent work exploring a bosonic analogue of the Dicke model of superradiance. Specifically, we study a system of bosonic modes subject to fully symmetric collective decay and a uniform on-site interaction, which is naturally realised in waveguide-coupled transmon arrays. Exploiting the permutation symmetry of the problem, we combine perturbative arguments with large-scale numerical simulations to analyse the collective emission dynamics in the weak- and strong-interaction limits. In both regimes, we find that the dynamics are well captured by rate equations closely analogous to those of standard Dicke superradiance. Building on this understanding, I will present evidence for a crossover in the scaling of the peak emission rate with system size, from sub-quadratic to quadratic. If time permits, I will also discuss the dynamics of different initial states with no counterparts in the case of two-level emitters.

Online seminar

Seminar: As we have have a couple of new members, especially younger ones, I wanted to take the time and briefly introduce Tensor Networks as a state-of-the-art numerical method and advertise its benefits and use. I will briefly introduce Matrix Product States (MPS) and the DMRG algorithm.
Then I will discuss the findings of https://doi.org/10.21468/SciPostPhys.18.4.142; the puzzling features of the MPS transfer matrix spectrum at a critical point. We set up an effective field theory formulation for the renormalization flow of MPS with finite bond dimension, focusing on systems exhibiting finite-entanglement scaling close to a conformally invariant critical fixed point. We show that the finite MPS bond dimension χ is equivalent to introducing a perturbation by a relevant operator to the fixed-point Hamiltonian. This phenomenon defines a renormalization group self-congruent point, where the relevant coupling constant ceases to flow due to a balance of two effects; When increasing χ, the infrared scale, set by the correlation length ξ(χ), increases, while the strength of the perturbation at the lattice scale decreases

Seminar Room, Serrano 121 (CFMAC)

Seminar: This seminar presents a comprehensive overview of the research initiatives in Quantum Technologies and Metrology led by the Universidad Nacional de Colombia, together with a detailed analysis of recent advancements in the engineering of Photonic Crystals (PhCs) for nanoscale light manipulation.

The first part of the seminar outlines the strategic initiatives developed under a nationally funded project on Quantum Metrology and Technologies. It presents the experimental milestones enabled by advanced instrumentation acquired through this grant, covering key research pillars such as quantum metrology, high-resolution spectroscopy, quantum information and computing, and quantum materials. Furthermore, the socio-economic and scientific impact of these developments is highlighted, emphasizing their role in fostering technological sovereignty and innovation within the Colombian scientific landscape.

The second part of the presentation provides a technical review of fundamental developments in PhC research, including:

All-optical logic gates and waveguides: Design and optimization of PhC-based architectures for optical signal processing.
Cavity–emitter interactions: Analysis of the coupling between quantum emitters and localized modes in PhC cavities to enhance light–matter interactions.
Topological and chiral photonics: Exploration of symmetry-protected states and non-reciprocal light propagation in periodic dielectric structures.
Coupled cavity systems: Study of modal coupling and energy transfer in multicavity arrays.

Finally, specific contributions from the research group are showcased, including original designs for high-sensitivity sensors, optimized waveguides, and structured environments for emitters in PhC slabs. These results illustrate the potential for synergy and collaborative research between Colombian institutions and international partners, particularly with the Instituto de Física Fundamental (IFF-CSIC).

Seminar Room, Serrano 113b

Seminar: We study the directed transport of bosons along a one dimensional lattice in a dissipative setting, where the hopping is only facilitated by coupling to a Markovian reservoir. By combining numerical simulations with a field-theoretic analysis, we investigate the current fluctuations for this process and determine its asymptotic behavior. These findings demonstrate that dissipative bosonic transport belongs to the Kardar-Parisi-Zhang universality class and therefore, in spite of the drastic difference in the underlying particle statistics, it features the same coarse-grained behavior as the corresponding asymmetric simple exclusion process for fermions. However, crucial differences between the two processes emerge when focusing on the full counting statistics of current fluctuations. By mapping both models to the physics of fluctuating interfaces, we find that dissipative transport of bosons and fermions can be understood as surface growth and erosion processes, respectively. Within this unified description, both the similarities and discrepancies between the full counting statistics of the transport are reconciled. Beyond purely theoretical interest, these findings are relevant for experiments with cold atoms or long-lived quasiparticles in nanophotonic lattices, where such transport scenarios can be realized.

Online seminar

Seminar: Lattice gauge theories are very complicated models, capturing a variety of interesting physics, but like most quantum many-body models, their study involves several challenges, both analytical and numerical. In my talk I will discuss an analogy between them and PEPS (projected entangled pair states), a high dimensional tensor network construction, and show how it can be used for studying such models while overcoming long standing bottlenecks.

Seminar Room, Serrano 121 (CFMAC)