How fast can protons decay?
https://arxiv.org/abs/2410.19045

Date: Wednesday, Feb. 5th, 2025
Time: 11:40 am
Place: 1.A1 (Faculty of Science & Technology, Leioa, UPV/EHU)

Title: Quantum Technologies for Fundamental Physics

Speaker: Diego Blas
ICREA & Institut de Física d’Altes Energies (IFAE), Barcelona.

Abstract:
The cutting-edge frontier of quantum technologies is expanding the possibilities of sensing phenomena of constantly decreasing
intensity. As a result, the new advances in metrology offer a fantastic opportunity to advance in some of the most pressing open
problems of particle physics and cosmology related to different fundamental backgrounds criss-crossing our laboratory devices
or other subtle phenomena related to yet-to-be discovered physics.

My aim in this talk is to describe some simple examples related to the detection of gravitational waves, dark matter and neutrinos
with quantum devices, and how their implementation may revolutionise our understanding of particle physics and cosmology.

TITLE: Deformed Commutation Relations in Quantum Cosmology

SPEAKER: Gabriele Barca

ABSTRACT: General Relativity predicts its own breakdown in the form of
spacetime singularities, but quantum effects are expected to play a role
in the high-energy regimes before singularities are reached. In
particular, the cosmological dynamics close to initial singularities
such as the Big Bang is the perfect arena to test Quantum Gravitational
effects. The formalism of Deformed Commutation Relations (DCRs) was
developed to easily implement on any Hamiltonian system effects and
properties expected from Quantum Gravity theories, such as minimal
lengths or energy cut-offs. I will introduce the main properties of
these DCRs, both on a quantum and on a (semi)classical level, in one
space dimension or higher. Then I will show how some specific forms can
be used in various cosmological models to introduce Quantum
Gravitational corrections, to remove singularities, to tame Chaos, and
to derive other interesting effects.

DATE: MONDAY, FEB. 12, 2025
TIME: 11:40 am

LOCATION: Theoretical Physics Seminar Room

TÍTULO:   Tecnologías Cuánticas 
SPEAKER: Jorge Casanova

Departamento de Química Física
EHU Quantum Center
UPV/EHU

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TÍTULO:   Computación Cuántica 
SPEAKER: Mikel Sanz

Departamento de Química Física
EHU Quantum Center

UPV/EHU

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TÍTULO:   Materia Condensada 
SPEAKER: Maria Blanco
Polímeros y Materiales Avanzados
Física, Química y Tecnología

UPV/EHU

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TÍTULO:   Física de Partículas 
SPEAKER: Miguel Garcia Echevarria

Departamento de Física
EHU Quantum Center

UPV/EHU

Observation of an ultra-high-energy cosmic neutrino with KM3NeT
https://www.nature.com/articles/s41586-024-08543-1

TITLE: Causality Bounds on the Primordial Power Spectrum

SPEAKER: Sebastian Cespedes (Imperial College, UK)

ABSTRACT: Effective field theories (EFTs) parametrize our ignorance of the underlying UV theory
through their Wilson coefficients. However, not all values of these coefficients are consistent with fundamental
physical principles. I will talk on a recent paper where we explore the consequences of imposing causal
propagation on the comoving curvature perturbation in the EFT of inflation, particularly its impact on the
primordial power spectrum and the effective sound speed $c_s^\text{eff}$. We investigate scenarios
where $c_s^\text{eff}$ undergoes a transition, remaining consistent with CMB constraints at early times
but later experiencing a drastic change, becoming highly subluminal. Such scenarios allow the primordial
power spectrum to grow at small scales, potentially leading to the formation of primordial black holes or the
generation of scalar-induced gravitational waves. We find the generic feature that in a causal theory, luminal
sound speeds imply a free theory, effectively constraining the dynamics. Additionally, we obtain that when
considering natural values for the Wilson coefficients, maintaining the validity of the EFT and the weakly
coupled regime, and enforcing causal propagation of the EFT modes, the power spectrum cannot increase
drastically. This imposes significant constraints on the parameter space of models aiming to produce such features.

TITLE: Galactic Halos and rotating bosonic dark matter

SPEAKER: Jorge Castelo Mourelle (IGFAE, Univ. de Santiago de Compostela).

ABSTRACT: Rotating bosonic dark matter halos are considered as potential candidates for modeling dark matter
in galactic halos. These bosonic dark matter halos can be viewed as a dilute and very extended version of bosonic stars,
and the methods used for the calculation and analysis of the latter objects can be directly applied. Bosonic stars, a hypothetical
type of astrophysical objects, are categorized into two primary families, based on the nature of the particles composing them:
Einstein-Klein-Gordon stars and Proca stars. We examine various models from both families and the rotation curves which
their contribution induces in different galaxies, to identify the most plausible candidates that explain the flattening of orbital
velocities observed in galactic halos. By exploring different combinations of our dark matter models with observable galactic
features, we propose an interesting source to compensate for the apparent lack of matter in dwarf and spiral galaxies, providing
a possible explanation for this long standing astronomical puzzle.

Radiation Exposure from the Dark
https://arxiv.org/abs/2411.10521

Title: Spin qubits in diamond

Speaker: Prof. Fedor Jelezko (Institute of Quantum Optics, Ulm University, Germany)

Abstract:
Optically active spin qubits in diamond have recently emerged as a candidate material for a range of quantum-based applications, including quantum information processing, quantum communication and quantum sensing. In this talk, we will show the realisation of a spin-based solid-state architecture for a scalable quantum register consisting of strongly dipolarly coupled electron spins assocoated with NV centers We will show that isotopic engineering of diamond allows the creation of regularly ordered arrays of nuclear spins, which can be explored as elements of quantum simulators. Application of nanodiamonds for nanoscale NMR and hyperpolarisation enhanced MRI will be discussed.

Certification of high-dimensional and multipartite entanglement with imperfect measurements

Deciding whether an unknown quantum state is entangled is one of the central challenges of quantum information. The most common approach are entanglement witnesses, where one assumes the state to be close to a known target and then finds suitable measurements that can reveal its entanglement. In principle, this allows for the detection of every entangled state. However, it requires the experimenter to flawlessly perform the stipulated measurements.

We move away from this idealized scenario to the more realistic situation in which measurement devices are not perfectly controlled, but nevertheless operate with bounded inaccuracy. We formalize this through an operational notion of inaccuracy that can be estimated directly in the laboratory and investigate the impact of measurement errors on standard entanglement detection techniques. To demonstrate the relevance of this approach, we show that small magnitudes of inaccuracy can significantly compromise several renowned entanglement witnesses.

We extend this analysis to the detection of high-dimensional and multipartite entanglement. To support our theoretical findings experimentally, we explicitly construct states that lead to a wrongful detection of high Schmidt numbers or genuine multipartite entanglement when the inaccuracies in the measurements are not accounted for.

Phase behavior of Cacio and Pepe sauce
https://arxiv.org/abs/2501.00536