Add to Calendar 2024-09-26T10:00:00 2024-09-26T11:00:00 Impact of Josephson junction materials on the performance of superconducting qubits Event Information: Superconducting qubits are a leading modality for quantum computing, offering a favorable balance between coherence, gate times, scalability, and fidelity. I will explore the interplay between materials science and qubit performance, with a particular focus on how the materials used in Josephson junctions (JJs) affect qubit behavior. The frequency of a qubit is largely determined by the properties of JJs, which typically consist of amorphous oxide tunnel barriers. These barriers are also the likely location of most two-level systems (TLS) defects. Recently, we discovered an Alternating-Bias Assisted Annealing (ABAA) process that enables us to fine-tune JJs to achieve the desired frequency. Characterizing these ABAA post-processed JJs provides insight into the structural and chemical bonding uniformity of the amorphous oxides after ABAA processing, as well as the impact on qubit performance and TLS density.  Event Location: AMPEL Rm 311

Add to Calendar 2024-10-03T10:00:00 2024-10-03T11:00:00 Introducing the Ramaniton: The quasiparticle for Raman scattering Event Information: In Raman scatering, pump photons that are incident on a material are able to emit or absorb materials' excitations such as phonons and orbital transitions. This process generates red-shifted (Stokes) and blue-shifted (antiStokes) photons that are usually uncorrelated with each other. When real or virtual excitations emitted by a Stokes photon are coherently absorbed by another pump photon, an entangled Stokes-antiStokes photon pair is created, in a process analogous to the formation of Cooper pairs in superconductors [1].In this talk we will show that this mechanism provides the microscopic underpinning for the phenomena of four-wave mixing in quantum optics, one of the main methods to generate squeezed states of light that are key to proposals of quantum computing, sensing, and communication with photons. We will argue that it's fruitful to take a "condensed matter physics approach" and treat Raman-interacting photons and phonons as a hybrid excitation, the Ramaniton quasiparticle [2]. The Ramaniton enables nonperturbative theories for the evolution of photons in waveguides formed by group IV semiconductors such as silicon and diamond, enabling the design of photonic devices that exploit optical phonons for optimal generation of two-mode squeezed states of light. [1] A. Saraiva, F.S.D.A. Júnior, R. De Melo E Souza, A.P. Pena, C.H. Monken, M.F. Santos, B. Koiller, and A. Jorio, Photonic Counterparts of Cooper Pairs, Phys. Rev. Lett. 119, 193603 (2017).[2] S. Timsina, T. Hammadia, S.G. Milani, F.S.D.A. Júnior, A. Brolo, and R. de Sousa, Resonant squeezed light from photonic Cooper pairs, Phys. Rev. Res. 6, 033067 (2024). Event Location: AMPEL 311

Add to Calendar 2024-10-10T10:00:00 2024-10-10T11:00:00 Atomic Cluster Expansion for "Learning" Many-Body Interaction Event Information: The integration of machine learning (ML) into the traditional modeling workflows is replacing decades-old - often ad hoc - approximations (e.g., in constitutive laws) leading to new models that far outstrip their predecessors in accuracy and transferability. ”Pure” ML approaches are rarely successful but remarkable results can be achieved when integrated with domain knowledge. I will introduce a general formalism, the Atomic Cluster Expansion, for parameterizing many-body interaction and how it can be used for reduced-order modelling. Examples are taken from interatomic potentials, coarse-grained MD, and VMC. Event Location: AMPEL 311

Add to Calendar 2024-10-10T10:00:00 2024-10-10T11:00:00 Atomic Cluster Expansion for "Learning" Many-Body Interaction Event Information: The integration of machine learning (ML) into the traditional modeling workflows is replacing decades-old - often ad hoc - approximations (e.g., in constitutive laws) leading to new models that far outstrip their predecessors in accuracy and transferability. ”Pure” ML approaches are rarely successful but remarkable results can be achieved when integrated with domain knowledge. I will introduce a general formalism, the Atomic Cluster Expansion, for parameterizing many-body interaction and how it can be used for reduced-order modelling. Examples are taken from interatomic potentials, coarse-grained MD, and VMC. Event Location: AMPEL 311

Add to Calendar 2024-10-17T10:00:00 2024-10-17T11:00:00 Quantum Sensation: a journey through arts and quantum physics Event Information: After a presentation of her artistic path and research, the painter Caroline Delétoille will share some insights about the "quantum sensation" art-science project embedded at the core of her upcoming residency. This research-creation based exhibition has been developed since the end of 2023 in close collaboration with a physicist and a philosopher. Its artistic creation and exploration will continue during the residency at the QMI laboratories. Event Location: AMPEL 311