Austrian Quantum Talks
This website is an overview of all quantum related talks and seminars.
Overview
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Phase Encoding for Super-Resolution Magnetic Microscopy with Diamond NV Centers
Shawn Storm (TU München)
28. 04.2023
10:00
Atominstitut, Seminarraum ZA
Julian Leonard
Over the last two decades, NV centers have gained interest in the life sciences due to their nanoscale sensing and imaging abilities. Real-space imaging techniques with NV centers are either limited by the optical diffraction limit of approximately 400 nm or require cumbersome point-by-point scanning probe techniques for nanoscale resolution. An alternative technique in Fourier imaging from conventional magnetic resonance imaging (MRI) has been shown to go beyond this limit, however, with scanning probe microscopy. This thesis provides a proof of concept of the Fourier imaging technique with widefield microscopy. The design is simulated with the use of COMSOL Multiphysics, and the theoretical spatial resolution is discussed.
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Dark dimension and a unification of the dark sector
Cumrun Vafa (Harvard University)
03. 05.2023
10:30
Schrödinger Lecture Hall, ESI, Boltzmanngasse 9/2
Markus Aspelmeyer
In this talk I apply consistency conditions of quantum gravity to the dark sector. Motivated by the smallness of the dark energy combined with other experimental data, one is naturally led to a corner of the quantum gravity landscape with one extra mesoscopic dimension in the micron range. Interestingly this also leads to graviton excitations in the 5th dimension as an unavoidable candidate for the dark matter. Moreover, TCC conjecture applied to the late time cosmology motivates specific initial conditions in this scenario, leading to the right abundance of dark matter gravitons and an explanation of the cosmological coincidence problem. I also explain how the cosmological S8 tension gets resolved.
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Femtosecond and attosecond electron microscopy: Seeing atoms and electrons in space and time
Peter Baum
03. 05.2023
16:30
Univ. Wien, Lise Meitner lecture hall, 1st floor Boltzmanngasse 5, 1090 Vienna
Thomas Juffmann
The fundamental reason behind almost any light-matter interaction are atomic and electronic motion in space and time. In order to provide a movie-like access to such dynamics, we unify electron microscopy with attosecond and femtosecond laser technology. In this way, we combine the awesome spatial resolution of modern electron beams with the spectacular time resolution that is offered by the cycle period of light [1-2].
Selected results will be reported on the electric fields within metamaterials [2-3], the Einstein-de-Haas effect on atomic dimensions [4], the reaction path of phase transitions [5] and the formation of free-electron qubit states [6]. Many breakthroughs in science and technology have been achieved by novel imaging techniques, and we will discuss how our ultrafast electron microscopy may contribute.
[1] D. Nabben, J. Kuttruff, L. Stolz, A. Ryabov, P. Baum, "Attosecond electron microscopy of sub-cycle optical dynamics“, Nature, accepted (2023).
[2] C. Kealhofer, W. Schneider, D. Ehberger, A. Ryabov, F. Krausz, P. Baum, “All-optical control and metrology of electron pulses”, Science 352, 429 (2016).
[3] A. Ryabov and P. Baum, “Electron microscopy of electromagnetic waveforms”, Science 353, 374 (2016).
[4] S. R. Tauchert, M. Volkov, D. Ehberger, D. Kazenwadel, M. Evers, H. Lange, A. Donges, A. Book, W. Kreuzpaintner, U. Nowak, P. Baum, “Polarized phonons carry angular momentum in femtosecond demagnetization”, Nature 602, 73 (2022).
[5] P. Baum, Ding-Shyue Yang, A. H. Zewail, “4D Visualization of Transitional Structures in Phase Transformations by Electron Diffraction”, Science 318, 788 (2007).
[6] M. Tsarev, A. Ryabov, P. Baum, “Free-Electron Qubits and Maximum-Contrast Attosecond Pulses via Temporal Talbot Revivals”, Phys. Rev. Res. 3, 043033 (2021).
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Electron-light coupling in photonic nanostructures: From coherent electron acceleration to a quantum-coherent coupling
Peter Hommelhoff
03. 05.2023
17:30
Univ. Wien, Lise Meitner lecture hall, 1st floor Boltzmanngasse 5, 1090 Vienna
Thomas Juffmann
It is well known that electrons and light do not couple efficiently in free space -- but with the introduction of appropriate nanostructures, they do. Based on this, we have built a nanoscale version of a classical RF accelerator, including optical forces to not only accelerate electrons but also collimate them in the 225 nm narrow nanophotonic channel, representing the first demonstration of the accelerator on a chip reaching substantial energy gains. In the second part, I will briefly show how a high-resolution spectrometer inside of a scanning elec! tron micr oscope allowed us to demonstrate that the electron-light coupling works in a quantum-coherent fashion. The talk will give an overview of the nascent yet already vibrant field of efficient free electron-light coupling.
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Towards an Artificial Muse for new ideas in Physics
Mario Krenn
04. 05.2023
14:00
Max Perutz Labs, Dep. for Structural Biology, Campus Vienna Biocenter 5, 1030 Wien
Thomas Juffmann
Artificial intelligence (AI) is a potentially disruptive tool for physics and science in general. One crucial question is how this technology can contribute at a conceptual level to help acquire new scientific understanding or inspire new surprising ideas. I will talk about how AI can be used as an artificial muse in quantum physics, which suggests surprising and unconventional ideas and techniques that the human scientist can interpret, understand and generalize to its fullest potential.
[1] Krenn, Kottmann, Tischler, Aspuru-Guzik, Conceptual understanding through efficient automated design of quantum optical experiments. Physical Review X 11(3), 031044 (2021).
[2] Krenn, Pollice, Guo, Aldeghi, Cervera-Lierta, Friederich, Gomes, Häse, Jinich, Nigam, Yao, Aspuru-Guzik, On scientific understanding with artificial intelligence. Nature Reviews Physics 4, 761–769 (2022).
[3] Krenn, Zeilinger, Predicting research trends with semantic and neural networks with an application in quantum physics. PNAS 117(4), 1910-1916 (2020).
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Engineering exotic superfluids with optically-dressed Bose-Einstein condensates
Letizia Tarruell (ICFO Barcelona)
05. 05.2023
10:00
Atominstitut, Helmut Rauch Lecture Hall
Julian Leonard
Spin-orbit coupled Bose-Einstein condensates, where the internal state of the atoms is linked to their momentum through optical coupling, are a flexible experimental platform to engineer synthetic quantum many-body systems. In my talk, I will present recent work where we have exploited the interplay of spin-orbit coupling and tunable interactions in potassium BECs to realize two unconventional superfluid phases.
In a first series of experiments, we optically couple two internal states of 39K with very unequal scattering lengths using two-photon Raman transitions. This results in a BEC where the interactions are effectively chiral, i.e. depend on the propagation direction of the atoms. We show that under appropriate conditions the Hamiltonian of the system corresponds to the chiral BF theory: a one-dimensional reduction of the celebrated Chern-Simons gauge that effectively describes fractional quantum Hall states [1]. Our chiral BECs allow us to reveal the key properties of the chiral BF theory: the formation of chiral solitons and the emergence of an electric field generated by the system itself [2]. Our results thus expand the scope of quantum simulation to topological gauge theories and open a route to implement analogous theories in higher dimensions.
In a second series of experiments, we address instead the regime of weak optical coupling, where the dispersion relation of the atoms acquires a characteristic double-well structure. When the intrawell interactions dominate over the interwell ones, both minima are occupied and their populations interfere, leading to a system with a modulated (striped) density profile. The BEC then behaves as a supersolid: a phase that spontaneously breaks both gauge and translation symmetry, and which combines the frictionless flow of a superfluid and the crystalline structure of a solid. We realize this situation in a spin-orbit coupled 41K, where the difference of intraspin and interspin scattering lengths results in a stable supersolid stripe phase over a broad range of Raman coupling parameters. Using a matter-wave lensing technique, we magnify the density profile of the cloud and measure in situ the contrast and spacing of the stripes. Our experiments visualize the crystalline nature of the supersolid stripe phase, and provide an excellent starting point to investigate its excitations.
[1] C. S. Chisholm, A. Frölian, E. Neri, R. Ramos, L. Tarruell, and A. Celi
Encoding a one-dimensional topological gauge theory in a Raman-coupled Bose-Einstein condensate
Phys. Rev. Research 4, 043088 (2022)
[2] A. Frölian, C. S. Chisholm, E. Neri, C. R. Cabrera, R. Ramos, A. Celi, and L. Tarruell
Realizing a 1D topological gauge theory in an optically dressed BEC
Nature 608, 293–297 (2022)
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Sculpted light nano and microsystems
Halina Rubinsztein-Dunlop (The University of Queensland, Australia)
11.05.2023
10:30
Atominstitut, Helmut Rauch Lecture hall, 1020 Vienna
Jörg Schmiedmayer
Sculpted light refers to the generation of custom designed light fields. These light fields can be applied in many diverse fields ranging from interrogating single atoms or atom assembly to using these fields for optical micromanipulation and optical tweezers as well as creating new quantum devices and sensors. We consider here the study and application of light with structured intensity, polarization and phase. We can create custom fields in multiple planes using dynamic and geometric phase control. Sculpted light can be generated using spatial light modulators (SLM) or digital micromirror devices (DMD) and enable the production of configurable and flexible confining potentials at the nano and micron-scale. This results in production of highly configurable time-averaged traps. All these methods achieve dynamical and flexible sculpted light fields and enable imaging of the amplitude patterns, phase and polarization. These sculpted light fields can be used for intricate studies of light -matter interactions in a variety of environments. I will describe their applications to trapping and manipulating nano and micron-size objects with examples ranging from atomtronics to measurements in-vivo inside biological cells and for studies of active matter.
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Quantum gas in a box
Zoran Hadzibabic (University of Cambridge)
12.05.2023
10:00
Atominstitut, Helmut Rauch Lecture hall, 1020 Vienna
Jörg Schmiedmayer
For nearly three decades ultracold atomic gases have been used with great success to study fundamental many-body phenomena such as Bose-Einstein condensation and superfluidity. While traditionally they were produced in harmonic electromagnetic traps and thus had inhomogeneous densities, it is now also possible to create homogeneous samples in the uniform potential of an optical box trap [1]. Box trapping simplifies the interpretation of experimental results, provides more direct connections with theory and, in some cases, allows qualitatively new, hitherto impossible experiments. I will give an overview of our recent experiments with box-trapped three- and two-dimensional Bose gases, focusing on a series of related experiments on far-from-equilibrium phenomena, including turbulence [2-4] and dynamic scaling in driven disordered gases [5].
[1] Quantum gases in optical boxes (review), N. Navon, R. P. Smith, and Z. Hadzibabic, Nat. Phys. 17, 1334 (2021).
[2] Emergence of a turbulent cascade in a quantum gas, N. Navon, A. L. Gaunt, R. P. Smith, and Z. Hadzibabic, Nature 539, 72 (2016).
[3] Emergence of isotropy and dynamic scaling in 2D wave turbulence in a homogeneous Bose gas, M. Galka et al., Phys. Rev. Lett. 129, 190402 (2022).
[4] Universal equation of state for wave turbulence in a quantum gas, L. H. Dogra et al., arXiv:2212.08652
[5] Observation of subdiffusive dynamic scaling in a driven and disordered box-trapped Bose gas, G. Martirosyan et al., arXiv:2304.06697
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From Superconducting Circuits to Topological Insulator Floquet Modes: Singal Amplification and Generating Entanglement
Seyed Shabir Barzanjeh (University of Calgary | CA)
16.05.2023
13:00
Institute of Science and Technology Austria (ISTA), Heinzel Seminar Room
Johannes Fink
My talk will cover the use of nonlinearity in quantum optics to design quantum-limited amplifiers or generate entanglement. In the first part, I will discuss a new design for microwave degenerate parametric amplifiers (DPAs) that uses kinetic inductance to overcome limitations caused by high-order nonlinearities from Josephson junctions. The resulting DPA exhibits phase-sensitive gains of up to 40 dB, operating close to the quantum noise limit, and provides new opportunities for sensitive microwave measurements. In the second part of my talk, I will discuss entanglement generation in silicon-based Topologically insulate Floquet defect mode resonance (FDMR) systems. Our study leverages a resonance effect in the bulk of an FDMR to demonstrate enhanced entangled photon pair generation. We achieve second-order cross correlation of photon pairs 300 times higher than without resonance, thanks to a wavelength-tunable FDMR with Q-factors up to 10^5 and FSR ~5 nm. Our results provide new insights into generating and manipulating entanglement in quantum systems, which has important implications for quantum communication and computation.
Upcoming Talks
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Sensing with undetected photons and 3 kinds of photon entanglement
Sven Ramelow - HU Berlin
26.05.2023
10:00
Atominstitut, Hörsaal
Philipp Haslinger
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T.B.C
Stefan Rotter - TU Wien
02.06.2023
10:00
Atominstitut, Hörsaal
Jörg Schmiedmayer
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Quantum reaction-diffusion systems
Igor Lesanovsky - Universität Tübingen
16.06.2023
10:00
Atominstitut, Hörsaal
Jörg Schmiedmayer
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Entanglement of trapped-ion qubits separated by 230 meters
Tracy Northup - Universität Innsbruck
23.06.2023
10:00
Atominstitut, Hörsaal
Julian Leonard
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