Programm für das Wintersemester 2021/2022

Thursdays, 14 Uhr c.t.

Institut für Physik
live at Zoom

21.10.21Prof. Tanya Zelevinsky, Columbia University
Techniques for controlling quantum states of atoms have led to extremely precise metrology and studies of degenerate gases.  Extending such techniques to various types of molecules further enriches the understanding of fundamental physics, basic chemical processes, and many-body science.  Samples of diatomic molecules can be created by binding laser-cooled atoms, or by direct molecular laser cooling.  We explore both approaches and demonstrate high-precision metrology with an optical-lattice based molecular clock, as well as photo-chemistry in the highly nonclassical domain.
14:00 Uhr s.t., at Zoom

28.10.21Prof. Ilja Gerhardt, Leibniz Universität Hannover
The past decade has seen a resurrection of experiments with hot atomic vapors. Their physics covers atomic clocks, magnetic and electric sensing and optical devices. In parallel the field of quantum technology develops ever better single photon sources and quantum sensing devices at the nano-scale. Our own efforts of combining both techniques started with single photon slow light experiments. [1,2]. They evolved towards the optimization of Faraday filters [3,4,5], and took the baby-steps towards storing a single photon into hot atomic vapor with Rydberg transitions [6]. With the technology at hand, we further aimed for the combination of solid-state samples with atomic vapors. This can be envisioned in a sensing setting [7] – but also other coupling schemes can be envisioned. In this talk I will review the prospects and challenges for combining single photon sources with hot atomic vapors. The valuable tool of atomic filtering and its combination with quantum optics will be explained and reviewed. References [1] Molecular photons interfaced with alkali atoms Petr Siyushev, Guilherme Stein, Jörg Wrachtrup, Ilja Gerhardt Nature, 2014, 509, 66-70 [2] Two-photon interference in an atom-quantum dot hybrid system Hüseyin Vural, Simone L. Portalupi, Julian Maisch, Simon Kern, Jonas H. Weber, Michael Jetter, Jörg Wrachtrup, Robert Löw, Ilja Gerhardt, Peter Michler Optica, 2018, 5, 367-373 [3] Na-Faraday rotation filtering: The optimal point Wilhelm Kiefer, Robert Löw, Jörg Wrachtrup, Ilja Gerhardt Scientific Reports, 2014, 4, 6552 [4] Simultaneous Faraday filtering of the Mollow triplet sidebands with the Cs-D1 clock transition Simone Luca Portalupi, Matthias Widmann, Cornelius Nawrath, Michael Jetter, Peter Michler, Jörg Wrachtrup, Ilja Gerhardt Nature Communications, 2016, 7, 13632 [5] How anomalous is my Faraday filter? Ilja Gerhardt Optics Letters, 2018, 43, 5295-5298 [6] Two Step Excitation in Hot Atomic Sodium Vapor Bernd Docters, Jörg Wrachtrup, Ilja Gerhardt Scientific Reports, 2017, 11760 [7] A Rubidium Mx-magnetometer for Measurements on Solid State Spins Daniel Arnold, Steven Siegel, Emily Grisanti, Jörg Wrachtrup, Ilja Gerhardt Review of Scientific Instruments, 2017, 88, 023103
14:00 Uhr s.t., at Zoom

04.11.21Prof. Cornelia Denz, Universität Münster
Within the last decades, customized light fields have proven their significance in various research areas, ranging from nano-scale complexity over optical micromanipulation to high-resolution imaging and material machining. Besides well-established amplitude and phase modulation, within recent years, structured light incorporated orbital and spin angular momentum. Moreover, polarization has been rediscovered as a degree of freedom that enriches the diversity of spatially structured light. In our contribution, we discuss creating 3d light landscapes by interfering counterpropagating beams or by tightly focusing polarization structured light. In this way, spatial entanglement of spin- and orbital angular momentum is created, leading to the observation of entanglement beating. Moreover, non-negligible longitudinal vector field components appear in focal light landscapes forming exotic singular and topological structures as arrays of Möbius strips or skyrmionics Hopfions. We evince the benefit of these fields for advanced optical trapping and information processing.
14:00 Uhr s.t., at Zoom

11.11.21Prof. Christine Silberhorn, Universität Paderborn
Quantum technologies promise a change of paradigm for many fields of application, for example in communication systems, in high-performance computing and simulation ofquantum systems, as well as in sensor technology. They can shift the boundaries of today’ssystems and devices beyond classical limits and seemingly fundamental limitations. Photonicsystems, which comprise multiple optical modes as well as many nonclassical light quantum states of light, have been investigated intensively in various theoretical proposals over the last decades. However, their implementation requires advanced setups of high complexity, which poses a considerable challenge on the experimental side. The successful realization of controlled quantum network structures is key for many applications in quantum optics and quantum information science. Here we present three differing approaches to overcome current limitations for the experimentalimplementation of multi-dimensional quantum networks: non-linear integrated quantum optics, pulsed temporal modes and time-multiplexing. Non-linear integrated quantum devices with multiple channels enable the combinations of different functionalities, such as sources and fast electro-optic modulations, on a single compact monolithic structure. Pulsed photon temporalmodes are defined as field orthogonal superposition states, which span a high dimensional system. They occupy only a single spatial mode and thus they can be efficiently used in singlemode fibre communication networks. Finally, time-multiplexed quantum walks are a versatile tool for the implementation of a highly flexible simulation platform with dynamic control of the underlying graph structures and propagation properties.
14:00 Uhr s.t., at Zoom

18.11.21Prof. Morgan Mitchell, The Institute of Photonic Sciences
In 1981, a newly-minted PhD named Carlton Caves proposed to use ``squeezed light'’ to beat the shot noise limit, and thereby improve the sensitivity of gravitational wave detectors. Thirty years later, the GEO600 gravitational wave detector demonstrated improved sensitivity using squeezed light. Today, forty years after his proposal, Caves is a Professor Emeritus, and gravitational waves are routinely detected with the help of squeezed light. Meanwhile, in 1993, the squeezing of atomic spins was proposed as a way to improve the sensitivity of atomic clocks, magnetometers, gravimeters, and so forth. If these atomic instruments proceed along the same time-line as gravitational-wave detectors, we should expect to see the first real-world use of squeezing in atomic instruments in the next few years. In this talk, I will describe some of the progress in this direction, including the use of squeezed light and squeezed spins in magnetometry. I will try to explain how quantum noise in a magnetometer is, and is not, like quantum noise in a gravitational wave detector, and some unexpected features that make magnetometers particularly well-suited for spin squeezing. If time permits, I will say something about the potential to use squeezing in optical lattice clocks, to improve the stability of our best time-keeping instruments.
14:00 Uhr s.t., at Zoom

25.11.21Dr. Sarah Skoff, Technische Universität Wien
Since quantum technology is becoming advanced, new ways are sought to make miniature systems for quantum networks and sensing. Solid-state quantum emitters have therefore moved into focus as they lend themselves for integration into nanophotonic platforms and come in a variety of forms and with a variety of different level structures. Here, I want to present two different kinds of solid-state platforms, single molecules in solids and quantum emitters in 2D materials. I will present measurements on coupling these quantum emitters to waveguides, in particular optical nanofibers. These are waveguides that are naturally integrated with optical fibers and enhance the light-matter interaction by their strong transverse confinement of the guided light field. I will also show how the light-matter interaction can be further increased by employing fiber-based cavities. These cavities have been shown to work equally well at room temperature and cryogenic temperatures, where the latter is still most often a requirement for solid-state system due to the phonons from the host material. However due to the 2D nature of the host material, quantum emitters in 2D hexagonal Boron nitride may provide a platform for quantum tech-nology that could also operate a room temperature and I will give an overview of recent measurements with these emitters and give an outlook of our endeavour to bring solid-state quantum optics to a room temperature environment.
14:00 Uhr s.t., at Zoom


02.12.21Dr. Romana Schirhagl, Groningen University Medical Center, Netherlands

Nanoscale free radical detection in living cells using diamond magnetometry 

Free radicals play a key role in many biological processes including cell communication, immune responses, metabolism or cell development. But they are also involved whenever something is wrong in a cell and are thus important in many diseases including cardiovascular diseases, cancer or bacterial and viral infection. Unfortunately, they are very reactive and short lived and thus difficult to detect for the state of the art. We have used diamond magnetometry to achieve this. We make use of nanodiamonds which we bring into cells. We then use of NV centers in diamonds to perform relaxometry measurements. These are sensitive to spin noise (in this case from radicals) and deliver signals that are equivalent to T1 in conventional MRI but from nanoscale voxels. Using this method, we are able to quantify free radical generation with nanoscale resolution in the nanomole range (1). In our recent work we were able to detect free radical generation in single mitochondria (the energy factories of the cell) in isolated form as well as in their cellular environment (2). 1 Perona Martínez, F., Nusantara, A.C., Chipaux, M., Padamati, S.K. and Schirhagl, R., 2020. Nanodiamond Relaxometry-Based Detection of Free-Radical Species When Produced in Chemical Reactions in Biologically Relevant Conditions. ACS Sensors. 2 Nie, L., Nusantara, A.C., Damle, V.G., Sharmin, R., Evans, E.P.P., Hemelaar, S.R., van der Laan, K.J., Li, R., Martinez, F.P., Vedelaar, T. and Chipaux, M., Schirhagl, R., 2021. Quantum monitoring of cellular metabolic activities in single mitochondria. Science Advances, 7(21), p.eabf0573.
14:00 Uhr s.t., at Zoom

zukünftige Termine
09.12.21Prof. Gerhard Rempe, Max-Planck-Institut für Quantenoptik; TUM
Quantum networks with long-lived memory devices are a promising platform for modular quantum computing and long-distance quantum communication. Using selected examples, the talk will discuss the state of the art achieved with single emitters in optical resonators for distributed quantum logic and secure quantum repeaters.
14:00 Uhr s.t., at Zoom

16.12.21Prof. Irina Novikova, College of William & Mary, Williamsburg, Virginia/USA
For some light-sensitive substances it is crucial to be able to measure their optical properties with minimal light exposure. At the same time, low-light imaging is technically challenging due to the dark noise of a CCD camera. In this talk I will describe a new imaging techniques that relies on quantum fluctuation analysis to image opaque objects at low-photon environment. We demonstrate that both squeezed vacuum and thermal vacuum can be effectively used for this purpose. At the same time, we successfully eliminate the camera dark noise problems by realizing a camera-based homodyne detection.
14:00 Uhr s.t., at Zoom

06.01.22Prof. Stefan Willitsch, Universität Basel
The development of quantum technologies for molecules has remained a long-standing challenge due to the complexity of molecular systems. We have recently developed a quantum-non-demolition technique for the non-destructive detection of the internal quantum state of a single trapped molecular ion [1,2,3]. The method is based on the state-dependent coherent excitation of the motion of the molecular ion and subsequent measurement of the motional quantum state using a co-trapped atomic ion. This approach offers new perspectives not only for the detection, but also for the preparation and the manipulation of molecular quantum states on the single-particle level with a sensitivity several orders of magnitude higher compared to previously used destructive schemes. We present a characterisation of the technique using the homonuclear diatomic ion N2+ as an example and show how it can be used for non-invasive spectroscopic measurements on single molecules. We also discuss applications of this technique in the realm of precision molecular spectroscopy [4] using a newly established fibre network for the precise transfer of frequencies within Switzerland and their comparison to the Swiss primary standard at METAS. References: [1] Z. Meir, G. Hegi, K. Najafian, M. Sinhal and S. Willitsch, "State-selective coherent motional excitation as a new approach for the manipulation, spectroscopy and state-to-state chemistry of single molecular ions”, Faraday Discuss. 217 (2019), 561. [2] M. Sinhal, Z. Meir, K. Najafian, G. Hegi and S. Willitsch, "Quantum non-demolition state detection and spectroscopy of single trapped molecules”, Science 367 (2020), 1213. [3] K. Najafian, Z. Meir, M. Sinhal and S. Willitsch, "Identification of molecular quantum states using phase-sensitive forces”, Nat. Commun. 11 (2020), 4470. [4] K. Najafian, Z. Meir and S. Willitsch, ”From megahertz to terahertz qubits encoded in molecular ions: theoretical analysis of dipole-forbidden spectroscopic transitions in N2+”, Phys. Chem. Chem. Phys. 22 (2020), 23083. [5] D. Husmann et al., “SI-traceable frequency dissemination at 1572.06 nm in a stabilized fiber network with ring topology”, Opt. Expr. 29 (2021), 24592.
14:00 Uhr s.t., at Zoom

13.01.22Prof. James Thompson, JILA; University of Colorado, Dept. of Physics, Boulder/USA
I will discuss a range of cavity QED experiments that explore how to exploit atom-light interactions to create atom-atom correlations and entanglement for quantum sensing and quantum simulation. Using rubidium atoms, we have implemented both cavity-enhanced quantum nondemolition measurements and cavity-mediated spin-spin interactions to realize an entangled light-pulse matterwave interferometer that is directly observed to operate below the standard quantum limit [1]. Using strontium atoms, we have achieved pulsed superradiant lasing on the millihertz clock transition [2,3], developed a new method for determining the intrinsic radiative lifetime of the clock state [4], and observed a dynamical phase transition [5] arising from a competition between cavity-mediated spin exchange interactions [6] and single particle dynamics. If time permits, I will briefly describe our progress toward a continuous superradiant laser. [1] Greve & Luo et al, arXiv:2110.14027 (2021) [2] Norcia et al, Science Adv. 2 e1601231 (2016) [3] Norcia et al, Phys. Rev. X 8 021036 (2018) [4] Muniz et al, Phys. Rev. Res. 3 023152 (2021) [5] Muniz et al, Nature 580 602 (2020) [6] Norcia et al, Science 361 259 (2018)
14:00 Uhr s.t., at Zoom

20.01.22Prof. Ania Bleszynski Jayich, University of California, Santa Barbara/USA
14:00 Uhr s.t., at Zoom

27.01.22Dr. Sandra Eibenberger-Arias, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin
14:00 Uhr s.t., at Zoom

03.02.22Prof. Ronald Fernando Garcia Ruiz, Massachusetts Institute of Technology (MIT), Cambridge, MA/USA
Molecules containing heavy and octupole deformed radioactive nuclei are predicted to provide enhanced sensitivity to investigate distinct nuclear phenomena, to test the violation of fundamental symmetries, and to search for new physics beyond the Standard Model of particle physics. However, experimental measurements of such radioactive systems are scarce, and their study requires to overcome major experimental challenges. This seminar will discuss recent spectroscopy measurements of short-lived radium fluoride molecules (RaF) alongside future perspectives in the study of these and other radioactive molecules.
14:00 Uhr s.t., at Zoom

Koordination: Kontakt:

Dr. Arne Wickenbrock
Institut für Physik und HIM Mainz

Dr. Laatiaoui Mustapha
Department Chemie und HIM Mainz

Andrea Graham
Institut für Physik