Ioannis Drougkakis poster at summer school: Machine learning in quantum physics and chemistry, 24 August - 3 September

Title: A simple and versatile detection technique for cold atoms

Ioannis Drougkakis

Abstract Ultracold atoms have demonstrated great prospects for both technological and fundamental science applications. In order to fully exploit their potential, a precise control of the atomic cloud that can manipulate the quantum features and harness quantum resources is required. We report a robust method for measurement and control of the atom number in an ultracold atomic ensemble. The measurement is based on the Faraday paramagnetic effect: off-resonant light, when traveling through a polarized atomic cloud, experiences optical rotation at an angle that is proportional to the number of atoms. The proposed measurement does not destroy quantum coherences and has an insignificant effect on the atomic temperature, so that it can be used to perform quantum-enhanced measurements and prepare the atomic state at the start of an interferometer sequence. Control of the atom number is realized by the unavoidable atom-loss that is introduced by the measurement, since even far off-resonant light has a non-zero probability for absorption. This atom-loss mechanism will be employed to shrink an initial ensemble to the targeted size. With the proposed method, for the first time the quantum back-action of the measurement probe is exploited to improve the stability of the experiment. Measuring with subatom- shot noise resolution will lead to number squeezed states of Bose Einstein Condensates and will pave the way for squeezing and entanglement generation for spectroscopy and interferometry. Preliminary results with a smaller than 1% precision in controlling the atom number has been achieved using this method and will be presented. Applications of the proposed research include atomic clocks, inertial sensors, quantum computing, quantum simulations and fundamental physics experiments such as gravitational detectors

Ioannis Drougkakis presented at Atomotronics 2022

Title: Matter-Waves lensing in Dynamic Wave-guides

Ioannis Drougkakis

Abstract Matterwaves are promising candidates for the realization of extremely sensitive sensors. Some of the most sensitive and precise measurements to date of gravity[1], inertia[2], and rotation are based on matter-wave interferometry with free-falling atomic clouds. A critical requirement to achieve very high sensitivities is the long interrogation time, which consequently leads to experimental apparatus up to a hundred meters tall or the requirement for experiments to be performed in microgravity in space[4—7]. To tackle this problem, the gravitational acceleration must be cancelled, e.g. by manipulating atomic waves in time- changeable traps and waveguides [8]. We have recently demonstrated smooth and controllable matter-wave guides by transporting Bose--Einstein condensates (BECs) over macroscopic distances without any heating or decohering their internal quantum states [9]. A neutral-atom accelerator ring was utilized to bring BECs to very high speeds (up to 16 times their sound velocity) and transport them in a magnetic matter-wave guide for 15 centimetres whilst fully preserving their internal coherence. We then use a magnetogravitational matter-wave lens to collimate and focus matterwaves in ring-shaped time-averaged adiabatic potentials [10]. This “Delta-kick cooling” sequence of Bose-Einstein condensates reduces their expansion energies by a factor of 46 down to 800 pK. Compared to the state-of-the-art experiments, requiring zero gravity or large free-flight distances, the ring-shaped atomtronic circuit has a diameter of less than one millimetre and exhibits a high level of control, providing an important step toward atomtronic quantum sensors and the investigation of very low energy effects in ultra-cold atoms.  

References

1. Rosi, G., Sorrentino, F., Cacciapuoti, L., Prevedelli, M. & Tino, G. M. Precision measurement of the Newtonian gravitational constant using cold atoms. Nature 510, 518–521 (2014).
2. Geiger, R. et al. Detecting inertial effects with airborne matter-wave interferometry. Nat. Commun. 2, 474 (2011).
3. Dutta, I. et al. Continuous cold-atom inertial sensor with 1 nrad/sec rotation stability. Phys. Rev. Lett. 116, 183003 (2016).
4. Kovachy, T. et al. Quantum superposition at the half-metre scale. Nature 528, 530–533 (2015).
5. van Zoest, T. et al. Bose–Einstein condensation in microgravity. Science 328, 1540–1543 (2010).
6. Barrett, B. et al. Dual matter-wave inertial sensors in weightlessness. Nat. Commun. 7, 13786 (2016).
7. Soriano, M. et al. Cold atom laboratory mission system design. In 2014 IEEE Aerospace Conference 1–11 (IEEE, 2014).
8. Wang, Y. J. et al. Atom Michelson interferometer on a chip using a Bose–Einstein condensate. Phys. Rev. Lett. 94, 090405 (2005).
9. Saurabh Pandey, Hector Mas, Giannis Drougakis, Premjith Thekkeppatt, Vasiliki Bolpasi, Georgios Vasilakis, Konstantinos Poulios, and Wolf von Klitzing Hypersonic Bose--Einstein condensates in accelerator rings Nature 570:7760 205--209 (2019)
10. Saurabh Pandey et al. Atomtronic Matter-Wave Lensing Phys. Rev. Let. 126 17 (2021)

Wolf von Klitzing (FORTH) invited talk at FINESS 2022

Title: Manipulating matterwaves in atomtronic waveguides

Wolf von Klitzing

Abstract Matterwaves are the atomic counterpart to photonic waves. Like light, they can be guided, focussed and expanded. Time-averaged Adiabatic Potentials (TAAPs) allow us to construct the first fully coherent waveguides for matterwave, where we propagate atoms over distances of tens of centimeters without any noticeable losses or heating from the waveguides. These compact devices now opened the possibility to perform extremely low energy/temperature experiments without the need for large drop-towers. Recently, we have used this to demonstrate gravito-magnetic lenses focusing or collimating matterwaves in a waveguide almost at will, e.g. reducing their expansion energies of condensates by a factor of 46 and thus measuring temperatures down to 800 pK. We will present the basic principles of TAAPs and its long-term prospects as a compact matterwave laboratory.

Johannes Fiedler (UiB) presented nanolace at the Network Meeting of the Alexander von Humboldt Foundation, 27- 29 April 2022, University of Rostock, Germany

Title: The Role of Dispersion Forces for Matter-Wave Diffraction Experiments

Johannes Fiedler

Abstract: Recent progress in matter-wave experiments led to technical applications, particularly for acceleration sensing, single-particle detectors, quantum microscopes or matter-wave lithography. Thus, they act on the nanometre length scale. Consequently, the quantised nature of the object is not neglectable. In particular, the quantum vacuum has to be taken into account. Hence, the interactions between the objects are dressed by the vacuum polarisability leading to the dispersion forces. The diffraction of matter waves is based on the wave-particle duality and has the advantage that waves with sub-nanometre wavelengths can be created and thus strongly increases the resolution compared to optical devices [1]. However, the additional interactions between the matter-wave particles and the diffraction object dramatically influence the propagation of the wave [2].   In this presentation, I will illustrate the impact of dispersion forces on the results of diffraction experiments and demonstrate possibilities for their manipulation to enhance the contrast for matter-wave lithography applications [3].   [1] Brand, C., Fiedler, J., Juffmann, T., Sclafani, M., Knobloch, C., Scheel, S., Lilach, Y., Cheshnovsky, O., Arndt, M. (2015): A Green’s function approach to modeling molecular diffraction in the limit of ultra-thin gratings. In: Ann. Phys. (Berlin) 527, 580-591. [2] Gack, N., Reitz, C., Hemmerich, J.L., Könne, M., Bennett, B., Fiedler, J., Gleiter, H., Buhmann, S.Y., Hahn, H., Reisinger, T. (2020): Signature of Short-Range van der Waals Forces Observed in Poisson Spot Diffraction with Indium Atoms. In: Phys. Rev. Lett. 125, 050401. [3] Fiedler, J., Holst. B. (2022): An atom passing through a hole in a dielectric membrane: impact of dispersion forces on mask-based matter-wave lithography. In: J. Phys. B: At. Mol. Opt. Phys. 55, 025401.

 

Title: The role of dispersion forces for matter-wave binary holography experiments.

Johannes Fiedler (UiB) presented a poster in contribution to the 2nd European Quantum Technologies Virtual Conference (EQTC 2021 - https://www.eqtc.org/), on 1 december 2021.

Abstract: Lithography is a commonly applied method to create and manipulate semiconductor devices. A further decrease of the size can currently be reached by using extreme-ultraviolet (EUV) photolithography that uses electromagnetic radiation with a wavelength of 13.5 nm that corresponds to an energy of 92eV [1]. The disadvantage of this method is the high energy transfer from the photons to the wafer. The ability to pattern materials at ever-smaller sizes using photolithography is driving advances in nanotechnology. When the feature size of materials is reduced to the nanoscale, individual atoms and molecules can be manipulated to dramatically alter material properties. Extreme ultraviolet – a next-generation lithography technology – can deliver even pattern sizes down to a few nanometer resolutions. However, the secondary electron blurring from extreme-ultraviolet photons hinders the creation of single-molecule patterns. An alternative approach is the use of matter waves which reaches similar and even much smaller wavelengths with a lower amount of kinetic energy [2]. Lithography with metastable atoms has been suggested as a cost-effective, less-complex alternative to EUV lithography. The great advantage of atom lithography is that the kinetic energy of an atom is much less than that of a photon for a given wavelength. Already in 1995, it was demonstrated experimentally that binary holography can be used to form arbitrary patterns using metastable atoms [2]. In binary holography, a pattern of holes is used to approximate a Fourier transform of the desired target pattern. Recently, it was shown theoretically that binary holography with metastable atoms can in principle be used to form arbitrary patterns with nanometer resolution [3]. However, this publication did not include interaction effects between the mask and the metastable atoms. Here we present an investigation of how the dispersion forces between the atoms and the mask affect the path of the atoms through silicon nitride masks. It was theoretically shown that binary holography with metastable atoms can in principle be used to form arbitrary patterns with nanometer resolution [3]. However, recent experiments and theories on matter-wave diffraction experiments have demonstrated that the dispersion forces play an important role in such systems, leading to a reduction of the transmission area on the one hand [4] and a spatially dependent phase shift imprinted on the matter-wave upon leaving the obstacles on the other hand [5]. Dispersion forces are caused by the ground-state fluctuations of the electromagnetic field which typically result in an attractive force between the constituents.    

The role of dispersion forces in matter-wave scattering experiments

Johannes Fiedler (UiB) presented a contribution to the FOMO lecture series (Lectures on Matter-Wave Interferometry) on July 21st 2021.

  Abstract: Dispersion forces, such as van der Waals forces between neutral particles or Casimir-Polder forces between neutral particles and dielectric surfaces, are caused by the ground-state fluctuations of the electromagnetic field. They can be understood via an exchange of virtual photons that are generated as a dipole response of the particle due to the vacuum fluctuation of the field surrounding it. These resulting forces are weak for large separations and dramatically increase with decreasing distances. To this end, in matter-wave scattering experiments, where the beam particles reach close distances to the diffracted object, which is typical in the order of a few nanometers, these forces dominate the interaction and have a large impact on the experimental results. In this talk, we will shortly introduce these forces and illustrate their impact on the diffraction of particle beams from porous materials. This is of particular relevance for  metastable atom lithography with binary holography masks, currently pursued in the FET-Open project Nanolace.   Link to the abstract: https://www.matterwaveoptics.eu/fomo2021/contributed-talks/fomo2021-abstract/fiedler-johannes-the-role-of-dispersion-forces-in-matter-wave-scattering-experiments/

The NanoLace project: Grid-based holograms for matter waves lithography

Veronica Perez (NTNU) presented a contribution to the FOMO lecture series (Lectures on Matter-Wave Interferometry) on July 21st 2021.

  Abstract: Grid-based binary holography (GBH) is an attractive method for patterning with light or matter waves. It is an approximate technique in which different holographic masks can be used to produce similar patterns. Mask-based pat- tern generation is a critical and costly step in microchip production. The next- generation extreme ultraviolet- (EUV) lithography instruments with a wave- length of 13.5 nm are currently under development. In principle, this should allow patterning down to a resolution of a few nanometers in a single expo- sure. However, lithography with metastable atoms has been suggested as a cost-effective, less-complex alternative to EUV lithography. The great advan- tage of atom lithography is that the kinetic energy of an atom is much less than that of a photon for the same wavelength. Until now, however, no method has been available for making masks for atom lithography that can produce arbitrary, high-resolution patterns; to achieve this is the aim of the NanoLace project. Here we present the resolution that can be achieved when making binary masks to create patterns in a target plane close to the mask with the use of an atom source. Through simulations, we investigate the diffraction and ideal size of the patterns formed by holographic masks using beams of room temperature metastable helium atoms. in an experimental setup. Our calculations are now being extended to consider all experimental key features.   Link to the abstract: https://www.matterwaveoptics.eu/fomo2021/contributed-talks/fomo2021-abstract/simonsen-veronica-p-the-nanolace-project-grid-based-holograms-for-matter-waves-lithography/  

Nanolace at the Innovation Norway Launch

Project Coordinator Bodil Holst presented Nanolace at the Innovation Norway Launch of the Horizon Europe - Pillar III Innovation Europe

The meeting took place as a virtual event on 9 march 9.00-11.00, with participation of the Norwegian ministers for research and higher education Henrik Aasheim and the minister of Trade and Industry Iselin Nybø   https://www.innovasjonnorge.no/no/tjenester/arrangementer/kick-off-for-horisont-europas-innovasjonspilar/

Wolf von Klitzing hot topic talk at the International Conference on Quantum Optics 2020.

Title: Ultra-smooth matter wave guides: Bose-Einstein Condensates at super-sonic speeds with(out) obstacles

Wolf von Klitzing

Abstract In this presentation, I will talk about our recent experiments of coherent transport of matterwaves in ultra-smooth waveguides over macroscopic distances of up to 40cm. We use optimal control theory to accelerate the atom clouds with minimal heating. The BECs move at speeds of many times the critical velocity of superfluidity. I will discuss the role of roughness of the guides and the limits for coherent transport.

An atom passing through a hole in a dielectric membrane: impact of dispersion forces on mask-based matter-wave lithography

Johannes Fiedler and Bodil Holst 2022 J. Phys. B: At. Mol. Opt. Phys. 55 025401

Abstract

Atomtronic Matter-Wave Lensing

Saurabh Pandey, Hector Mas, Georgios Vasilakis, and Wolf von Klitzing

Phys. Rev. Lett. 126, 170402 – Published 28 April 2021

Abstract: In this Letter, we demonstrate magnetogravitational matter-wave lensing as a novel tool in atom-optics in atomtronic waveguides. We collimate and focus matter waves originating from Bose-Einstein condensates and ultracold thermal atoms in ring-shaped time-averaged adiabatic potentials. We demonstrate “delta-kick cooling” of Bose-Einstein condensates, reducing their expansion energies by a factor of 46 down to 800 pK. The atomtronic waveguide ring has a diameter of less than one millimeter, compared to other state-of-the-art experiments requiring zero gravity or free-flight distances of ten meters and more. This level of control with extremely reduced spatial requirements is an important step toward atomtronic quantum sensors.   Synopsis

Article about Nanolace in Gemini,  a Norwegian magazine on research news published by NTNU and Sintef.   https://gemini.no/2020/06/fremtidens-raskeste-datadingser-kan-fa-norsk-hjelp/

Nanolace is cover story in the Norwegian magazine for professional electronics Elektronikk 11/2019, p. 1-12: Gjennombrudd ved UiB: 1 nanometer i sikte. http://viewer.zmags.com/publication/1a09e128#/1a09e128/1