Beyond CMOS: Alternative computing paradigms Second Severo Ochoa Workshop on ICT

The need for alternative computation requires we consider disruptive scientific and technological options using novel state variable and approaches. So far, one driving vector has been computational speed and the other efficient energy use in computation. In this Severo Ochoa Workshop on Information and Communication Technologies entitled “Beyond CMOS: Alternative computing paradigms” leading scientists and engineers are brought together to offer their perspectives and to share their experience in several novel approaches.

Friday 22 April 2022
From 9:00 to 17:30 (CET)
ICN2 Seminar Room and Online
Register here and choose your attendance modality (in person / online)

The workshop topics will cover spins, photons, mechanical waves, phonons and hybrid states of photons and phonons as a state variables, as well as materials for neuromorphic computing and nanofabrication technologies to engineer silicon qubits. The workshop is part of the series organised within the framework of the Spanish Excelencia Severo Ochoa Programme.

Phillip Ben-Abdallah

Philippe Ben-Abdallah is Research Director at CNRS in France and adjunct Professor at Sherbrooke University in Canada. He is head of the team “thermoplasmonic” of Charles Fabry Laboratory at the Institut d’Optique at Paris. He is currently associate editor of journal Optics Express. He got his PhD in Physics at ENSMA, the national school of aerotechnics in 1997. During the years 1998-1999, he was a Post-doctoral fellow at Quebec University in Canada where he worked on radiative heat transfers at mesoscopic scale in heterogeneous media. He held a tenured position at CNRS at Poitiers in 2000 and became Senior Researcher at CNRS in 2008 at Nantes where he led the group “heat transfer in materials”. Since 2011 he is CNRS Senior Research Fellow at Charles Fabry Laboratory where he develops the “thermoplasmonics” group.

His research activities are mainly on nanophysics and mesoscopic physics, plasmonics and near-field heat transfer in many-body systems with applications in the fields of nanoscale thermal management, energy conversion/harvesting, IR spectroscopy and data recording. He is author of more than 250 scientific communications and publications.

Information treatment with thermal photonsIn solid state physics it is well known that electric currents can be controlled using building blocks such as diode or transistor and these building blocks can be used to design logic gates and make Boolean treatment of information. Astonishing, thermal counterparts of these devices had not been considered until very recently. In this talk I will make a brief overview of capabilities offered by many-body systems to make logical operations using thermal photons in near-field regime. I will first discuss the possibility to develop thermal analogs of diode, memory and transistor and I will demonstrate the possibility to perform basic logical operations at submicrometric scale by controlling the near-field radiative heat exchanges in many-body systems.

- P. Ben-Abdallah and S.-A. Biehs, Phys. Rev. Lett. 112, 044301 (2014).
- V. Kubytskyi, S.-A. Biehs, and P. Ben-Abdallah, Phys. Rev. Lett. 113, 074301 (2014).
- A. Fiorino, Anthony, D. Thompson, LX Zhu, R. Mittapally, S.-A. Biehs, O. Bezencenet, El-Bondry N., S. Bansropun, P. Ben-Abdallah, E. Meyhofer and P. Reddy, ACS NANO, 12, 6, 5774-5779 (2018).
- S. -A. Biehs, R. Messina, P. S. Venkataram, A. W. Rodriguez, J. C. Cuevas, and P. Ben-Abdallah, Rev. Mod. Phys. 93, 025009 (2021).

Tobias J. Kippenberg

Tobias J. Kippenberg is Full Professor in the Institute of Physics and Electrical Engineering at EPFL in Switzerland since 2013 and joined EPFL in 2008 as Tenure Track Assistant Professor. Prior to EPFL, he was Independent Max Planck Junior Research group leader at the Max Planck Institute of Quantum Optics in Garching, Germany. While at the MPQ he demonstrated radiation pressure cooling of optical micro-resonators, and developed techniques with which mechanical oscillators can be cooled, measured and manipulated in the quantum regime that are now part of the research field of Cavity Quantum Optomechanics. Moreover, his group discovered the generation of optical frequency combs using high Q micro-resonators, a principle known now as micro-combs or Kerr combs.

For his early contributions in these two research fields, he has been recipient of the EFTF Award for Young Scientists (2011), The Helmholtz Prize in Metrology (2009), the EPS Fresnel Prize (2009), ICO Award (2014), Swiss Latsis Prize (2015), as well as the Wilhelmy Klung Research Prize in Physics (2015), the 2018 ZEISS Research Award and 2020 OSA R. Wood Award. Moreover, he is 1st prize recipient of the "8th European Union Contest for Young Scientists" in 1996 and is listed in the Highly Cited Researchers List of 1% most cited Physicists in 2014-2019. He is founder of the startup LIGENTEC SA, an integrated photonics foundry.

Cavity Quantum Optomechanics The mutual coupling of optical and mechanical degrees of freedom via radiation pressure has been a subject of interest in the context of quantum limited displacements measurements for Gravity Wave detection for many decades(1, 2). The pioneering work of Braginsky predicted that radiation pressure can give rise to dynamical backaction, which allows cooling and amplification of the internal mechanical modes of a mirror coupled to an optical cavity and moreover establishes a fundamental measurement limit via radiation pressure quantum fluctuations. A decade ago, it was discovered that optical microresonators with ultra high Q, not only possess ultra high Q optical modes, but moreover mechanical modes that are mutually coupled via radiation pressure(3). The high Q of the microresonators, not only enhances nonlinear phenomena – which enables for instance optical frequency comb generation(4, 5) as well as temporal soliton formation(6, 7)– but also enhances the radiation pressure interaction. This has allowed the observation of radiation pressure phenomena in an experimental setting and is an underlying principle of the research field of cavity quantum optomechanics(8, 9).

In this talk, I will describe a range of optomechanical phenomena that we observed using high Q optical microresonators. Radiation pressure back-action of photons is shown to lead to effective cooling(1, 2, 10, 11) of the mechanical oscillator mode using dynamical backaction. Sideband resolved cooling, combined with cryogenic precooling enables cooling the oscillators such that it resides in the quantum ground state more than 1/3 of its time(12). Increasing the mutual coupling further, it is possible to observe quantum coherent coupling(12) in which the mechanical and optical mode hybridize and the coupling rate exceeds the mechanical and optical decoherence rate (7). This regime enables a range of quantum optical experiments, including state transfer from light to mechanics using the phenomenon of optomechanically induced transparency(13). Moreover, the optomechanical coupling can be exploited for measuring the position of a nanomechanical oscillator in the timescale of its thermal decoherence(14), a basic requirement for preparing its ground-state using feedback as well as (Markovian) quantum feedback. This regime moreover enables to explore quantum effects due to the radiation pressure interaction, notably quantum correlations in the light field that give rise to optical squeezing or sideband asymmetry(15).

The optomechanical toolbox developed in the past decades enables to extend quantum control, first developed for atoms, and recently for superconducting quantum circuits, to be extended to solid state mechanical oscillators. New frontiers that are now possible include for example the generation of non-classical states of motion via post-selection(16), mechanical quantum squeezing, or interfaces from radio-frequency to the optical domain(17). Time, permitting, recent experiments that probe cavity optomechanics reserved dissipation regime in a microwave opto-mechanical system will be discussed, which provide a means to realize a cold dissipative reservoir for microwave light(18) a building block for non-reciprocal devices(19).

1. V. B. Braginsky, S. P. Vyatchanin, Low quantum noise tranquilizer for Fabry-Perot interferometer. Physics Letters A 293, 228 (Feb 4, 2002).
2. V. B. Braginsky, Measurement of Weak Forces in Physics Experiments. (University of Chicago Press, Chicago, 1977).
3. T. J. Kippenberg, H. Rokhsari, T. Carmon, A. Scherer, K. J. Vahala, Analysis of Radiation-Pressure Induced Mechanical Oscillation of an Optical Microcavity. Physical Review Letters 95, 033901 (2005).
4. T. J. Kippenberg, R. Holzwarth, S. A. Diddams, Microresonator-based optical frequency combs. Science 332, 555 (Apr 29, 2011).
5. P. Del'Haye et al., Optical frequency comb generation from a monolithic microresonator. Nature 450, 1214 (Dec 20, 2007).
6. T. Herr et al., Temporal solitons in optical microresonators. Nature Photonics 8, 145 (2013).
7. V. Brasch et al., Photonic chip–based optical frequency comb using soliton Cherenkov radiation. Science 351, 357 (2016).
8. M. Aspelmeyer, T. J. Kippenberg, F. Marquardt, Cavity optomechanics. Reviews of Modern Physics 86, 1391 (2014).
9. T. J. Kippenberg, K. J. Vahala, Cavity optomechanics: back-action at the mesoscale. Science 321, 1172 (Aug 29, 2008).
10. A. Schliesser, P. Del'Haye, N. Nooshi, K. J. Vahala, T. J. Kippenberg, Radiation pressure cooling of a micromechanical oscillator using dynamical backaction. Physical Review Letters 97, 243905 (Dec 15, 2006).
11. A. Schliesser, R. Rivière, G. Anetsberger, O. Arcizet, T. J. Kippenberg, Resolved-sideband cooling of a micromechanical oscillator. Nature Physics 4, 415 (2008).
12. E. Verhagen, S. Deleglise, S. Weis, A. Schliesser, T. J. Kippenberg, Quantum-coherent coupling of a mechanical oscillator to an optical cavity mode. Nature 482, 63 (Feb 2, 2012).
13. S. Weis et al., Optomechanically induced transparency. Science 330, 1520 (Dec 10, 2010).
14. D. J. Wilson et al., Measurement and control of a mechanical oscillator at its thermal decoherence rate. Nature doi:10.1038/nature14672, (2015, 2014).
15. V. Sudhir, D. Wilson, A. Ghadimi, T. J. Kippenberg, Appearance and disappearance of quantum correlations in measurement-based feedback control of a mechanical oscillator. quant-ph > arXiv:1602.05942, (2016).
16. C. Galland, N. Sandguard, N. Piro, N. Gisin, T. J. Kippenberg, Heralded single phonon preparation, storage and readout in cavity optomechanics. Physical Review letters
17. R. W. andrews et al., Bidirectional and efficient conversion between microwave and optical light Nature Physics 10.1038/NPHYS2911, (2014).
18. D. Toth, N. Bernier, A. Nunnenkamp, A. K. Feofanov, T. J. Kippenberg, Engineered dissipative reservoir for microwave light using circuit optomechanics. arXiv:1602.05180, (2016).
19. A. Metelmann, A. Clerk, Nonreciprocal Photon Transmission and Amplification via Reservoir Engineering PRX 5, (2015).

Sayani Majumdar

Sayani Majumdar is a Senior Scientist in Microelectronics and Quantum Technologies at the VTT Technical Research Centre of Finland and Adjunct Professor (Docent) at the University of Turku. She received her Ph.D. in 2006 from Jadavpur University, India and worked as a postdoctoral fellow at the Åbo Akademi University, University of Turku and in Aalto University as Academy of Finland research fellow. She worked as a visiting scientist at the Francis Bitter Magnet Laboratory of Massachusetts Institute of Technology and Max-Planck Institute for Polymer Research. Her current research focuses on CMOS and flexible substrate compatible heterostructures for neuromorphic computing and adaptive sensing.

Neuromorphic Computing and Adaptive Sensing - A Device to Systems Level PerspectiveDevelopment of unconventional computing architectures, including neuromorphic computing, relies heavily on novel devices with properly engineered properties. This requires exploration of new functional materials and their designed interfaces. Ferroelectric memories including two-terminal ferroelectric tunnel junctions and three-terminal ferroelectric field-effect transistors have shown promising performances in recent years as analog, multibit memory components with ultralow power consumption. However, for ferroelectric memory technology to become a mainstream technology, CMOS integration of these components is of major importance. For further diversifying their application to edge computing and smart sensing industry, a vast unchartered territory of low-temperature processable and CMOS back-end-of-line compatible materials needs to be researched. In the first part of my talk, I will discuss the potentials for these emerging devices from scalability, performance and 3D integration perspectives. In the next part, I will discuss the near and in-sensor computing approaches for intelligent, adaptive microsystems operating at extreme edge. Finally, I will move to the integrated device-to-system level performance benchmarking aspect, identifying the major challenges that need to be overcome for turning the opportunities to a technological reality.

Can Onur Avci

Can Onur Avci is a principal investigator at the Institute of Materials Science of Barcelona (ICMAB-CSIC). He received his PhD degree from ETH Zürich in 2015 and was awarded the ETH Medal for the outstanding doctoral thesis. He has worked at MIT (2016-2018) and at ETH Zürich (2018-2021) as a postdoc before joining ICMAB last year. Dr. Avci has published 34 papers, which received over 3800 citations with an h-index of 20. He holds one US patent and has delivered more than 30 invited talks and seminars at international venues, including APS March Meeting, INTERMAG, SPIE, etc. He is the recipient of an ERC Starting Grant and the 2021 IUPAP Young Scientist Prize in the Field of Magnetism. He is currently leading a research team of 5 people and two full-scale laboratories. His research covers a wide breadth of subjects in spintronics and magnetism with a focus on electrical control of magnetization, spin-orbit-driven transport phenomena in thin films, spin currents, and magnetic memory/logic devices.

Trends and opportunities in metallic and insulating spintronics Spintronics, the concept of harnessing electron spin as an active variable in electronic circuits, has evolved into a broad and interdisciplinary research field at the intersection of physics, materials science, and nanotechnology. Especially in the past two decades, the improved understanding of transport phenomena and magnetic interactions in solid-state along with the discovery of new materials and experimental techniques enabled rapid progress towards applications. Electrical control of magnetization lies at the heart of these research efforts as it will ultimately lead to highly efficient solid-state memory, logic, and signal transmission devices. These devices will boost the capabilities of the contemporary CMOS technologies and potentially offer beyond-CMOS concepts leading to paradigm shifts in the microelectronic industry.

This talk will overview some of the most recent progress in spintronic research focusing on two material systems: metallic multilayers and magnetic insulators. Metals are historically important in spintronics as earlier concepts, such as giant magnetoresistance and spin-transfer torque, exclusively relied on metallic thin film structures. We now know that many different forms of spin-orbit coupling in bulk and at interfaces of metals enable efficient control of magnetism by electricity for future spintronic devices. On the other side, magnetic insulators constitute an immense family of materials offering great flexibility in property engineering and myriad opportunities for low-loss and highly efficient spintronic concepts. We will explain some cornerstone experiments and conclude the talk by providing future directions in spintronics that may benefit from the progress in these two material families.

Francesc Perez-Murano

Francesc Perez-Murano (0000-0002-4647-8558) is Research Professor at the Institute of Microelectronics of Barcelona (IMB-CNM, CSIC). His main activity is centered in nanofabrication, with pioneering work in developing novel nanolithography methods, including their combination with semiconductor integrated circuit technologies. Some achievements are: Fabrication of the first CNT transistors in Spain (2003); First works worldwide on the integration of Nanomechanical resonators in CMOS circuits (2006); Determination of a novel piezoresistive transduction phenomena in silicon nanowire resonators (2014); Use of focused ion beam implantation for the fabrication of single electron devices (2016); Development of directed self-assembly as a nanolithography method (2012-2021). He is regularly in collaboration with many European research groups in top Institutions like EPFL, CEA-LETI, CNRS, CNR, PSI, Franhoufer, HZDR or IBM- Zurich. Relevant Scientific and Academic positions: Vice-director of the Engineering School of the Universitat Autonoma de Barcelona (2000-2001);); Vice-director of IMB-CNM (2016-2021); Coordinator of the Manufacturing pillar of the CSIC Quantum Technologies Platform (2018-2022); Member of the Steering Committee of Micro and Nano Engineering (2003-2021); Chair of MNE 2006 (Barcelona) and co-Chair of MNE 2017 (Braga); Member of the Program Committee of IEEE IEDM in 2018 and 2019; Member of the editorial board of Microelectronic Engineering (Elsevier) since 2014

Advanced nanofabrication opportunities for silicon spin qubits Quantum computing offers the potential to carry out exponentially more efficient algorithms for a variety of specialized problem classes. Devices for quantum computing are very different from conventional devices, and fine-tuning device characteristics to avoid de-coherence is very demanding. Achieving digital stabilization of quantum information via fault-tolerant error correction is a major goal of the field.

Semiconductor-based devices for quantum computing technologies rely on formation of quantum dots, by electrostatic and/or geometrical confinement, to define, control and operate spin qubits. They are experiencing recently a tremendous evolution, showing outstanding properties as high quality qubits, along with the scalability potential delivered by the semiconductor technology. The technology for fabrication of semiconductor quantum devices for quantum technologies uses state-of-the art processes which are at the frontier of present knowledge. The development of new and improved fabrication processes will allow to obtain devices currently unavailable, in order to explore experimentally novel concepts aiming to increase the quality of spin qubits.

In this talk, challenges and limitations of the present processes for the fabrication of silicon based qubits, as well as some alternative approaches based on novel nanofabrication metods will be presented.

Val Zwiller

Val Zwiller is a professor in Quantum Nano Photonics at the Royal Institute of Technology since 2014. The group develops new schemes for the generation, manipulation and detection of light at the single photon level. The work centers on quantum devices based on superconducting and semiconducting nanostructures that operate at cryogenic temperatures. Val co-founded Single Quantum in 2012.

Quantum Hardware for the generation, manipulation and detection of light at the single photon level We develop single photon sources based on semiconductor quantum dots to generate single photons as well as entangled photon pairs at telecom wavelengths to enable the implementation of long distance quantum communication in optical fibers. Operation at telecom wavelengths also allows us to implement experiments at the single photon level with off-the-shelf components such as modulators. Schemes to manipulate light on-chip, allowing for integration, scalability and higher reliability are also carried out with the aim of operating at telecom frequencies.

Single photon detectors with high detection efficiency, low noise and high time resolution are required to realize quantum communication and quantum sensing experiments. For this purpose, we develop superconducting nanowire single photon detectors, these find a wide range of applications including lidar and quantum microscopy. To allow for complex systems, integrated quantum optics circuits where we combine quantum sources and superconducting detectors are under development.

Finally, we demonstrate single photon transmission over 34 km of deployed optical fibers, paving the way to secure telecommunication links using quantum technologies

Eva M. Weig

Eva Weig is a Full Professor at the Department of Electrical and Computer Engineering of the Technical University of Munich (TUM) in Germany. She holds the Chair of Nano and Quantum Sensors and is a Director of the Center for Quantum Engineering. Before joining TUM in 2020, she spent eight years as a Full Professor at the Department of Physics at the University of Konstanz in Germany. Eva got a PhD in Physics from Ludwig-Maximilians-University (LMU) in Munich, Germany, in 2004, where she also worked as a Junior Research Group Leader following her postdoc at the California NanoSystems Institute at the University of California at Santa Barbara (UCSB).

Research in the Weig group is dedicated to nanomechanical systems. Among others, the group has pioneered the integrated dielectric control of high Q nanomechanical resonators. Research interests include the nonlinear dynamics and the coherent control of nanomechanical systems, the study of coupled nanoresonators and nanomechanical arrays, and cavity opto- and electromechanical systems.

A phononic frequency comb from a single resonantly driven nanomechanical modeDoubly-clamped nanostring resonators excel as high Q nanomechanical systems enabling room temperature quality factors of several 100,000 in the 10 MHz eigenfrequency range. Dielectric transduction via electrically induced gradient fields provides an integrated control scheme while retaining the large mechanical quality factor [1]. Dielectrically controlled nanostrings are an ideal testbed to explore a variety of dynamical phenomena ranging from multimode coupling to coherent control [2]. Here I will focus on the nonlinear dynamics of a single, resonantly driven mode. The broken time reversal symmetry gives rise to the squeezing of the string’s fluctuations. As a result of the high mechanical Q factor, the squeezing ratio is directly accessible from a spectral measurement [3]. It is encoded in the intensities of the two spectral peaks arising from the slow dynamics of the system in the rotating frame. For stronger driving, an onset of self-sustained oscillation is observed which leads to the generation of a nanomechanical frequency comb. The effect is a consequence of a resonantly induced negative effective friction force induced by the drive. This is the first observation of a frequency comb arising solely from a single mode and a single, resonant drive tone [4].

[1] Q. P. Unterreithmeier et al., Nature 458, 1001 (2009)
[2] T. Faust et al., Nature Physics 9, 485 (2013)
[3] J. Huber et al., Phys. Rev. X 10, 021066 (2020)
[4] J. Ochs et al., in preparation

09:00 – 09:10 Welcome by Pablo Ordejon (ICN2 Director)
Chair: Juan Sierra (ICN2)
09:10 – 10:00 Can Onur Avci (ICMAB-CSIC, Bellaterra)
Trends and opportunities in metallic and insulating spintronics
10:00 – 10:50 Sayani Majumdar (VTT Espoo)
Neuromorphic Computing and Adaptive Sensing - A Device to Systems Level Perspective
10:50 – 11:10 Coffee break
Chair: Clivia Sotomayor Torres (ICN2)
11:10 – 12:00 Francesc Perez-Murano (CNM-CSIC, Bellaterra)
Advanced nanofabrication opportunities for silicon spin qubits
12:00 – 12:50 Val Zwiller (KTH, Kista)
Quantum Hardware for the generation, manipulation and detection of light at the single photon level
12:50 – 14:20 Lunch
Chair: Emigdio Chavez-Angel (ICN2)
14:20 – 15:10 Tobias Kippenberg (EPFL) ONLINE
Cavity Quantum Optomechanics
15:10 – 16:00 Phillip Ben-Abdallah (Institut d’Optique, Paris Saclay)
Information treatment with thermal photons
16:00 – 16:20 Tea break
Chair: Martin Poblet (ICN2)
16:20 – 17:10 Eva Weig (TU Munich) ONLINE
A phononic frequency comb from a single resonantly driven nanomechanical mode
17:10 – 17:30 Wrap up and end of workshop - Clivia Sotomayor Torres (ICN2)
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