Tag Archives: Heidelberg University

Optical memristors and neuromorphic computing

A June 5, 2023 news item on Nanowerk announced a paper which reviews the state-of-the-art of optical memristors, Note: Links have been removed,

AI, machine learning, and ChatGPT may be relatively new buzzwords in the public domain, but developing a computer that functions like the human brain and nervous system – both hardware and software combined – has been a decades-long challenge. Engineers at the University of Pittsburgh are today exploring how optical “memristors” may be a key to developing neuromorphic computing.

Resistors with memory, or memristors, have already demonstrated their versatility in electronics, with applications as computational circuit elements in neuromorphic computing and compact memory elements in high-density data storage. Their unique design has paved the way for in-memory computing and captured significant interest from scientists and engineers alike.

A new review article published in Nature Photonics (“Integrated Optical Memristors”), sheds light on the evolution of this technology—and the work that still needs to be done for it to reach its full potential. Led by Nathan Youngblood, assistant professor of electrical and computer engineering at the University of Pittsburgh Swanson School of Engineering, the article explores the potential of optical devices which are analogs of electronic memristors. This new class of device could play a major role in revolutionizing high-bandwidth neuromorphic computing, machine learning hardware, and artificial intelligence in the optical domain.

A June 2, 2023 University of Pittsburgh news release (also on EurekAlert but published June 5, 2023), which originated the news item, provides more detail,

“Researchers are truly captivated by optical memristors because of their incredible potential in high-bandwidth neuromorphic computing, machine learning hardware, and artificial intelligence,” explained Youngblood. “Imagine merging the incredible advantages of optics with local information processing. It’s like opening the door to a whole new realm of technological possibilities that were previously unimaginable.” 

The review article presents a comprehensive overview of recent progress in this emerging field of photonic integrated circuits. It explores the current state-of-the-art and highlights the potential applications of optical memristors, which combine the benefits of ultrafast, high-bandwidth optical communication with local information processing. However, scalability emerged as the most pressing issue that future research should address. 

“Scaling up in-memory or neuromorphic computing in the optical domain is a huge challenge. Having a technology that is fast, compact, and efficient makes scaling more achievable and would represent a huge step forward,” explained Youngblood. 

“One example of the limitations is that if you were to take phase change materials, which currently have the highest storage density for optical memory, and try to implement a relatively simplistic neural network on-chip, it would take a wafer the size of a laptop to fit all the memory cells needed,” he continued. “Size matters for photonics, and we need to find a way to improve the storage density, energy efficiency, and programming speed to do useful computing at useful scales.”

Using Light to Revolutionize Computing

Optical memristors can revolutionize computing and information processing across several applications. They can enable active trimming of photonic integrated circuits (PICs), allowing for on-chip optical systems to be adjusted and reprogrammed as needed without continuously consuming power. They also offer high-speed data storage and retrieval, promising to accelerate processing, reduce energy consumption, and enable parallel processing. 

Optical memristors can even be used for artificial synapses and brain-inspired architectures. Dynamic memristors with nonvolatile storage and nonlinear output replicate the long-term plasticity of synapses in the brain and pave the way for spiking integrate-and-fire computing architectures.

Research to scale up and improve optical memristor technology could unlock unprecedented possibilities for high-bandwidth neuromorphic computing, machine learning hardware, and artificial intelligence. 

“We looked at a lot of different technologies. The thing we noticed is that we’re still far away from the target of an ideal optical memristor–something that is compact, efficient, fast, and changes the optical properties in a significant manner,” Youngblood said. “We’re still searching for a material or a device that actually meets all these criteria in a single technology in order for it to drive the field forward.”

The publication of “Integrated Optical Memristors” (DOI: 10.1038/s41566-023-01217-w) was published in Nature Photonics and is coauthored by senior author Harish Bhaskaran at the University of Oxford, Wolfram Pernice at Heidelberg University, and Carlos Ríos at the University of Maryland.

Despite including that final paragraph, I’m also providing a link to and a citation for the paper,

Integrated optical memristors by Nathan Youngblood, Carlos A. Ríos Ocampo, Wolfram H. P. Pernice & Harish Bhaskaran. Nature Photonics volume 17, pages 561–572 (2023) DOI: https://doi.org/10.1038/s41566-023-01217-w Published online: 29 May 2023 Issue Date: July 2023

This paper is behind a paywall.

Brain-inspired computer with optimized neural networks

Caption: Left to right: The experiment was performed on a prototype of the BrainScales-2 chip; Schematic representation of a neural network; Results for simple and complex tasks. Credit: Heidelberg University

I don’t often stumble across research from the European Union’s flagship Human Brain Project. So, this is a delightful occurrence especially with my interest in neuromorphic computing. From a July 22, 2020 Human Brain Project press release (also on EurekAlert),

Many computational properties are maximized when the dynamics of a network are at a “critical point”, a state where systems can quickly change their overall characteristics in fundamental ways, transitioning e.g. between order and chaos or stability and instability. Therefore, the critical state is widely assumed to be optimal for any computation in recurrent neural networks, which are used in many AI [artificial intelligence] applications.

Researchers from the HBP [Human Brain Project] partner Heidelberg University and the Max-Planck-Institute for Dynamics and Self-Organization challenged this assumption by testing the performance of a spiking recurrent neural network on a set of tasks with varying complexity at – and away from critical dynamics. They instantiated the network on a prototype of the analog neuromorphic BrainScaleS-2 system. BrainScaleS is a state-of-the-art brain-inspired computing system with synaptic plasticity implemented directly on the chip. It is one of two neuromorphic systems currently under development within the European Human Brain Project.

First, the researchers showed that the distance to criticality can be easily adjusted in the chip by changing the input strength, and then demonstrated a clear relation between criticality and task-performance. The assumption that criticality is beneficial for every task was not confirmed: whereas the information-theoretic measures all showed that network capacity was maximal at criticality, only the complex, memory intensive tasks profited from it, while simple tasks actually suffered. The study thus provides a more precise understanding of how the collective network state should be tuned to different task requirements for optimal performance.

Mechanistically, the optimal working point for each task can be set very easily under homeostatic plasticity by adapting the mean input strength. The theory behind this mechanism was developed very recently at the Max Planck Institute. “Putting it to work on neuromorphic hardware shows that these plasticity rules are very capable in tuning network dynamics to varying distances from criticality”, says senior author Viola Priesemann, group leader at MPIDS. Thereby tasks of varying complexity can be solved optimally within that space.

The finding may also explain why biological neural networks operate not necessarily at criticality, but in the dynamically rich vicinity of a critical point, where they can tune their computation properties to task requirements. Furthermore, it establishes neuromorphic hardware as a fast and scalable avenue to explore the impact of biological plasticity rules on neural computation and network dynamics.

“As a next step, we now study and characterize the impact of the spiking network’s working point on classifying artificial and real-world spoken words”, says first author Benjamin Cramer of Heidelberg University.

Here’s a link to and a citation for the paper,

Control of criticality and computation in spiking neuromorphic networks with plasticity by Benjamin Cramer, David Stöckel, Markus Kreft, Michael Wibral, Johannes Schemmel, Karlheinz Meier & Viola Priesemann. Nature Communications volume 11, Article number: 2853 (2020) DOI: https://doi.org/10.1038/s41467-020-16548-3 Published: 05 June 2020

This paper is open access.

Chemistry of opera

Kate Yandell has written a thoroughly fascinating article about opera and chemistry (Atoms and Arias) for the Mar. 23, 2013 issue of The Scientist,

In a paper published earlier this year (January 14) in the Journal of Chemical Education, André [João Paulo André], who is now a professor at the University of Minho in Portugal, described his strategy for exploring the links between chemistry and opera for educational purposes.

According to André, the pairing is a natural one, as opera actually chronicled the heady, early days of chemical discovery. Joseph Haydn’s Der Apotheker (also known as Lo Speziale) and Gaetano Donizetti’s one-act opera, Il Campanello, for example, both featured pharmacists as main characters. In 1768, as Joseph Priestley, Antoine Lavoisier, and Carl Wilhelm Scheele, who would eventually discover oxygen, were immersed in their chemical labors, Haydn debuted Der Apotheker, a story about competition and love that plays out in the pharmacy. “There was something in the air. Chemistry was coming to be called a modern science,” Andé says. Il Campanello was first performed publicly in 1836, a time when many natural compounds were being isolated. It includes songs about long, complicated prescriptions. These “apothecary operas” illustrate the cultural pull chemistry used to have.

The researcher’s paper, published in the Journal of Chemical Education, has received worldwide interest. Meanwhile, Yandell’s article inspired this Mar. 24, 2013 posting on Les Vérités Scientifiques,

La constatation que nous livre l’auteur constitue-t-elle une surprise ? Non, car il en est de l’Opéra comme il en est de toute d’autre production artistique, littérature, peinture, musique : la mise en évidence d’une interpénétration entre l’actualité de  la science et l’art. Chaque époque de la société se reflète dans ce que choisissent d’exprimer ses différents acteurs ce qui permet de regarder efficacement derrière soi (cf l’exposition L’ange du bizarre. Le romantisme noir de Goya à Max Ernst au musée d’Orsay).

This is going to be a rough (very) translation and any errors are entirely mine,

The relationship between opera and chemistry should not be a surprise since opera like all the other artistic enterprises such as literature, painting, music always reflect the social and scientific interests of their own epochs as we can see in various venues, e.g. L’ange du bizarre: the dark romanticism of artists ranging from Goya to Max Ernst at the musée d’Orsay [in Paris].

As Yandell’s article notes others have observed a relationship between opera and chemistry (Links have been removed),

Jorge Calado, a retired Portuguese chemistry professor and an opera critic for the Portuguese newspaper Expresso, saw André’s talk and helped edit the Journal of Chemical Education paper. …

Calado published a book in Portuguese in 2011 whose title translates to Let There be Light! A History of Chemistry Through Everything, in which he tells the story of chemistry’s early roots through the lens of the arts and humanities, including opera.

He says that André’s paper made him want to write his own follow-up paper, and that he could think of even more examples of operas with connections to chemistry—from Jacques Offenbach’s Le Docteur Ox (1877), based on a story by science fiction writer Jules Verne, to John Adams’ Doctor Atomic (2005), which chronicles the creation of the atom bomb in Los Alamos.

Aside from the fact that it’s well worth reading, Yandell’s article is studded with opera videos that enhance the opera/chemistry relationships being described.

Here’s a link to and a citation for the research article,

Opera and Poison: A Secret and Enjoyable Approach To Teaching and Learning Chemistry by João Paulo André. J. Chem. Educ., 2013, 90 (3), pp 352–357 DOI: 10.1021/ed300445b
Publication Date (Web): January 14, 2013
Copyright © 2013 The American Chemical Society and Division of Chemical Education, Inc.

This article is behind a paywall.

The Feb. 14, 2013 posting on the Smithsonian blog offers a little more information about the project,

Any good opera needs a dramatic twist, and death by poison and potions fits the bill. When a team of chemists took a closer look at the formulas behind these concoctions in 20 operas, they found 25 different natural and synthetic chemical materials featured. The researchers suggest that teachers use these poison plots to engage students with chemistry, and while opera isn’t exactly an easy sell with most teenagers, learning about death by deadly nightshade probably ranks higher for most than memorizing yet another chemical formula.

The Smithsonian posting also offers a few tidbits from beyond the article’s paywall.

I believe this is a case where a few people independently had similar ideas as there is a professor in Germany who has also combined chemistry and opera although he has turned to performance. Professor Dr. Gerald Linti, at Heidelberg University has been staging musical chemistry experiments since 2004 if I’ve properly understood the German on his Special Events webpage,

  • Lange Nacht im Schloss (März 2004)

  “Chemie und Oper für Jedermann: Tannhäuser”

More recently (2009), Linti produced a Puccini night as part of his ongoing Chemistry and Opera series,

Under the title “Turandot’s Three Chemical Riddles” Gerald Linti, professor at Heidelberg University’s Institute of Inorganic Chemistry, and his students will be giving another demonstration of their legendary skill in the musical staging of chemical experiments at 6 p.m. on 26 June 2009.

He seems to have followed that up with a 2011 opera night at a conference titled, Modeling Molecular Properties, according to an Oct. 11, 2011 article by Sarah Miller for Chemistry Views,

The first day concluded with the spectacular “Chemistry and Opera” arranged by Professor Gerald Linti, University of Heidelberg. This demonstrated the beauty and fun of chemistry as Linti told the story of a Chinese Princess while his assistants performed chemistry experiments in time to live opera.

This sounds like a restaging of ‘Turandot’s Three Chemical Riddles’ from 2009. Here’s one of the images which illustrates Miller’s article,

[Downloaded from: http://www.chemistryviews.org/details/ezine/1371029/Modeling_Molecular_Properties_and_Opera.html]

[Downloaded from: http://www.chemistryviews.org/details/ezine/1371029/Modeling_Molecular_Properties_and_Opera.html]

Maybe it’s time for a new ‘chemistry’ opera. Any takers?

Montréal Neuro and one of Europe’s biggest research enterprises, the Human Brain Project

Its official title is the Montréal Neurological Institute and Hospital (Montréal Neuro) which is and has been, for several decades, an international centre for cutting edge neurological research. From the Jan. 28, 2013 news release on EurekAlert,

The Neuro

The Montreal Neurological Institute and Hospital — The Neuro, is a unique academic medical centre dedicated to neuroscience. Founded in 1934 by the renowned Dr. Wilder Penfield, The Neuro is recognized internationally for integrating research, compassionate patient care and advanced training, all key to advances in science and medicine. The Neuro is a research and teaching institute of McGill University and forms the basis for the Neuroscience Mission of the McGill University Health Centre.

Neuro researchers are world leaders in cellular and molecular neuroscience, brain imaging, cognitive neuroscience and the study and treatment of epilepsy, multiple sclerosis and neuromuscular disorders. For more information, visit theneuro.com.

Nonetheless, it was a little surprising to see that ‘The Neuro’ is part one of the biggest research projects in history since it’s the European Union, which is bankrolling the project (see my posting about the Jan. 28, 2013 announcement of the winning FET Flagship Initatives). Here’s more information about the project, its lead researchers, and Canada’s role, from the news release,

The goal of the Human Brain Project is to pull together all our existing knowledge about the human brain and to reconstruct the brain, piece by piece, in supercomputer-based models and simulations. The models offer the prospect of a new understanding of the human brain and its diseases and of completely new computing and robotic technologies. On January 28 [2013], the European Commission supported this vision, announcing that it has selected the HBP as one of two projects to be funded through the new FET [Future and Emerging Technologies] Flagship Program.

Federating more than 80 European and international research institutions, the Human Brain Project is planned to last ten years (2013-2023). The cost is estimated at 1.19 billion euros. The project will also associate some important North American and Japanese partners. It will be coordinated at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, by neuroscientist Henry Markram with co-directors Karlheinz Meier of Heidelberg University, Germany, and Richard Frackowiak of Centre Hospitalier Universitaire Vaudois (CHUV) and the University of Lausanne (UNIL).

Canada’s role in this international project is through Dr. Alan Evans of the Montreal Neurological Institute (MNI) at McGill University. His group has developed a high-performance computational platform for neuroscience (CBRAIN) and multi-site databasing technologies that will be used to assemble brain imaging data across the HBP. He is also collaborating with European scientists on the creation of ultra high-resolution 3D brain maps. «This ambitious project will integrate data across all scales, from molecules to whole-brain organization. It will have profound implications for our understanding of brain development in children and normal brain function, as well as for combatting brain disorders such as Alzheimer’s Disease,» said Dr. Evans. “The MNI’s pioneering work on brain imaging technology has led to significant advances in our understanding of the brain and neurological disorders,” says Dr. Guy Rouleau, Director of the MNI. “I am proud that our expertise is a key contributor to this international program focused on improving quality of life worldwide.”

“The Canadian Institutes of Health Research (CIHR) is delighted to acknowledge the outstanding contributions of Dr. Evans and his team. Their work on the CBRAIN infrastructure and this leading-edge HBP will allow the integration of Canadian neuroscientists into an eventual global brain project,” said Dr. Anthony Phillips, Scientific Director for the CIHR Institute of Neurosciences, Mental Health and Addiction. “Congratulations to the Canadian and European researchers who will be working collaboratively towards the same goal which is to provide insights into neuroscience that will ultimately improve people’s health.”

“From mapping the sensory and motor cortices of the brain to pioneering work on the mechanisms of memory, McGill University has long been synonymous with world-class neuroscience research,” says Dr. Rose Goldstein, Vice-Principal (Research and International Relations). “The research of Dr. Evans and his team marks an exciting new chapter in our collective pursuit to unlock the potential of the human brain and the entire nervous system – a critical step that would not be possible without the generous support of the European Commission and the FET Flagship Program.”

Canada is not the only non-European Union country making an announcement about its role in this extraordinary project. There’s a Jan. 28, 2013 news release on EurekAlert touting Israel’s role,

The European Commission has chosen the Human Brain Project, in which the Hebrew University of Jerusalem is participating, as one of two Future and Emerging Technologies Flagship topics. The enterprise will receive funding of 1.19 billion euros over the next decade.

The project will bring together top scientists from around the world who will work on one of the great challenges of modern science: understanding the human brain. Participating from Israel will a team of eight scientists, led by Prof. Idan Segev of the Edmond and Lily Safra Center for Brain Sciences (ELSC) at the Hebrew University, Prof. Yadin Dudai of the Weizmann Institute of Science, and Dr. Mira Marcus-Kalish of Tel Aviv University.

More than 80 universities and research institutions in Europe and the world will be involved in the ten-year Human Brain Project, which will commence later this year and operate until the year 2023. The project will be centered at the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland, headed by Prof. Henry Markram, a former Israeli who was recruited ten years ago to the EPFL.

The participation of the Israeli scientists testifies to the leading role that Israeli brain research occupies in the world, said Israeli President Shimon Peres. “Israel has put brain research at the heart of its efforts for the coming decade, and our country is already spearheading the global effort towards the betterment of our understanding of mankind. I am confident that the forthcoming discoveries will benefit a wide range of domains, from health to industry, as well as our society as a whole,” Peres said.

“The human brain is the most complex and amazing structure in the universe, yet we are very far from understanding it. In a way, we are strangers to ourselves. Unraveling the mysteries of the brain will help us understand our functioning, our choices, and ultimately ourselves. I congratulate the European Commission for its vision in selecting the Human Brain Project as a Flagship Mission for the forthcoming decade,” said Peres.

What’s amusing is that as various officials and interested parties (such as myself) wax lyrical about these projects, most of the rest of the world is serenely oblivious to it all.