Category Archives: nanophotonics

KAIST’s (Korea Advanced Institute of Science and Technology) smart patch can run tests using sweat instead of blood​

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There’s been talk of running tests on sweat instead of blood for many years. If memory serves I first came across the idea in 2010 (or thereabouts). Presumably, scientists have been working on a needlefree way to conduct tests longer that that.

A September 8, 2025 news item on Nanowerk announced a long awaited step forward, Note: A link has been removed,

A new wearable patch could one day replace certain blood tests with a quick check of sweat. A research team at KAIST has created a flexible sensor that attaches to the skin and continuously tracks changes in the body by analyzing sweat in real time (Nature Communications, “All-flexible chronoepifluidic nanoplasmonic patch for label-free metabolite profiling in sweat”).

The device, developed by Professor Ki-Hun Jeong and his team in the Department of Bio and Brain Engineering, overcomes a long-standing challenge in sweat-based health monitoring. Traditional methods struggled to collect sweat efficiently or required fluorescent tags to detect specific molecules. The new patch does both collection and analysis without added labels, making the process simpler and more precise.

Caption: <Figure 1. Flexible microfluidic nanoplasmonic patch (left). Sequential sample collection using the patch (center) and label-free metabolite profiling (right). In this study, we designed and fabricated a fully flexible nanoplasmonic microfluidic patch for label-free sweat analysis and performed SERS signal measurement and analysis directly from human sweat. Through this, we propose a platform capable of precisely identifying physiological changes induced by physical activity and dietary conditions.> Credit: KAIST

A September 8, 2025 The Korea Advanced Institute of Science and Technology (KAIST) press release (also on EurekAlert), formed the basis for the edited news item,

An era is opening where it’s possible to precisely assess the body’s health status using only sweat instead of blood tests. A KAIST research team has developed a smart patch that can precisely observe internal changes through sweat when simply attached to the body. This is expected to greatly contribute to the advancement of chronic disease management and personalized healthcare technologies.

KAIST (President Kwang Hyung Lee) announced on September 7th that a research team led by Professor Ki-Hun Jeong of the Department of Bio and Brain Engineering has developed a wearable sensor that can simultaneously and in real-time analyze multiple metabolites in sweat.

Recently, research on wearable sensors that analyze metabolites in sweat to monitor the human body’s precise physiological state has been actively pursued. However, conventional “label-based” sensors, which require fluorescent tags or staining, and “label-free” methods have faced difficulties in effectively collecting and controlling sweat. Because of this, there have been limitations in precisely observing metabolite changes over time in actual human subjects.

To overcome these limitations, the research team developed a thin and flexible wearable sweat patch that can be directly attached to the skin. This patch incorporates both microchannels for collecting sweat and an ultrafine nanoplasmonic structure* that label-freely analyzes sweat components using light. Thanks to this, multiple sweat metabolites can be simultaneously analyzed without the need for separate staining or labels, with just one patch application.

* Nanoplasmonic structure: An optical sensor structure where nanoscale metallic patterns interact with light, designed to sensitively detect the presence or changes in concentration of molecules in sweat.

The patch was created by combining nanophotonics technology, which manipulates light at the nanometer scale (one-hundred-thousandth the thickness of a human hair) to read molecular properties, with microfluidics technology, which precisely controls sweat in channels thinner than a hair.

In other words, within a single sweat patch, microfluidic technology enables sweat to be collected sequentially over time, allowing for the measurement of changes in various metabolites without any labeling process. Inside the patch are six to seventeen chambers (storage spaces), and sweat secreted during exercise flows along the microfluidic structures and fills each chamber in order.

The research team applied the patch to actual human subjects and succeeded in continuously tracking the changing components of sweat over time during exercise. Previously, only about two components could be checked simultaneously through a label-free approach, but in this study, they demonstrated for the first time in the world that three metabolites—uric acid, lactic acid, and tyrosine—can be quantitatively analyzed simultaneously, as well as how they change depending on exercise and diet. In particular, by using artificial intelligence analysis methods, they were able to accurately distinguish signals of desired substances even within the complex components of sweat.

Professor Ki-Hun Jeong said, “This research lays the foundation for precisely monitoring internal metabolic changes over time without blood sampling by combining nanophotonics and microfluidics technologies.” He added, “In the future, it can be expanded to diverse fields such as chronic disease management, drug response tracking, environmental exposure monitoring, and the discovery of next-generation biomarkers for metabolic diseases.”

…

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

All-flexible chronoepifluidic nanoplasmonic patch for label-free metabolite profiling in sweat by Jaehun Jeon, Sangyeon Lee, Seongok Chae, Joo Hoon Lee, Hanjin Kim, Eun-Sil Yu, Hamin Na, Taejoon Kang, Hyung-Soon Park, Doheon Lee & Ki-Hun Jeong. Nature Communications volume 16, Article number: 8017 (2025) DOI: https://doi.org/10.1038/s41467-025-63510-2 Published: 27 August 2025 Version of record: 27 August 2025

This paper is open access.

I have another image featuring the ‘sweat patch’,

Caption: <Figure 2. Example of the fabricated patch worn (left) and images of sequential sweat collection and storage (right). By designing precise microfluidic channels based on capillary burst valves, sequential sweat collection was implemented, which enabled label-free analysis of metabolite changes associated with exercise and diet.> Credit: KAIST

Sometimes, the future looks very encouraging, indeed, for those don’t like blood tests. Although it could still be a while, the most recent previous story here on sweat, health monitoring, and microfluidics was in a May 20, 2015 posting titled “A ‘sweat’mometer—sensing your health through your sweat.”

The importance of photonics (science of light) in African science

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A May 14, 2025 essay (h/t to phys.org) written by Andrew Forbes, professor, University of the Witwatersrand, and Patience Mthunzi-Kufa, distinguished professor, University of South Africa, for The Conversation describes the history, current work, and hopes for photonics on the African continent, Note: Some links have been removed,

Light is all around us, essential for one of our primary senses (sight) as well as life on Earth itself. It underpins many technologies that affect our daily lives, including energy harvesting with solar cells, light-emitting-diode (LED) displays and telecommunications through fibre optic networks.

The smartphone is a great example of the power of light. Inside the box, its electronic functionality works because of quantum mechanics [Note; Link removed]. The front screen is an entirely photonic device: liquid crystals controlling light. The back too: white light-emitting diodes for a flash, and lenses to capture images.

We use the word photonics, and sometimes optics, to capture the harnessing of light for new applications and technologies. Their importance in modern life is celebrated every year on 16 May with the International Day of Light.

Scientists on the African continent, despite the resource constraints they work under, have made notable contributions to photonics research. Some of these have been captured in a recent special issue of the journal Applied Optics [Note: Link removed]. Along with colleagues in this field from Morocco and Senegal, we introduced this collection of papers [Note: Link removed], which aims to celebrate excellence and show the impact of studies that address continental issues.

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Africa’s history in formal optics stems back thousands of years, [emphasis mine] with references to lens design already recorded in ancient Egyptian writings.

In more recent times, Africa has contributed to two Nobel prizes based on optics. Ahmed Zewail (Egyptian born) watched the ultrafast processes in chemistry with lasers (1999, Nobel Prize for Chemistry) and Serge Harouche (Moroccan born) studied the behaviour of individual particles of light, photons (2012, Nobel Prize for Physics).

…

The papers in the special journal issue touch on a diversity of continent-relevant topics.

One is on using optics to communicate across free-space (air) even in bad weather conditions. This light-based solution was tested using weather data from two African cities, Alexandria in Egypt and Setif in Algeria.

Another paper is about tiny quantum sources of quantum entanglement for sensing. The authors used diamond, a gem found in South Africa and more commonly associated with jewellery. Diamond has many flaws, one of which can produce single photons as an output when excited. The single photon output was split into two paths, as if the particle went both left and right at the same time. This is the quirky notion of entanglement, in this case, created with diamonds. If an object is placed in any one path, the entanglement can detect it. Strangely, sometimes the photons take the left-path but the object is in the right-path, yet still it can be detected.

One contributor proposes a cost-effective method to detect and classify harmful bacteria in water.

New approaches in spectroscopy (studying colour) [Note: Link removed] for detecting cell health; biosensors to monitor salt and glucose levels in blood; and optical tools for food security all play their part in optical applications on the continent.

Another area of African optics research that has important applications is the use of optical fibres for sensing the quality of soil and its structural integrity. Optical fibres are usually associated with communication, but a modern trend is to use the existing optical fibre already laid to sense for small changes in the environment, for instance, as early warning systems for earthquakes. The research shows that conventional fibre can also be used to tell if soil is degrading, either from lack of moisture or some physical shift in structure (weakness or movement). It is an immediately useful tool for agriculture, building on many decades of research.

…

The last century was based on electronics and controlling electrons. This century will be dominated by photonics, controlling photons.

Professor Zouheir Sekkat of University Mohamed V, Rabat, and director of the Pole of Optics and Photonics within MAScIR of University Mohamed VI Polytechnic Benguerir, Morocco, contributed to this article.

Light-based technologies have wide practical applications. Wikimedia Commons, CC BY [downloaded from https://theconversation.com/light-is-the-science-of-the-future-the-africans-using-it-to-solve-local-challenges-256031]

Here’s the special issue with two links:

Virtual Feature Issue

Joint feature issue in Applied Optics and Optics Continuum: Optical Science and Photonics in Africa (OSPA)

Zouheir Sekkat, Optics & Photonics Center, MAScIR-UM6P, Ben Guerir, and University Mohamed 5, Morocco (Lead Editor)
Andrew Forbes, University Witwatersrand, South Africa
Patience Mthunzi-Kufa, CSIR, South Africa
Balla Diop Ngom, University Cheikh Anta Diop, Senegal

OR

20 March 2025, Volume 64, Issue 9, pp. 2102-2323; Feat. pp: OSPA1–3; C1–C163  

Enjoy!

Graphene-like materials for first smart contact lenses with AR (augmented reality) vision, health monitoring, & content surfing?

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A March 6, 2024 XPANCEO news release on EurekAlert (also posted March 11, 2024 on the Graphene Council blog) and distributed by Mindset Consulting announced smart contact lenses devised with graphene-like materials,

XPANCEO, a deep tech company developing the first smart contact lenses with XR vision, health monitoring, and content surfing features, in collaboration with the Nobel laureate Konstantin S. Novoselov (National University of Singapore, University of Manchester) and professor Luis Martin-Moreno (Instituto de Nanociencia y Materiales de Aragon), has announced in Nature Communications a groundbreaking discovery of new properties of rhenium diselenide and rhenium disulfide, enabling novel mode of light-matter interaction with huge potential for integrated photonics, healthcare, and AR. Rhenium disulfide and rhenium diselenide are layered materials belonging to the family of graphene-like materials. Absorption and refraction in these materials have different principal directions, implying six degrees of freedom instead of a maximum of three in classical materials. As a result, rhenium disulfide and rhenium diselenide by themselves allow controlling the light propagation direction without any technological steps required for traditional materials like silicon and titanium dioxide.

The origin of such surprising light-matter interaction of ReS2 and ReSe2 with light is due to the specific symmetry breaking observed in these materials. Symmetry plays a huge role in nature, human life, and material science. For example, almost all living things are built symmetrically. Therefore, in ancient times symmetry was also called harmony, as it was associated with beauty. Physical laws are also closely related to symmetry, such as the laws of conservation of energy and momentum. Violation of symmetry leads to the appearance of new physical effects and radical changes in the properties of materials. In particular, the water-ice phase transition is a consequence of a decrease in the degree of symmetry. In the case of ReS2 and ReSe2, the crystal lattice has the lowest possible degree of symmetry, which leads to the rotation of optical axes – directions of symmetry of optical properties of the material, which was previously observed only for organic materials. As a result, these materials make possible to control the direction of light by changing the wavelength, which opens a unique way for light manipulation in next-generation devices and applications. 

“The discovery of unique properties in anisotropic materials is revolutionizing the fields of nanophotonics and optoelectronics, presenting exciting possibilities. These materials serve as a versatile platform for the advancement of optical devices, such as wavelength-switchable metamaterials, metasurfaces, and waveguides. Among the promising applications is the development of highly efficient biochemical sensors. These sensors have the potential to outperform existing analogs in terms of both sensitivity and cost efficiency. For example, they are anticipated to significantly reduce the expenses associated with hospital blood testing equipment, which is currently quite costly, potentially by several orders of magnitude. This will also allow the detection of dangerous diseases and viruses, such as cancer or COVID, at earlier stages,” says Dr. Valentyn S. Volkov, co-founder and scientific partner at XPANCEO, a scientist with an h-Index of 38 and over 8000 citations in leading international publications.

Beyond the healthcare industry, these novel properties of graphene-like materials can find applications in artificial intelligence and machine learning, facilitating the development of photonic circuits to create a fast and powerful computer suitable for machine learning tasks. A computer based on photonic circuits is a superior solution, transmitting more information per unit of time, and unlike electric currents, photons (light beams) flow across one another without interacting. Furthermore, the new material properties can be utilized in producing smart optics, such as contact lenses or glasses, specifically for advancing AR [augmented reality] features. Leveraging these properties will enhance image coloration and adapt images for individuals with impaired color perception, enabling them to see the full spectrum of colors.

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

Wandering principal optical axes in van der Waals triclinic materials by Georgy A. Ermolaev, Kirill V. Voronin, Adilet N. Toksumakov, Dmitriy V. Grudinin, Ilia M. Fradkin, Arslan Mazitov, Aleksandr S. Slavich, Mikhail K. Tatmyshevskiy, Dmitry I. Yakubovsky, Valentin R. Solovey, Roman V. Kirtaev, Sergey M. Novikov, Elena S. Zhukova, Ivan Kruglov, Andrey A. Vyshnevyy, Denis G. Baranov, Davit A. Ghazaryan, Aleksey V. Arsenin, Luis Martin-Moreno, Valentyn S. Volkov & Kostya S. Novoselov. Nature Communications volume 15, Article number: 1552 (2024) DOI: https://doi.org/10.1038/s41467-024-45266-3 Published: 06 March 2024

This paper is open access.

New system for imaging rare-earth doped nanoparticles

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The Institut national de la recherche scientifique (INRS; Québec, Canada) has issued a January 30,2024 news release (also on EurekAlert) announcing new work in the field of imaging, Note: Links have been removed,

Teams led by professors Jinyang Liang and Fiorenzo Vetrone from the Énergie Matériaux Télécommunications Research Centre at the Institut national de la recherche scientifique (INRS) have developed a new system for imaging nanoparticles. It consists of a high-precision, short-wave infrared imaging technique capable of capturing the photoluminescence lifetimes of rare-earth doped nanoparticles in the micro- to millisecond range.

This groundbreaking discovery, which was published in the journal Advanced Science, paves the way for promising applications, particularly in the biomedical and information security fields.

Rare-earth elements are strategic metals that possess unique light-emitting properties that make them very attractive research tools in cutting-edge science. What’s more, the photoluminescence lifetime of nanoparticles doped with these ions has the advantage of being minimally affected by external conditions. As a result, measuring it through imaging provides data from which accurate and highly reliable information can be derived.

Although this field is seeing remarkable progress, existing optical systems for this type of measurement were less than ideal.

“Until now, existing optical systems have offered limited possibilities due to inefficient photon detection, limited imaging speed, and low sensitivity,” explains Professor Jinyang Liang, a specialist in ultrafast imaging and biophotonics.

To date, the most common technique for measuring the photoluminescence lifetime of rare-earth doped nanoparticles has involved counting time-correlated single photons.

“This method requires a large number of repeated excitations at the same location because the detector can only process a limited number of photons for each excitation,” says the study’s first author Miao Liu, a Ph.D. student in energy and materials science supervised by Profs. Liang and Vetrone.

However, the long photoluminescence lifetimes of rare-earth doped nanoparticles in the infrared spectrum, from hundreds of microseconds to several milliseconds, restrict the excitation’s repetition rate. As a result, the pixel dwelling time needed to build the photoluminescence intensity decay curve is much longer.

Pushing the limits

To overcome this challenge, Liang and Vetrone’s teams have combined streak optics with a high-sensitivity camera. The resulting device is called SWIR-PLIMASC (SWIR for short-wave infrared and PLIMASC for photoluminescence lifetime imaging microscopy using an all-optical streak camera). It vastly improves mapping of the optical properties of short-wave infrared photoluminescence lifetimes. It is the first high-sensitivity, high-speed SWIR imaging system in the optics field.

“It has several advantages,” says Miao Liu. “For instance, it responds to a wide spectral range, from 900 nm to 1700 nm, allowing photoluminescence to be detected at different wavelengths and/or spectral bands.”

The Ph.D. student adds that with the help of this device, photoluminescence lifetimes in the infrared spectrum, from microseconds to milliseconds, can be directly captured in one snapshot with a 1D imaging speed that can be tuned from 10.3 kHz to 138.9 kHz.

Finally, the operation that allocates the temporal information of photoluminescence to different spatial positions ensures that the entire process of 1D photoluminescence intensity decay can be recorded in a single snapshot, without repeated excitation. “You save time, but still get high sensitivity,” sums up Miao Liu.

Biomedical and security applications

The work carried out as part of this research will have a very tangible impact. In the biomedical field, the advances made possible by SWIR-PLIMASC could be used to fight cancer, believes Professor Fiorenzo Vetrone, whose expertise lies in nanomedicine.

“As our system applies to the temperature-based photoluminescence lifetime imaging of rare-earth ions, we believe that the data obtained could, for example, help to detect cancer cells even earlier and more accurately. The metabolism of those cells raises the temperature of the surrounding tissues,” says Professor Vetrone.

The innovative system can also be used to store information at enhanced security levels, more specifically to prevent documents and data from being falsified. Finally, in fundamental science, these unprecedented results will allow scientists to synthesize rare-earth nanoparticles with even more interesting optical properties.

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

Short-wave Infrared Photoluminescence Lifetime Mapping of Rare-Earth Doped Nanoparticles Using All-Optical Streak Imaging by Miao Liu, Yingming Lai, Miguel Marquez, Fiorenzo Vetrone, Jinyang Liang. Advanced Science DOI: https://doi.org/10.1002/advs.202305284 First published: 06 January 2024

This paper is open access.

Optical memristors and neuromorphic computing

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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.

Nanoscopic advance of colossal (!) significance by Danish quantum physicists

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it’s not often you see the word ‘colossal’ in a science news release but it seems these Danish researchers are very excited about their breakthrough. From a January 26, 2023 news item on Nanowerk,

In a new breakthrough, researchers at the University of Copenhagen, in collaboration with Ruhr University Bochum, have solved a problem that has caused quantum researchers headaches for years. The researchers can now control two quantum light sources rather than one. Trivial as it may seem to those uninitiated in quantum, this colossal breakthrough allows researchers to create a phenomenon known as quantum mechanical entanglement. This in turn, opens new doors for companies and others to exploit the technology commercially.

…

A January 26, 2023 University of Copenhagen press release (also on EurekAlert), which originated the news item, provides context and more detail,

Going from one to two is a minor feat in most contexts. But in the world of quantum physics, doing so is crucial. For years, researchers around the world have strived to develop stable quantum light sources and achieve the phenomenon known as quantum mechanical entanglement – a phenomenon, with nearly sci-fi-like properties, where two light sources can affect each other instantly and potentially across large geographic distances. Entanglement is the very basis of quantum networks and central to the development of an efficient quantum computer.  

Today [January 26, 2023], researchers from the Niels Bohr Institute published a new result in the highly esteemed journal Science, in which they succeeded in doing just that. According to Professor Peter Lodahl, one of the researchers behind the result, it is a crucial step in the effort to take the development of quantum technology to the next level and to “quantize” society’s computers, encryption and the internet.

“We can now control two quantum light sources and connect them to each other. It might not sound like much, but it’s a major advancement and builds upon the past 20 years of work. By doing so, we’ve revealed the key to scaling up the technology, which is crucial for the most ground-breaking of quantum hardware applications,” says Professor Peter Lodahl, who has conducted research the area since 2001.  

The magic all happens in a so-called nanochip – which is not much larger than the diameter of a human hair – that the researchers also developed in recent years.

Quantum sources overtake the world’s most powerful computer 

Peter Lodahl’s group is working with a type of quantum technology that uses light particles, called photons, as micro transporters to move quantum information about.

While Lodahl’s group is a leader in this discipline of quantum physics, they have only been able to control one light source at a time until now. This is because light sources are extraordinarily sensitive to outside “noise”, making them very difficult to copy. In their new result, the research group succeeded in creating two identical quantum light sources rather than just one.

“Entanglement means that by controlling one light source, you immediately affect the other. This makes it possible to create a whole network of entangled quantum light sources, all of which interact with one another, and which you can get to perform quantum bit operations in the same way as bits in a regular computer, only much more powerfully,” explains postdoc Alexey Tiranov, the article’s lead author. 

This is because a quantum bit can be both a 1 and 0 at the same time, which results in processing power that is unattainable using today’s computer technology. According to Professor Lodahl, just 100 photons emitted from a single quantum light source will contain more information than the world’s largest supercomputer can process.

By using 20-30 entangled quantum light sources, there is the potential to build a universal error-corrected quantum computer – the ultimate “holy grail” for quantum technology, that large IT companies are now pumping many billions into.

Other actors will build upon the research

According to Lodahl, the biggest challenge has been to go from controlling one to two quantum light sources. Among other things, this has made it necessary for researchers to develop extremely quiet nanochips and have precise control over each light source.

With the new research breakthrough, the fundamental quantum physics research is now in place. Now it is time for other actors to take the researchers’ work and use it in their quests to deploy quantum physics in a range of technologies including computers, the internet and encryption.

“It is too expensive for a university to build a setup where we control 15-20 quantum light sources. So, now that we have contributed to understanding the fundamental quantum physics and taken the first step along the way, scaling up further is very much a technological task,” says Professor Lodahl.  

The research was conducted at the Danish National Research Foundation’s “Center of Excellence for Hybrid Quantum Networks (Hy-Q)” and is a collaboration between Ruhr University Bochum in Germany and the the University of Copenhagen’s Niels Bohr Institute.

Here’s a link to and a citation for this colossal research,

Collective super- and subradiant dynamics between distant optical quantum emitters by Alexey Tiranov, Vasiliki Angelopoulou, Cornelis Jacobus van Diepen, Björn Schrinski, Oliver August Dall’Alba Sandberg, Ying Wang, Leonardo Midolo, Sven Scholz, Andreas Dirk Wieck, Arne Ludwig, Anders Søndberg Sørensen, and Peter Lodahl. Science 26 Jan 2023 Vol 379, Issue 6630 pp. 389-393 DOI: 10.1126/science.ade9324

This paper is behind a paywall.

Teeny adventures, Latent Life, and photonic writing—a March 28, 2023 talk at 1 pm PT at the University of British Columbia

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After reading the latest newsletter (received via email on March 20, 2023), featuring Scott Billings’ talk ‘Latest Life’, from the University of British Columbia’s (UBC) Belkin Gallery I was reminded of a book produced at the nanoscale back in 2009 (May 21, 2009 posting; scroll down to the final paragraph) and which I wrote about again in 2012 (October 12, 2012 posting) when ‘Teeny Ted from Turnip Town’ was added to the Guinness Book of Records as the world’s smallest book. (‘Teeny Ted’ also has a Wikipedia entry.)

The March 20, 2023 Belkin Gallery (also known as the Morris and Helen Belkin Art Gallery) newsletter is promoting the next Ars Scientia events (the information can also be found on this webpage),

We hope you’ll join us this spring for talks and presentations related
to our ongoing research projects in art and science, and the
Anthropocene. Over the past years, we have developed a deep and
abiding interdisciplinary research practice related to these themes,
working with diverse disciplines that are fortified through oppositions,
collaborations and the celebration of new perspectives. We have shared
our different fields of experience, expertise and resources to catalyze
meaningful responses to research, pedagogy, communication and outreach,
and in doing so build responses that are more than the sum of their
parts. This methodology of bringing the unique perspectives and
practices of artists and curators to academic units presents an
opportunity to foster new modes of knowledge exchange. In this spirit,
we hope you’ll join us in thinking through these critical areas of
inquiry.

Ars Scientia

Building on exhibitions like The Beautiful Brain and Drift, the Ars Scientia research project connects artists with physicists to explore the intersections between the disciplines of art and science. A collaboration between the Belkin, the Department of Physics and Astronomy, and the Blusson Quantum Matter Institute [QMI], [emphases mine] this spring’s artists’ residencies culminate in a series of talks by JG Mair, Scott Billings and Timothy Taylor, followed by a symposium in May with keynote speaker Kavita Philip.

Tuesday, March 28 [2023] at 1 pm [PT]

Artist Talk with Scott Billings

Tuesday, April 4 [2023] at 2 pm [PT]

Artist Talk with Timothy Taylor

Monday, May 15 [2023]

Symposium with keynote by Kavita Philip

…

I have more details (logistics in particular) about the Scott Billings talk, from the QMI Ars Scientia Artist Talks 2023: Latent Life by Scott Billings events page,

Please join Scott Billings for Latent Life, a presentation based on his recent research in the Ars Scientia residency. Drawing from a 1933 lecture in which Neils Bohr asserts that the impossibility of using a physical explanation for the phenomenon of life is analogous to the insufficiency of using a mechanical analysis to understand phenomena of the atom, Billings will discuss his seemingly conflicting dual practice as both visual artist and mechanical engineer. Reflecting upon a preoccupation with the animality of cinematic machine, among (many) other things, Billings will relay his recent direct experience with photonic writing [emphasis mine] at QMI’s NanoFab Lab and the wonderful new conundrum of making and exhibiting micro-sculptures that are far too small to see with the naked eye.

…

Date & time: March 28 [2023], 1:00-2:00pm [PT]

Location: 311, Brimacombe Building (2355 East Mall, Vancouver, BC V6T 1Z4)

For more information on this event, please click here.

Photonic writing and sculpture? I’m guessing the word ‘writing’ in this context doesn’t mean what it usually means. Still, it did bring back memories of the world’s smallest book. I always did wonder about the point of producing book that couldn’t be read without expensive equipment. And now, there’s sculpture that can’t be seen.

I hope Billings’s talk will shed some light on this phenomenon of artists and writers creating objects than cannot be seen with the naked eye. Scientists do this sort of thing for fun but the motivation for writers and artists seems to be about proving something and not at all about play.

Neuromorphic computing and liquid-light interaction

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Simulation result of light affecting liquid geometry, which in turn affects reflection and transmission properties of the optical mode, thus constituting a two-way light–liquid interaction mechanism. The degree of deformation serves as an optical memory allowing to store the power magnitude of the previous optical pulse and use fluid dynamics to affect the subsequent optical pulse at the same actuation region, thus constituting an architecture where memory is part of the computation process. Credit: Gao et al., doi 10.1117/1.AP.4.4.046005

This is a fascinating approach to neuromorphic (brainlike) computing and given my recent post (August 29, 2022) about human cells being incorporated into computer chips, it’s part o my recent spate of posts about neuromorphic computing. From a July 25, 2022 news item on phys.org,

Sunlight sparkling on water evokes the rich phenomena of liquid-light interaction, spanning spatial and temporal scales. While the dynamics of liquids have fascinated researchers for decades, the rise of neuromorphic computing has sparked significant efforts to develop new, unconventional computational schemes based on recurrent neural networks, crucial to supporting wide range of modern technological applications, such as pattern recognition and autonomous driving. As biological neurons also rely on a liquid environment, a convergence may be attained by bringing nanoscale nonlinear fluid dynamics to neuromorphic computing.

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A July 25, 2022 SPIE (International Society for Optics and Photonics) press release (also on EurekAlert), which originated the news item,

Researchers from University of California San Diego recently proposed a novel paradigm where liquids, which usually do not strongly interact with light on a micro- or nanoscale, support significant nonlinear response to optical fields. As reported in Advanced Photonics, the researchers predict a substantial light–liquid interaction effect through a proposed nanoscale gold patch operating as an optical heater and generating thickness changes in a liquid film covering the waveguide.

The liquid film functions as an optical memory. Here’s how it works: Light in the waveguide affects the geometry of the liquid surface, while changes in the shape of the liquid surface affect the properties of the optical mode in the waveguide, thus constituting a mutual coupling between the optical mode and the liquid film. Importantly, as the liquid geometry changes, the properties of the optical mode undergo a nonlinear response; after the optical pulse stops, the magnitude of liquid film’s deformation indicates the power of the previous optical pulse.

Remarkably, unlike traditional computational approaches, the nonlinear response and the memory reside at the same spatial region, thus suggesting realization of a compact (beyond von-Neumann) architecture where memory and computational unit occupy the same space. The researchers demonstrate that the combination of memory and nonlinearity allow the possibility of “reservoir computing” capable of performing digital and analog tasks, such as nonlinear logic gates and handwritten image recognition.

Their model also exploits another significant liquid feature: nonlocality. This enables them to predict computation enhancement that is simply not possible in solid state material platforms with limited nonlocal spatial scale. Despite nonlocality, the model does not quite achieve the levels of modern solid-state optics-based reservoir computing systems, yet the work nonetheless presents a clear roadmap for future experimental works aiming to validate the predicted effects and explore intricate coupling mechanisms of various physical processes in a liquid environment for computation.

Using multiphysics simulations to investigate coupling between light, fluid dynamics, heat transport, and surface tension effects, the researchers predict a family of novel nonlinear and nonlocal optical effects. They go a step further by indicating how these can be used to realize versatile, nonconventional computational platforms. Taking advantage of a mature silicon photonics platform, they suggest improvements to state-of-the-art liquid-assisted computation platforms by around five orders magnitude in space and at least two orders of magnitude in speed.

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

Thin liquid film as an optical nonlinear-nonlocal medium and memory element in integrated optofluidic reservoir computer by Chengkuan Gao, Prabhav Gaur, Shimon Rubin, Yeshaiahu Fainman. Advanced Photonics, 4(4), 046005 (2022). https://doi.org/10.1117/1.AP.4.4.046005 Published: 1 July 2022

This paper is open access.

Physics of a singing saw could lead to applications in sensing, nanoelectronics, photonics, etc.

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I’d forgotten how haunting a musical saw can sound,

An April 22, 2022 news item on Nanowerk announces research into the possibilities of a singing saw,

The eerie, ethereal sound of the singing saw has been a part of folk music traditions around the globe, from China to Appalachia, since the proliferation of cheap, flexible steel in the early 19th century. Made from bending a metal hand saw and bowing it like a cello, the instrument reached its heyday on the vaudeville stages of the early 20th century and has seen a resurgence thanks, in part, to social media.

As it turns out, the unique mathematical physics of the singing saw may hold the key to designing high quality resonators for a range of applications.

In a new paper, a team of researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Department of Physics used the singing saw to demonstrate how the geometry of a curved sheet, like curved metal, could be tuned to create high-quality, long-lasting oscillations for applications in sensing, nanoelectronics, photonics and more.

An April 21, 2022 Harvard University John A. Paulson School of Engineering and Applied Sciences (SEAS) news release by Leah Burrows (also on EurekAlert but published on April 22, 2022) delves further into physics of singing saws,

“Our research offers a robust principle to design high-quality resonators independent of scale and material, from macroscopic musical instruments to nanoscale devices, simply through a combination of geometry and topology,” said L Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, of Organismic and Evolutionary Biology, and of Physics and senior author of the study.

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While all musical instruments are acoustic resonators of a kind, none work quite like the singing saw.

“How the singing saw sings is based on a surprising effect,” said Petur Bryde, a graduate student at SEAS and co-first author of the paper. “When you strike a flat elastic sheet, such as a sheet of metal, the entire structure vibrates. The energy is quickly lost through the boundary where it is held, resulting in a dull sound that dissipates quickly. The same result is observed if you curve it into a J-shape. But, if you bend the sheet into an S-shape, you can make it vibrate in a very small area, which produces a clear, long-lasting tone.”

The geometry of the curved saw creates what musicians call the sweet spot and what physicists call localized vibrational modes — a confined area on the sheet which resonates without losing energy at the edges.

Importantly, the specific geometry of the S-curve doesn’t matter. It could be an S with a big curve at the top and a small curve at the bottom or visa versa. 

“Musicians and researchers have known about this robust effect of geometry for some time, but the underlying mechanisms have remained a mystery,” said Suraj Shankar, a Harvard Junior Fellow in Physics and SEAS and co-first author of the study.  “We found a mathematical argument that explains how and why this robust effect exists with any shape within this class, so that the details of the shape are unimportant, and the only fact that matters is that there is a reversal of curvature along the saw.”

Shankar, Bryde and Mahadevan found that explanation via an analogy to very different class of physical systems — topological insulators. Most often associated with quantum physics, topological insulators are materials that conduct electricity in their surface or edge but not in the middle and no matter how you cut these materials, they will always conduct on their edges.

“In this work, we drew a mathematical analogy between the acoustics of bent sheets and these quantum and electronic systems,” said Shankar.

By using the mathematics of topological systems, the researchers found that the localized vibrational modes in the sweet spot of singing saw were governed by a topological parameter that can be computed and which relies on nothing more than the existence of two opposite curves in the material. The sweet spot then behaves like an internal “edge” in the saw.

“By using experiments, theoretical and numerical analysis, we showed that the S-curvature in a thin shell can localize topologically-protected modes at the ‘sweet spot’ or inflection line, similar to exotic edge states in topological insulators,” said Bryde. “This phenomenon is material independent, meaning it will appear in steel, glass or even graphene.”

The researchers also found that they could tune the localization of the mode by changing the shape of the S-curve, which is important in applications such as sensing, where you need a resonator that is tuned to very specific frequencies.

Next, the researchers aim to explore localized modes in doubly curved structures, such as bells and other shapes.

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

Geometric control of topological dynamics in a singing saw by Suraj Shankar, Petur Bryde, and L. Mahadevan. The Proceedings of the National Academy of Sciences (PNAS) April 21, 2022 | 119 (17) e2117241119 DOI: https://doi.org/10.1073/pnas.2117241119

This paper is open (free) access.

Quantum memristors

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This March 24, 2022 news item on Nanowerk announcing work on a quantum memristor seems to have had a rough translation from German to English,

In recent years, artificial intelligence has become ubiquitous, with applications such as speech interpretation, image recognition, medical diagnosis, and many more. At the same time, quantum technology has been proven capable of computational power well beyond the reach of even the world’s largest supercomputer.

Physicists at the University of Vienna have now demonstrated a new device, called quantum memristor, which may allow to combine these two worlds, thus unlocking unprecedented capabilities. The experiment, carried out in collaboration with the National Research Council (CNR) and the Politecnico di Milano in Italy, has been realized on an integrated quantum processor operating on single photons.

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Caption: Abstract representation of a neural network which is made of photons and has memory capability potentially related to artificial intelligence. Credit: © Equinox Graphics, University of Vienna

A March 24, 2022 University of Vienna (Universität Wien) press release (also on EurekAlert), which originated the news item, explains why this work has an impact on artificial intelligence,

At the heart of all artificial intelligence applications are mathematical models called neural networks. These models are inspired by the biological structure of the human brain, made of interconnected nodes. Just like our brain learns by constantly rearranging the connections between neurons, neural networks can be mathematically trained by tuning their internal structure until they become capable of human-level tasks: recognizing our face, interpreting medical images for diagnosis, even driving our cars. Having integrated devices capable of performing the computations involved in neural networks quickly and efficiently has thus become a major research focus, both academic and industrial.

One of the major game changers in the field was the discovery of the memristor, made in 2008. This device changes its resistance depending on a memory of the past current, hence the name memory-resistor, or memristor. Immediately after its discovery, scientists realized that (among many other applications) the peculiar behavior of memristors was surprisingly similar to that of neural synapses. The memristor has thus become a fundamental building block of neuromorphic architectures.

A group of experimental physicists from the University of Vienna, the National Research Council (CNR) and the Politecnico di Milano led by Prof. Philip Walther and Dr. Roberto Osellame, have now demonstrated that it is possible to engineer a device that has the same behavior as a memristor, while acting on quantum states and being able to encode and transmit quantum information. In other words, a quantum memristor. Realizing such device is challenging because the dynamics of a memristor tends to contradict the typical quantum behavior. 

By using single photons, i.e. single quantum particles of lights, and exploiting their unique ability to propagate simultaneously in a superposition of two or more paths, the physicists have overcome the challenge. In their experiment, single photons propagate along waveguides laser-written on a glass substrate and are guided on a superposition of several paths. One of these paths is used to measure the flux of photons going through the device and this quantity, through a complex electronic feedback scheme, modulates the transmission on the other output, thus achieving the desired memristive behavior. Besides demonstrating the quantum memristor, the researchers have provided simulations showing that optical networks with quantum memristor can be used to learn on both classical and quantum tasks, hinting at the fact that the quantum memristor may be the missing link between artificial intelligence and quantum computing.

“Unlocking the full potential of quantum resources within artificial intelligence is one of the greatest challenges of the current research in quantum physics and computer science”, says Michele Spagnolo, who is first author of the publication in the journal “Nature Photonics”. The group of Philip Walther of the University of Vienna has also recently demonstrated that robots can learn faster when using quantum resources and borrowing schemes from quantum computation. This new achievement represents one more step towards a future where quantum artificial intelligence become reality.

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

Experimental photonic quantum memristor by Michele Spagnolo, Joshua Morris, Simone Piacentini, Michael Antesberger, Francesco Massa, Andrea Crespi, Francesco Ceccarelli, Roberto Osellame & Philip Walther. Nature Photonics volume 16, pages 318–323 (2022) DOI: https://doi.org/10.1038/s41566-022-00973-5 Published 24 March 2022 Issue Date April 2022

This paper is open access.