Friday, January 10, 2025

Light Hype and the Optical Revolution


Study suggests optogenetics can drive muscle contraction with greater control, less fatigue than electrical stimulation
May 2024, phys.org

Optogenetics meets neuroprosthetics - Instead of using electricity to stimulate muscles, they used light, and synthetic nerve fibers activate the muscles 

via MIT's Center for Bionics: Guillermo Herrera-Arcos et al, Closed-loop optogenetic neuromodulation enables high-fidelity fatigue-resistant muscle control, Science Robotics (2024). DOI: 10.1126/scirobotics.adi8995.



New 'game-changing' discovery for light-driven artificial intelligence
Aug 2024, phys.org

photonic AI accelerator - an emerging technology where photons are used instead of electrons to perform AI computations.

via Universities of Oxford, Muenster, Heidelberg, and Ghent: Bowei Dong et al, Partial coherence enhances parallelized photonic computing, Nature (2024). DOI: 10.1038/s41586-024-07590-y

Everything is Everywhere All of the Sudden


I usually don't post artist renderings like this, but this is what I see when imagining everything made of computers, using ambient energy like light to control different particles each designed to take it and do different things with it but all in one jumble of matter, like an intelligent matter: Above image: An artistic depiction of a wavelength-multiplexed diffractive optical processor for 3D quantitative phase imaging. Credit: UCLA Engineering Institute for Technology Advancement [link]

On what could be called "ubiquitous computing", a legend of artificial intelligence (Hinton) describes it really well:
(What's next in computing?) My last years at Google I was thinking about analog computing ... run these big language models in analog hardware ... if you're gonna use that low power analog computation, every piece of hardware is gonna be a bit different. And the idea is that the learning is gonna make use of the specific properties of that hardware.
--Geoffrey Hinton interview, "On Working w Ilya, Choosing Problems, and the Power of Intuition", July 2024 30min?

Researchers use 'smart' rubber structures to carry out computational tasks
May 2024, phys.org

"We now know how to design simple materials so they can process information."

The research team created a rubber computer that can act as a two-bit binary counter using slender rubber elements as mechanical bits, and assembling multiple bits together in a metamaterial.

Note: The title of their demonstration video is "Can Rubber Compute?" and I now see it all as a series of experiments like the Will It Blend series, where they just do it to everything - can crystals compute? (Yes, we already know that) Can light compute? (Yes we already know that too) Can slime mold compute? But can salt compute? (Actually yes, like in a gradient of fresh water and salt water, but I was talking about a pile of table salt.) Can my sneakers compute? (I mean obviously) Can my front door compute? (Also obvious, its whole thing is to open and close like 1/0) I'm not talking about a computer screwed on top of my doorknob, I mean the door itself, the whole thing, is a computer, just by the way its materials are put together.  The garbage can? Definitely garbage cans will compute. 

via Leiden University and AMOLF: Jingran Liu et al, Controlled pathways and sequential information processing in serially coupled mechanical hysterons, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2308414121


Using DNA origami, researchers create diamond lattice for future semiconductors of visible light
May 2024, phys.org

With headlines like that, there is no further explanation. 

via Ludwig Maximilian University of Munich: Gregor Posnjak et al, Diamond-lattice photonic crystals assembled from DNA origami, Science (2024). DOI: 10.1126/science.adl2733

Also: Hao Liu et al, Inverse design of a pyrochlore lattice of DNA origami through model-driven experiments, Science (2024). DOI: 10.1126/science.adl5549


Mechanical computer relies on kirigami cubes, not electronics
Jun 2024, phys.org

It's a mechanical computer, one that doesn't use electronics. Is that all we need to call it? A mechanical computer?

Historically, these mechanical components have been things like levers or gears. But cubes can have five or more different states. Theoretically, that means a given cube can convey not only a 1 or a 0, but also a 2, 3 or 4.

When any of the cubes are pushed up or down, this changes the geometry—or architecture—of all of the connected cubes. This can be done by pushing up or down on one of the cubes with a magnetic field. These 64-cube functional units can be grouped together into increasingly complex metastructures that allow for storing more data or for conducting more complex computations.

The cubes are connected by thin strips of elastic tape. To edit data, you have to change the configuration of functional units. That requires users to pull on the edges of the metastructure, which stretches the elastic tape and allows you to push cubes up or down. When you release the metastructure, the tape contracts, locking the cubes—and the data—in place.

"One potential application for this is that it allows for users to create three-dimensional, mechanical encryption or decryption"

via North Carolina State University: Yanbin Li et al, Reprogrammable and reconfigurable mechanical computing metastructures with stable and high-density memory, Science Advances (2024). DOI: 10.1126/sciadv.ado6476 , www.science.org/doi/10.1126/sciadv.ado6476


New material paves the way to on-chip energy harvesting
Jul 2024, phys.org

They utilize the waste heat generated during operation and convert it back into electrical energy, called "on-chip energy harvesting", and it works because they put tin in the germanium (Ge+Sn). 

via Forschungszentrum Jülich and IHP—Leibniz Institute for High Performance Microelectronics in Germany, University of Pisa, University of Bologna, University of Leeds: Omar Concepción et al, Room Temperature Lattice Thermal Conductivity of GeSn Alloys, ACS Applied Energy Materials (2024). DOI: 10.1021/acsaem.4c00275


A first physical system to learn nonlinear tasks without a traditional computer processor
Jul 2024, phys.org

They made a contrastive local learning network where components evolve on their own based on local rules without knowledge of the larger structure, similar to how neurons in the human brain don't know what other neurons are doing and yet learning emerges.

"It can learn, in a machine learning sense, to perform useful tasks, similar to a computational neural network, but it is a physical object."

(Physical object, that's the key)

"Because the way that it both calculates and learns is based on physics, it's way more interpretable. You can actually figure out what it's trying to do because you have a good handle on the underlying mechanism. That's kind of unique because a lot of other learning systems are black boxes where it's much harder to know why the network did what it did.

via University of Pennsylvania: Sam Dillavou et al, Machine learning without a processor: Emergent learning in a nonlinear analog network, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2319718121

The optical era of science reporting where every picture has rainbows in it: Artistic depiction of diffractive information processing - Ozcan Lab at UCLA - Jul 2024

Scientists demonstrate chemical reservoir computation using the formose reaction
Jul 2024, phys.org

Good explanation by the writeup author here, Tejasri Gururaj: The field of molecular computing interests researchers who wish to harness the computational power of chemical and biological systems. In these systems, the chemical reactions or molecular processes act as the reservoir computer, transforming inputs into high-dimensional outputs. ...

The formose reaction is the only example of a self-organizing reaction network with a highly non-linear topology, containing numerous positive and negative feedback loops.

The researchers used a continuous stirred tank reactor (CSTR) to implement the formose reaction. The input concentrations of four reactants—formaldehyde, dihydroxyacetone, sodium hydroxide, and calcium chloride—are controlled to modulate the reaction network's behavior.

The output molecule is identified using a mass spectrometer, which allows them to track up to 106 molecules. 

This setup can be used to do calculations, with the reactant concentrations being the input value to any function that needs to be computed.

The team showed that it could predict the behavior of a complex metabolic network model of E. coli, accurately capturing both linear and nonlinear responses to fluctuating inputs across various concentration ranges.

Furthermore, the system demonstrated the ability to forecast future states of a chaotic system (the Lorenz attractor), accurately predicting two out of three input dimensions several hours into the future.

via Institute for Molecules and Materials at Radboud University: Mathieu G. Baltussen et al, Chemical reservoir computation in a self-organizing reaction network, Nature (2024). DOI: 10.1038/s41586-024-07567-x

Thursday, January 9, 2025

Body Problems


Many Body is the New Three-Body:

Fluctuating hydrodynamics theory could describe chaotic many-body systems, study suggests
Sep 2024, phys.org

"The entire behavior of a system may be determined by a single quantity: the diffusion constant - even though the physics are very complex and chaotic at the microscopic level." This is similar to how we measure the randomness of fluctuating hydrodynamics. 

The team prepared a quantum system of ultracold cesium atoms in optical lattices in a non-equilibrium initial state and then let it evolve freely, so they could measure it. They found that despite their microscopic complexity, these systems can be described simply as a macroscopic diffusion process - similar to Brownian motion.

via Ludwig Maximilian University of Munich: Julian F. Wienand et al, Emergence of fluctuating hydrodynamics in chaotic quantum systems, Nature Physics (2024). DOI: 10.1038/s41567-024-02611-z

Totally unrelated image credit: SARS-CoV-2 blocking expression of interferons - NIAD NIH - Aug 2024


Researcher discusses a new type of collective interference effect
Sep 2024, phys.org

In our interference scenario, the particles' entanglement bridges the spatial gap between separate interferometers, introducing an interference pattern that depends on the overall quantum state of all the particles involved, and is inaccessible when one or more particles are excluded from the dynamics.

So interference patterns are influenced not only by the quantum states of the individual particles but also by the entanglement shared among some of them (like the total state).

via Department of Experimental Physics at University of Innsbruck, University of Freiburg, and Heriot-Watt University UK: Tommaso Faleo et al, Entanglement-induced collective many-body interference, Science Advances (2024). DOI: 10.1126/sciadv.adp9030


Say That


Language is like a life form, but we don't think about it that way. Every day new words are being born, like a new species, and with them, entire new branches on the tree of life, or at least, the tree of knowledge. 

This first article is long only because the part about controlling people's dreams is pretty cool:

Parasomnia: What happens inside a sleepwalker's brain?
May 2024, phys.org

Parasomnia - sleepwalking

Those who experience parasomnias during non-REM sleep sometimes report having dream-like experiences and sometimes appear completely unconscious (i.e., on automatic pilot).

They provoke a parasomnia episode in the lab, where on the first night the patient sleeps normally, but on the second night is kept awake and only allowed to sleep the next morning, when they are exposed to a loud sound upon entering the deep-sleep stage. In some cases, this results in a parasomnia episode. 

In 56% of episodes, patients reported that they had been dreaming during the episode. "It was often about an impending misfortune or danger. Some reported that they thought the ceiling was going to come down. One patient thought they'd lost their baby and was searching through the bedsheets, and stood up in bed to try to save ladybugs from gliding down the wall and dying," Siclari explains.

"In 19% of the cases, the patients weren't experiencing anything and simply awoke to find themselves doing things, almost like a trance."

"Interestingly, patients almost never mention the sound that initiated the parasomnia episode, but rather some other type of impending danger. The louder we go with the sound volume, the higher the chance that we provoke an episode."

via Netherlands Institute for Neuroscience: Jacinthe Cataldi et al, Shared EEG correlates between non-REM parasomnia experiences and dreams, Nature Communications (2024). DOI: 10.1038/s41467-024-48337-7

Above image credit: We can see in the image above, that the robots don't know what a child is, or we don't have enough well-labelled samples in the noosphere aka the internet: AI Art - Child's Handwriting 1 - 2024

Astronomers discover at least one in a dozen stars show evidence of planetary ingestion
Mar 2024, phys.org

Planetary ingestion - when a star eats a planet.

via ARC Centre of Excellence for All Sky Astrophysics in 3D (ASTRO 3D) and Monash University: Fan Liu, At least one in a dozen stars exhibits evidence of planetary ingestion, Nature (2024). DOI: 10.1038/s41586-024-07091-y. 


Study outlines spectroscopic signatures of fractionalization in octupolar quantum spin ice
Mar 2024, phys.org

π-flux octupolar quantum spin ice (π-O-QSI) - a new 3D quantum spin liquid that can host fractionalized excitations.

via University of Toronto: Félix Desrochers et al, Spectroscopic Signatures of Fractionalization in Octupolar Quantum Spin Ice, Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.132.066502. 


Red light therapy for repairing spinal cord injury passes milestone
May 2024, phys.org

Photobiomodulation - It's light therapy, delivered either by implantable device or transcutaneous delivery, where the light source is placed against the skin.

via University of Birmingham: Andrew R. Stevens et al, Implantable and transcutaneous photobiomodulation promote neuroregeneration and recovery of lost function after spinal cord injury, Bioengineering & Translational Medicine (2024). DOI: 10.1002/btm2.10674


Creating chimeroids by mixing stem cells from different donors to create multiple cell line organoids
Jun 2024, phys.org

Chimeroids - functional organoids with multiple cell lines; achieved by obtaining pluripotent stem cells from multiple individuals, then broken into multiple parts, mixed all together to allow the results to grow into a multi-cell-line organoid, which they call a chimeroid.

F*** right off. 

via Broad Institute of MIT and Harvard: Noelia Antón-Bolaños et al, Brain Chimeroids reveal individual susceptibility to neurotoxic triggers, Nature (2024). DOI: 10.1038/s41586-024-07578-8

Also: Aparna Bhaduri, Chimeric brain organoids capture human genetic diversity, Nature (2024). DOI: 10.1038/d41586-024-01648-7


Picotaur—the unrivaled microrobot
Aug 2024, phys.org

Picotaur - a tiny robot

via Carnegie Mellon University Mechanical Engineering: Sukjun Kim et al, Picotaur: A 15 mg Hexapedal Robot with Electrostatically Driven, 3D‐Printed Legs, Advanced Intelligent Systems (2024). DOI: 10.1002/aisy.202400196


Two-way mathematical 'dictionary' could connect quantum physics with number theory
Sep 2024, phys.org

Big Als - "big algebras," a two-way mathematical 'dictionary' between symmetry, algebra, and geometry, that could strengthen the connection between the distant worlds of quantum physics and number theory.

via Institute of Science and Technology Austria: Tamás Hausel, Commutative avatars of representations of semisimple Lie groups, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2319341121


Quantum research breakthrough uses synthetic dimensions to efficiently process quantum information
Oct 2024, phys.org

Synthetic photonic networks - they can process quantum information based on the quantum walks of high-dimensional photons entangled in their temporal states.

via Institut National de la Recherche Scientifique at Énergie Matériaux Télécommunications Research Centre: Monika Monika et al, Quantum state processing through controllable synthetic temporal photonic lattices, Nature Photonics (2024). DOI: 10.1038/s41566-024-01546-4

Wednesday, January 8, 2025

On the Misunderstandings of Thermodynamics


Thermodynamics is hard. 

The very concept of the green roof is an abomination, because it's antithetical to the purpose of a roof to begin with - a green roof is literally storing water on top of the building, on purpose. Roofs are sloped and bound by drainage systems to get the water out as thoroughly and quickly as possible. Water is the enemy, and yet with a  green roof, we're inviting it into the building on purpose. Sounds cool, looks cool, dumbest thing ever.

But then again, cool roofs are also a problem. One of the ways a building gets rid of unintended and uncontrolled water intrusion is through the silent, invisible power of the stack effect (heat rises). A hot roof facilitates and amplifies this stack effect, cooking-out excess moisture that gets into the interstitial spaces in a building. You can make a building as perfect as possible, but water will get in there, because that's what it does, and because nothing is perfect. 

What can sometimes appear like a deficit (roofs get too hot) can actually be an integral part of the overall design (ridding excess moisture). 

This is similar to highly efficient (almost magically efficient) ambient heat pumps - they only use the exact amount of energy needed. Traditional air conditioners are over-designed in that they cool the air way more than they need to. But for hot and humid climates, this has the benefit of removing moisture from the air. A modern, magical heat pump that removes the heat but not the moisture, does not make a comfortable indoor environment, and could actually lead to unintended side effects like mold growth. 


Cool roofs outperform green roofs in urban climate modeling study
July 2024, phys.org

A three-dimensional urban climate model of Greater London tested the thermal effects of different passive and active urban heat management systems, including painted "cool roofs," rooftop solar panels, green roofs, ground level tree vegetation and air conditioning during the two hottest days of the summer of 2018, and found that if adopted widely throughout London, cool roofs could reduce outdoor temperatures across the city about 1.2 C up to 2 C.

Other systems, such as extensive street-level vegetation or solar panels would provide a smaller net cooling effect, only about 0.3 degrees C on average across London, though they offer other environmental benefits. Similarly, while green roofs offer benefits like water drainage and wildlife habitats, their net cooling effect on the city was found to be negligible on average.

Though on average the effect of green roofs was negligible, the researchers found that their effect on temperature varied significantly throughout the day. During the warmest times of day, the wide adoption of green roofs could lower urban temperatures by an average of 0.5 degrees C. However, this would be offset overnight as the thermal mass from the roofs would retain daytime heat, releasing when the sun was down and increasing night-time temperatures by about the same amount.

via University College London: Cool roofs could be most effective at reducing outdoor urban temperatures in London compared with other roof top and vegetation interventions: a mesoscale urban climate modelling study, Geophysical Research Letters (2024). DOI: 10.1029/2024GL109634

Research shows how common plastics could passively cool and heat buildings with the seasons
Jun 2024, phys.org

Roofs and walls are not the same. Roofs have a clear view of the sky, where they can radiate their heat upwards. Walls can't radiate upwards, they're blocked by other things, and they absorb a lot of heat from surrounding buildings and pavement. They're also affected by different "kinds" of heat:

Radiant heat moves from buildings to the sky in a narrow portion of the infrared spectrum known as the atmospheric transmission window, so the researchers call this narrowband. At ground level, radiant heat moves across the entire infrared spectrum, and the researchers call that broadband.

"By coating walls and windows with materials that only radiate or absorb heat in the atmospheric window (like propylene), we can reduce broadband heat gain from the ground in the summer, and loss in the winter, while maintaining the cooling effect of the sky.

via Oak Ridge National Lab, Arizona State University, Princeton and UCLA: Radiative Cooling and Thermoregulation in the Earth's Glow, Cell Reports Physical Science (2024). DOI: 10.1016/j.xcrp.2024.102065.

New fabric makes urban heat islands more bearable
Jun 2024, phys.org

Only hats, shoulder coverings and the tops of shoes - about 3% of clothing - face direct sunlight. The other 97% of are being heated by thermal radiation from the sides and below.

"Solar is visible light, thermal radiation is infrared, so they have different wavelengths. That means you need to have a material that has two optical properties at the same time."

In tests under the Arizona sun, the material kept 2.3 C (4.1 F) cooler than the broadband emitter fabric used for outdoor endurance sports and 8.9 C (16 F) cooler than the commercialized silk commonly used for shirts, dresses and other summer clothing.

via University of Chicago: Ronghui Wu et al, Spectrally engineered textile for radiative cooling against urban heat islands, Science (2024). DOI: 10.1126/science.adl0653

Quantum Progress


Someone said Majorana fermions so I listened:
Physicists move one step closer to topological quantum computing
Jul 2024, phys.org

Theory predicts that a combination of superconductivity and the quantum anomalous Hall effect will give rise to topologically protected particles called Majorana fermions that will potentially revolutionize future technologies such as quantum computers.

Such a combination can be achieved by inducing superconductivity in the edge of a quantum anomalous Hall insulator that is already resistance-free. The resultant chiral Majorana edge state, which is a special type of Majorana fermions, is a key to realizing "flying qubits" (or quantum bits) that are topologically protected.

via University of Cologne, KU Leuven, the University of Basel, and Forschungszentrum Jülich joint Cluster of Excellence Matter and Light for Quantum Computing ML4Q: Anjana Uday et al, Induced superconducting correlations in a quantum anomalous Hall insulator, Nature Physics (2024). DOI: 10.1038/s41567-024-02574-1

Image credit: Quantum computer with outer shielding of dilution refrigerator removed - Anna-Lena Lundqvist at Chalmers University of Technology - 2023


'Kink state' control may provide pathway to quantum electronics
Jul 2024, phys.org

Careful now

Kink states are electrical conduction pathways at the edge of the semiconducting material Bernal bilayer graphene that can regulate the flow of electrons in a quantum system via the quantum valley Hall effect. 

via Pennsylvania State University: Ke Huang et al, High-temperature quantum valley Hall effect with quantized resistance and a topological switch, Science (2024). DOI: 10.1126/science.adj3742


New method could yield fast, cross-country quantum network
Jul 2024, phys.org

They're building long quantum channels using vacuum sealed tubes with an array of spaced-out lenses. These vacuum beam guides, about 20 centimeters in diameter, would have ranges of thousands of kilometers and capacities of more than 1,013 qubits per second, better than any existing quantum communication approach. Photons of light encoding quantum data would move through the vacuum tubes and remain focused thanks to the lenses.

via University of Chicago Pritzker School of Molecular Engineering, Stanford University and the California Institute of Technology Laser Interferometer Gravitational-Wave Observatory LIGO: Yuexun Huang et al, Vacuum Beam Guide for Large Scale Quantum Networks, Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.133.020801.


Test of a prototype quantum internet runs under New York City for half a month
Aug 2024, phys.org

"Progress toward a fully automated practical entanglement network"

Qunnect researchers used a leased 34-kilometer-long fiber circuit they called the GothamQ loop. Using polarization-entangled photons, they operated the loop for 15 continuous days, with fidelity nearly 90%. 

via Qunnect Inc. in Brooklyn, New York: Alexander N. Craddock et al, Automated Distribution of Polarization-Entangled Photons Using Deployed New York City Fibers, PRX Quantum (2024). DOI: 10.1103/PRXQuantum.5.030330

Tuesday, January 7, 2025

On Intermental Access and Semantic Phrenology


Now they're using pairs of epilepsy patients, talking to each other.

Context contingent networks is the new wordcloud. But this is literally the baby steps of mind-reading, word-by-word:

Brain activity associated with specific words is mirrored between speaker and listener during a conversation
Aug 2024, phys.org

The team collected brain activity data and conversation transcripts from pairs of epilepsy patients during natural conversations, using electrocorticography and GPT-2

"We can see linguistic content emerge word-by-word in the speaker's brain before they actually articulate what they're trying to say, and the same linguistic content rapidly reemerges in the listener's brain after they hear it."

Word-specific brain activity peaked in the speaker's brain around 250 ms before they spoke each word, and corresponding spikes in brain activity associated with the same words appeared in the listener's brain approximately 250 ms after they heard them.

via Princeton and New York University School of Medicine Comprehensive Epilepsy Center: A shared model-based linguistic space for transmitting our thoughts from brain to brain in natural conversations, Neuron (2024). DOI: 10.1016/j.neuron.2024.06.025.


Words like 'this' and 'that' act as attention tools across languages
Jul 2024, phys.org

This and that and here and there are 'demonstrative' words are used to direct listeners' focus of attention and to establish joint attention.

There is debate about whether directing the listener's attention - the 'mentalistic' representation - is part of the meaning (semantics) of demonstratives, or whether it arises from general principles of social cognition (pragmatics). The researchers used computational modeling and experiments with speakers of ten different languages from eight different language groups to investigate this question.

Results showed that participants were not only sensitive to the location of the target but also to the listener's attention. As expected, the meaning of demonstratives varied within and across languages. For example, the 'near' demonstrative (such as English 'this one') sometimes had a spatial meaning ('the one close to me'). But it also had a joint attention meaning ('the one we are both looking at') or a 'mentalistic' meaning ('the one over here'), directing the listener's attention towards the speaker.

Interestingly, speakers of languages with a three-word system used the medial word (such as Spanish 'ese') to indicate joint attention.

via Yale University and the Max Planck Institute of Psycholinguistics in Nijmegen: Jara-Ettinger, Julian et al, Demonstratives as attention tools: Evidence of mentalistic representations within language, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2402068121.