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Computer Programming

Physics of Irregular Objects on Inclined Planes Unveiled

How gravity causes a perfectly spherical ball to roll down an inclined plane is part of elementary school physics canon. But the world is messier than a textbook. Scientists have sought to quantitatively describe the much more complex rolling physics of real-world objects. They have now combined theory, simulations, and experiments to understand what happens when an imperfect, spherical object is placed on an inclined plane.

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The physics of everyday objects has long been a staple of elementary school education. However, real-world objects rarely conform to the idealized shapes and scenarios presented in textbooks. A team of scientists at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS) has taken on the challenge of understanding the complex rolling physics of imperfect, spherical objects placed on inclined planes.

Led by L. Mahadevan, a Lola England de Valpine Professor of Applied Mathematics, Physics, and Organismic and Evolutionary Biology in SEAS and FAS, the researchers combined theory, simulations, and experiments to gain insights into this phenomenon. Their findings were published in Proceedings of the National Academy of Sciences and offer fundamental implications for various fields, including nanoscale cellular transport and robotics.

“We often overlook the intricacies of the world around us,” Mahadevan said. “By pausing to wonder, we can learn about ourselves and the world.” The team’s exploration of this simple problem drew connections between different mathematical disciplines, making it both enjoyable and potentially useful in the long run.

The researchers began with simulations of slightly irregular objects (spheres or cylinders) rolling down various inclines, noting that an irregularly shaped object does not always roll. As the ramp became steeper, the likelihood of the object rolling increased, while a flattening ramp led to a decrease in rolling speed. The critical angle of inclination marked the transition from non-rolling to rolling behavior, where some fascinating physics emerged.

First author Daoyuan Qian described the terminal rolling speed near this critical point as “a simple measure of order,” which varied depending on factors such as object dimensions and inertia. For example, the time period of rolling diverged near the transition, while stable rolling motion was established away from the critical point. Cylindrical objects were predicted to behave differently from spherical ones due to differences in rotational dynamics.

The researchers tested their calculations with experiments observing irregular rolling cylinders and spheres on different inclines, verifying that their results matched theoretical predictions for behavior near the onset of motion.

A surprising observation emerged when experimenting with irregularly shaped spheres: the motion exhibited a periodic pattern, repeating itself indefinitely once reaching steady state. This was an unexpected finding, but upon reflection, it made sense – a sphere rolling jerkily forward would resemble a dung beetle’s trajectory, seeming to be completely random and requiring complex mathematical descriptions.

However, mapping out the motions of the balls as distinct trajectories revealed a pattern: regardless of irregularity, the motion was periodic. Furthermore, the ball rolled over itself twice in each period of motion before returning to its original state.

These results provided vivid physical manifestations of topological theorems, including a demonstration of the “Hairy Ball Theorem,” which states that you cannot comb the hair on a sphere without a cowlick. This was seen in how the rolling trajectories looked on the surface of the sphere. The experiments also served to illustrate Dirac’s Plate Trick, positing that a rotating object with strings must rotate twice to return to its original state.

“It’s quite interesting how we can see these kinds of abstract mathematics made visible with this simple experiment,” said co-author and postdoctoral fellow Yeonsu Jung. “And then the question could be, ‘What else can we do?’ … Maybe we could explore something that hasn’t been studied by mathematicians yet.”

The study was funded by Transition Bio Ltd, Cambridge University, the National Research Foundation of Korea, the Simons Foundation, and the Henri Seydoux Fund.

Computational Biology

A Quantum Leap Forward – New Amplifier Boosts Efficiency of Quantum Computers 10x

Chalmers engineers built a pulse-driven qubit amplifier that’s ten times more efficient, stays cool, and safeguards quantum states—key for bigger, better quantum machines.

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Quantum computers have long been touted as revolutionary machines capable of solving complex problems that stymie conventional supercomputers. However, their full potential has been hindered by the limitations of qubit amplifiers – essential components required to read and interpret quantum information. Researchers at Chalmers University of Technology in Sweden have taken a significant step forward with the development of an ultra-efficient amplifier that reduces power consumption by 90%, paving the way for more powerful quantum computers with enhanced performance.

The new amplifier is pulse-operated, meaning it’s activated only when needed to amplify qubit signals, minimizing heat generation and decoherence. This innovation has far-reaching implications for scaling up quantum computers, as larger systems require more amplifiers, leading to increased power consumption and decreased accuracy. The Chalmers team’s breakthrough offers a solution to this challenge, enabling the development of more accurate readout systems for future generations of quantum computers.

One of the key challenges in developing pulse-operated amplifiers is ensuring they respond quickly enough to keep pace with qubit readout. To address this, the researchers employed genetic programming to develop a smart control system that enables rapid response times – just 35 nanoseconds. This achievement has significant implications for the future of quantum computing, as it paves the way for more accurate and powerful calculations.

The new amplifier was developed in collaboration with industry partners Low Noise Factory AB and utilizes the expertise of researchers at Chalmers’ Terahertz and Millimeter Wave Technology Laboratory. The study, published in IEEE Transactions on Microwave Theory and Techniques, demonstrates a novel approach to developing ultra-efficient amplifiers for qubit readout and offers promising prospects for future research.

In conclusion, the development of this highly efficient amplifier represents a significant leap forward for quantum computing. By reducing power consumption by 90%, researchers have opened doors to more powerful and accurate calculations, unlocking new possibilities in fields such as drug development, encryption, AI, and logistics. As the field continues to evolve, it will be exciting to see how this innovation shapes the future of quantum computing.

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Artificial Intelligence

AI Uncovers Hidden Heart Risks in CT Scans: A Game-Changer for Cardiovascular Care

What if your old chest scans—taken years ago for something unrelated—held a secret warning about your heart? A new AI tool called AI-CAC, developed by Mass General Brigham and the VA, can now comb through routine CT scans to detect hidden signs of heart disease before symptoms strike.

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The Massachusetts General Brigham researchers have developed an innovative artificial intelligence (AI) tool called AI-CAC to analyze previously collected CT scans and identify individuals with high coronary artery calcium (CAC) levels, indicating a greater risk for cardiovascular events. Their research, published in NEJM AI, demonstrated the high accuracy and predictive value of AI-CAC for future heart attacks and 10-year mortality.

Millions of chest CT scans are taken each year, often in healthy people, to screen for lung cancer or other conditions. However, this study reveals that these scans can also provide valuable information about cardiovascular risk, which has been going unnoticed. The researchers found that AI-CAC had a high accuracy rate (89.4%) at determining whether a scan contained CAC or not.

The gold standard for quantifying CAC uses “gated” CT scans, synchronized to the heartbeat to reduce motion during the scan. However, most chest CT scans obtained for routine clinical purposes are “nongated.” The researchers developed AI-CAC, a deep learning algorithm, to probe through these nongated scans and quantify CAC.

The AI-CAC model was 87.3% accurate at determining whether the score was higher or lower than 100, indicating a moderate cardiovascular risk. Importantly, AI-CAC was also predictive of 10-year all-cause mortality, with those having a CAC score over 400 having a 3.49 times higher risk of death over a 10-year period.

The researchers hope to conduct future studies in the general population and test whether the tool can assess the impact of lipid-lowering medications on CAC scores. This could lead to the implementation of AI-CAC in clinical practice, enabling physicians to engage with patients earlier, before their heart disease advances to a cardiac event.

As Dr. Raffi Hagopian, first author and cardiologist at the VA Long Beach Healthcare System, emphasized, “Using AI for tasks like CAC detection can help shift medicine from a reactive approach to the proactive prevention of disease, reducing long-term morbidity, mortality, and healthcare costs.”

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Computer Modeling

Harnessing True Randomness from Entangled Photons: The Colorado University Randomness Beacon (CURBy)

Scientists at NIST and the University of Colorado Boulder have created CURBy, a cutting-edge quantum randomness beacon that draws on the intrinsic unpredictability of quantum entanglement to produce true random numbers. Unlike traditional methods, CURBy is traceable, transparent, and verifiable thanks to quantum physics and blockchain-like protocols. This breakthrough has real-world applications ranging from cybersecurity to public lotteries—and it’s open source, inviting the world to use and build upon it.

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The Colorado University Randomness Beacon (CURBy) is a pioneering service that harnesses the true randomness of entangled photons to produce unguessable strings of numbers. This breakthrough was made possible by the work of scientists at the National Institute of Standards and Technology (NIST) and their colleagues at the University of Colorado Boulder.

“True randomness is something that nothing in the universe can predict in advance,” said Krister Shalm, a physicist at NIST. “If God does play dice with the universe, then you can turn that into the best random number generator that the universe allows.”

The CURBy system uses a Bell test to measure pairs of entangled photons whose properties are correlated even when separated by vast distances. When researchers measure an individual particle, the outcome is random, but the properties of the pair are more correlated than classical physics allows, enabling researchers to verify the randomness.

This is the first random number generator service to use quantum nonlocality as a source of its numbers, and the most transparent source of random numbers to date. The results are certifiable and traceable to a greater extent than ever before.

The CURBy system consists of a nonlinear crystal that generates entangled photons, which travel via optical fiber to separate labs at opposite ends of the hall. Once the photons reach the labs, their polarizations are measured. The outcomes of these measurements are truly random.

NIST passes millions of these quantum coin flips to a computer program at the University of Colorado Boulder, where special processing steps and strict protocols are used to turn the outcomes into 512 random bits of binary code (0s and 1s). The result is a set of random bits that no one, not even Einstein, could have predicted.

The CURBy system has been operational for several months now, with an impressive success rate of over 99.7%. The ability to verify the data behind each random number was made possible by the Twine protocol, a novel set of quantum-compatible blockchain technologies developed by NIST and its collaborators.

“The Twine protocol lets us weave together all these other beacons into a tapestry of trust,” said Jasper Palfree, a research assistant on the project at the University of Colorado Boulder. This allows any user to verify the data behind each random number, providing security and traceability.

The CURBy system can be used anywhere an independent, public source of random numbers would be useful, such as selecting jury candidates, making a random selection for an audit, or assigning resources through a public lottery.

“I wanted to build something that is useful. It’s this cool thing that is the cutting edge of fundamental science,” said Gautam Kavuri, a graduate student on the project. The whole process is open source and available to the public, allowing anyone to not only check their work but even build on the beacon to create their own random number generator.

The CURBy system has the potential to revolutionize fields such as cryptography, gaming, and finance, where true randomness is essential. By harnessing the power of entangled photons, scientists have created a truly independent source of random numbers that can be trusted.

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