All posts tagged: quantum physics

Photons behave very strangely if you try to cut them

Photons behave very strangely if you try to cut them

Published by skeptic

Cutting photons is infinitely weird Muhammad Fawaid/Alamy In Greek mythology, cutting one head off the Hydra of Lerna simply resulted in two more heads growing to replace it – and it turns out it’s even worse for photons. If you try to cut a piece off a particle of light, the result is infinitely many more of them being created. Some particles are elementary, which means that they cannot be broken into smaller pieces. For instance, a proton can be torn into three quarks, but each quark cannot be subdivided further. But what would happen if you tried to cut an elementary particle anyway? Johannes Skaar at the University of Oslo in Norway and his colleagues have looked into the case of a photon encountering a mirror that could do just this. Because it is quantum, light can be described both as made from photons and as being an electromagnetic wave. Accordingly, a photon isn’t perfectly localised, like a solid object, but rather has a tail that extends across space. In the proposed scenario, the …

First quantum grandfather clock could probe where gravity comes from

First quantum grandfather clock could probe where gravity comes from

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Pendulum clocks were much more accurate than those that came before Panumas Nikhomkhai / Alamy The first complete design for a quantum grandfather clock uses a single atom, tiny mirrors and light. Building it could help our understanding of what makes any clock accurate in the quantum realm and explore ideas at the edge of physics. At the most rudimentary level, time can be measured with something simple, like sand trickling through an hourglass. But timekeeping became a lot more accurate once mechanical clocks, like the grandfather or pendulum clock, were invented in the 17th century. Matteo Brunelli at Collège de France and his colleagues have now shown that such clocks have a quantum equivalent. “We asked ourselves the question: ‘Can a pendulum clock work according to the laws of quantum mechanics?’ We couldn’t be sure,” he says. Each pendulum clock has three basic elements, starting with the pendulum that defines the clock’s ticks with its swings. Next are the weights within the clock that leverage gravity’s downward pull to make the pendulum move. Finally, …

We may finally know why gold stays so shiny

We may finally know why gold stays so shiny

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Gold doesn’t tarnish like other metals mauritius images GmbH/Alamy Silver goes dull, copper turns green and iron rusts, but gold always stays shiny. Why this is the case has remained a mystery, but researchers may have finally figured out what makes the valuable metal so resistant to change and how to tarnish it. Gold is chemically inert, meaning that it doesn’t react with molecules from its surroundings, such as oxygen in the air. This is great news for jewelry, but it limits gold’s usefulness in chemistry, where researchers think it could be a useful catalyst – if only it could be nudged out of its inertness. Matthew Montemore and Santu Biswas at Tulane University in Louisiana investigated a phenomenon called reconstruction, which happens when a piece of gold is cut, creating a new surface. “The atoms just hate being on a surface so much that they completely rearrange,” says Montemore. Often, they rearrange into a pattern resembling repeating hexagons, then don’t shuffle further because their energy is low in this arrangement. Reconstruction isn’t common among …

Does gravity create reality? A shocking path to a theory of everything

Does gravity create reality? A shocking path to a theory of everything

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Sometimes, you work tirelessly on a problem, only to realise you have been going about it all backwards. Imagine trying to fit a massive antique piano through a tiny doorway. You have tried everything – rotating it, removing the legs, forceful shoving – but you just can’t get it to fit. Eventually, you realise it is easier to construct a room to house the piano where it already sits. Now, some physicists are grappling with a similar rethink. For decades, the accepted route to an ultimate theory of everything has involved taking our best theory of gravity and squeezing it into the frame of quantum mechanics. Given that quantum theory is wildly successful in describing the other three of the four fundamental forces of nature, it is an understandable approach. Yet, almost a century later, scientists still haven’t managed to make gravity fit. That’s why a few mavericks have championed an alternative strategy. They suggest that tweaking the equations of quantum mechanics – constructing a new room for gravity – helps explain how the strange world of particles gives rise to our everyday reality. Various experimental avenues are opening up to probe this approach, involving everything from levitating diamonds and glowing metals to swinging pendulums and ticking clocks. The tests promise to shine a light on how the quantum world operates and …

Quantum ‘Jamming’ Could Help Unlock the Mysteries of Causality

Quantum ‘Jamming’ Could Help Unlock the Mysteries of Causality

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The original version of this story appeared in Quanta Magazine. For the past few decades, researchers have understood that quantum computers should eventually be able to crack the widely used codes that secure much of the digital world. To protect against this fate, they’ve spent years developing new codes that appear to be safe from future safecrackers armed with quantum computers. At the same time, they’ve also devised ingenious ways to use the rules of quantum mechanics to keep communications secure. But quantum mechanics, just like the “classical” mechanics that preceded it, is just a theory of nature. What if it eventually gets superseded by a fuller theory, just as quantum mechanics supplanted Newtonian physics a century ago? Will these quantum communication techniques still be secure in a world where there’s an even more fundamental set of rules? “In terms of these cryptographic protocols, it’s good to be paranoid,” said Ravishankar Ramanathan, a quantum information theorist at the University of Hong Kong who works on quantum cryptography. “Let’s try to minimize the assumptions behind the …

Can we harness quantum effects to create a new kind of healthcare?

Can we harness quantum effects to create a new kind of healthcare?

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If you have even a passing interest in your health, you can’t spend long on social media before the algorithm brings you into contact with the infamous Q-word. Are you in touch with your quantum energy fields? Could you benefit from a consultation with a quantum dietician? A dismissive snort is fully justified. But all the woo around “quantum therapies” can make it hard to talk about science that is much more serious. In recent years, clinical research has suggested that exposure to light, as well as electric and magnetic fields, could help to treat everything from acne and hair loss to wounds and cancer. These therapies don’t necessarily involve quantum mechanics in any meaningful way. Still, there are hints from parallel experiments in test tubes that life might respond to electricity and magnetism via quantum effects – at least on some level. “We have something that works; we don’t really know why,” says Margaret Ahmad, a photobiologist at Sorbonne University in France who studies how electromagnetic fields affect living organisms. All this ties into …

Odd “butterfly” molecule could lead to new parts of the quantum realm

Odd “butterfly” molecule could lead to new parts of the quantum realm

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A laser system used to create butterfly molecules Prof. Herwig Ott A large, cold molecule that resembles a butterfly, with “wings” made from electrons, has been made for the first time, completing the search for a “zoo” of similar molecules. The result could provide a gateway to completely new parts of the quantum realm. Herwig Ott at RPTU University Kaiserslautern-Landau in Germany and his colleagues made the molecule by cooling rubidium atoms to a few millionths of a degree above absolute zero by using lasers and electromagnetic forces. The researchers then used lasers again to make some atoms very large by pushing their outermost electron very far from their nuclei. The quantum properties of atoms that have been cooled and enlarged in this way can be precisely manipulated with lasers, which the team leveraged to move a giant atom’s electron towards a normal-sized rubidium atom, binding them together to create a new type of molecule with extreme properties. Each molecule was about 25 nanometres in size – bigger than the diameter of a DNA strand …

3 things you need to know about quantum computers, from an expert

3 things you need to know about quantum computers, from an expert

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Quantum computers are strange-looking machines ROBERT GHEMENT/EPA/Shutterstock Picture a quantum computer. Are you imagining an ordinary computer, but somehow just better? If so, that would be a mistake, because quantum computers are fundamentally different. They rely on exotic quantum phenomena occurring between their constituent parts, known as qubits, but their strange nature often invites myths and misconceptions. Quantum computing expert Shayan Majidy at Harvard University, the lead author of Building Quantum Computers, is here to get you up to speed. 1. Quantum computers already exist I was just on a flight and another passenger asked me: “When we will we actually have quantum computers?” But they do exist and we use them daily! Scientists all over the world are using them, and some companies have even made them publicly available so people sitting in their homes can get access to quantum computers and use them. Having said that, quantum computers are not yet similar to something like large language models, where you just open your laptop and use it all the time. They are still …

Why do particle physicists like spending time in fields?

Why do particle physicists like spending time in fields?

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There is more than once kind of field Bennekom/Alamy When we were first preparing to launch my column for New Scientist, my editor asked me what I would like to call it. “Field notes from space-time,” I said. This title has a bit of a double entendre that might not be obvious, but was fun for me as a physicist. It is a reference to the scientific idea of taking notes while out in the field – a lab notebook of sorts. Simultaneously, it alludes to a specific concept that is very important in particle physics: the field itself. You might think that a field is a big open space you find on a farm, but in physics it is more abstract. Essentially, a field is a mathematical relation that assigns a number to each point in space and time. The intention is to characterise some physical phenomenon at that location. For example, when you feel the pull of a fridge magnet close to a refrigerator door, there is a magnetic force working between the …

The 50-year quest to create a quantum spin liquid may finally be over

The 50-year quest to create a quantum spin liquid may finally be over

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For minerologists, a mine is an invitation. The earth has been broken open, its veins laid bare – and those who enter hope to find unknown wonders. In the 1970s, Kali Kafi mine near the small Iranian town of Anarak fulfilled that hope. There, among the dusty desert rocks, Joachim Otteman and Darius Adib saw a bluish-green glow. They took samples of the glassy mineral and analysed its structure back in the lab. What they knew was that this geological species had never been catalogued – they named it anarakite, and it lay forgotten for decades. What they didn’t know was that the emerald glow they unearthed may have been hiding a remarkable quantum secret. This isn’t any ordinary rock. Anarakite – later renamed herbertsmithite – could be a rare type of matter known as a quantum spin liquid (QSL). Whether these occur naturally is hotly debated, but if the physicists who think they can are right, nature could be creating highly entangled states. Physicists know how to create entanglement, too, but only in limited …