In quantum mechanics, the whole can be much greater than the sum of its parts, according to new calculations. They suggest that several low-energy quantum states could be combined into a state containing regions that are dozens of times more energetic than any of the constituent components. The research may ultimately have real-world applications, such as in producing better high-resolution microscopes.
One of the more shocking revelations of quantum mechanics is that every object can be viewed as a wave if the circumstances are just right – and the mathematics of…
Time may not be a fundamental element of our physical reality. New calculations add credence to the idea that it emerges from quantum entanglement, in which two objects are so inextricably linked that disturbing one disrupts the other, no matter how distant they are.
“For centuries, time has entered physics as an essential ingredient that is not to be questioned. It is so deeply rooted in our conception of reality that people thought that a definition of time was not needed,” says Alessandro Coppo at…
These futuristic batteries could eventually charge electric vehicles at a fraction of today’s speeds
da-kuk/Getty Images
Quantum batteries could one day charge electronics much quicker than standard ones thanks to the odd quantum phenomenon of being able to be in two places at once.
Electrochemical batteries, including those that power remotes and cars, store energy from chemical reactions between metals. But quantum batteries would be built from quantum bits, or qubits, and extract energy from quantum processes, such as those involved in moving particles of light or atoms. Physicists expect that full-fledged…
For Alan Barr, it started during the covid-19 lockdowns. “I had a bit more time. I could sit and think,” he says.
He had enjoyed being part of the success at CERN’s Large Hadron Collider (LHC) near Geneva, Switzerland — the particle collider that discovered the Higgs boson. But now, he wondered, were they missing a trick? “I had spent long hours screwing bits of it together. And I thought, ‘Well, we’ve built this beautiful piece of apparatus, but maybe we could be doing more with it,’ ” he says.
The LHC is typically seen as a machine for finding new particles. But now Barr and a slew of other physicists are asking if it can also be used to probe the underlying meaning of quantum theory and why it paints reality as being so deeply weird.
That’s exactly what Barr and his colleagues are now investigating in earnest. Last year, they published the results of an experiment in which they showed that pairs of fundamental particles called top quarks could be put into the quantum state known as entanglement.
This was just the first of many entanglement experiments at particle colliders that could open up a whole new way of studying the nature of the universe. We can now ask why reality in quantum mechanics is so hard to pin down and what this has to do with experimenters — or even particles — having free will. Doing so could reveal whether space-time is fundamental or perhaps unveil a deeper reality that is even stranger than quantum mechanics. “We can do really different things with this collider,” says Barr.
Physicists have been searching for gravitons, the hypothetical particles thought to carry gravity, for decades. These have never been detected in space, but graviton-like particles have now been seen in a semiconductor. Using these to understand gravitons’ behaviour could help unite the general theory of relativity and quantum mechanics, which have long been at odds.
“This is a needle in a haystack [finding]. And the paper that started this whole thing is from way back in 1993,” says Loren Pfeiffer at Princeton University. He wrote that paper with several colleagues including Aron Pinczuk, who passed away in 2022 before they could find hints of the elusive particles.
Pinczuk’s students and collaborators, including Pfeiffer, have now completed the experiment the two began discussing 30 years ago. They focused on electrons within a flat piece of the semiconductor gallium arsenide, which they placed in a powerful refrigerator and exposed to a strong magnetic field. Under these conditions, quantum effects make the electrons behave strangely – they strongly interact with each other and form an unusual incompressible liquid.
This liquid is not calm but features collective motions where all the electrons move in concert, which can give rise to particle-like excitations. To examine those excitations, the team shined a carefully tuned laser on the semiconductor and analysed the light that scattered off it.
This revealed that the excitation had a kind of quantum spin that has only ever been theorised to exist in gravitons. Though this isn’t a graviton per se, it is the closest thing we have seen.
Ziyu Liu at Columbia University in New York who worked on the experiment says he and his colleagues knew that graviton-like excitations could exist in their semiconductor, but it took years to make the experiment precise enough to detect them. “From the theoretical side, the story was kind of complete, but in experiments, we were really not sure,” he says.
The experiment isn’t a true analogue to space-time – electrons are confined to a flat, two-dimensional space and move more slowly than objects governed by the theory of relativity.
But it is “extremely important” and bridges different branches of physics, like the physics of materials and theories of gravity, in a previously underappreciated way, says Kun Yang at Florida State University, who was not involved in the work.
However, Zlatko Papic at the University of Leeds in the UK cautions against equating the new finding with detection of gravitons in space. He says the two are sufficiently equivalent for electron systems like those in the new experiment to become testing grounds for some theories of quantum gravity, but not for every single quantum phenomenon that happens to space-time at cosmic scales.
Connections between this particle-like excitation and theoretical gravitons also raise new ideas about exotic electron states, says team member Lingjie Du at Nanjing University in China.
ARE there vastly many near-duplicates of you reading vastly many near-duplicates of this article in vastly many parallel universes? Is consciousness a fundamental property of all matter? Could reality be a computer simulation? Reader, I can hear your groans from here in California.
We are inclined to reject ideas like these on the grounds that they sound preposterous. And yet some of the world’s leading scientists and philosophers advocate for them. Why? And how should you, assuming you aren’t an expert, react to these sorts of hypotheses?
When we confront fundamental questions about the nature of reality, things quickly get weird. As a philosopher specialising in metaphysics, I submit that weirdness is inevitable, and that something radically bizarre will turn out to be true.
Which isn’t to say that every odd hypothesis is created equal. On the contrary, some weird possibilities are worth taking more seriously than others. Positing Zorg the Destroyer, hidden at the galactic core and pulling on protons with invisible strings, would rightly be laughed away as an explanation for anything. But we can mindfully evaluate the various preposterous-seeming ideas that deserve serious consideration, even in the absence of straightforward empirical tests.
The key is to become comfortable weighing competing implausibilities, something that we can all try – so long as we don’t expect to all arrive at the same conclusions.
Let us start by clarifying that we are talking here about questions monstrously large and formidable: the foundations of reality and the basis of our understanding of those foundations. What is the underlying structure…
A new type of cooling relies on an exotic quantum mechanical property rather than putting objects into cold environments like refrigerators – and it might one day help us chill things to temperatures lower than any we have reached before.
How cold or warm an object is depends on how its constituent atoms are jiggling, with more and faster jiggling corresponding to more heat and a higher temperature. As such, making objects colder involves finding ways to slow that atomic jiggling –…
An optical cavity like this could be used in a quantum engine
Max Planck Institute of Quantum Optics
A single atom inside of a reflective cavity could be enough to drive a piston in a tiny, quantum version of an engine.
The essential feature of any engine is that it converts heat into work which can then set mechanical parts into motion. For internal combustion engines, burning gas makes it expand and push on and pistons, which eventually results in car wheels or turbine blades moving. Álvaro Tejero at the University of Granada in Spain and…
