To store energy with a time crystal, make it a double. A mathematical analysis shows that putting two time crystals into a coordinated state could create a quantum battery-like device.
Time crystals differ from other quantum states of matter by having a structure that repeats in time – they cycle through the same set of configurations over and over without any energy input. Though physicists once worried that this would violate fundamental laws of physics and render them impossible, over the course of the past decade researchers have created…
An ion trap helped create a quantum defect in two places at once
ANDREW BROOKES, NATIONAL PHYSICAL LABORATORY/SCIENCE PHOTO LIBRARY
Exotic quantum rifts have been created with charged atoms, and they exist in a superposition of being in two places at once. This is a first step towards better understanding the behaviour of such quantum defects in everything from materials to an entire universe.
Defects are ubiquitous – think of tears in textiles or cloudy imperfections in shiny crystals – but in quantum systems, they can have the extra property of being topological. That means the overall structure of the…
Quantum theory is poking holes in our understanding of entropy
VICTOR de SCHWANBERG/SCIENCE PHOTO LIBRARY
Measuring disorder in the quantum realm is creating a bit of a mess. A mathematical study found that three different definitions of entropy that were previously thought to be equivalent don’t always match for quantum objects. This could have far-reaching implications, as it could force a rewrite of well-established models for thermodynamics.
When two objects are connected – say a container of hot gas is linked to a colder gas reservoir – the entropy of the colder one can increase because the two will…
Gravitational wave detectors use laser beams in tubes that span kilometres
The Virgo Collaboration
Gravitational waves that span thousands to billions of miles can be obscured in our detectors by the smallest of quantum fluctuations that permeate space-time. But now, researchers at the Laser Interferometer Gravitational-Wave Observatory (LIGO) have found a way to beat this quantum noise. And as a result, they are finding nearly twice as many cosmic events as before.
“We realised that quantum noise will be limiting us a long time ago. It’s not just a fancy [quantum] thing to demonstrate, it’s something that really affects the actual detector,” says Wenxuan Jia at the Massachusetts Institute of Technology.
LIGO detects gravitational waves, ripples in the fabric of space-time created by dramatic cosmic events like collisions between black holes. To do so, it fires a laser beam along each of its two 4-kilometre-long arms, which sit perpendicular to each other. A passing gravitational wave squashes and expands the part of space-time where these arms reside, introducing a small difference between the distances travelled by the two beams.
But that discrepancy is so tiny it can be hard to tell when it is caused by gravitational waves and when it is due to the nearly-imperceptible flickers of quantum fields that permeate all of space, including the laser light itself. The researchers found changing the quantum properties of the light could help them suppress the crackles of quantum fields and get a more distinct gravitational wave signal.
They added a series of devices to the detector, including a special crystal and several lenses and mirrors, which all work together to “squeeze” LIGO’s light into a quantum state where correlations between light particles diminish the flickering.
LIGO completed its first run with squeezed light in 2020, but the method only worked for gravitational waves with relatively high frequencies – those with lower frequencies actually produced more noisy signals than before. Jia and his colleagues modified the squeezing process to work equally well at both high and low frequencies before LIGO’s 2023 run. This change had a stunning effect: the number of gravitational waves it detected nearly doubled, effectively allowing the machine to reveal a larger part of our universe.
“Pushing the boundaries of quantum measurement has pushed the boundaries of space-time measurement, which is truly a beautiful thing,” says Chad Hanna at the Pennsylvania State University. He says this advanced precision will enable LIGO to see black hole mergers “all the way back to the formation of the first stars”.
Bruce Allen at the Max Planck Institute for Gravitational Physics in Germany says there are several new kinds of gravitational waves physicists would like to see with LIGO’s newfound precision. This includes those emitted constantly by bumpy neutron stars as they rotate, as opposed to the ones they emit when they collide with something, which has been the origin of most gravitational waves detected to date.
The upgrade also opens the door for fully new discoveries, as it could help probe the gravitational wave background that permeates space-time. “Every time you increase the sensitivity [of your detectors], you increase your chances of encountering the unexpected,” says Allen.
If the multiverse exists, our world could fit right in
MARK GARLICK/SCIENCE PHOTO LIBRARY/Getty Images
Could we live in a quantum multiverse without ever noticing its oddness? A simulation suggests that the answer may be “yes” surprisingly often.
“We live in a quantum world, as far as the experiments we do can tell. So then why do I end up having all these [non-quantum] classical experiences?” says Joseph Schindler at the Autonomous University of Barcelona in Spain. He and his colleagues explored this question and found that even in the multiverse, if the microscopic world is quantum the emergence…
Can effect come before cause in the quantum realm? Maybe not
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First comes cause, then comes effect – or does it? This order of events has previously been upended in the quantum realm, with the possibility of both A-causes-B and B-causes-A happening simultaneously. But a new mathematical analysis suggests this quantum quirk may be hemmed in by the very structure of space-time.
For more than a decade, physicists have been grappling with the idea of indefinite causal order –instances where it is impossible to tell whether cause came…
As one of the original architects of quantum theory, perhaps our most successful scientific idea, you would think that Niels Bohr would have been interested in the nature of reality. The subjects of his studies were atoms, electrons, photons – the things we think of as the fundamental ingredients of the universe.
But for Bohr, reality was actually none of his business. “It is wrong to think that the task of physics is to find out how nature is,” he said in an often-repeated quote from the early days of quantum theory. “Physics concerns what we can say about nature.”
Though this distinction may sound pedantic, it can’t be dismissed when it comes to quantum physics. The picture this theory paints of the subatomic world is perplexing: particles can seemingly exist in two places at once, time stands still and there is no such thing as empty space. Can that really be what reality is like?
Some physicists shrug off the question. Like Bohr, they aren’t talking about reality at all, only our pale perception of it. But many find this viewpoint deeply unsatisfying and want to believe in a world composed of sensible objects that exist independently of what we know about them. They are, in other words, realists. One of them is Robert Spekkens at the Perimeter Institute in Canada, who has a plan…
An experiment with beams of photons has confirmed quantum weirdness exists
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The world is as weird as we feared. A new experiment confirms yet again the existence of correlations between distant entangled quantum particles – and this time we have measured the phenomenon so precisely, there is only a minuscule chance it is a fluke.
This is sometimes called “spooky action at a distance”, a phrase used by Albert Einstein in the 1930s when he protested the possibility of two entangled particles exhibiting correlated behaviours across extreme distances, appearing…
Do quantum interactions help brain cells stay in sync?
Andriy Onufriyenko/Getty Images
Nerve fibres in the brain could produce pairs of particles linked by quantum entanglement. If backed by experimental observations, this phenomenon could explain how millions of cells in the brain synchronise their activity to make it function.
“When a brain is active, millions of neurons fire simultaneously,” says Yong-Cong Chen at Shanghai University in China. Doing so requires even distant cells to coordinate their timing – but what mechanism do they use? “If the power of evolution was looking for handy action over a distance, quantum entanglement…
Splitting qubits inside a quantum computer into high and low-energy groups can charge a battery
Shutterstock / Pavel Chukhov
A 19th-century thought experiment, considered for decades to break the laws of thermodynamics, has been brought to life inside a quantum computer and used to charge a quantum battery.
Physicist James Clerk Maxwell imagined his demon in 1867 while thinking about how to cheat the laws of thermodynamics. He considered two boxes of gas separated by a weightless door and a tiny demon that controls which particles can go through it. The demon uses this control to make one box hotter…
