- Trio win Nobel physics prize for tiny light pulses that give snapshot of atoms Reuters
- Nobel in medicine goes to 2 Penn scientists whose work enabled creation of mRNA vaccines 6abc Philadelphia
- Scientists Katalin Karikó and Drew Weissman win Nobel for mRNA vaccine: How their cutting edge technology helped us tame COVID-19 The Indian Express
- With Nobel Prize in medicine, a new laurel for ‘eds and meds’ in Philadelphia | Editorial The Philadelphia Inquirer
- Karikó and Weissman’s Nobel for mRNA Shows Power of Perseverance Bloomberg
Tag Archives: atoms
Dan Levitt’s ‘What’s Gotten Into You’ traces atoms’ long trip from the big bang to the human body
Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.
CNN
—
In its violent early years, Earth was a molten hellscape that ejected the moon after a fiery collision with another protoplanet, scientists now suspect. Later, it morphed from a watery expanse to a giant snowball that nearly snuffed out all existing life.
Then hyper-hurricanes with waves as high as 300 feet pummeled the newly thawed ocean. But that’s nothing compared with the celestial turmoil and fireworks in the 9 billion years before the birth of our planet.
Science and history documentarian Dan Levitt’s upcoming book, “What’s Gotten Into You: The Story of Your Body’s Atoms, From the Big Bang Through Last Night’s Dinner,” evokes a series of striking and often forceful images in tracing how our cells, elements, atoms and subatomic particles all found their way to our brains and bones and bodies. The book comes out on January 24.
“Now we know that the origin of the universe, the making of elements in stars, the creation of the solar system and Earth and the early history of our planet was incredibly tumultuous,” Levitt told CNN.
The nearly incomprehensible explosions, collisions and temperatures, though, were essential for life.
A disturbance in Jupiter’s orbit, for example, may have sent a hail of asteroids to Earth, seeding the planet with water in the process. And the molten iron forming Earth’s core has created a magnetic field that protects us from cosmic rays.
“So many things happened that could’ve gone another way,” Levitt said, “in which case we wouldn’t be here.”
Reconstructing the epic step-by-step journey of our atoms across billions of years, he said, has filled him with awe and gratitude.
“Sometimes when I look at people, I think, ‘Wow, you are such incredible organisms and our atoms all share the same deep history that goes back to the big bang,’ ” he said. He hopes that readers will recognize “that even the simplest cell is incredibly complex and worthy of great respect. And all people are, too.”
Our bodies contain 60 or so elements, including the torrent of hydrogen unleashed after the big bang and the calcium forged by dying stars known as red giants. As Levitt assembled the evidence for how they and more complex organic molecules made their way to us, he weaved in the tumultuous history of the scientific process itself.
He didn’t initially set out to parallel the turbulence in the universe with upheavals in the scientific world, but it definitely came with the territory. “So many scientific certainties have been overthrown since our great-grandparents were alive,” he said. “That’s part of the fun of the book.”
After Levitt finished his first draft, he realized to his surprise that part of the scientific turmoil was due to various kinds of recurring bias. “I wanted to get into the heads of scientists who made great discoveries — to see their advances as they did and understand how they were received at the time,” he said. “I was surprised that almost every time, the initial reaction to groundbreaking theories was skepticism and dismissal.”
Throughout the book, he pointed out six recurring mental traps that have blinded even brilliant minds, such as the view that it’s “too weird to be true” or that “if our current tools haven’t detected it, it doesn’t exist.”
Albert Einstein initially hated the strange idea of an expanding universe, for example, and had to be persuaded over time by Georges Lemaître, a little known but persistent Belgian priest and cosmologist. Stanley Miller, the “father of prebiotic chemistry” who ingeniously simulated early-Earth conditions in glass flasks, was a notoriously fierce opponent of the hypothesis that life could have evolved in the deep ocean, fueled by mineral-rich enzymes and super-heated vents. And so on.
“The history of science is littered with elder statesmen’s grand pronouncements of certainties that would soon be overturned,” Levitt writes in his book. Thankfully for us, the history of science is also full of radicals and freethinkers who delighted in poking holes in those pronouncements.
Levitt described how many of the leaps forward came about by researchers who never received due credit for their contributions. “I’m drawn to unsung heroes with dramatic stories that people haven’t heard before,” he said. “So, I was pleased that many of the most gripping stories in the book turned out to be about people who I hadn’t known about.”
They are scientists such as Austrian researcher Marietta Blau, who helped physicists see some of the first signs of subatomic particles; Dutch physician and philosopher Jan Ingenhousz, who discovered that sunlit leaves can create oxygen via photosynthesis; and chemist Rosalind Franklin, who was instrumental in working out the three-dimensional structure of DNA.
Wonders of the universe
The lightning spark of new ideas often struck independently around the world. To his surprise, Levitt found that multiple scientists worked out plausible scenarios for how life’s building blocks could have begun assembling.
“Our universe is awash in organic molecules — many of them are precursors to the molecules that we’re made of,” he said. “So I alternate between thinking that it’s just so improbable that creatures like us exist, and thinking that life must exist in many places in the universe.”
Nothing about our own journey from the big bang has been straightforward, though.
“If you try to envision how life evolved from the first organic molecules, it had to have been a herky-jerky process, full of twisted pathways and failures,” Levitt said. “Most of them must have gone nowhere. But evolution has a way of creating winners from countless experiments over long periods of time.”
Nature also has a way of recycling the building blocks to create new life. A nuclear physicist named Paul Aebersold found that “we swap out half of our carbon atoms every one to two months, and we replace a full 98 percent of all our atoms every year,” Levitt writes.
Like a house constantly under renovation, we are ever-changing and replacing old parts with new ones: our water, proteins and even cells, most of which we apparently replace every decade.
Eventually, our own cells will grow quiet, but their parts will reassemble into other forms of life. “Although we may die, our atoms don’t,” Levitt writes. “They revolve through life, soil, oceans, and sky in a chemical merry-go-round.”
Just like the death of stars, in other words, our own destruction opens up another remarkable world of possibility.
Dan Levitt’s ‘What’s Gotten Into You’ traces atoms’ long trip from the big bang to the human body
Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.
CNN
—
In its violent early years, Earth was a molten hellscape that ejected the moon after a fiery collision with another protoplanet, scientists now suspect. Later, it morphed from a watery expanse to a giant snowball that nearly snuffed out all existing life.
Then hyper-hurricanes with waves as high as 300 feet pummeled the newly thawed ocean. But that’s nothing compared with the celestial turmoil and fireworks in the 9 billion years before the birth of our planet.
Science and history documentarian Dan Levitt’s upcoming book, “What’s Gotten Into You: The Story of Your Body’s Atoms, From the Big Bang Through Last Night’s Dinner,” evokes a series of striking and often forceful images in tracing how our cells, elements, atoms and subatomic particles all found their way to our brains and bones and bodies. The book comes out on January 24.
“Now we know that the origin of the universe, the making of elements in stars, the creation of the solar system and Earth and the early history of our planet was incredibly tumultuous,” Levitt told CNN.
The nearly incomprehensible explosions, collisions and temperatures, though, were essential for life.
A disturbance in Jupiter’s orbit, for example, may have sent a hail of asteroids to Earth, seeding the planet with water in the process. And the molten iron forming Earth’s core has created a magnetic field that protects us from cosmic rays.
“So many things happened that could’ve gone another way,” Levitt said, “in which case we wouldn’t be here.”
Reconstructing the epic step-by-step journey of our atoms across billions of years, he said, has filled him with awe and gratitude.
“Sometimes when I look at people, I think, ‘Wow, you are such incredible organisms and our atoms all share the same deep history that goes back to the big bang,’ ” he said. He hopes that readers will recognize “that even the simplest cell is incredibly complex and worthy of great respect. And all people are, too.”
Our bodies contain 60 or so elements, including the torrent of hydrogen unleashed after the big bang and the calcium forged by dying stars known as red giants. As Levitt assembled the evidence for how they and more complex organic molecules made their way to us, he weaved in the tumultuous history of the scientific process itself.
He didn’t initially set out to parallel the turbulence in the universe with upheavals in the scientific world, but it definitely came with the territory. “So many scientific certainties have been overthrown since our great-grandparents were alive,” he said. “That’s part of the fun of the book.”
After Levitt finished his first draft, he realized to his surprise that part of the scientific turmoil was due to various kinds of recurring bias. “I wanted to get into the heads of scientists who made great discoveries — to see their advances as they did and understand how they were received at the time,” he said. “I was surprised that almost every time, the initial reaction to groundbreaking theories was skepticism and dismissal.”
Throughout the book, he pointed out six recurring mental traps that have blinded even brilliant minds, such as the view that it’s “too weird to be true” or that “if our current tools haven’t detected it, it doesn’t exist.”
Albert Einstein initially hated the strange idea of an expanding universe, for example, and had to be persuaded over time by Georges Lemaître, a little known but persistent Belgian priest and cosmologist. Stanley Miller, the “father of prebiotic chemistry” who ingeniously simulated early-Earth conditions in glass flasks, was a notoriously fierce opponent of the hypothesis that life could have evolved in the deep ocean, fueled by mineral-rich enzymes and super-heated vents. And so on.
“The history of science is littered with elder statesmen’s grand pronouncements of certainties that would soon be overturned,” Levitt writes in his book. Thankfully for us, the history of science is also full of radicals and freethinkers who delighted in poking holes in those pronouncements.
Levitt described how many of the leaps forward came about by researchers who never received due credit for their contributions. “I’m drawn to unsung heroes with dramatic stories that people haven’t heard before,” he said. “So, I was pleased that many of the most gripping stories in the book turned out to be about people who I hadn’t known about.”
They are scientists such as Austrian researcher Marietta Blau, who helped physicists see some of the first signs of subatomic particles; Dutch physician and philosopher Jan Ingenhousz, who discovered that sunlit leaves can create oxygen via photosynthesis; and chemist Rosalind Franklin, who was instrumental in working out the three-dimensional structure of DNA.
Wonders of the universe
The lightning spark of new ideas often struck independently around the world. To his surprise, Levitt found that multiple scientists worked out plausible scenarios for how life’s building blocks could have begun assembling.
“Our universe is awash in organic molecules — many of them are precursors to the molecules that we’re made of,” he said. “So I alternate between thinking that it’s just so improbable that creatures like us exist, and thinking that life must exist in many places in the universe.”
Nothing about our own journey from the big bang has been straightforward, though.
“If you try to envision how life evolved from the first organic molecules, it had to have been a herky-jerky process, full of twisted pathways and failures,” Levitt said. “Most of them must have gone nowhere. But evolution has a way of creating winners from countless experiments over long periods of time.”
Nature also has a way of recycling the building blocks to create new life. A nuclear physicist named Paul Aebersold found that “we swap out half of our carbon atoms every one to two months, and we replace a full 98 percent of all our atoms every year,” Levitt writes.
Like a house constantly under renovation, we are ever-changing and replacing old parts with new ones: our water, proteins and even cells, most of which we apparently replace every decade.
Eventually, our own cells will grow quiet, but their parts will reassemble into other forms of life. “Although we may die, our atoms don’t,” Levitt writes. “They revolve through life, soil, oceans, and sky in a chemical merry-go-round.”
Just like the death of stars, in other words, our own destruction opens up another remarkable world of possibility.
Mysterious Quantum Phenomenon Lets Us Peek Inside an Atom’s Heart : ScienceAlert
Silently churning away at the heart of every atom in the Universe is a swirling wind of particles that physics yearns to understand.
No probe, no microscope, and no X-ray machine can hope to make sense of the chaotic blur of quantum cogs whirring inside an atom, leaving physicists to theorize the best they can based on the debris of high-speed collisions inside particle colliders.
Researchers now have a new tool that is already providing them with a small glimpse into the protons and neutrons that form the nuclei of atoms, one based on the entanglement of particles produced as gold atoms brush past each other at speed.
Using the powerful Relativistic Heavy Ion Collider (RHIC) at the US Department of Energy’s Brookhaven National Laboratory, scientists have shown how it’s possible to glean precise details on the arrangement of gold’s protons and neutrons using a kind of quantum interference never before seen in an experiment.
“This technique is similar to the way doctors use positron emission tomography (PET scans) to see what’s happening inside the brain and other body parts,” says physicist James Daniel Brandenburg, formerly a Brookhaven researcher and now a member of the STAR collaboration.
“But in this case, we’re talking about mapping out features on the scale of femtometers – quadrillionths of a meter – the size of an individual proton.”
In textbook terms, the anatomy of a proton can be described as a trio of fundamental building blocks called quarks bound together by the exchange of a force-carrying particle called a gluon.
Were we to zoom in and observe this collaboration firsthand, we’d see nothing so neat. Particles and antiparticles pop in and out of existence in a seething foam of statistical madness, where the rules on particle distribution are anything but consistent.
Putting constraints on the movements and momenta of quarks and gluons requires some clever thinking, but hard evidence is what physicists really desire.
Unfortunately, simply shining a light onto a proton won’t result in a snapshot of its moving parts. Photons and gluons play by very different rules, meaning they are effectively invisible to one another.
There is a loophole, however. Imbued with enough energy, waves of light can occasionally churn up pairs of particles that sit on the brink of existence before vanishing again, among which are quarks and antiquarks.
Should this spontaneous emergence occur within earshot of an atom’s nucleus, the poltergeist flicker of opposing quarks could mix with the swirling volleys of gluons and temporarily form a conglomerate known as a rho particle, which in a fraction of a second shatters into a pair of charged particles called pions.
Those pairs consist of a positive pion, composed of an up quark and down antiquark, and a negative pion made up of a down quark and an up antiquark.
Tracing the path and properties of pions formed this way might tell us something about the hornet’s nest it was born in.
A couple of years ago, researchers at RHIC discovered it was possible to use the electromagnetic fields surrounding gold atoms moving at high speeds as a source of photons.
“In that earlier work, we demonstrated that those photons are polarized, with their electric field radiating outward from the center of the ion,” says Brookhaven physicist Zhangbu Xu.
“And now we use that tool, the polarized light, to effectively image the nuclei at high energy.”
When two gold atoms barely avoid crashing as they circle the collider in opposing directions, the photons of light passing through each nucleus can give birth to a rho particle and, therefore, pairs of charged pions.
The physicists measured the pions ejected from the passing gold nuclei and showed they did indeed have opposing charges. An analysis of the wave-like properties of the shower of particles showed signs of interference that could be traced back to the light’s polarization and hinted at something far less expected.
In typical applied and experimental quantum settings, entanglement is observed between the same kinds of particles: electrons with electrons, photons with photons, and atoms with atoms.
The patterns of interference observed in the analysis of the particles produced in this experiment could only be explained by the entanglement of non-identical particles – a negatively charged pion with a positively charged pion.
Though far from a theoretical anomaly, it’s far from an everyday occurrence in the laboratory, amounting to the first experimental observation of entanglement involving dissimilar particles.
Back-tracing the entangled interference patterns to the gold nuclei, the physicists could tease out a two-dimensional portrait of its gluon distribution, providing new insights into the structures of nuclear particles.
“Now we can take a picture where we can really distinguish the density of gluons at a given angle and radius,” says Brandenburg.
“The images are so precise that we can even start to see the difference between where the protons are and where the neutrons are laid out inside these big nuclei.”
This research was published in Science Advances.
Entanglement of many atoms discovered for the first time
Be it magnets or superconductors, materials are known for their various properties. However, these properties may change spontaneously under extreme conditions. Researchers at the Technische Universität Dresden (TUD) and the Technische Universität München (TUM) have discovered an entirely new type of these phase transitions. They display the phenomenon of quantum entanglement involving many atoms, which previously has only been observed in the realm of a few atoms. The results were recently published in the scientific journal Nature.
New fur for the quantum cat
In physics, Schroedinger’s cat is an allegory for two of the most awe-inspiring effects of quantum mechanics: entanglement and superposition. Researchers from Dresden and Munich have now observed these behaviors on a much larger scale than that of the smallest of particles. Until now, materials that display properties, like magnetism, have been known to have so-called domains—islands in which the materials properties are homogeneously either of one or a different kind (imagine them being either black or white, for example).
Looking at lithium holmium fluoride (LiHoF4), the physicists have now discovered a completely new phase transition, at which the domains surprisingly exhibit quantum mechanical features, resulting in their properties becoming entangled (being black and white at the same time). “Our quantum cat now has a new fur because we’ve discovered a new quantum phase transition in LiHoF4 which has not previously been known to exist,” says Matthias Vojta, Chair of Theoretical Solid State Physics at TUD.
Phase transitions and entanglement
We can easily observe the spontaneously changing properties of a substance if we look at water—at 100 degrees Celsius it evaporates into a gas, at zero degrees Celsius it freezes into ice. In both cases, these new states of matter form as a consequence of a phase transition where the water molecules rearrange themselves, thus changing the characteristics of the matter. Properties like magnetism or superconductivity emerge as a result of electrons undergoing phase transitions in crystals. For phase transitions at temperatures approaching absolute zero at -273.15 degrees Celsius, quantum mechanical effects such as entanglement and quantum phase transitions come into play.
“Even though there are more than 30 years of extensive research dedicated to phase transitions in quantum materials, we had previously assumed that the phenomenon of entanglement played a role only on a microscopic scale, where it involves only a few atoms at a time,” explains Christian Pfleiderer, Professor of Topology of Correlated Systems at the TUM.
Quantum entanglement is a state in which the entangled quantum particles exist in a shared superposition state that allows for usually mutually exclusive properties (e.g., black and white) to occur simultaneously. As a rule, the laws of quantum mechanics only apply to microscopic particles. The research teams from Munich and Dresden have now succeeded in observing effects of quantum entanglement on a much larger scale, that of thousands of atoms. For this, they have chosen to work with the well-known compound LiHoF4.
Spherical samples enable precision measurements
At very low temperatures, LiHoF4 acts as a ferromagnet where all magnetic moments spontaneously point in the same direction. If you then apply a magnetic field exactly vertically to the preferred magnetic direction, the magnetic moments will change direction, which is known as fluctuations. The higher the magnetic field strength, the stronger these fluctuations become, until, eventually, the ferromagnetism disappears completely at a quantum phase transition. This leads to the entanglement of neighboring magnetic moments. “If you hold up a LiHoF4 sample to a very strong magnet, it suddenly ceases to be spontaneously magnetic. This has been known for 25 years,” says Vojta.
What is new is what happens when you change the direction of the magnetic field. “We discovered that the quantum phase transition continues to occur, whereas it had previously been believed that even the smallest tilt of the magnetic field would immediately suppress it,” explains Pfleiderer. Under these conditions, however, it is not individual magnetic moments but rather extensive magnetic areas, so-called ferromagnetic domains, that undergo these quantum phase transitions. The domains constitute entire islands of magnetic moments pointing in the same direction.
“We have used spherical samples for our precision measurements. That is what enabled us to precisely study the behavior upon small changes in the direction of the magnetic field,” adds Andreas Wendl, who conducted the experiments as part of his doctoral dissertation.
From fundamental physics to applications
“We have discovered an entirely new type of quantum phase transitions where entanglement takes place on the scale of many thousands of atoms instead of just in the microcosm of only a few,” explains Vojta. “If you imagine the magnetic domains as a black-and-white pattern, the new phase transition leads to either the white or the black areas becoming infinitesimally small, i.e., creating a quantum pattern, bevor dissolving completely.” A newly developed theoretical model successfully explains the data obtained from the experiments.
“For our analysis, we generalized existing microscopic models and also took into account the feedback of the large ferromagnetic domains to the microscopic properties,” says Heike Eisenlohr, who performed the calculations as part of her Ph.D. thesis.
The discovery of the new quantum phase transitions is important as a foundation and general frame of reference for the research of quantum phenomena in materials, as well as for new applications. “Quantum entanglement is applied and used in technologies like quantum sensors and quantum computers, amongst other things,” says Vojta. Pfleiderer adds, “Our work is in the area of fundamental research, which, however, can have a direct impact on the development of practical applications, if you use the materials properties in a controlled way.”
Speed limits for quantum phenomena have been extended to macro-sized objects
More information:
Andreas Wendl et al, Emergence of mesoscale quantum phase transitions in a ferromagnet, Nature (2022). DOI: 10.1038/s41586-022-04995-5
Andreas Wendl et al, Emergence of mesoscale quantum phase transitions in a ferromagnet, Nature (2022). DOI: 10.1038/s41586-022-04995-5
Provided by
Dresden University of Technology
Dresden University of Technology
Citation:
New fur for the quantum cat: Entanglement of many atoms discovered for the first time (2022, September 2)
retrieved 3 September 2022
from https://phys.org/news/2022-09-fur-quantum-cat-entanglement-atoms.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.
Physicists harness quantum ‘time reversal’ to measure vibrating atoms
The quantum vibrations in atoms hold a miniature world of information. If scientists can accurately measure these atomic oscillations, and how they evolve over time, they can hone the precision of atomic clocks as well as quantum sensors, which are systems of atoms whose fluctuations can indicate the presence of dark matter, a passing gravitational wave, or even new, unexpected phenomena.
A major hurdle in the path toward better quantum measurements is noise from the classical world, which can easily overwhelm subtle atomic vibrations, making any changes to those vibrations devilishly hard to detect.
Now, MIT physicists have shown they can significantly amplify quantum changes in atomic vibrations, by putting the particles through two key processes: quantum entanglement and time reversal.
Before you start shopping for DeLoreans, no, they haven’t found a way to reverse time itself. Rather, the physicists have manipulated quantumly entangled atoms in a way that the particles behaved as if they were evolving backward in time. As the researchers effectively rewound the tape of atomic oscillations, any changes to those oscillations were amplified, in a way that could be easily measured.
In a paper appearing today in Nature Physics, the team demonstrates that the technique, which they dubbed SATIN (for signal amplification through time reversal), is the most sensitive method for measuring quantum fluctuations developed to date.
The technique could improve the accuracy of current state-of-the-art atomic clocks by a factor of 15, making their timing so precise that over the entire age of the universe the clocks would be less than 20 milliseconds off. The method could also be used to further focus quantum sensors that are designed to detect gravitational waves, dark matter, and other physical phenomena.
“We think this is the paradigm of the future,” says lead author Vladan Vuletic, the Lester Wolfe Professor of Physics at MIT. “Any quantum interference that works with many atoms can profit from this technique.”
The study’s MIT co-authors include first author Simone Colombo, Edwin Pedrozo-Peñafiel, Albert Adiyatullin, Zeyang Li, Enrique Mendez, and Chi Shu.
Entangled timekeepers
A given type of atom vibrates at a particular and constant frequency that, if properly measured, can serve as a very precise pendulum, keeping time in much shorter intervals than a kitchen clock’s second. But at the scale of a single atom, the laws of quantum mechanics take over, and the atom’s oscillation changes like the face of a coin each time it is flipped. Only by taking many measurements of an atom can scientists get an estimate of its actual oscillation—a limitation known as the Standard Quantum Limit.
In state-of-the-art atomic clocks, physicists measure the oscillation of thousands of ultracold atoms, many times over, to increase their chance of getting an accurate measurement. Still, these systems have some uncertainty, and their time-keeping could be more precise.
In 2020, Vuletic’s group showed that the precision of current atomic clocks could be improved by entangling the atoms—a quantum phenomenon by which particles are coerced to behave in a collective, highly correlated state. In this entangled state, the oscillations of individual atoms should shift toward a common frequency that would take far fewer attempts to accurately measure.
“At the time, we were still limited by how well we could read out the clock phase,” Vuletic says.
That is, the tools used to measure atomic oscillations were not sensitive enough to read out, or measure any subtle change in the atoms’ collective oscillations.
Reverse the sign
In their new study, instead of attempting to improve the resolution of existing readout tools, the team looked to boost the signal from any change in oscillations, such that they could be read by current tools. They did so by harnessing another curious phenomenon in quantum mechanics: time reversal.
It’s thought that a purely quantum system, such as a group of atoms that is completely isolated from everyday classical noise, should evolve forward in time in a predictable manner, and the atoms’ interactions (such as their oscillations) should be described precisely by the system’s “Hamiltonian”—essentially, a mathematical description of the system’s total energy.
In the 1980s, theorists predicted that if a system’s Hamiltonian were reversed, and the same quantum system was made to de-evolve, it would be as if the system was going back in time.
“In quantum mechanics, if you know the Hamiltonian, then you can track what the system is doing through time, like a quantum trajectory,” Pedrozo-Peñafiel explains. “If this evolution is completely quantum, quantum mechanics tells you that you can de-evolve, or go back and go to the initial state.”
“And the idea is, if you could reverse the sign of the Hamiltonian, every small perturbation that occurred after the system evolved forward would get amplified if you go back in time,” Colombo adds.
For their new study, the team studied 400 ultracold atoms of ytterbium, one of two atom types used today’s atomic clocks. They cooled the atoms to just a hair above absolute zero, at temperatures where most classical effects such as heat fade away and the atoms’ behavior is governed purely by quantum effects.
The team used a system of lasers to trap the atoms, then sent in a blue-tinged “entangling” light, which coerced the atoms to oscillate in a correlated state. They let the entangled atoms evolve forward in time, then exposed them to a small magnetic field, which introduced a tiny quantum change, slightly shifting the atoms’ collective oscillations.
Such a shift would be impossible to detect with existing measurement tools. Instead, the team applied time reversal to boost this quantum signal. To do this, they sent in another, red-tinged laser that stimulated the atoms to disentangle, as if they were evolving backward in time.
They then measured the particles’ oscillations as they settled back into their unentangled states, and found that their final phase was markedly different from their initial phase—clear evidence that a quantum change had occurred somewhere in their forward evolution.
The team repeated this experiment thousands of times, with clouds ranging from 50 to 400 atoms, each time observing the expected amplification of the quantum signal. They found their entangled system was up to 15 times more sensitive than similar unentangled atomic systems. If their system is applied to current state-of-the-art atomic clocks, it would reduce the number of measurements these clocks require, by a factor of 15.
Going forward, the researchers hope to test their method on atomic clocks, as well as in quantum sensors, for instance for dark matter.
“A cloud of dark matter floating by Earth could change time locally, and what some people do is compare clocks, say, in Australia with others in Europe and the U.S. to see if they can spot sudden changes in how time passes,” Vuletic says. “Our technique is exactly suited to that, because you have to measure quickly changing time variations as the cloud flies by.”
New type of atomic clock could help scientists detect dark matter and study gravity’s effect on time
More information:
Simone Colombo et al, Time-reversal-based quantum metrology with many-body entangled states, Nature Physics (2022). DOI: 10.1038/s41567-022-01653-5
Simone Colombo et al, Time-reversal-based quantum metrology with many-body entangled states, Nature Physics (2022). DOI: 10.1038/s41567-022-01653-5
Provided by
Massachusetts Institute of Technology
Massachusetts Institute of Technology
Citation:
Physicists harness quantum ‘time reversal’ to measure vibrating atoms (2022, July 14)
retrieved 15 July 2022
from https://phys.org/news/2022-07-physicists-harness-quantum-reversal-vibrating.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.
Physicists Say They’ve Built an Atom Laser That Can Run ‘Forever’
A new breakthrough has allowed physicists to create a beam of atoms that behaves the same way as a laser, and that can theoretically stay on “forever”.
This might finally mean the technology is on its way to practical application, although significant limitations still apply.
Nevertheless, this is a huge step forward for what is known as an “atom laser” – a beam made of atoms marching as a single wave that could one day be used for testing fundamental physical constants, and engineering precision technology.
Atom lasers have been around for a minute. The first atom laser was created by a team of MIT physicists back in 1996. The concept sounds pretty simple: just as a traditional light-based laser consists of photons moving with their waves in sync, a laser made of atoms would require their own wave-like nature to align before being shuffled out as a beam.
As with many things in science, however, it is easier to conceptualize than to realize. At the root of the atom laser is a state of matter called a Bose-Einstein condensate, or BEC.
A BEC is created by cooling a cloud of bosons to just a fraction above absolute zero. At such low temperatures, the atoms sink to their lowest possible energy state without stopping completely.
When they reach these low energies, the particles’ quantum properties can no longer interfere with each other; they move close enough to each other to sort of overlap, resulting in a high-density cloud of atoms that behaves like one ‘super atom’ or matter wave.
However, BECs are something of a paradox. They’re very fragile; even light can destroy a BEC. Given that the atoms in a BEC are cooled using optical lasers, this usually means that a BEC’s existence is fleeting.
Atom lasers that scientists have managed to achieve to date have been of the pulsed, rather than continuous variety; and involve firing off just one pulse before a new BEC needs to be generated.
In order to create a continuous BEC, a team of researchers at the University of Amsterdam in the Netherlands realized something needed to change.
“In previous experiments, the gradual cooling of atoms was all done in one place. In our setup, we decided to spread the cooling steps not over time, but in space: we make the atoms move while they progress through consecutive cooling steps,” explained physicist Florian Schreck.
“In the end, ultracold atoms arrive at the heart of the experiment, where they can be used to form coherent matter waves in a BEC. But while these atoms are being used, new atoms are already on their way to replenish the BEC. In this way, we can keep the process going – essentially forever.”
That ‘heart of the experiment’ is a trap that keeps the BEC shielded from light, a reservoir that can be continuously replenished for as long as the experiment runs.
Protecting the BEC from the light produced by the cooling laser, however, while simple in theory, was again a bit more difficult in practice. Not only were there technical hurdles, but there were also bureaucratic and administrative ones too.
“On moving to Amsterdam in 2013, we began with a leap of faith, borrowed funds, an empty room, and a team entirely funded by personal grants,” said physicist Chun-Chia Chen, who led the research.
“Six years later, in the early hours of Christmas morning 2019, the experiment was finally on the verge of working. We had the idea of adding an extra laser beam to solve a last technical difficulty, and instantly every image we took showed a BEC, the first continuous-wave BEC.”
Now that the first part of the continuous atom laser has been realized – the “continuous atom” part – the next step, the team said, is working on maintaining a stable atom beam. They could achieve this by transferring the atoms to an untrapped state, thereby extracting a propagating matter wave.
Because they used strontium atoms, a popular choice for BECs, the prospect opens exciting opportunities, they said. Atom interferometry using strontium BECs, for example, could be used to conduct investigations of relativity and quantum mechanics, or detect gravitational waves.
“Our experiment is the matter wave analogue of a continuous-wave optical laser with fully reflective cavity mirrors,” the researchers wrote in their paper.
“This proof-of-principle demonstration provides a new, hitherto missing piece of atom optics, enabling the construction of continuous coherent-matter-wave devices.”
The research has been published in Nature.
The ‘Cosmic Dawn’ of Our Universe Ended Far Later Than We Thought
For tens of millions of years, our newborn Universe was shrouded in hydrogen. Bit by bit, this vast mist was torn apart by the light of the very first stars in a dawn that defined the shape of the emerging cosmos.
Having a timeline for this colossal shift would go a long way in helping us understand the Universe’s evolution, yet so far our best attempts have been fuzzy estimates based on low-quality data.
An international team of astronomers led by the Max Planck Institute for Astronomy in Germany used the light from dozens of distant objects called quasars to strip away uncertainties, determining the last major wisps of hydrogen ‘fog’ burned away far later than we first thought, more than a billion years after the Big Bang.
The first 380,000 years were a static hiss of subatomic particles congealing out of the cooling vacuum of expanding space-time.
Once the temperature dropped, hydrogen atoms formed – simple structures consisting of solitary protons teaming up with single electrons.
Soon the entire Universe was filled with uncharged atoms, a sea of them bobbing back and forth in the infinite darkness.
Where crowds of the neutral hydrogen atoms collected under the unpredictable nudge of quantum laws, gravity took over, pulling more and more gas into balls where nuclear fusion could erupt.
This first sun-rise – the breaking of cosmic dawn – bathed the surrounding hydrogen fog in radiation, driving their electrons from their protons and turning the atoms back into the ions they once were.
Just how long this dawn took, from the first light of those early stars to the reionization of the last remaining pockets of primordial hydrogen, has never been clear.
Studies conducted more than 50 years ago made use of the way light from violently active galactic cores (called quasars) was absorbed by interceding gas floating about in the nearby intergalactic medium. Find a series of quasars stretching into the distance, you can effectively see a timeline of neutral hydrogen gas being ionized.
Knowing the theory is one thing. In practical terms, it’s hard to interpret a precise timeline from a handful of quasars. Not only is their light distorted by the expansion of the Universe, but it also passes through pockets of neutral hydrogen formed well after the cosmic dawn.
To get a better sense of this stutter of ionized hydrogen across the sky, researchers supersized their sample, tripling the previous number of high-quality spectral data by analyzing the light from a total of 67 quasars.
The goal was to better understand the impact of these fresher pockets of hydrogen atoms, allowing the researchers to better identify more distant bursts of ionization.
According to their own figures, the last dregs of original hydrogen fell to the rays of first-generation starlight around 1.1 billion years after the Big Bang.
“Until a few years ago, the prevailing wisdom was that reionization completed almost 200 million years earlier,” says astronomer Frederick Davies from the Max Planck Institute for Astronomy in Germany.
“Here we now have the strongest evidence yet that the process ended much later, during a cosmic epoch more readily observable by current generation observational facilities.”
Future technology capable of directly detecting the spectral lines emitted by the reionization of hydrogen should be able to further clarify not just when this epoch ended, but provide critical details on how it unfolded.
“This new dataset provides a crucial benchmark against which numerical simulations of the Universe’s first billion years will be tested for years to come,” says Davies.
This research was published in the Monthly Notices of the Royal Astronomical Society.
Two Time Crystals Have Been Successfully Linked Together For The First Time
Physicists have just taken an amazing step towards quantum devices that sound like something out of science fiction.
For the first time, isolated groups of particles behaving like bizarre states of matter known as time crystals have been linked into a single, evolving system that could be incredibly useful in quantum computing.
Following the first observation of the interaction between two time crystals, detailed in a paper two years ago, this is the next step towards potentially harnessing time crystals for practical purposes, such as quantum information processing.
Time crystals, only officially discovered and confirmed a few years ago in 2016, were once thought to be physically impossible. They are a phase of matter very similar to normal crystals, but for one additional, peculiar, and very special property.
In regular crystals, the atoms are arranged in a fixed, three-dimensional grid structure, like the atomic lattice of a diamond or quartz crystal. These repeating lattices can differ in configuration, but any movement they exhibit comes exclusively from external pushes.
In time crystals, the atoms behave a bit differently. They exhibit patterns of movement in time that can’t be so easily explained by an external push or shove. These oscillations – referred to as ‘ticking’ – are locked to a regular and particular frequency.
Theoretically, time crystals tick at their lowest possible energy state – known as the ground state – and are therefore stable and coherent over long periods of time. So, where the structure of regular crystals repeats in space, in time crystals it repeats in space and time, thus exhibiting perpetual ground state motion.
“Everybody knows that perpetual motion machines are impossible,” says physicist and lead author Samuli Autti of Lancaster University in the UK.
“However, in quantum physics perpetual motion is okay as long as we keep our eyes closed. By sneaking through this crack we can make time crystals.”
The time crystals the team have been working with consist of quasiparticles called magnons. Magnons are not true particles, but consist of a collective excitation of the spin of electrons, like a wave that propagates through a lattice of spins.
Magnons emerge when helium-3 – a stable isotope of helium with two protons but just one neutron – is cooled to within one ten thousandth of a degree of absolute zero. This creates what is called a B-phase superfluid, a zero-viscosity fluid with low pressure.
In this medium, time crystals formed as spatially distinct Bose-Einstein condensates, each consisting of a trillion magnon quasiparticles.
A Bose-Einstein condensate is formed from bosons cooled to just a fraction above absolute zero (but not reaching absolute zero, at which point atoms stop moving).
This causes them to sink to their lowest-energy state, moving extremely slowly, and coming together close enough to overlap, producing a high density cloud of atoms that acts like one ‘super atom’ or matter wave.
When the two time crystals were allowed to touch each other, they exchanged magnons. This exchange influenced the oscillation of each of the time crystals, creating a single system with an option of functioning in two, discrete states.
In quantum physics, objects that can have more than one state exist in a mix of those states before they’ve been pinned down by a clear measurement. So having a time crystal operating in a two-state system provides rich new pickings as a basis for quantum-based technologies.
Time crystals are a fair way from being deployed as qubits, as there are a significant number of hurdles to solve first. But the pieces are starting to fall into place.
Earlier this year, a different team of physicists announced that they had successfully created room temperature time crystals that don’t need to be isolated from their ambient surroundings.
More sophisticated interactions between time crystals, and the fine control thereof, will need to be developed further, as will observing interacting time crystals without the need for cooled superfluids. But scientists are optimistic.
“It turns out putting two of them together works beautifully, even if time crystals should not exist in the first place,” Autti says. “And we already know they also exist at room temperature.”
The research has been published in Nature Communications.
Warp drive experiment to turn atoms invisible could finally test Stephen Hawking’s most famous prediction
A new warp speed experiment could finally offer an indirect test of famed physicist Stephen Hawking’s most famous prediction about black holes.
The new proposal suggests that, by nudging an atom to become invisible, scientists could catch a glimpse of the ethereal quantum glow that envelops objects traveling at close to the speed of light.
The glow effect, called the Unruh (or Fulling-Davies-Unruh) effect, causes the space around rapidly accelerating objects to seemingly be filled by a swarm of virtual particles, bathing those objects in a warm glow. As the effect is closely related to the Hawking effect — in which virtual particles known as Hawking radiation spontaneously pop up at the edges of black holes — scientists have long been eager to spot one as a hint of the other’s existence.
Related: ‘X particle’ from the dawn of time detected inside the Large Hadron Collider
But spotting either effect is incredibly hard. Hawking radiation only occurs around the terrifying precipice of a black hole, and achieving the acceleration needed for the Unruh effect would probably need a warp drive. Now, a groundbreaking new proposal, published in an April 26 study in the journal Physical Review Letters, could change that. Its authors say they have uncovered a mechanism to dramatically boost the strength of the Unruh effect through a technique that can effectively turn matter invisible.
“Now at least we know there is a chance in our lifetimes where we might actually see this effect,” co-author Vivishek Sudhir, an assistant professor of mechanical engineering at MIT and a designer of the new experiment, said in a statement. “It’s a hard experiment, and there’s no guarantee that we’d be able to do it, but this idea is our nearest hope.”
First proposed by scientists in the 1970s, the Unruh effect is one of many predictions to come out of quantum field theory. According to this theory, there is no such thing as an empty vacuum. In fact, any pocket of space is crammed with endless quantum-scale vibrations that, if given sufficient energy, can spontaneously erupt into particle-antiparticle pairs that almost immediately annihilate each other. And any particle — be it matter or light — is simply a localized excitation of this quantum field.
In 1974, Stephen Hawking predicted that the extreme gravitational force felt at the edges of black holes — their event horizons — would also create virtual particles.
Gravity, according to Einstein’s theory of general relativity, distorts space-time, so that quantum fields get more warped the closer they get to the immense gravitational tug of a black hole’s singularity. Because of the uncertainty and weirdness of quantum mechanics, this warps the quantum field, creating uneven pockets of differently moving time and subsequent spikes of energy across the field. It is these energy mismatches that make virtual particles emerge from what appears to be nothing at the fringes of black holes.
“Black holes are believed to be not entirely black,” lead author Barbara Šoda, a doctoral student in physics at the University of Waterloo in Canada, said in a statement. “Instead, as Stephen Hawking discovered, black holes should emit radiation.”
Much like the Hawking effect, the Unruh effect also creates virtual particles through the weird melding of quantum mechanics and the relativistic effects predicted by Einstein. But this time, instead of the distortions being caused by black holes and the theory of general relativity, they come from near light-speeds and special relativity, which dictates that time runs slower the closer an object gets to the speed of light.
According to quantum theory, a stationary atom can only increase its energy by waiting for a real photon to excite one of its electrons. To an accelerating atom, however, fluctuations in the quantum field can add up to look like real photons. From an accelerating atom’s perspective, it will be moving through a crowd of warm light particles, all of which heat it up. This heat would be a telltale sign of the Unruh effect.
But the accelerations required to produce the effect are far beyond the power of any existing particle accelerator. An atom would need to accelerate to the speed of light in less than a millionth of a second — experiencing a g force of a quadrillion meters per second squared — to produce a glow hot enough for current detectors to spot.
“To see this effect in a short amount of time, you’d have to have some incredible acceleration,” Sudhir said. “If you instead had some reasonable acceleration, you’d have to wait a ginormous amount of time — longer than the age of the universe — to see a measurable effect.”
To make the effect realizable, the researchers proposed an ingenious alternative. Quantum fluctuations are made denser by photons, which means that an atom made to move through a vacuum while being hit by light from a high-intensity laser could, in theory, produce the Unruh effect, even at fairly small accelerations. The problem, however, is that the atom could also interact with the laser light, absorbing it to raise the atom’s energy level, producing heat that would drown out the heat generated by the Unruh effect.
But the researchers found yet another workaround: a technique they call acceleration-induced transparency. If the atom is forced to follow a very specific path through a field of photons, the atom will not be able to “see” the photons of a certain frequency, making them essentially invisible to the atom. So by daisy-chaining all these workarounds, the team would then be able to test for the Unruh effect at this specific frequency of light.
Making that plan a reality will be a tough task. The scientists plan to build a lab-size particle accelerator that will accelerate an electron to light speeds while hitting it with a microwave beam. If they’re able to detect the effect, they plan to conduct experiments with it, especially those that will enable them to explore the possible connections between Einstein’s theory of relativity and quantum mechanics.
“The theory of general relativity and the theory of quantum mechanics are currently still somewhat at odds, but there has to be a unifying theory that describes how things function in the universe,” co-author Achim Kempf, a professor of applied mathematics at the University of Waterloo, said in a statement. “We’ve been looking for a way to unite these two big theories, and this work is helping to move us closer by opening up opportunities for testing new theories against experiments.”
Originally published on Live Science.