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Can’t Use Quantum Entanglement To Communicate Faster Than Light

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Chris Monroe, University of Maryland

One of the most fundamental rules of physics, undisputed since Einstein first laid it out in 1905, is that no information-carrying signal of any type can travel through the Universe faster than the speed of light. Particles, either massive or massless, are required for transmitting information from one location to another, and those particles are mandated to travel either below (for massive) or at (for massless) the speed of light, as governed by the rules of relativity.

Since the development of quantum mechanics, however, many have sought to leverage the power of quantum entanglement to subvert this rule, devising clever schemes to attempt to transmit information to “cheat” relativity and communicate faster-than-light after all. Although it’s an admirable attempt to work around the rules of our Universe, faster-than-light communication is still an impossibility. Here’s the science of why.

Nicu Buculei / flickr

Conceptually, quantum entanglement is a simple idea. You can start by imagining the classical Universe and one of the simplest “random” experiments you could perform: conducting a coin flip. If you and I each have a fair coin and flip it, we’d each expect that there’s a 50/50 chance of each of us getting heads and a 50/50 chance that each of us would get tails. Your results and my results should not only be random, they should be independent and uncorrelated: whether I get heads or tails should still have 50/50 odds irrespective of what you get with your flip.

But if this isn’t a classical system after all, and a quantum one instead, it’s possible that your coin and my coin will be entangled. We might each still have a 50/50 chance of getting heads or tails, but if you flip your coin and measure heads, you’ll instantly be able to statistically predict to better than 50/50 accuracy whether my coin was likely to land on either heads or tails.

Melissa Meister, of laser photons through a beam splitter

How is this possible? In quantum physics, there exists a phenomenon known as quantum entanglement, which is where you create more than one quantum particle — each with their own individual quantum state — where you know something important about the sum of both states together. It’s as though there’s an invisible thread connecting your coin and my coin, and when one of us makes a measurement about the coin we have, we instantly know something about the state of the other coin that goes beyond the familiar classical randomness.

This isn’t mere theoretical work, either. We’ve created pairs of entangled quanta (photons, to be specific) that are then carried away from one another until they’re separated by large distances, then we have two independent measurement apparatuses that tell us what the quantum state of each particle is. We make those measurements as close to simultaneously as possible, and then get together to compare our results.

Richard Gill, 22 December 2013, drawn with R

What we find, perhaps surprisingly, is that your results and my results are correlated! We’ve separated two photons by distances of hundreds of kilometers before making those measurements, and then measuring their quantum states within nanoseconds of one another. If one of those photons has spin +1, the other one’s state can be predicted to about a 75% accuracy, rather than the standard 50%.

Moreover, we can “know” that information instantaneously, rather than waiting for the other measurement apparatus to send us the results of that signal, which would take about a millisecond. It seems, on the surface, that we can know some information about what’s going on at the other end of the entangled experiment not only faster than light, but tens of thousands of times faster than the speed of light could ever transmit information.

Wikimedia Commons user David Koryagin

Does that mean, though, that we can use quantum entanglement to communicate information at faster-than-light speeds?

It might seem so. For example, you might attempt to concoct an experiment as follows:

  • You prepare a large number of entangled quantum particles at one (source) location.
  • You transport one set of the entangled pairs a long distance away (to the destination) while keeping the other set at the source.
  • You have an observer at the destination look for some sort of signal, and force their entangled particles into either the +1 state (for a positive signal) or a -1 state (for a negative signal).
  • Then, you make your measurements of the entangled pairs at the source, and determine with better than 50/50 likelihood what state was chosen by the observer at the destination.

Dr. Tonomura and Belsazar of Wikimedia Commons

This seems like a great setup for enabling faster-than-light communication. All you need is a sufficiently prepared system of entangled quantum particles, an agreed-upon system for what the various signals will mean when you make your measurements, and a pre-determined time at which you’ll make those critical measurements. From even light-years away, you can instantly learn about what was measured at a destination by observing the particles you’ve had with you all along.

Right?

It’s an extremely clever scheme, but one that won’t pay off at all. When you, at the original source, go to make these critical measurements, you’ll discover something extremely disappointing: your results simply show 50/50 odds of being in the +1 or -1 state. It’s as though there’s never been any entanglement at all.

Chad Orzel

Where did our plan fall apart? It was at the step where we had the observer at the destination make an observation and try to encode that information into their quantum state.

When you take that step — forcing one member of an entangled pair of particles into a particular quantum state — you break the entanglement between the two particles. That is to say, the other member of the entangled pair is completely unaffected by this “forcing” action, and its quantum state remains random, as a superposition of +1 and -1 quantum states. But what you’ve done is completely break the correlation between the measurement results. The state you’ve “forced” the destination particle into is now 100% unrelated to the quantum state of the source particle.

Wikimedia Commons user Patrick Edwin Moran

The only way that this problem could be circumvented is if there were some way of making a quantum measurement to force a particular outcome. (Note: this is not something permitted by the laws of physics.)

If you could do this, then someone at the destination could conduct observations — for example, learning whether a planet they were visiting were inhabited or not — and then use some unknown process to:

  • measure their quantum particle’s state,
  • where the outcome will turn out to be +1 if the planet is inhabited,
  • or -1 if the planet is uninhabited,
  • and thereby enable the source observer with the entangled pairs to instantaneously figure out whether this distant planet is inhabited or not.

Unfortunately, the results of a quantum measurement are unavoidably random; you cannot encode a preferred outcome into a quantum measurement.

Maksim / CSTAR of Wikimedia Commons

As quantum physicist Chad Orzel has written, there is a big difference between making a measurement (where the entanglement between pairs is maintained) and forcing a particular result — which itself is a change of state — followed by a measurement (where the entanglement is not maintained). If you want to control, rather than simply measure, the state of a quantum particle, you’ll lose your knowledge of the full state of the combined system as soon as you make that change-of-state operation happen.

Quantum entanglement can only be used to gain information about one component of a quantum system by measuring the other component so long as the entanglement remains intact. What you cannot do is create information at one end of an entangled system and somehow send it over to the other end. If you could somehow make identical copies of your quantum state, faster-than-light communication would be possible after all, but this, too, is forbidden by the laws of physics.

MinutePhysics / YouTube

There’s an awful lot that you can do by leveraging the bizarre physics of quantum entanglement, such as by creating a quantum lock-and-key system that’s virtually unbreakable with purely classical computations. But the fact that you cannot copy or clone a quantum state — as the act of merely reading the state fundamentally changes it — is the nail-in-the-coffin of any workable scheme to achieve faster-than-light communication with quantum entanglement.

There are a lot of subtleties associated with how quantum entanglement actually works in practice, but the key takeaway is this: there is no measurement procedure you can undertake to force a particular outcome while maintaining the entanglement between particles. The result of any quantum measurement is unavoidably random, negating this possibility. As it turns out, God really does play dice with the Universe, and that’s a good thing. No information can be sent faster-than-light, allowing causality to still be maintained for our Universe.

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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