Posted on 05/09/2019 4:33:28 PM PDT by ETL
For the first time, researchers have performed a version of the famous double-slit experiment with antimatter particles.
The double-slit experiment demonstrates one of the fundamental tenets of quantum physics: that pointlike particles are also waves.
In the standard version of the experiment, particles travel through a pair of slits in a solid barrier.
On a screen on the other side, an interference pattern typical of waves appears.
Crests and troughs emerging from each slit reinforce each other or cancel each other out as they overlap, creating alternating bands of high and low particle density on the screen.
This kind of experiment has revealed the wave-particle duality of photons, electrons, atoms and even large molecules (SN: 11/20/10, p. 20).
But its very difficult to generate a strong, uniform beam of antiparticles to do the experiment with antimatter.
Now, a new double-slitstyle experiment, reported online May 3 in Science Advances, has confirmed the wavelike nature of the electrons antimatter counterpart: the positron.
The researchers designed a device in which positrons, generated through the radioactive decay of the isotope sodium-22, travel through two successive rows of vertical rods less than a micrometer thick.
The gaps between these rods, each a few hundred nanometers across, work like the slits in the classic double-slit experiment.
The positron waves propagate out to a nuclear emulsion detector, where the antiparticles alter the chemical structure of silver bromide crystals. ..."
(Excerpt) Read more at sciencenews.org ...
One of the strangest aspects of quantum physics is entanglement: If you observe a particle in one place, another particle, even one light-years away, will instantly change its properties, as if the two are connected by a mysterious communication channel.
Scientists have observed this phenomenon in tiny objects such as atoms and electrons.
But in two new studies, researchers report seeing entanglement in devices nearly visible to the naked eye.
There really is an interesting open question, which is: How far can you go up in scale? says Andrew Armour, a physicist at the University of Nottingham in the United Kingdom who wasnt involved in the work.
The advance could also pave the way for ultrasensitive measurements of gravity and a hack-proof quantum internet.
Albert Einstein colorfully dismissed quantum entanglementthe ability of separated objects to share a condition or stateas spooky action at a distance.
Over the past few decades, however, physicists have demonstrated the reality of spooky action over ever greater distanceseven from Earth to a satellite in space.
But the entangled particles have typically been tiny, which makes it easier to shield their delicate quantum states from the noisy world.
Two research groups have now scaled up entanglement to engineered objects barely visible to the naked eye.
Simon Gröblacher, a physicist at Delft University of Technology in the Netherlands, and his colleagues etched beams about 10 micrometers long into silicon chips.
The beams, roughly the size of a bacterium, could oscillate up and down like a plucked guitar string.
The researchers connected the chips with an optical fiber and cooled the whole setup close to absolute zero to damp out vibrations.
Then, using cleverly controlled laser pulses, the team added just enough energy to get one beam vibrating a bit more strongly than the other.
By measuring light coming out of the apparatus, the researchers verified that the energy boost occurred but did not learn which beam got the energy, meaning that the added energy was shared by both beams, the hallmark of quantum entanglement.
The delicate entangled state lasted just a fraction of a second, the group reports today in Nature.
Mika Sillanpää, a physicist at Aalto University in Finland, and his colleagues took a different approach, manufacturing pairs of aluminum drum heads, or vibrating disks, about the width of a human hair onto a silicon chip.
After cooling the setup, the researchers used microwaves to nudge the drum heads into correlated motions, as one throbbed up and down, the other did the opposite.
A second set of microwave pulses probed the motions, and an analysis of the signals showed the drum heads shared a single quantum state, the team reports in a second Nature paper.
When we took the data, we had no idea if we were entangled or not, Sillanpää says.
It turns out the answer was yes. The entanglement can last indefinitely, he saysas long as the drum heads stay immersed in their microwave bath.
The two setups have different potential applications.
Gröblacher designed his beams to vibrate at the same rate as light sent through fiber-optics, to make them compatible with existing telecommunications systems.
The setup is completely engineerable, Gröblacher says.
If he can get the entangled states to last longer and increase the distance between chips, he envisions such devices serving as nodes in an eventual quantum internet that could transmit ultrasecure information between future quantum-enabled computers.
Sillanpää says his drumheads may be better suited to precision measurement.
Because quantum sensors are so sensitive, they excel at picking up extremely weak signals such as gravitational waves, the space-time ripples that were recently detected for the first time.
As the devices get larger, they could also test theories of gravity that extend Einsteins general theory of relativity into the quantum realm, connecting two areas of physics that have remained stubbornly separate.
Both experiments have pros and cons, says John Teufel, a physicist at the National Institute of Standards and Technology in Boulder, Colorado.
The entanglement of Gröblachers beams was short-lived, but it was detected with certainty.
Sillanpääs entanglement was longer-lasting, but his team needed a complicated chain of theoretical reasoning to infer that the drum heads motions were truly entangled.
Ideally what youd want is a little bit of both, Teufel says.
Regardless, he says, the results are very exciting first steps.
Thanks ETL.
I watch Star Trek so I know about anti-matter and such : )
Thanks for your multiple links on entanglement and gravitational waves.
Very helpful.
Fascinating stuff.
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