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Wave–particle duality quantified for the first time
Physics World ^
| 9/1/2021
| Karmela Padavic-Callaghan
Posted on 09/18/2021 9:44:43 AM PDT by LibWhacker
Quantum mechanics
Complementarity A new twist on the double-slit experiment. (Courtesy: Shutterstock/Andrey VP)
One of the most counterintuitive concepts in physics – the idea that quantum objects are complementary, behaving like waves in some situations and like particles in others – just got a new and more quantitative foundation. In a twist on the classic double-slit experiment, scientists at Korea’s Institute for Basic Sciences (IBS) used precisely controlled photon sources to measure a photon’s degree of wave-ness and particle-ness. Their results, published in Science Advances, show that the properties of the photon’s source influence its wave and particle character – a discovery that complicates and challenges the common understanding of complementarity.
The double-slit experiment is the archetypal example of complementarity at work. When a single photon encounters a barrier with two thin openings, it produces an interference pattern on a screen placed behind the openings – but only if the photon’s path is not observed. This interference pattern identifies the photon as a wave since a particle would create only one point of light on the screen. However, if detectors are placed at the openings to determine which slit the photon went through, the interference pattern disappears, and the photon behaves like a particle. The principle of complementarity states that both experimental outcomes are needed to fully understand the photon’s quantum nature.
Signal and idler
The new study adds to this principle by showing that the properties of the slits also matter. In their experiment, the IBS researchers shone so-called “seed beams” of laser light onto two crystals of lithium niobate. Each crystal produces two photons when illuminated: a “signal” photon and an “idler” photon. The researchers sent the signal photon into an interferometer to create interference patterns and quantify the photon’s wave nature, while observing the path of the idler photon to pinpoint its particle character. Because the signal and idler photons are produced together, they form a single quantum state described by both the wave and the particle property measurements.Waves and particles The experimental set-up. (Courtesy: Institute for Basic Science)
By changing the intensity of the seed beams in each crystal, the researchers independently altered the crystals’ chances of emitting photons – a process akin to controlling a photon’s “attraction” to each slit in the classic experiment. When one of the crystals was very likely to emit photons, the pattern the interferometer produced was barely visible, implying that the photon was mostly particle-like. When the crystals’ emission probabilities were equal, the interference pattern was sharp, highlighting the photon’s wave character. “The wave nature of the photon could be extracted as a visibility of the interference pattern,” explains Tai Hyun Yoon, a physicist at IBS and a co-author of the study.
Corroborating theoretical results
In their experiments, Yoon and co-author Minhaeng Cho focused on regimes where the photon was acting partly as a wave and partly as a particle. Previous theoretical studies indicated that the amount of wave-ness and particle-ness in such a system should satisfy a simple equation involving source purity – that is, the likelihood that a particular crystal source will be the one that emits light. The new study is the first complementarity experiment to account for and precisely control this source purity, and it corroborates a prediction made by Xiaofeng Qian and colleagues that source purity µs, interference pattern visibility V and path distinguishability P are related through the expression P2 + V2 = μs2.
“Having this experimental capability makes it possible to confirm the theoretical structures that we were discussing, to test how the source is controlling a single quantum particle’s wave–particle duality,” says Qian, a physicist at Stevens Institute of Technology in New Jersey, US who was not involved in the present study. “This was a great achievement, that they could produce a single photon state where all the parameters were at their control,” agrees Girish Agrawal, a physicist at Texas A&M University, US and Qian’s collaborator on this earlier theoretical work.Read more
Double slits with single atoms
The new study also showed that controlling and quantitatively measuring the photon’s wave and particle character can be recast as measuring the entanglement between idler photons and the detectors that identified their path. In this way, researchers connected complementarity to a property of photons that is commonly exploited in practical quantum devices. “This extra controllability [in our set-up] could be an interesting and useful way to quantum engineer states that might be of interest in quantum information,” says Cho.
Besides its possible applied value, the researchers say that their study challenges physicists’ traditional thinking about complementarity. “In the context of pure theory and fundamental experiments, this experiment does add something new,” agrees Peter Milonni, a physicist at the University of Rochester, US who was not an author of the present paper. Qian adds that the experiment quantitatively proves that instead of a photon behaving as a particle or a wave only, the characteristics of the source that produces it – like the slits in the classic experiment – influence how much of each character it has. “This experimental test and the theoretical quantitative analysis really deliver the message that a quantum particle can behave simultaneously, but partially, as both,” he concludes.
TOPICS: Science
KEYWORDS: duality; particle; photons; physics; quantummechanics; science; stringtheory; wave
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Wow, bravo for these guys. Wave-Particle duality, as stated for decades now, never quite set right for me... It seemed like something was missing. Yoon and Cho have pulled back the curtain a bit and revealed a peek, a hint, at something more. imho
To: LibWhacker
2
posted on
09/18/2021 9:49:25 AM PDT
by
Weirdad
(Orthodox Americanism: It's what's good for the world! (Not communofascism!))
To: LibWhacker
Finally
Now I can get some sleep.
3
posted on
09/18/2021 9:50:04 AM PDT
by
blueunicorn6
("A crack shot and a good dancer”)
To: LibWhacker
It’s all done with mirrors
4
posted on
09/18/2021 9:56:03 AM PDT
by
Regulator
(It's fraud, Jim)
To: LibWhacker
Just bookmarked. Fascinating stuff!
Thank you!
5
posted on
09/18/2021 9:57:29 AM PDT
by
proud American in Canada
("Fear is a reaction; Courage is a decision." Winston Churchill)
To: LibWhacker
“This experimental test and the theoretical quantitative analysis really deliver the message that a quantum particle can behave simultaneously, but partially, as both, Wait, they kicked the can UP the road?
6
posted on
09/18/2021 9:58:17 AM PDT
by
Sirius Lee
(They intend to murder us. Prep if you want to live and live like you are prepping for eternal life)
To: 6SJ7; AdmSmith; AFPhys; Arkinsaw; allmost; aristotleman; autumnraine; bajabaja; ...
7
posted on
09/18/2021 10:02:27 AM PDT
by
SunkenCiv
(Imagine an imaginary menagerie manager imagining managing an imaginary menagerie.)
To: LibWhacker
This is most interesting.
Something I've learned recently is that a photon has spin. This seems very strange to me, because a photon has no mass. How can it have spin?
But that is no stranger (I guess) than the fact that a photon carries momentum, even though it has no mass. Perhaps its momentum is what's spinning, even though there's no mass there to spin.
It has energy though, so its mass-energy (E/c2) not zero.
I learned about this from the YouTube lecture series of David Butler, which is the best I've ever seen... and I've watched a lot of them.
If you watch all five of his "How small is it?" videos in order, he will take you from what you see through a magnifying glass right down to the Higgs boson, and explain everything with amazing insight. As I said, the best I've ever seen.
8
posted on
09/18/2021 10:04:54 AM PDT
by
Steely Tom
([Voter Fraud] == [Civil War])
To: LibWhacker
I have thought of it as if the particle exists and is sustained in a linear spatial configiration, while the wave nature of that energy is in a planar configuration. The planar configuration is what goes through two slits but the particle configuration can only go through one slit.
9
posted on
09/18/2021 10:20:03 AM PDT
by
MHGinTN
(A dispensation perspective is a powerful tool for discernment)
To: LibWhacker
100% of the “difference” is in the equipment (the nature of the equipment) doing the identification and measuring and not in quantum item being identified and measured.
It is a “wave” as known to a “detector” whose natural state is to identify a “wave”, and it is a particle to a “detector” whose natural state is to identify a “particle”.
In its own state, it (light) is neither while to us (because of our means of detection) it is both.
It truth the difference is not in the “property” of light but only in how it appears (to us) to behave, depending on which mode of detection is being used.
10
posted on
09/18/2021 10:20:08 AM PDT
by
Wuli
To: Steely Tom
Thanks for your tip on Butler’s lecture series. I’m going to check him out.
And no, I can’t answer your question about spinning objects that have no mass. It never would have occurred to me to question whether or not such things exist. That’s what I love about FR; there’s always someone who asks the question that stops you in your tracks and makes you go, “Whoa,” but in the end, after much head scratching, can lead you closer to understanding, thank you!
To: Steely Tom
Photons have zero rest mass. But anything that has energy also has mass per Einstein’s equation.
As far as small things, that is also relative; to the naked eye, a human cell would be infinitesimally small (invisible), and on average an adult has 300 trillion of those. Bit hard but not impossible to wrap one’s mind around going smaller, to subatomic particles.
12
posted on
09/18/2021 11:22:59 AM PDT
by
Olog-hai
("No Republican, no matter how liberal, is going to woo a Democratic vote." -- Ronald Reagan, 1960)
To: SunkenCiv
Could you put me on the ping list? Thank-you
To: Wuli
Great post—science now recognizes (at least at the theoretical level) how critical the observer is (whether human or machine).
However, they have been hesitant to think through all of the implications for metaphysics and physics.
That will be the next “big jump” in human understanding.
14
posted on
09/18/2021 11:34:50 AM PDT
by
cgbg
(A kleptocracy--if they can keep it. Think of it as the Cantillon Effect in action.)
To: cgbg
Allowing life to be cause over matter and energy is a place they don’t want to go. They are Materialists after all.
15
posted on
09/18/2021 11:45:26 AM PDT
by
Seruzawa
("The Political left is the Garden of Eden of incompetence" - Marx the Smarter (Groucho))
To: LibWhacker
At first glance, the experimental setup seems similar to the quantum eraser experiments that are all the rage these days...
Will have to read the actual paper before making any comments...
However, seems pretty neat...
Of course I like almost any experiment that does require the LHC at Cern...
16
posted on
09/18/2021 11:46:47 AM PDT
by
SuperLuminal
(Where is another Sam Adams now that we desperately need him?)
To: Seruzawa
They are Materialists after all.
Yup--that is their fundamental error.
Once they can overcome that basic error, then science can really explode with new discoveries.
17
posted on
09/18/2021 11:48:15 AM PDT
by
cgbg
(A kleptocracy--if they can keep it. Think of it as the Cantillon Effect in action.)
To: M_Continuum
18
posted on
09/18/2021 11:49:46 AM PDT
by
SunkenCiv
(Imagine an imaginary menagerie manager imagining managing an imaginary menagerie.)
To: SuperLuminal
“does require...” ==>”does NOT require...”
19
posted on
09/18/2021 11:52:47 AM PDT
by
SuperLuminal
(Where is another Sam Adams now that we desperately need him?)
To: LibWhacker
Wow.
Now they will figure out how to make a Transporter. And Photon torpedos.
I just won’t be here to see it.
5.56mm
20
posted on
09/18/2021 11:53:27 AM PDT
by
M Kehoe
(Quid Pro Joe and the Ho need to go.)
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