Duality principle is 'safe and sound': Researchers clear up apparent violation of wave-particle duality

Aug 26, 2014

Decades of experiments have verified the quirky laws of quantum theory again and again. So when scientists in Germany announced in 2012 an apparent violation of a fundamental law of quantum mechanics, a physicist at the University of Rochester was determined to find an explanation.

"You don't destroy the laws of that easily," said Robert Boyd, professor of optics and of physics at Rochester and the Canada Excellence Research Chair in Quantum Nonlinear Optics at the University of Ottawa.

In their 2012 version of the famous Young two-split experiment, Ralf Menzel and his colleagues at the University of Potsdam simultaneously determined a photon's path and observed high contrast interference fringes created by the interaction of waves from the two slits.

"This result was extremely surprising, as one of the basic tenets of quantum mechanics holds that there should be no when it is known through which slit the particle (a photon in this case) had passed," said Boyd.

Inspired by these intriguing results, Boyd and his colleagues replicated the Menzel experiment. Their findings were recently published online in an early edition of the Proceedings of the National Academy of Sciences.

"The data of the Menzel experiment were very clean, so we weren't surprised to obtain the same initial result," said Boyd. "My coworkers and I asked what could explain this apparent violation of a key principle of quantum mechanics. What we found is that the resolution of the problem requires great subtly in the way that one needs to analyze the data for this type of measurement."

Following the method of Menzel and the Potsdam researchers, Boyd's group generated an entangled pair of photons, one called a signal and the other called an idler. By measuring the position of the idler photon, they thereby determined through which slit the signal photon had passed. They then observed that the signal photons produced an , in agreement with the results of the Potsdam group and in apparent conflict with the duality principle.

A careful examination of the results shows that the visibility of the interference pattern is stronger in some places and weaker in others. In particular, the strongest recorded visibility was much higher than the average visibility of the entire pattern.

Wave-particle duality suggests that elementary particles, like electrons and photons, cannot be completely described as either waves or particles, because they exhibit both types of properties. In the double-slit experiment, observing a photon pass through one of the two slits is an example of a particle-like property; a particle can only pass through one or the other. When two waves converge to form an interference pattern, the photon must have passed through both slits simultaneously—a wave-like property. Trying to measure both types of properties simultaneously, however, is problematic. The interference pattern disappears as soon as it is known through which slit the photon has passed.

Boyd and his colleagues discovered that the German physicists had inadvertently sampled the sections of high visibility with greater probability than the other sections. While only a handful of photons produced high visibility interference, they used the entire set of photons to determine the predictability of knowing through which slit they had passed.

This phenomenon, called biased sampling, occurs when certain measurements of a system are selected with a higher probability than others, and that subset of measurements is mistakenly taken to be representative of the entire system. In this case, the high visibility photon subsystem was more likely to be sampled. When Boyd's team "fairly" sampled each variable—giving each subsystem an equal opportunity to be detected and sampled—the problem went away and the results were consistent with the standard interpretation of quantum mechanics.

Boyd emphasizes that the Menzel group had interpreted its data just as anyone else would have. The results were both "strange" and "incredible," but it took Boyd and his colleagues nearly a year and a half to figure out what was going on. He said in some ways everyone is relieved that our understanding of quantum laws has been reaffirmed.

Explore further: Physicists take quantum leap toward ultra-precise measurement

More information: Proceedings of the National Academy of Sciences, www.pnas.org/content/early/2014/08/06/1400106111.abstract

Related Stories

Patterns of interfering massive particles

Mar 04, 2014

Two-particle interference has been the focus of many studies, specifically in quantum optics with photons. However, interference between two massive, identical particles is not so well understood. In a study published in ...

Quantum reality more complex than previously thought

Oct 28, 2013

Imagine you order a delivery of several glass vases in different colors. Each vase is sent as a separate parcel. What would you think of the courier if the parcels arrive apparently undamaged, yet when you ...

Viewing deeper into the quantum world

Jun 11, 2014

One of the important tasks for quantum physics researchers and engineers is designing more sensitive instruments to study the tiny fields and forces that govern the world we live in. The most precise measuring ...

Recommended for you

Boron-based atomic clusters mimic rare-earth metals

Apr 17, 2015

Rare Earth elements, found in the f-block of the periodic table, have particular magnetic and optical properties that make them valuable commodities. This has been particularly true over the last thirty years ...

User comments : 18

Adjust slider to filter visible comments by rank

Display comments: newest first

arom
1 / 5 (15) Aug 26, 2014
Decades of experiments have verified the quirky laws of quantum theory again and again. So when scientists in Germany announced in 2012 an apparent violation of a fundamental law of quantum mechanics, a physicist at the University of Rochester was determined to find an explanation.

"You don't destroy the laws of quantum mechanics that easily," said Robert Boyd, professor of optics and of physics at Rochester and the Canada Excellence Research Chair in Quantum Nonlinear Optics at the University of Ottawa…..

Boyd emphasizes that the Menzel group had interpreted its data just as anyone else would have. The results were both "strange" and "incredible," but it took Boyd and his colleagues nearly a year and a half to figure out what was going on. He said in some ways everyone is relieved that our understanding of quantum laws has been reaffirmed.


It seems that everyone should be happy that our understanding of quantum laws has been reaffirmed; unfortunately what which still bother us is that we really do not know how the quantum laws work in that way! Maybe this 'working mechanism' could help to pave the way …
http://www.vacuum...19〈=en
Doug_Huffman
1 / 5 (9) Aug 26, 2014
Well I have just recently discovered a personalist Bayesian interpretation of QM in QBism that is very interesting, particularly in the context of Lee Smolin's work, with its citation of Popper, and intersection with Taleb/Mandelbrot.
Vyhea
5 / 5 (12) Aug 26, 2014
Maybe this 'working mechanism' could help to pave the way

Have you not been reading the accident reports? Your "working mechanism" is irreparably broken. Your paving mechanism slid off the mountain, along with the entire roadway, years ago. The ill-conceived route required an impossible-to-design foundation and was doomed from the start. The NTSB recommends you bury the "mechanism" where it lay, choose a more plausible route and stop designing in a vacuum.
bloopotheclown
1 / 5 (7) Aug 26, 2014
Could all particles be Wave Structures of Matter, standing wave centers of elastic space?
antialias_physorg
5 / 5 (14) Aug 26, 2014
Boyd and his colleagues discovered that the German physicists had inadvertently sampled the sections of high visibility with greater probability than the other sections. While only a handful of photons produced high visibility interference, they used the entire set of photons to determine the predictability of knowing through which slit they had passed.


Dang it. That's one subtle piece of business. Good job by Boyd and his group on figuring out the flaw. That sounds like some serious piece of detective work.
Jixo
Aug 27, 2014
This comment has been removed by a moderator.
swordsman
1 / 5 (1) Aug 27, 2014
Investigators would do well to apply the Heaviside method of analysis of the waves passing through slits. This results in the interference fringes observed from the waves passing through the two slits. Note that the architects of quantum mechanics, Dirac, Born, Heisenberg, Hilbert, Von Neumann and Wiener all utilized and extended Heaviside's operator method.
johanfprins
1.7 / 5 (6) Aug 27, 2014
In the double-slit experiment, observing a photon pass through one of the two slits is an example of a particle-like property;
Why? Can a single wave not pass through a single slit?
a particle can only pass through one or the other.
So can a wave if you collapse its size before it arrives at the two slits.
When two waves converge to form an interference pattern, the photon must have passed through both slits simultaneously—a wave-like property.
Exactly, but if you are stupid enough to put two detectors behind the slits to measure through which slit a non-collapsed photon-wave has moved, you collapse the wave that has moved through BOTH slits, so that the diffracted wavefront is destroyed before it reaches the screen: Furthermore it collapses into the detector with which it resonates FIRST. Thus 50% collapses within one detector and 50% within the other.

Now if you are insanely stupid, you will conclude the photon-wave has only moved through one slit.
Jixo
Aug 27, 2014
This comment has been removed by a moderator.
Jixo
Aug 27, 2014
This comment has been removed by a moderator.
Jixo
Aug 27, 2014
This comment has been removed by a moderator.
Hakan1997
1 / 5 (1) Aug 27, 2014
To be honest, the above article doesn't bother with wave-particle duality as such, as its existence is out of discussions already. What the physicists are discussing today actually is, if both particle, both wave aspects of matter can be observed at the same moment with single observer during single pass experiment. IMO this question just depends on the size of observer and localeness of experiment. The realistic (i.e. rather large) observers or experimental devices can interact with matter by mean of both transverse, both longitudinal waves at the same moment, so that the wave and particle aspects of matter will not be quite mutually exclusive for them. The strictly local arrangement of arrangement would disallow this uncertainty, but such an experiment is of rather theoretical importance.

Jixo
Aug 27, 2014
This comment has been removed by a moderator.
Jixo
Aug 27, 2014
This comment has been removed by a moderator.
johanfprins
4 / 5 (8) Aug 27, 2014
Zephyr=Jixo,

PLEASE go and learn calculus and solve Maxwell's equations: THERE IS NO AETHER.!!
Jixo
Aug 27, 2014
This comment has been removed by a moderator.
no fate
1.8 / 5 (5) Aug 27, 2014
"There can be no concentration of energy without a field to bind it" - Einstein

At the quantum level there are no particles, just waves and fields. You would think that the necessity to catalogue every "particle" by its vibrational energy or oscillation frequency would be a tip off...or the fact that it isn't called "the cosmic microparticle background".
johanfprins
2.5 / 5 (11) Aug 27, 2014
But the Maxwell's equations were originally derived just with using of aether model...;-)
A blatant lie!!!!! they were derived from the experiments that showed magnetic-field and electric-field induction. No aether was assumed by Maxwell ANYWHERE to obtain these equations.

Maxwell only WRONGLY interpreted that waves can ONLY move in an aether. If he had solved his own equations for stationary EM -waves in a reflecting cavity, it would have hit him like a sledgehammer that these waves cannot move within a medium: For if they did it would violate energy-conservation.

PLEAAAASE Zephyr: Stop spouting when you cannot even solve a differential equation but can only imagine ducks farting in a non-existing aether.
Aligo
Aug 27, 2014
This comment has been removed by a moderator.
johanfprins
1.7 / 5 (11) Aug 27, 2014
Oh my God! Now is Aligo !! ha ha ha!
He considered this instead and he assumed, that the light waves are formed WITH aether, not moving IN it.
Bullshit! No matter how you want to word it, an aether-wave means a continuouis harmonic exchange between potential energy and kinetic energy while the wave moves: This is not possible for a light-wave since a light-wave moving through space has ONLY kinetic energy WITHIN ALL inertial reference-frames.!
Who should know better, how the Maxwell's theory was derived and interpreted, than Maxwell himself?
He did not know about the constancy of the speed of light within all inertial reference- frames: So how the HELL could he know better? You are an arsehole!!
Aligo
Aug 28, 2014
This comment has been removed by a moderator.
Aligo
Aug 28, 2014
This comment has been removed by a moderator.
johanfprins
3.7 / 5 (3) Aug 29, 2014
He did not know about the constancy of the speed of light within all inertial reference- frames
Maxwell couldn't know about it, because his original theory was much more deep, complex and it actually http://www.chenie...706.htm.

Wrong again: His theory DID predict it: He just did not realise that it did. Maxwell's equations when solved within any inertial reference frame, gives the SAME speed for light c=1/(SRT(eps0*mu0)) where eps0 and mu0 are constants which are THE SAME in any and all inertial reference frames. So PLEAAASE Zephyr: Stop spouting claptrap.
johanfprins
3.7 / 5 (3) Aug 29, 2014
The Maxwell equations become consistent with speed of light just after their symmetrization with http://en.wikiped...ndition, which removes the spin-0 components.
Maxwell was right: Tthe Lorentz equations are a result of Maxwell's equations in electric- and magnetic-field format. And these equations already DEMAND that the speed of light must be the same within any and all inertial reference frames.
Jixo
Aug 29, 2014
This comment has been removed by a moderator.
johanfprins
1 / 5 (1) Aug 29, 2014
Maxwell's equations when solved within any inertial reference frame, gives the SAME speed for light
Nope, such an equations behave so, only when they're symmetrized with Lorenz and transformed from quaternion notation with Heaviside into vector format.
The Heavyside notation only simplifies the equqtions. It does not change the physics.

It's a simplification. Of course, the Maxwell's equations are a simplification too - as I explained above, they even cannot predict the existence of photon and quantum phenomena by itself.
Oh but they do this. You can directly derive the Lorentz equations from them since they predict that light speed must be c in all IRF's. One can then derive the de Broglie wavelength from the Lorentz transformation, which gives for any moving matter object with mass m a frequency f=(m*c^2)/h. Note that h has NOTHING to do with a matter quantum.

continued
johanfprins
1 / 5 (1) Aug 29, 2014
When such a matter-wave aborbs light, it increases its mass energy to M*c^2, so that it now has a frequency F=(M*c^2)/h. Thus the energy E that it absorbs by slicing this energy from a continuous light-wave as modelled by Maxwell's equations is thus;

E=M*c^2-m*c^2=h*F-h*f=h(F-f)=h*nu, where nu is the frequency that the light wave must have.

The light-wave does not need to consist of light-quanta since the matter-wave, like any antenna (for examplefor radio-waves) only absorbs a part of the energy from the light-wave, notwithstanding that the light-wave is continuous energy, as it must be when it has been emitted by a coherent, harmonic source. This wave-energy is stupidly called a photon-"particle". IT IS NOT A "PARTICLE" , but still a wave that has continous energy as demanded by Maxwell's equations. Only its energy is restricted to h*nu, since the electron absorber changes in energy by E=h*(F-f)=h*nu.

Thus Maxwell's equations and quantum mechanics dovetail seamlessly!
Da Schneib
5 / 5 (1) Sep 01, 2014
The particle wave duality isn't mutually inclusive, as Afshar already demonstrated in 2004. Even at the trivial double slit experiment the particles do behave in http://www.sps.ch...d288.jpg - both like the dots at the target, both like the wave-like pattern in density distribution of these dots.
Afshar's interpretation of his results remains extremely controversial at this time. He also doesn't properly understand quantum erasure.

I certainly wouldn't call it decided either way, but this result puts a lot of the burden back on Afshar to show the result cannot be due to a biased measurement like the one in this article.
Jixo
Sep 01, 2014
This comment has been removed by a moderator.
Da Schneib
5 / 5 (1) Sep 12, 2014
Unfortunately this article says not. The title says, "Researchers clear up apparent violation of wave-particle duality."
Aligo
Sep 13, 2014
This comment has been removed by a moderator.
Aligo
Sep 13, 2014
This comment has been removed by a moderator.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.