Proposed test of quantum superposition measures 'quantum revivals'

December 19, 2018 by Lisa Zyga, Phys.org feature
A nanoscale rotor (black rod) is levitated by two counter-propagating laser beams. When the beams are switched off, the quantum state of the rotor disperses into a superposition of all possible orientations, except at certain intervals of time at which quantum revivals occur and the rotor assumes its initial orientation. The rotor can then be recaptured by the lasers and the process repeated. Credit: Stickler et al. ©2018 IOP Publishing

Physicists have proposed an entirely new way to test the quantum superposition principle—the idea that a quantum object can exist in multiple states at the same time. The new test is based on examining the quantum rotation of a macroscopic object—specifically, a nanoscale rotor, which is considered macroscopic despite its tiny size.

Until now, most tests of have been based on linear, rather than rotational, motion. By examining , the may lead to applications such as quantum-enhanced torque sensing, and could provide insight into a variety of open questions, such as what causes the quantum wave function to collapse.

The physicists, led by Klaus Hornberger at the University of Duisburg-Essen, Germany, have published a paper on the proposed test in a recent issue of the New Journal of Physics.

Quantum superposition arises because, at the quantum scale, particles behave like waves. Similar to the way in which multiple waves can overlap each other to form a single new wave, quantum particles can exist in multiple overlapping at the same time. If quantum superposition occurred in everyday life, we might observe phenomena like Schrödinger's cat, which is dead and alive at the same time until it is measured, forcing it to assume a single state.

In the new paper, the researchers propose levitating a nanoscale using , which are formed by two counter-propagating polarized laser beams that cause the rotor to tightly align with the field polarization. When the beams are switched off, however, the tightly oriented rotor is predicted to quickly disperse into a superposition of all possible rotation states as it falls toward the ground due to gravity.

Animation showing how a nanorotor can disperse into a quantum superposition of rotation states, and then, due to quantum interference, undergo a revival, proving that a quantum state has existed. Credit: James Millen, King’s College London

Interestingly, the rotor is predicted to experience "quantum revivals" in which, at regular intervals in time, the collective interference of all of the rotation states leads to the re-emergence of the initial state that it occupied when it was aligned by the . The orientation can potentially be measured by illuminating the rotor with a weak probe laser, and the trapping laser could be switched back on to catch the rotor in this state before it reaches the ground.

So far, orientational quantum revivals have been observed only in gases of diatomic molecules. As the nanorods consist of at least 10,000 atoms, they are much larger than the diatomic molecules, allowing for quantum mechanics to be tested in an uncharted regime.

The physicists expect that it will be possible to observe quantum revivals of the nanorods using existing technology, such as by using a carbon nanotube as the rotor. If so, the observation would represent a new macroscopic test of quantum superposition.

"By observing the quantum revivals, we hope to confirm at an unprecedented mass and complexity scale, thereby exploring the quantum-to-classical borderline," Hornberger told Phys.org.

In the future, coauthor James Millen, now at King's College London, plans to perform the proposed experiment to detect macroscopic quantum revivals.

"Testing whether quantum physics breaks down at a high mass is an exciting, yet daunting, challenge," Millen said. "We may have to develop entirely new technologies to isolate nanoscale particles, or even perform experiments in space. However, this experiment which we propose opens up an entirely new route to probing enigmatic quantum effects, in a way which I firmly believe is feasible with today's technology. Furthermore, we will be able to harness this physics to develop useful devices of unprecedented sensitivity."

Explore further: How Einstein's equivalence principle extends to the quantum world

More information: Benjamin A. Stickler et al. "Probing macroscopic quantum superpositions with nanorotors." New Journal of Physics. DOI: 10.1088/1367-2630/aaece4

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Spaced out Engineer
4 / 5 (4) Dec 19, 2018
Amazing test. It is interesting to see the ontology of superposition. From a geometric perspective one wonders if not discriminating buys you anything computationally. as their exists auxiliaries. And yet with non-repeated tiling, it is not until an overlay, relation maybe extracted. It seems both substrate and distinguishable conditional. The reduction necessary, the unitarity a geometric miracle.
If only we knew how to swap the environmental background. Negative curvature has features closer the farther you move outward. Positive curvature has features farther apart, the further from the center. With a lack of clarity, it may as well be reversible. Nothing lost, perspective, not entropy, the boss.
captainclause
1 / 5 (1) Dec 19, 2018
wow! this super anime looks like *** 'YAW IN YAW' INFINITY *** ...And as a waveform collapse!?? I Can't also wait to see the results !!!!
Surveillance_Egg_Unit
1 / 5 (3) Dec 19, 2018
....quantum objects interact with gravity only through curved space-time.
"Einstein's equivalence principle contends that the total inertial and gravitational mass of any objects are equivalent, meaning all bodies fall in the same way when subject to gravity," Dr. Zych said.
"Physicists have been debating whether the principle applies to quantum particles, so to translate it to the quantum world we needed to find out how quantum particles interact with gravity.
"We realised that to do this we had to look at the mass."
Mass is dynamic quantity and can have different values, and in quantum physics, mass of a particle can be in a quantum 'superposition' of two different values.
According to the famous equation E=MC2, the mass of any object is held together by energy.


In reality, quantum objects interact within their OWN gravitational field - not with macrogravity that we are all familiar with above quantum level. "Curved" space-time? Doesn't exist at quantum level
Surveillance_Egg_Unit
2 / 5 (2) Dec 19, 2018
oops sorry - the above was submitted to the wrong forum.
sassifras69
2.3 / 5 (3) Dec 19, 2018
Wow, if this theory is correct it should open up whole new fields of study. I like quantum mechanics but I am often a little disappointed by some of the ideas that the use. Like the cat that may be dead or alive. Do you realize this is solely based on one little human not knowing if the cat is dead or alive. One little humans knowledge has no affect on the universe because the universe is not affected by what is known or not known inside of our thoughts. It's like when Einstein said that if we moved at the speed of light away from something time would stand still. That is not true. One insignificant person moving away from an object has no affect on time.
Surveillance_Egg_Unit
2 / 5 (4) Dec 19, 2018
"By observing the quantum revivals, we hope to confirm quantum mechanics at an unprecedented mass and complexity scale, thereby exploring the quantum-to-classical borderline," Hornberger told Phys.org.
In the future, coauthor James Millen,... plans to perform the proposed experiment to detect macroscopic quantum revivals.
"Testing whether quantum physics breaks down at a high mass is an exciting, yet daunting, challenge," Millen said. "We may have to develop entirely new technologies to isolate nanoscale particles, or even perform experiments in space. However, this experiment which we propose opens up an entirely new route to probing enigmatic quantum effects, in a way which I firmly believe is feasible with today's technology. Furthermore, we will be able to harness this physics to develop useful devices of unprecedented sensitivity."

It is a big mistake for these scientists to keep sticking their noses into that to which they could bring total disaster to the Universe.
Surveillance_Egg_Unit
2 / 5 (4) Dec 19, 2018
-contd-
These scientists are planning to go into "Uncharted Waters" for which they have no understanding, nor do they have any knowledge of how to reverse what they have done, in the event that an effect which they could not have foreseen, is put into motion which cannot be stopped or reversed or undone.
This is Quantum Physics which they are playing around with. Quantum Mechanics is the basis for all Matter/Mass and Energy in our Universe - as well as the Life Forms of which humans and animals are a big part.
If they continue with this immoral idiocy of theirs - that very well may cause the collapse/destruction of our macro Universe beginning at the Quantum level - what will these scientists DO in that future conundrum where the possibility of the planets, Stars, Galaxies being reduced to the Quantum level also, or exploding?
I firmly OBJECT to their cavalier attitude towards the Quantum origins of OUR VERY EXISTENCE. This is dangerous experimentation with our lives.
torbjorn_b_g_larsson
5 / 5 (2) Dec 26, 2018
Like the cat that may be dead or alive. Do you realize this is solely based on one little human not knowing if the cat is dead or alive.


Not really, and it was suggested as a paradoxical consequence of some collapse interpretations. The experiment may contribute to work it out. "Back of man, they are scientists." ;-)

It's like when Einstein said that if we moved at the speed of light away from something time would stand still. That is not true. One insignificant person moving away from an object has no affect on time.


Again, you misinterpret. _Relativistic_ theory tells you what will happen relative to other observers in order to keep physics laws the same for all observers. So it is only time for that gedanken experiment person that will stand still. In the same way we can see there is no universal, unaffected "time" or "event order" independent of observers. The best you can do is to use universe expansion to keep "time" and use light cone causality.
torbjorn_b_g_larsson
5 / 5 (2) Dec 26, 2018
It is a big mistake for these scientists to keep sticking their noses into that to which they could bring total disaster to the Universe.


You are conspiracy theory nuts. Scientists cannot affect physics laws. they are *exploring* them. Which is no mistake but what we want them to do, since it is what works to understand nature.

"Back of man, they are scientists."

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