Micron sized object observed in quantum state

[xlines]

In a following link:

http://physicsworld.com/cws/article/news/42019

authors claim to design a 40 micron sized resonator which they were able to set into a superposition of states. Should this be true, I find it fascinating and a new, fruitful way to explore quantum-classical border. Any opinions or comments?

 

[Dmitry67]

In a following link:

http://physicsworld.com/cws/article/news/42019

authors claim to design a 40 micron sized resonator which they were able to set into a superposition of states. Should this be true, I find it fascinating and a new, fruitful way to explore quantum-classical border. Any opinions or comments?

cool, but there is no surprise and because "quantum-classical border" does not exist

 

[xlines]

cool, but there is no surprise and because "quantum-classical border" does not exist

God, I really don't want to initiate another ("Local realism ruled out? (was: Photon entanglement and...) ") zillion posts thread, but how the hell do you think that there is no border? Because things around look mighty non-unitary to me ...

 

[Dmitry67]

Do you think that systems with N atoms can be in superposition while systems with N+1 atoms cant? There are no people who seriously defend collapse interpretations after the discovery of Quantum Decoherence and (partial) resoltion of the measurement problem.

If we exclude Mascoscopic realism aka Shut up and calculate interpretation, and with Collapse ruled out, there are only non-collapse interpretations left, so the is no any "border". Any system can be put in superposition: atom, C60 molecule or a cat

 

[Frame Dragger]

Do you think that systems with N atoms can be in superposition while systems with N+1 atoms cant? There are no people who seriously defend collapse interpretations after the discovery of Quantum Decoherence and (partial) resoltion of the measurement problem.

If we exclude Mascoscopic realism aka Shut up and calculate interpretation, and with Collapse ruled out, there are only non-collapse interpretations left, so the is no any "border". Any system can be put in superposition: atom, C60 molecule or a cat

Well said, and in my opinion that's the view of many people actually working in the field. I don't really understand why people are so obsessed with formulating Interpretations for an incomplete (albiet AMAZING and fruitful) theory? QM is an amazing collection of principles, but so many of the problems it creates exist only in the minds of theoreticians and such, and are simply resolved incrementally as we are able to observe new phenomena, or old ones with new methods (and higher energy levels).

We're at a point where people are honestly debating whether a kind of... elongated... dipole in a spin-ice is a magnetic monopole in "The Dirac Sea". Everything has to be formulated now in terms of an ultimate theory, when the reality IS incremental steps with tipping points. We can't CHOOSE our tipping points...

 

[f95toli]

In a following link:

http://physicsworld.com/cws/article/news/42019

authors claim to design a 40 micron sized resonator which they were able to set into a superposition of states. Should this be true, I find it fascinating and a new, fruitful way to explore quantum-classical border. Any opinions or comments?

It is not actually very surprising that they've succeded. People have been working on exactly this type of experiment for a few years now (I've actually been involved in one such project myself) and there are several papers where people have managed to cool a MEMS resonator into a very low state. There are at least a couple of other groups that are likely to manage to repeat the same experiment later this year, Cleland and co just happened to be faster than anyone else.
So yes, it is certainly true. The physics is also quite well understood since people have been doing exactly the same type of experiement with qubits and electromagnetic resonators for a few years (since 2004). It would have been more suprising if it had NOT worked with a good MEMS resonator.

So yes, it is a very impressive experiment and a nice demonstration of QM; but the result is not surprising to me or anyone else that knows something about the field, and I am not sure it really tells us something new about QM.

 

[Frame Dragger]

It is not actually very surprising that they've succeded. People have been working on exactly this type of experiment for a few years now (I've actually been involved in one such project myself) and there are several papers where people have managed to cool a MEMS resonator into a very low state. There are at least a couple of other groups that are likely to manage to repeat the same experiment later this year, Cleland and co just happened to be faster than anyone else.
So yes, it is certainly true. The physics is also quite well understood since people have been doing exactly the same type of experiement with qubits and electromagnetic resonators for a few years (since 2004). It would have been more suprising if it had NOT worked with a good MEMS resonator.

So yes, it is a very impressive experiment and a nice demonstration of QM; but the result is not surprising to me or anyone else that knows something about the field, and I am not sure it really tells us something new about QM.

True, but every Apollo mission needs its predecessors.

 

[xlines]

Do you think that systems with N atoms can be in superposition while systems with N+1 atoms cant?

Yeah, there are serious lack of diffuse boundaries in physics. You are aware you just pulled classical sophism on me as an argument?

There are no people who seriously defend collapse interpretations after the discovery of Quantum Decoherence and (partial) resoltion of the measurement problem.

Ok, I looked it up and you seem to know what you are talking about and others seem to support you. So, IIUC When interacting with environment, state of isolated system get's "lost" by a unitary development in larger phase space. Due to a much larger number of dimensions, part of new phase space that state is lost in can usually be projected to only one eignestate of original isolated system thus giving appearance of collapse - did I get that right?

Because there is only unitary development and correlation don't end - thay basically quickly become so "fine" that we can no longer practically difference them from any alike correlation thus giving us random view.

If we exclude Mascoscopic realism aka Shut up and calculate interpretation, and with Collapse ruled out, there are only non-collapse interpretations left, so the is no any "border". Any system can be put in superposition: atom, C60 molecule or a cat

This is really interesting. I am far from convinced, but interested.

And no offence but ... I will not take your work for that cat. :)

 

[IttyBittyBit]

Cool experiment, but it would only get really interesting if they managed to make the metal strip interfere with itself. I'm talking about something analogous to the double-slit experiment. Now that would be something.

 

[Dmitry67]

What exactly is interesing?
Do you still believe in Copenhagen Interpretation and Collapse? Then you are probably the last one on this forum :)

 

[yoda jedi]

So yes, it is a very impressive experiment and a nice demonstration of QM; but the result is not surprising to me or anyone else that knows something about the field, and I am not sure it really tells us something new about QM.

right, quantum mechanics is demonstrated, like say you; unsurprising, foreseeable, expected.
but what is really at stake, is, the standard quantum mechanics vs nonlinear quantum mechanics, not the superposition itself (per se), but the time of the superposition vs the time of decoherence, if last more or less; if last less, nonlinear model are the correct, if last more, linear models are.
from various sources there is growing evidence for nonlinear models (specific tests must be developed for them, to see which one is the correct).

 

[Dmitry67]

ah, you look at it as a test of objective collapse theories?

 

[ManyNames]

Do you think that systems with N atoms can be in superposition while systems with N+1 atoms cant? There are no people who seriously defend collapse interpretations after the discovery of Quantum Decoherence and (partial) resoltion of the measurement problem.

If we exclude Mascoscopic realism aka Shut up and calculate interpretation, and with Collapse ruled out, there are only non-collapse interpretations left, so the is no any "border". Any system can be put in superposition: atom, C60 molecule or a cat

Decoherence is a collapse. A natural collapse of many systems.

 

[Dmitry67]

Decoherence is a collapse. A natural collapse of many systems.

No, decoherence is vanishing of the non-diagonal elements.
Collapse is more: only one element (one branch) is left.

 

[ManyNames]

No, decoherence is vanishing of the non-diaginal elements.
Collapse is more: only one element (one braanch) is left.

Correct me if i am wrong, but decoherence is when particles systems fall into quantum mechanically-defined states. This is still found by their constituent wave functions to be a probability yes of $\int |\psi|^2$?

Perhaps wiki is more your street?

''Quantum decoherence gives the appearance of wave function collapse''

http://en.wikipedia.org/wiki/Quantum_decoherence

 

[Dmitry67]

From the same article:

However, decoherence by itself may not give a complete solution of the measurement problem, since all components of the wave function still exist in a global superposition, which is explicitly acknowledged in the many-worlds interpretation. All decoherence explains, in this view, is why these coherences are no longer available for inspection by local observers. To present a solution to the measurement problem in most interpretations of quantum mechanics, decoherence must be supplied with some nontrivial interpretational considerations (as for example Wojciech Zurek tends to do in his Existential interpretation). However, according to Everett and DeWitt the many-worlds interpretation can be derived from the formalism alone, in which case no extra interpretational layer is required.

So decoherence explains why we don't see superposition of dead and alive cat, but it does not explain why nature cohses the specific state of a cat. For me, as I like MWI, both cats exist.

 

[ManyNames]

From the same article:



So decoherence explains why we don't see superposition of dead and alive cat, but it does not explain why nature cohses the specific state of a cat. For me, as I like MWI, both cats exist.

I've never seen a problem with this. The ''why'' seems quite obvious; the more a particles wave function entangles with a system of other quantum entangled objects, the more probability of a wave function-like appearance of a collapse. It's like a natural cut-off for frequencies in their wave functions.

 

[Dmitry67]

Yes, as a result of decoherence superposition collapses into:

sad observer looking at dad cat
+
happy observer looking at alive cat

so cat is dead AND alive, but it does not explain why cat is dead OR alive
In another words, QM without collapse (with decoherence) is deterministic, so if it is deterministic, why the world looks random for us? There are different ways to explain this: MWI, BM for example

 

[ManyNames]

Both states cannot exist. One must exist in more a defined state than the other. Macroevents do not exist as states $|\psi>=\frac{1}{2}A|\psi>+\frac{1}{2}B|\psi>$ - macroevents are not in a high wave function state like quantum particles. It has a vanishingly small wavefunction in fact. You will by quantum mechanical laws of decoherence, find either the cat dead or alive, but never both.

 

[Dmitry67]

No, they DO exist. If you have 2 outcomes with the same probability, then in deterministic theory (and QM with decoherence withoutcollapse is the one) you can not in principle explain why only one specific outcome exist. Why, for example, that specific neutron decayed at 745th second, while another one at 739th?

And yes, macroevents can't coexist - in one branch but they can coexist in different branches! so yes, it is "vanishingly small" possibility to observe another branch. Different branches simple stop interacting.

 

[Dmitry67]

Another example: I have 2 neutrons: Left and Right. Setup is symmetric
I wait which neutron decays first. Say, L decayed first. Now P symmetry is broken.

Do you understand that deterministic theory can't, in principle, break P symmetry?

 

[ManyNames]

No, they DO exist. If you have 2 outcomes with the same probability, then in deterministic theory (and QM with decoherence withoutcollapse is the one) you can not in principle explain why only one specific outcome exist. Why, for example, that specific neutron decayed at 745th second, while another one at 739th?

And yes, macroevents can't coexist - in one branch but they can coexist in different branches! so yes, it is "vanishingly small" possibility to observe another branch. Different branches simple stop interacting.

The last post was specifically aimed at your macro-environmental approach - nothing to do with quantum objects. You can't have the experiment say two cats are dead and alive when their is a cutoff in the wave function for them.

 

[Dmitry67]

Yes, and this is the whole point of the decoherence: it explains why it is true.

But decoherence (check again wiki article) itselft does not explain how deterministic evolution of global wavefunction of the universe appears 'random' to the observers. It just explains why observers don't see a superposition of outcomes, but it does not explain how particular outcome is chosen.

 

[ManyNames]

Observers do not have many explanations in physics, from were we stand. Our lack of knowledge in a system makes the universe appear so ''randomly-chosen''. Deterministic physics will always question how and why the great blue-print manifested.

 

[Dmitry67]

We don't know what the "consciousness" is, but we still can talk about the dead observers in terms of the state of their memory. For example, a question how photo-camera + computer behaves is a valid physical question which does not include consiousness.

Non-collapse interpretations, like MWI and BM are motivated by the fact that decoherence does not explain that apparent randomness.

 

[yoda jedi]

ah, you look at it as a test of objective collapse theories?

yes, objective collapse, self collapse, intrinsic collapse...

From the same article:

However, decoherence by itself may not give a complete solution of the measurement problem, since all components of the wave function still exist in a global superposition, which is explicitly acknowledged in the many-worlds interpretation. All decoherence explains, in this view, is why these coherences are no longer available for inspection by local observers. To present a solution to the measurement problem in most interpretations of quantum mechanics, decoherence must be supplied with some nontrivial interpretational considerations (as for example Wojciech Zurek tends to do in his Existential Interpretation). However, according to Everett and DeWitt the many-worlds interpretation can be derived from the formalism alone, in which case no extra interpretational layer is required.

So decoherence explains why we don't see superposition of dead and alive cat, but it does not explain why nature cohses the specific state of a cat. For me, as I like MWI, both cats exist.

or the Consistent Histories, but as article state there is no need of extra interpretational layer.

 

[dmtr]

We don't know what the "consciousness" is, but we still can talk about the dead observers in terms of the state of their memory. For example, a question how photo-camera + computer behaves is a valid physical question which does not include consiousness.

Non-collapse interpretations, like MWI and BM are motivated by the fact that decoherence does not explain that apparent randomness.

Nope. You can't. With any classical memory and MWI you are going to run into the Tegmark's quantum immortality paradox. One classical bit is enough. Once a classical bit is initialized to '1' there is always going to be a 'branch' where this bit is still '1'...

 

[Dmitry67]

Nope. You can't. With any classical memory and MWI you are going to run into the Tegmark's quantum immortality paradox. One classical bit is enough. Once a classical bit is initialized to '1' there is always going to be a 'branch' where this bit is still '1'...

I don't understand what you are saying. What is a "classical" bit? There is nothing "classical" because all macroscopic things are made of microscopic. Then, where do you see the paradox (inconsitency) in Quantum Immortality? There is well known criticism (such branches have very low probability) but there are no inconsistencies.

Finally "Once a classical bit is initialized to '1' there is always going to be a 'branch' where this bit is still '1'" - in all subranches of the branch where it had been initialized to 1 - yes. Where it had been initalized to 0 - no. What is your point?

 

[dmtr]

I don't understand what you are saying. What is a "classical" bit? There is nothing "classical" because all macroscopic things are made of microscopic.

AFAIK a classical bit is pretty much a state of entanglement between an observer and some microscopic or macroscopic object. For example you can set a spin of an electron to |up> and it would stay for you |up>, as a classical bit (because of an entanglement between you and the spin of that electron).

I don't know of any other way to create a classical bit. Can you think of any?

 

[Dmitry67]

Classical is an illusion.
When you 'observe' bit=1, you in another branch observe bit=0.
Of course, our past memories (in every branch) are consistent.

 

[yoda jedi]

right, quantum mechanics is demonstrated, like say you; unsurprising, foreseeable, expected.
but what is really at stake, is, the standard quantum mechanics vs nonlinear quantum mechanics, not the superposition itself (per se), but the time of the superposition vs the time of decoherence, if last more or less; if last less, nonlinear model are the correct, if last more, linear models are.
from various sources there is growing evidence for nonlinear models (specific tests must be developed for them, to see which one is the correct).

it as a test of objective collapse theories?

for nonlinear quantum mechanics.
the next experiments.

The Vienna Experiment, Nature 460 724, Nature Physics 5 485. 2009.
The CalTech Experiment, http://www.kschwabresearch.com/articles/detail/8 , http://media.caltech.edu/press_releases/13271
The LIGO Science Collaboration Experiment, New J. Phys. 11 073032 2009.

...