hi
- Thread starter Dice4x
- Start date
hi
ahw sad to see you go, ill see u next season
Bye
probably early august (but thats just my guess)
woah.. i relate so muchI did the math to see when the season will reset:
(Image: Shutterstock)
The nonclassical behavior of large measuring devices has been proven within standard QM by the insolubility theorem. If the structure of QM does hold for all systems, then at the end of a measurement process the observer, the measuring apparatus, and the object being measured exist in a quantum superposition of all states consistent with the wavefunction of the object being measured.
Given this, the quantum measurement problem can be summarized thusly: Why do measurements taken by complex, large-scale quantum devices (including ourselves) appear to have a single, definite result? If some aspect of QM interactions does cause the measurement process to narrow to a specific result, what is it? Does it exist within properties of quantum systems having many degrees of freedom, or does QM need to be extended?
So what did the QPNR poll say about the quantum measurement problem?
- The original notions of collapsing wavefunctions and classical observers were an attempt to answer this question, but the insolubility theorem shows this is inadequate for the purpose.
- Some have proposed that the Schrödinger equation should be altered to include some nonlinear terms that will produce pure states under measurement. These attempts have their own problems, primarily because standard quantum mechanics works so well – it is difficult to change its fundamental equation without spoiling the good parts.
- In Everett-type many-worlds theories, carrying out a measurement with multiple results causes the formation of a set of alternate universes – one for each possible result. This avoids the measurement problem – the observer splits with the measuring device, and so doesn't notice the multiplicity. But you have to be able to believe that bouncing a photon off an atom creates new universes...
- Decoherence, which results from the interaction of a quantum system with its surroundings, can render the superposed states of the wavefunction incapable of interfering with each other, at which point their probabilities become independent. Some believe this takes the place of wavefunction collapse, but others believe it has no bearing at all on the measurement problem, as all that is accomplished is to make a superposition with the entangled environment.
These results are nearly indistinguishable from random choices.
- Pseudoproblem (will go away with additional work) – 20%
- Solution through decoherence – 11%
- Solution in some other manner – 30%
- Seriously threatens QM – 18%
- None of the above – 20%
Schrödinger's cat and macroscopic superpositions
(Image: Dhatfield via Wikimedia Commons)
The plight of Schrödinger's Cat is known to many readers. A cat, a conscious, complex quantum system, is placed in a box. Also in the box is a radiation-triggered hammer positioned to smash a glass bottle containing cyanide when radiation is detected. Finally, a very weak radiation source that on average emits one particle per hour is placed in the box, and the box is soundproof, opaque, and sealed. You are sitting outside the box. An hour later, is the cat dead, alive, neither, or both?
The structure of the experiment amplifies an issue accurately described by QM (has a particular radioactive atom decayed?) into what appears to be a classical issue (is the cat alive or dead?). We want to see at what step in the experiment the result stops being quantum mechanical and becomes a definite classical yes or no.
One direction of argument holds that until the box is opened, that cat is in a quantum superposition of dead cat and live cat. On the other hand, if the cat qualifies as an observer, it at least knows if it is alive. (In order for the cat to know it is dead depends on the physical existence of an afterlife – not a standard assumption in QM.) Discussions can become heated, as there are many possible answers.
Schrödinger's Cat in a many-worlds quantum mechanical world
In the many-worlds theories, the fate of the cat is a bit different. When the box is opened, the universe splits into two – one containing a live cat, the other containing a dead cat.
Schrödinger's Cat led to a specific quantum mechanics question on the QPNR poll: Are superpositions of macroscopically distinct states (such as a dead/alive cat) possible in principle, possible in a laboratory, or impossible in principle?
This issue is significant, as it can be tested experimentally.
- Macroscopic superpositions are possible in principle – 55%
- Macroscopic superpositions can be formed in a lab – 30%
- Macroscopic superpositions are impossible in principle – 15%
(Photo: Aaron O'Connell via Wikimedia Commons)
The largest system that has been successfully put into quantum superposition is a quantum microphone weighing about a nanogram (ten trillion atoms) with a volume around 450 cubic microns. This isn't very large, but is far beyond sizes associated with the usual atomic and subatomic interactions which we usually associate with quantum mechanics. The rapid evolution of the field in creating quantum superpositions of larger and larger objects is probably part of the reason that the QPNR poll was rather positive about macroscopic superpositions. This will be a theme – if you can test an idea, consensus forms over time.
Reality or description?
One issue at the foundations of QM involves the physical reality of quantum states. The QPNR poll asked if quantum states only describe reality (are epistemic), or if quantum states are as real as an electric field whose strength can easily be measured (are ontic).
The answers to this very crucial question are consistent with random responses – the collective confusion appears very large.
- Epistemic – 27%
- Ontic – 24%
- Both – 33%
- Purely statistical – 3%
- Other – 13%
Randomness in QM
Another fundamental issue in quantum mechanics involves the randomness of individual quantum events, such as the decay of a radioactive atom. Quantum mechanics predicts behavior that is consistent with random decays having a characteristic half-life for a given decay mode. But is the decay process actually random, or does it just seem that way? The QPNR poll offers four options: Hidden determinism; only appears to be random; irreducible randomness; and randomness is a fundamental concept in nature. Hidden determinism is Einstein's view – there is a hidden clockwork underlying what we perceive as quantum reality. Phenomena are really classical and mechanistic, but we can't see that at present.
The universe only appears to be random in Everett-like many-world interpretations, in which the perception of randomness is an artifact of finding yourself in only one of the new branches of the universe.
The tricky part is deciding on the difference between irreducible randomness and randomness as a fundamental concept in nature. The meaning of the latter is particularly fuzzy. Roughly speaking, irreducible randomness describes a universe in which measured phenomena yield unpredictable results, while fundamental randomness describes a universe whose innermost workings are random. Fundamental randomness is not hidden determinism, saying rather that if there are sublevels of reality, they are also random.
The QPNR answers are:
The lack of support for hidden determinism is probably related to the many experimental tests of Bell's Theorem, which strongly suggest the inapplicability of hidden-variable theories to our universe.
- Hidden determinism – 0%
- Apparent randomness – 7%
- Irreducible randomness – 40%
- Fundamental randomness – 53%
Apparent randomness received fewer than half the votes received by Everett-like interpretations, suggesting that not all Everett supporters agree that the randomness observed therein is apparent.
Irreducible randomness received 40 percent of the votes, while fundamental randomness received 53 percent. It would appear that confusion between these two positions is not limited to your scribe, as all fundamentally random systems are also irreducibly random, but the voting went the other way.
Science or personal prejudice?
To sum up the state of the field of QM interpretations, one particular QPNR poll question is quite revealing. The question is simply: How much is the choice of interpretation a matter of personal philosophical prejudice?
So what this tell us, is that the reset has different opportunitys to be in diffrent times, here are the chances:
- Reset in a long time– 58%
- Reset in a short amount of time– 27%
- No reset at all – 15%
- where I got this from.
Yeah I got confused about the insolubility theorem, it's kinda confusing.
Survival