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The scientific method relies on facts, established through repeated measurements and agreed upon universally, independently of who observed them. In quantum mechanics the objectivity of observations is not so clear, most markedly exposed in Wigner’s eponymous thought experiment where two observers can experience seemingly different realities. The question whether the observers’ narratives can be reconciled has only recently been made accessible to empirical investigation, through recent no-go theorems that construct an extended Wigner’s friend scenario with four observers. In a state-of-the-art six-photon experiment, we realize this extended Wigner’s friend scenario, experimentally violating the associated Bell-type inequality by five standard deviations. If one holds fast to the assumptions of locality and free choice, this result implies that quantum theory should be interpreted in an observer-dependent way.
That's a loaded statement...scientists don't even agree with each other on this subject. Not even 50% of the physicists polled believed the Copenhagen interpretation taught in textbooks is correct (which teaches wave function collapse).
originally posted by: hombero
I'm going to go with the many scientists that disagree...
a reply to: neoholographic
originally posted by: neoholographic
Simply, no collapse or measurement occurs. Here’s an explanation from Relational Quantum Mechanics that’s just mind blowing.
All physical interactions are, at bottom, quantum interactions, and must ultimately be governed by the same rules.
Counterfactual quantum cryptography (CQC) is used here as a tool to assess the status of the quantum state: Is it real/ontic (an objective state of Nature) or epistemic (a state of the observer's knowledge)? In contrast to recent approaches to wave function ontology, that are based on realist models of quantum theory, here we recast the question as a problem of communication between a sender (Bob), who uses interaction-free measurements, and a receiver (Alice), who observes an interference pattern in a Mach-Zehnder set-up. An advantage of our approach is that it allows us to define the concept of "physical", apart from "real". In instances of counterfactual quantum communication, reality is ascribed to the interaction-freely measured wave function (ψ) because Alice deterministically infers Bob's measurement. On the other hand, ψ does not correspond to the physical transmission of a particle because it produced no detection on Bob's apparatus. We therefore conclude that the wave function in this case (and by extension, generally) is real, but not physical. Characteristically for classical phenomena, the reality and physicality of objects are equivalent, whereas for quantum phenomena, the former is strictly weaker. As a concrete application of this idea, the nonphysical reality of the wavefunction is shown to be the basic nonclassical phenomenon that underlies the security of CQC.
Significance
Recent theoretical studies have shown that quantum mechanics allows counterfactual communication, even without actual transmission of physical particles, which raised a heated debate on its interpretation. Although several papers have been published on the theoretical aspects of the subject, a faithful experimental demonstration is missing. Here, by using the quantum Zeno effect and a single-photon source, direct communication without carrier particle transmission is implemented successfully. We experimentally demonstrate the feasibility of direct counterfactual communication with the current technique. The results of our work can help deepen the understanding of quantum mechanics. Furthermore, our experimental scheme is applicable to other quantum technologies, such as imaging and state preparation.
Tell me, when single photons are shot at the barrier in the double slit experiment and end up on the screen to form an interference pattern or behave like particles if a measuring apparatus is placed at the sides of one of the slits, how did the single photon get from the source to the back of the screen if it didn't travel?
If you have a better theory than Quantum Theory that has given us the modern world we live in and is the most accurate theory we have to date
There's no need for Wave Function collapse or Measurement in Quantum Mechanics
Unfortunately, people writing about quantum mechanics often use the phrase "collapse of the wave-function" to describe what happens when an object is observed. This phrase gives a misleading idea that the wave-function itself is a physical object. A physical object can collapse when it bumps into an obstacle. But a wave-function cannot be a physical object. A wave-function is a description of a probability, and a probability is a statement of ignorance. Ignorance is not a physical object, and neither is a wave-function. When new knowledge displaces ignorance, the wave-function does not collapse; it merely becomes irrelevant.
The wave function is nothing like a movie, so that analogy isn't relevant. In a movie frame an object is either at point A or point B, not 50% probability of being at point A and 50% probability of being at point B.
originally posted by: Krakatoa
Think of it this way, if you take a frame out of a movie, does that negate the movie's existence? No, it merely means you have selected a singe momentary frame in a continuum. The continuum (or wave function) remains.
Unfortunately, people writing about quantum mechanics often use the phrase "collapse of the wave-function" to describe what happens when an object is observed. This phrase gives a misleading idea that the wave-function itself is a physical object. A physical object can collapse when it bumps into an obstacle. But a wave-function cannot be a physical object. A wave-function is a description of a probability, and a probability is a statement of ignorance. Ignorance is not a physical object, and neither is a wave-function. When new knowledge displaces ignorance, the wave-function does not collapse; it merely becomes irrelevant.
originally posted by: Bandu
a reply to: Arbitrageur
Unfortunately, people writing about quantum mechanics often use the phrase "collapse of the wave-function" to describe what happens when an object is observed. This phrase gives a misleading idea that the wave-function itself is a physical object. A physical object can collapse when it bumps into an obstacle. But a wave-function cannot be a physical object. A wave-function is a description of a probability, and a probability is a statement of ignorance. Ignorance is not a physical object, and neither is a wave-function. When new knowledge displaces ignorance, the wave-function does not collapse; it merely becomes irrelevant.
exactly !!!
any time one observe a system, one interacts with the system, so the system is changed, the "function" ( mathematical calculation ) needs to be "rewritten" to take in count the interaction.