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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.
In the non-intuitive quantum domain, the phenomenon of counterfactuality is defined as the transfer of a quantum state from one site to another without any quantum or classical particle transmitted between them. Counterfactuality requires a quantum channel between sites, which means that there exists a tiny probability that a quantum particle will cross the channel—in that event, the run of the system is discarded and a new one begins. It works because of the wave-particle duality that is fundamental to particle physics: Particles can be described by wave function alone.
Using this effect, the authors of the new study achieved direct communication between sites without carrier particle transmission. In the setup they designed, two single-photon detectors were placed in the output ports of the last of an array of beam splitters. According to the quantum Zeno effect, it's possible to predict which single-photon detector will "click" when photons are allowed to pass. The system's nested interferometers served to measure the state of the system, thereby preventing it from changing.
Alice transfers a single photon to the nested interferometer; it is detected by three single photon detectors, D0, D1 and Df. If D0 or D1 click, Alice concludes a logic result of one or zero. If Df clicks, the result is considered inconclusive, and is discarded in post-processing. After the communication of all bits, the researchers were able to reassemble the image—a monochrome bitmap of a Chinese knot. Black pixels were defined as logic 0, while white pixels were defined as logic 1.
At the heart of the weirdness for which the field of quantum mechanics is famous is the wavefunction, a powerful but mysterious entity that is used to determine the probabilities that quantum particles will have certain properties. Now, a preprint posted online on 14 November1 reopens the question of what the wavefunction represents — with an answer that could rock quantum theory to its core. Whereas many physicists have generally interpreted the wavefunction as a statistical tool that reflects our ignorance of the particles being measured, the authors of the latest paper argue that, instead, it is physically real.
The debate over how to understand the wavefunction goes back to the 1920s. In the ‘Copenhagen interpretation’ pioneered by Danish physicist Niels Bohr, the wavefunction was considered a computational tool: it gave correct results when used to calculate the probability of particles having various properties, but physicists were encouraged not to look for a deeper explanation of what the wavefunction is.
Albert Einstein also favoured a statistical interpretation of the wavefunction, although he thought that there had to be some other as-yet-unknown underlying reality. But others, such as Austrian physicist Erwin Schrödinger, considered the wavefunction, at least initially, to be a real physical object.
Such experiments have persuaded many physicists to live comfortably with the wave function’s probabilities, happy to comply with an often-repeated quantum theorist creed: “Shut up and calculate.” But others insist that the wave function or quantum state has real physical existence. Whether it’s real or merely a tool for calculating probabilities is today “perhaps the most hotly debated issue in all of quantum foundations,” quantum physicist Matthew Leifer writes in a recent paper in the journal Quanta.
Dressing this debate in philosophical jargon, Leifer and others in the field label the two possibilities as “ontic” and “epistemic.” These are not words you should try to use at home. But when eavesdropping on quantum debates, you should know that “ontic” refers to something physically real; “epistemic” alludes to mere knowledge about something.
originally posted by: swanne
a reply to: neoholographic
Whatever man, believe what you want to believe. Seems to me like you have all figured it out, as always.
originally posted by: Alien Abduct
a reply to: neoholographic
" Albert Einstein also favoured a statistical interpretation of the wavefunction...."
Didn't Einstein say that God doesn't play dice?
A fundamental scientific assumption called local realism conflicts with certain predictions of quantum mechanics. Those predictions have now been verified, with none of the loopholes that have compromised earlier tests.
Albert Einstein once said that “God does not play dice with the universe,” implying that quantum particles are not strictly randomized. According to his principle of local realism, Einstein believed that each particle needs to have a pre-existing value to be measurable. In other words, if there is no value before a measurement is made, a measurement can’t be made.
For those studying in the field of quantum mechanics, however, local realism just doesn’t pan out, and scientists have been trying to prove it ever since John Stewart Bell first created ‘Bell’s Theorem,’ which states that “No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics.”
Participants contributed to the study by playing a video game created by the scientists who ran the project. In the game, players independently introduced sequences of 0s and 1s as randomly as they could. Those sequences, in turn, controlled the experiments by determining the measurements of quantum particles in 12 labs.
Each of the bits created by the players gave the scientists millions of unpredictable, independent decisions with which to measure their particles. The independence of the decisions was critical as without it the experiment would not be able to reach a valid conclusion about the Bell theory. Going by that theory, experimenters must do their measurements using human decisions, and when they calculate the “Bell parameter” (or, parameter S), S cannot be greater than 2. If it is, then the inequality has been violated, and an intrinsically quantum phenomenon is present. Translation: if S is greater than 2, then there is an element of randomness within quantum mechanics.
So, local reality may be a big load of bunk as far as quantum mechanics is concerned, and randomness may be necessary to understand quantum mechanics.
Upon looking over the data from the experiment, it was determined that Bell’s theory had been violated, confirming the importance of randomness in quantum mechanics and refuting Einstein’s theory of local realism.
Cosmological constant problem
In cosmology, the cosmological constant problem or vacuum catastrophe is the disagreement in measured values of the cosmological constant. In general relativity, the value is measured by the vacuum energy density to be a small value. In cosmological constant, the zero-point energy suggested by c, is measured to be much larger.
Depending on the assumptions, the discrepancy ranges from 40 to more than 100 orders of magnitude, a state of affairs described by Hobson et al. (2006) as "the worst theoretical prediction in the history of physics."[1]
The Texas Tech University professor of chemistry and biochemistry said that quantum mechanics is a strange realm of reality. Particles at this atomic and subatomic level can appear to be in two places at once. Because the activity of these particles is so iffy, scientists can only describe what's happening mathematically by "drawing" the tiny landscape as a wave of probability. Chemists like Poirier draw these landscapes to better understand chemical reactions. Despite the "uncertainty" of particle location, quantum wave mechanics allows scientists to make precise predictions. The rules for doing so are well established. At least, they were until Poirier's recent "eureka" moment when he found a completely new way to draw quantum landscapes. Instead of waves, his medium became parallel universes. Though his theory, called "Many Interacting Worlds," sounds like science fiction, it holds up mathematically. Read more at: phys.org...
Many Interacting Worlds theory doesn't prove that the quantum wave does not exist, or that many worlds do exist, Poirier said. The standard wave theory is perfectly fine in most respects, providing agreement with experiment, for example. "Our theory, though based on different mathematics, makes exactly the same experimental predictions," he said. "So what we have done is to open the possibility that the quantum wave may not exist. It now has only as much right to that claim as do many interacting worlds – no more and no less. This may be as definitive a statement as one can hope to make about a subject that has confounded the best minds of physics for a hundred years and still continues to generate controversy." Read more at: phys.org...
At a certain point, Poirier wondered what would happen if you left the wave computations out and just worked with the quantum trajectories and if the simpler numerical simulation still would be valid. "My key insight was to realize that all you really need are the moving quantum trajectories themselves," he said. "The quantum wave is not actually needed to tell your trajectories how to move. The trajectories tell themselves how to move. Moreover, you don't need the wave for anything else either. Any scientific question that might be answered by knowing the motion of the wave can also be answered just as easily by knowing the motion of the trajectories alone. So the wave becomes completely extraneous and can be discarded altogether." Read more at: phys.org...
originally posted by: Alien Abduct
a reply to: neoholographic
" Albert Einstein also favoured a statistical interpretation of the wavefunction...."
Didn't Einstein say that God doesn't play dice?