Question Can time as a torus make sense of quantum physics?

Sep 18, 2021
2
0
10
What we think of as time can be seen in an abstract form of a torus. Where the 'now' is at the top, (if the torus was upright like the tire on a car) and the future in front going around the torus to the bottom where it runs into the past. This is not to say that time loops or repeats, it's just an model of how to think about these specific mysteries in quantum physics. Therefore, when a photon goes through the slit and is observed, be it in the interference pattern on the wall or in non interference pattern - when the observation is made, the information travels into the future and resolves with all the other information in the future and continues until it goes around the torus and eventually comes into the past and back to the present moment, while at the same time 'resolving' with other information from the past, up to the present moment. In this way, the outcome is already resolved with the future and the past and the outcome conforms with both. It may be that the changes in the 'now' also makes changes in the future and maybe even changes the past or that it doesn't make changes and it just resolves to be in sync with what the future and the past requires of it. This model can work for the double slit mystery and for entangled particles, including where future actions may influence past events as predicted by physicist Asher Peres in 2000 and realized in a paper reporting the experiment published online April 22 in the journal Nature Physics, led by Xiao-song Ma of the Institute for Quantum Optics and Quantum Information at the University of Vienna.
 
Jan 27, 2020
243
85
680
Mr Joubert -

I'm not sure if time acts like a torus in the " mystery and for entangled particles, including where future actions may influence past events as predicted by physicist Asher Peres in 2000 and realized in a paper reporting the experiment published online April 22 (2012) in the journal Nature Physics, led by Xiao-song Ma of the Institute for Quantum Optics and Quantum Information at the University of Vienna," which you mention above.

See: "Quantum Theory Needs No Interpretation", Article Published in Physics Today · September 2000, https://www.researchgate.net/publication/2462691

See: "Experimental Delayed-Choice Entanglement Swapping", Published 22 April 2012, https://www.nature.com/articles/nphys2294

However, a view of the apparatus used in 2012 experiment might help in better understanding the experiment in question.

If one views the quantum state as a real physical object, one could get the seemingly paradoxical situation that future actions appear as having an influence on past and already irrevocably recorded events. However, there is never a paradox if the quantum state is viewed as to be no more than a “catalogue of our knowledge” . Then the state is a probability list for all possible measurement outcomes, the relative temporal order of the three observer’s events is irrelevant and no physical interactions whatsoever between these events, especially into the past, are necessary to explain the delayed-choice entanglement swapping. What, however, is important is to relate the lists of Alice, Bob and Victor’s measurement results (see below). On the basis of Victor’s measurement settings and results, Alice and Bob can group their earlier and locally totally random results into subsets which each have a different meaning and interpretation. This formation of subsets is independent of the temporal order of the measurements.

According to the physicist John Wheeler, NeilsBohr said: “No elementary phenomenon is a phenomenon until it is a registered phenomenon.” This should be extended to include: “Some registered phenomena do not have a meaning unless they are put in relationship with other registered phenomena.”

Screen Shot 2021-09-18 at 11.18.50 PM.png
Screen Shot 2021-09-18 at 11.20.10 PM.png


Screen Shot 2021-09-18 at 11.29.03 PM.png
Screen Shot 2021-09-18 at 11.31.26 PM.png

The experimental scheme and the time diagram of the relevant events is shown in Fig. 1 showed that the generation of photons 1 and 2 (event GI) happened at 0 ns (nano-seconds), as the origin of the diagram. The generation of photons 3 and 4 (event GII) happened 1.6 ns later. At 35 ns, the measurements of Alice and Bob (events MA and MB) occurred. The choice of Victor (event CV) was made by the QRNG in the time interval ranging from 49 ns to 348 ns and sent to the tunable BiSA. Due to the fibre delay of photons 2 and 3, at 520 ns Victor performed the bipartite state measurement (event MV) according to the bit value of his choice. Note that our definition of the choice event is very conservative. This is because in addition to the fixed amount of the electrical delay of the EOMs’ driver (45 ns), QRNG (75 ns) and connecting cables (20 ns), we also included 3 times the QRNG autocorrelation time (3⋅10.7 ns ≈ 32 ns) and the on-time of the EOMs (299 ns). This on-time gave the time of event CV a lower bound of 49 ns and an upper bound of 348 ns. As shown in Fig. 1, it is clear to see for each successful run (a 4-fold coincidence count) that not only event MV happened 485 ns later than events MA and MB, but also event CV happened 14 ns to 313 ns later than events MA and MB even in this conservative consideration. Therefore, this configuration unambiguously fulfilled the delayed-choice condition. Note that the main uncertainty of the experiment in time for measurements is the detector jitter, which is about 800 ps.

In the entanglement swapping 1-3 procedure, two pairs of entangled photons are produced, and one photon from each pair is sent to Victor. The two other photons from each pair are sent to Alice and Bob, respectively. If Victor projects his two photons onto an entangled state, Alice’s and Bob’s photons are entangled although they have never interacted or shared any common past. What might be considered as even more puzzling is Peres’ idea of “delayed-choice for entanglement swapping” . In this gedanken (thought) experiment, Victor is free to choose either to project his two photons onto an entangled state and thus project Alice’s and Bob’s photons onto an entangled state, or to measure them individually and then project Alice’s and Bob’s photons onto a separable state. If Alice and Bob measure their photons’ polarization states before Victor makes his choice and projects his two photons either onto an entangled state or onto a separable state, it implies that whether their two photons are entangled (showing quantum correlations) or separable (showing classical correlations) can be defined after they have been measured. In order to experimentally realize Peres’ thought experiment, Victor ’s choice and measurement must be placed in the time-like future of Alice’s and Bob’s measurements, providing a “delayed-choice” configuration in any and all reference frames. This is accomplished by (1) proper optical delays for Victor’s photons and (2) a high-speed tunable bipartite state analyzer, which (3) is controlled in real time by a quantum random number generator. Both delay and randomness are needed to avoid the possibility that the photon pairs can “know” in advance which setting will be implemented after they are registered and can behave accordingly by producing results of a definite entangled or a definite separable state. Whether Alice’s and Bob’s photons can be assigned an entangled state or a separable state depends on Victor’s later choice. In Peres’ words: “if we attempt to attribute an objective meaning to the quantum state of a single system, curious paradoxes appear: quantum effects mimic not only instantaneous action-at-a-distance but also, as seen here, influence of future actions on past events, even after these events have been irrevocably recorded.”

Historically, delayed-choice entanglement swapping can be seen as the fascinating consequence of emerging from combining the gedanken* (thought) experiments by Neils Bohr (gedanken, Bohr's term), illustrated by a quantum entanglement double-slit setup, and John Wheeler, illustrated by the complementarity principle, one of the most basic principles of quantum mechanics, with a double-slit apparatus. If both slits are open, the input quantum system exhibits “wave-like” behavior and shows interference on the detector screen. If only one slit is open, the system can only propagate through this slit. In this case, no interference will be observed and the system exhibits “particle-like” behavior with a well-defined path.

In accordance with the complementarity principle, full interference and full path information will never be obtained simultaneously. As an explanation it is often said that any attempt to determine which path a particle takes inside an interferometer disturbs the particle and thus prevents the interference pattern from forming. From a modern point of view, however, interference patterns can arise if and only if no information about the path taken exists either on the particle itself or in the environment, regardless of whether or not an observer accesses this information.

If the choice between complementary experimental settings—one demonstrating interference, one revealing which-path information—is made in the past, an explanation of Bohr’s complementarity can be given in the following way: before the particle enters the interferometer, it “receives” information which setting has been prepared and then behaves correspondingly. For example, the two complementary settings in a photonic Mach-Zehnder configuration can be implemented by inserting or removing the output beam splitter that recombines the two interfering paths. To avoid the possibility that the photon will somehow “know” in advance whether the output beam splitter is chosen to be inserted or not, Wheeler suggested to delay this choice after the photon has passed the input beam splitter.

Many so-called “delayed-choice” experiments have been performed, including the scheme when the choice to insert or remove the output beam splitter is made at a space-time location that is space-like separated from the entrance of the photon in the interferometer According to Wheeler, “we have a strange inversion of the normal order of time. We, now, by moving the mirror in or out have an unavoidable effect on what we have a right to say about the already past history of that photon.” Evidently, even in such a delayed-choice scenario, the choice has to be made in the past light cone of the final detection of the photon.

On the other hand, delayed-choice experiments with entangled photons pave the way for new possibilities, where the choice of measurement settings on the distant photon can be made even after the other photon has been registered. This has been shown in a delayed-choice quantum eraser experiment where the which-path
information of one photon was erased by a later suitable measurement on the other photon. This allowed a posteriori to decide a single-particle characteristic, namely whether the already measured photon behaved as a wave or as a particle. However, while all previous delayed-choice experiments focused on the characteristics of individual particles, delayed-choice entanglement swapping, using a four-partite entangled state, allows, a posteriori, to decide a two-particle characteristic and thus has qualitatively new features. Just as there is a wave-particle duality for single particles, there is an entanglement-separability duality for two particles. Entanglement and separability correspond to two mutually exclusive types of correlations between two particles.

I hope the diagrams of the apparatus used in the 2012 experiments, performed by Xiao-song Ma and his co-authors, and their explanations, as well as an overview of the work of Christopher Fuchs and Asher Perez in their 2000 paper, help to clarify this rather difficult area to grasp. Particle-wave duality, entanglement-separability and delayed choice entanglement are as hard to grasp as the idea of life and death and Schrödinger's cat being in both those states until you open the box the cat is in.
Hartmann352

See: https://arxiv.org/vc/arxiv/papers/1203/1203.4834v1.pdf

* gedanken experiment (German: “thought experiment”) term used by German-born physicist Albert Einstein to describe his unique approach of using conceptual rather than actual experiments in creating the theory of relativity.

For example, Einstein described how at age 16 he watched himself in his mind’s eye as he rode on a light wave and gazed at another light wave moving parallel to his. According to classical physics, Einstein should have seen the second light wave moving at a relative speed of zero. However, Einstein knew that Scottish physicist James Clerk Maxwell’s electromagnetic equations absolutely require that light always move at 3 × 108 metres (186,000 miles) per second in a vacuum. Nothing in the theory allows a light wave to have a speed of zero. Another problem arose as well: if a fixed observer sees light as having a speed of 3 × 108 metres per second, whereas an observer moving at the speed of lightsees light as having a speed of zero, it would mean that the laws of electromagnetism depend on the observer. But in classical mechanics the same laws apply for all observers, and Einstein saw no reason why the electromagnetic laws should not be equally universal. The constancy of the speed of light and the universality of the laws of physics for all observers are cornerstones of special relativity.

See: https://www.britannica.com/science/Gedankenexperiment
 
Last edited:

ASK THE COMMUNITY