What happens in a superposition-the circumstance in which particles can be in two or more places or states at the same time?
So, it is a big question in quantum mechanics. Sadly, no one can answer this question. Recently, in a new paper, a group of researchers in Israel and Japan tried to propose an experiment that in the end, we can say something for sure about this big and mysterious phenomenon.
It only takes a few months for these researchers to carry out their experiment. Of course, this experiment also enables scientists to sneak at a glance at where an object called a photon (a particle of lights) resides when it is in a superposition. These researchers predict that the answer will be shocking than two places at the same time.
Perhaps you have known about the old example of a superposition. Research involves firing photons at two parallel slits in a barrier. One says that tiny particles can act like waves so these will pass through one slit “interfere” with those going through the other. The wavy ripples can boost or cancel one another. At this point, it creates a character pattern on a detector screen. This interference happens even though it is only one particle at a time. So, the particle passes through both slits at once, interfering itself and that is known as superposition.
Everything is getting weirder because measuring which slit that particle goes through will only indicate that it goes through one, but then the wavelike interference disappears. The act of measurement is likely to collapse the superposition. Avshalom Elitzur of the Israeli Institue for Advanced Research said that he caught something fishy in a superposition. He explained that it is not allowed to measure it and that is the reason why quantum mechanics so diabolical.
So far, researchers took decades, and they cannot explain what a superposition is without looking at it. On the other hands, when they try to look at it, it vanishes. To handle this problematic issue is by using one potential solution developed by the former mentor of Elitzur, the Israeli physicist, Yakir Aharonov, at Chapman University and his collaborators. They suggest the proper way to deduce something about quantum particles before measuring them. The approach made by Aharonov called the two-state-vector formalism or TSVF of quantum mechanics and postulates quantum events determined by quantum states not just in the past, but in the future as well. So, TSVF believes that quantum mechanics can work the same way, forward and backward in time.
But, you do not have to take this strange notion, literally. In the TSVF, you can select the outcome to know what happened in the quantum system. So, you do not have to measure where a particle ends up. Here, a researcher chooses a particular location to look for it, and it is known as post-selection. It supplies more information than any unconditional peek at outcomes could. The reason is that the researcher evaluates the particle’s state at any instant retrospectively in light of its history, including its measurement. The weird part is that the researcher chooses to look for a particular outcome and then it causes that outcome to happen. It seems like concluding that if you turn on your television when your favorite program is scheduled, your action will cause the program to be broadcast at that moment.
Another example is about the double-slit experiment of Aharonov and his co-worker, Lev Vaidman. He did this experiment in 2003 that they interpreted with the TSVF. They described an optical system in a single photon, and it works as a “shutter” that closes a slit by causing another probe photon approaching the slit to be reflected back the way it came.
Aharonov and Vaidman applied post-selection to the measurements of the probe photon, and they could discern a shutter photo in a superposition closing both slits simultaneously. It means this theory can say the shutter photon is both “here” and “there” at the same time. Even if this situation sounds paradoxical from our everyday experience, we can call it nonlocal properties of quantum particles.
Ryo Okamoto and Shigeki Takeuchi of Kyoto University verified the predictions of Aharonov and Vaidman in 2016. They used a light-carrying circuit in which the quantum router created the shutter photon. The router is a device that allows one photon to control the route taken by another. This experiment became the pioneer that allowed one to infer the simultaneous position of a particle in two places as Elitzur’s colleague, Eliahu Cohen of the University of Ottawa in Ontario, explained.
So, Elitzur and Cohen teamed up with Takeuchi and Okamoto to concoct more mind-blowing experiment. They believe this way can help to find something about the location of a particle in a superposition in different points in time. For this experiment, they used partial mirrors to split the probe photon’s route into three. Each of those paths it may interact with a shutter photon in the superposition. The interactions will take place within boxes labeled A, B, and C.
The goal of this experiment is to see the probe photon that can show interference if it interacted with the shutter photon in the particular sequence of places ad times. The shutter photon was in both boxes A and C at the same time, and then later only in C, and at the later time in both B and C. So, there will be t1, t2, and t3. So, the interference in the probe photon could be the definitive sign of the shutter photon created the bizarre and logic-defying sequence of disjointed appearances among the boxes at a different time.
Even though “two places at once” view of supervision are odd enough, but Elitzur said that it is possible a superposition is a collection of states. He even added that quantum mechanics only tells you about the average. But post-selection allows one to isolate. And then, inspect greater resolution for the states.
Also, researchers explain that conducting the actual experiment required fine-tuning the performance of the quantum routers. They expected to have their system ready in three to five months. Also, Wharton said that the experiment would be a success. But, it would not convince anyone since they use the standard quantum mechanics to predict the results.