The Famous Schrödinger’s Cat Dead or Alive?

admin — Sat, 25 Sep 2021 15:36:25 +0000

Can a cat be dead and alive at the same time? If it helps explain quantum physics, then why not!

Austrian physicist Erwin Schrödinger is considered as one of the founders of quantum mechanics. However, he got repute for something that he never envisioned he would – a thought experiment involving a cat.

In this thought experiment, he imagined taking a cat and placing it in a sealed box with a device that had a 50% chance of killing the cat in the next hour. Hence, after an hour the cat will be either alive or dead. Interestingly enough, Schrödinger pointed out that according to quantum physics, at the instant just before opening the box, the cat is in equal parts and at the same time, both alive and dead.

There will be single definite state of the cat when the box is opened. Until then, the cat is a blur of equal probability of dead and alive. This seems absurd, which was Schrödinger’s original point. As a result, quantum physics so philosophically disturbing to Schrödinger’s that he abandoned it (the theories he created) and turned to writing about biology. As absurd as it may seem, Schrödinger’s cat is very much real. More than that, it is essential. If it was not possible for the quantum object to be in two states at once, the quantum computer the enable us to observe this could not exist. The quantum phenomenon of superposition is a consequence of coexistence of particle and wave duality of “every” object. In order for an object to possess a wavelength, it must extend over some region of space. It is only possible when the object occupies many positions at the same time. Having said that, the wavelength of an object limited to a small region of space cannot be perfectly defined.

Therefore, it exists in many different wavelengths at the same time. The wave properties for “everyday” objects is not manifested because the wavelength decreases as the momentum increases. Additionally, a cat is relatively big and heavy. If we took a single atom and blew it up to the size of the Solar System, the wavelength of a cat running from a physicist would be as small as an atom within that Solar System. That is extremely minuscule to detect, so we can never perceive wave behavior from a cat.

A tiny particle, such as an electron, can show dramatic evidence of its duality principle. If an electron beam is shot (one at a time) at a set of two narrow slits (Double slit experiment wiki link) cut in a barrier, each electron on the far side is detected at a single place at a specific instant, like how a particle would. However, if on repeating this experiment multiple times while keeping track of all the individual detection, a trace out a pattern emerges. It is characteristic of wave behavior, a set of stripes – regions with many electrons separated by regions where there is none at all. Block one of the slits and the stripes go away. This shows that the pattern is a result of each electron going through both slits at the same time. A single electron is not choosing to go either left or right, but left and right simultaneously.

This superposition of states also leads to modern and advanced technology. An electron near the nucleus of an atom exists in a spread out, wave-like orbit. Bring two atoms close together, and the electrons do not choose a single atom, but are shared between them resulting in chemical bonds. An electron in a molecule is not a part of either atom A or atom B, but part of A+ B. The number of atoms increases the number of spread out electrons shared between vast numbers of atoms at the same time. The electrons in a solid are not bound to a particular atom but shared among all of them and extends over a large range of space.

This gigantic superposition of states determines the method by which electrons traverse through different material, be a conductor or an insulator or a semiconductor. Understanding electrons sharing among atoms allows precise control of the properties of semiconductor materials such as silicon. Combining different semiconductors in a proper technique produces transistors on a tiny scale. Millions of transistors build a single computer chip.

Those chips and their spread out electrons power the computer to read this article. An old joke says that the internet exists to allow the sharing of cat videos (Read more). Deep down, the Internet owes a part of its existence to an Austrian physicist and his imaginary cat.

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Evading The Uncertainty Principle in Quantum Physics

admin — Tue, 01 Jun 2021 16:00:02 +0000

The uncertainty principle, first introduced by Werner Heisenberg in the late 1920’s, is a fundamental concept of quantum mechanics. In the quantum world, particles like the electrons that power all electrical product can also behave like waves. As a result, particles cannot have a well-defined position and momentum simultaneously. For instance, measuring the momentum of a particle leads to a disturbance of position, and therefore the position cannot be precisely defined.

In recent research, published in Science, a team led by Prof. Mika Sillanpää at Aalto University in Finland has shown that there is a way to get around the uncertainty principle. The team included Dr. Matt Woolley from the University of New South Wales in Australia, who developed the theoretical model for the experiment.

Instead of elementary particles, the team carried out the experiments using much larger objects: two vibrating drumheads one-fifth of the width of a human hair. The drumheads were carefully coerced into behaving quantum mechanically.

“In our work, the drumheads exhibit a collective quantum motion. The drums vibrate in an opposite phase to each other, such that when one of them is in an end position of the vibration cycle, the other is in the opposite position at the same time. In this situation, the quantum uncertainty of the drums’ motion is cancelled if the two drums are treated as one quantum-mechanical entity,” explains the lead author of the study, Dr. Laure Mercier de Lepinay.

This means that the researchers were able to simultaneously measure the position and the momentum of the two drumheads — which should not be possible according to the Heisenberg uncertainty principle. Breaking the rule allows them to be able to characterize extremely weak forces driving the drumheads.

“One of the drums responds to all the forces of the other drum in the opposing way, kind of with a negative mass,” Sillanpää says.

Furthermore, the researchers also exploited this result to provide the most solid evidence to date that such large objects can exhibit what is known as quantum entanglement. Entangled objects cannot be described independently of each other, even though they may have an arbitrarily large spatial separation. Entanglement allows pairs of objects to behave in ways that contradict classical physics, and is the key resource behind emerging quantum technologies. A quantum computer can, for example, carry out the types of calculations needed to invent new medicines much faster than any supercomputer ever could.

In macroscopic objects, quantum effects like entanglement are very fragile, and are destroyed easily by any disturbances from their surrounding environment. Therefore, the experiments were carried out at a very low temperature, only a hundredth a degree above absolute zero at -273 degrees.

In the future, the research group will use these ideas in laboratory tests aiming at probing the interplay of quantum mechanics and gravity. The vibrating drumheads may also serve as interfaces for connecting nodes of large-scale, distributed quantum networks.

Source: https://www.aalto.fi/en/news/evading-the-uncertainty-principle-in-quantum-physics

The post Evading The Uncertainty Principle in Quantum Physics appeared first on Welcome to Quantum Guru.

Quantum Physics Archives - Welcome to Quantum Guru

The Famous Schrödinger’s Cat Dead or Alive?

Can a cat be dead and alive at the same time? If it helps explain quantum physics, then why not!

Evading The Uncertainty Principle in Quantum Physics