The intriguing world of quantum physics is vastly different to the one humans may perceive on a day to day basis. In Earth’s classical environment apples fall to the ground, cars travel at measurable speeds and reactions occur when matter comes together. People might therefore be forgiven if they find quantum physics a challenge. A subject proposing that particles may be in two places at once, and that they may react to one another when apart is challenging to comprehend. However, quantum physics is at the forefront of human knowledge, attempting to explain the complex workings of the universe. The quantum world constantly produces more answers and questions, whilst allowing scientists and engineers to create new technology with this knowledge.
The idea of quantum physics has been circulating through scientific communities since the early 20th century, as physicists were challenged by new, observable phenomenon on the micro scale. Quantum physics acknowledges that all matter that makes up the universe behaves as both a particle and a wave. For example light appears to behave like a wave, however it simultaneously has properties of a particle (described as the photon). Predicting where you find these wave – particles also relies only on probability. Whereas in classical physics scientists may determine the exact outcome of an experiment, in quantum physics they are only able to predict with a certain probability. The outcome is random.
Another quantum phenomenon is that the act of measuring a wave – particle directly affects its outcome. The most famous example of this is the double slit experiment where measuring the path of an electron determines which path (or slit) it will take. In an unmeasured version the electron takes both paths simultaneously. This is known as superposition where the electron exists in all possible states until it is measured. The effect inspired Schrödinger to postulate his famous cat in a box thought experiment, where the cat is both alive and passed away at the same time, until the box is opened.
Last month a group of researchers at the Austrian Academy of Sciences in Vienna created an image of Schrödinger’s cat using the quantum entanglement effect. Entanglement demonstrates that when two quantum particles interact in a specific way, one particle’s state may depend on the other, and vice versa. However, this interaction occurs regardless of how far apart the two are. When measured, at whatever distance, the two are always in the same state. The image of Schrödinger’s cat was indirectly produced using entangled photons that never interacted with either the stencil or the camera. Some researchers, such as Tollaksen et al from Chapman University in California have taken the entanglement principle to the next level, and believe that all particles are correlated through this effect.
Quantum physics, whilst providing might be one of the more challenging puzzles of modern science, does produce results that may be translated to modern technology. Even something as simple as the light bulb relies on the effects of quantum tunneling whereby electrons are able to penetrate the potential energy barrier to create the appearance of light. When throwing a ball into the air for example, it reaches a peak before its energy dictates it will begin falling back to Earth again. In quantum tunneling electrons are sometimes found beyond this energy peak – where the ball would normally fall back to Earth. This principle is vital to quantum computers, which are able to perform tasks far faster than the classic computer. Companies such as Google and NASA have invested in developing such technology.
Famous physicists Einstein and Bohr had many debates over the scientific and philosophical consequences of quantum effects. Might the superposition of particles mean that at each measurement countless parallel worlds are created with a different result? Questions such as this still echo through today’s scientific community. The world of quantum is both fascinating and challenging, especially as people are so familiar with classical physics. However, with a scientific approach, anybody may be involved in the understanding of the subject.
What other questions might quantum physics raise about the nature of the universe?