Quantum Physics Basics 2

    Over the past five decades or so three theories have been brought together in a catch-as-catch-can manner, known as the “standard model” of particle physics. Despite the fact that this model on close examination appears to be held together by spit and chewing gum, it turns out that until recently, it was the most accurate basic picture of how matter works that had ever been devised.  

   The “standard model” proved its worth in 2012 with the discovery of Higgs boson, the particle that gives all other fundamental particles their mass, whose existence was predicted on the basis of quantum field theories as far back as 1964.

   Conventional quantum field theories work well in describing the results of experiments at high-energy particle smashers such as CERN’s Large Hadron Collider, where the Higgs was discovered, which probe matter at its smallest scales. (CERN is the world’s largest particle physics laboratory—an international scientific collaboration without parallel in its scale and ambition—located on the border between Switzerland and France.)

   CERN was established by international convention in the aftermath of the second world war by the European Council for Nuclear Research and was originally intended to foster collaborative research into fundamental physics for peaceable purposes. Today, some 12,000 researchers from across the globe use its facilities each year, and it has been the scene of seminal scientific and technological breakthroughs—notably the World Wide Web, invented in 1989  within its doors to allow particle physicists to exchange data across borders.

   In spite of these great scientific breakthroughs using quantum physics, there are some lesser problems that still remain insoluble—e.g., how electrons move or do not move through a solid material and so make a material a metal, an insulator, or a semiconductor.

   The multiplied billions of interactions in these crowded environments require the development of what are called “effective field theories” that gloss over some of the gory details. The challenge quantum physicists face in constructing such theories explains why many important questions in solid-state physics remain unresolved—e.g., why at low temperatures some materials are superconductors that allow current without electrical resistance, and why scientists cannot find a way to get this to work at room temperature.

   Beyond these practical problems lies a huge quantum mystery. At a basic level, quantum physics predicts very strange things about how matter works that are completely at odds with how things seem to work in the “apparent world.”

   For example, quantum particles have the capacity to behave like particles that are located in a single place; or they can act like waves, distributed all over space or in several places. How they appear seems to depend on how scientists choose to measure them, and before they are measured, they seem to have no definite properties at all. This leads to a fundamental insoluble problem related to the nature of basic reality itself.

   One example of this is the paradox of Schrödinger’s cat, in which, thanks to an uncertain quantum process, a cat is left dead and alive at the same time. Quantum particles also seem to be able to affect each other instantaneously even when they are far away from each other. This is called entanglement or, in a phrase coined by Einstein, who contributed to, but was quite critical of quantum theory, “spooky actions at a distance.”

   Even though these quantum powers are by no means completely understood, yet they are in fact the basis of emerging technologies such as ultra-secure quantum cryptography and ultra-powerful quan-tum computing.