Author: haroonkhan
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The Semiconductor
Aside from the odd molecule here and there, up until now we have focused pretty much on atoms (and nuclei) in isolation. A quick glance around you, though, reveals that this is really a small part of the picture. Your house is filled with solid objects, from in your hands to the wires in your…
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The Global Positioning System
You’ve likely heard of the Global Positioning System—or at least its acronym, GPS—since you probably have a receiver in your car, your cellphone, or both. But did you know that GPS wouldn’t tick if not for the laws of quantum physics? This is because on board each GPS satellite is an atomic clock, the most…
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The Laser
The laser is one of the best examples of a quantum application because it is so widely used. We explained that excited atoms emit photons by making a quantum jump to a lower energy state. In most cases this occurs without any influence from the outside, and emissions of this variety are called spontaneous. It turns…
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The Neon Light
The forerunner for the iconic neon light was first demonstrated in 1855 by the German physicist Heinrich Geissler. He observed that a soft glow was emitted when an electric field was applied across a gas tube containing a low-pressure gas. We now understand that the applied electric field was stripping electrons from the atoms in…
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Introduction
Quantum physics has not only improved our fundamental understanding of nature. It has also spawned a new breed of technology, thanks in part to the ingenious experiments that validated many aspects of quantum theory over the past century. We will begin our survey of today’s quantum technologies, carefully relating each to the principles we developed…
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Beyond Experiment?
The testing of hypotheses and theoretical predictions is such an integral part of science that we really have to question any theory that cannot be tested. If a scientific theory cannot be tested, is it really a scientific theory at all? Is it good enough that experimental tests may be possible in the distant future?…
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Loop Quantum Gravity
Loop quantum gravity (LQG) is a theoretical framework that tries to quantize space and time directly. This seems to make a lot of sense, given that general relativity relates gravity to the shape of spacetime itself. If the ultimate goal is a quantum theory that applies to gravity, it stands to reason that space and…
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String Theory
String theory is actually a name for a class of theories which may eventually give us a theory of everything. The basic principle of string theory is that all of the elementary particles of the standard model are just different modes of vibration of a more fundamental object: a tiny, one-dimensional “string.” These are not…
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Supersymmetry
The first extension of the standard model that attempts to address some of its shortcomings and incorporate gravity is called supersymmetry, or SUSY for short. SUSY proposes that every fermion has a boson partner that is a totally new particle (not one of the known exchange bosons). Not only that, but all the known bosons…
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Possible Quantum Theories of Gravity
In the next few sections, we’ll briefly describe some of the ways that theorists are taking on the huge challenge of bringing gravity into the standard model.