Author: Haroon Khalil
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The Electron Microscope
Since the seventeenth century, the ordinary optical microscope has been used to observe objects too small to detect with the naked eye. It uses lenses to bend visible light and create magnified images of these small structures. Its invention brought about breakthroughs in many branches of science. However, since an electromagnetic wave can only resolve…
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Medical Imaging
Many types of medical imaging techniques use quantum physics to reveal, diagnose, or examine disease in the human body. The first application came a mere two months after the German physicist Wilhelm Roentgen discovered the X-ray in 1895. X-rays are produced when a beam of highly energetic electrons is directed onto a sold metal target.…
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Introduction
Throughout this book, we’ve paid many a visit to the so-called “quantum realm,” where particles smaller than a speck of dust begin to demonstrate all the lovely features that we have studied so far. It should be no surprise, then, that one of the most successful applications of quantum physics has been to the imaging…
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Superconductivity
As its name suggests, about the only thing better than a semiconductor is a superconductor. You’ve probably heard this term before, and may have even learned about some of its interesting features. But just what is so super about it anyway? The name comes from the fact that these materials can carry something known as supercurrents,…
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The Solar Panel and the Light-Emitting Diode
We have just mentioned that a little bit of thermal energy (heat) is enough to promote an electron from the valence band of a semiconductor into the conduction band, and therefore to initiate the flow of electricity. We also know, of course, that electrons can undergo upward quantum jumps by absorbing photons. This remains true…
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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…