Author: haroonkhan
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Bits vs. Qubits
The basic unit of information in a classical computer is a bit, which is a little register that can take on two possible values usually called “0” and “1.” If one bit can take two values (0 and 1), then two bits can take four (22) values (00, 01, 10, and 11). Three bits offers…
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The Quantum Computer
Computers are used practically everywhere and in just about everything. In the 1960s the first computers could fill a small room. Today, computers are small enough to fit in the palms of our hands, or even smaller, thanks to improved semiconductor technologies. Manufacturers are now capable of making nanometer-sized (10-9 meter) computer chips, or nanochips. The…
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Introduction
We have learned throughout this book that discoveries in quantum physics have allowed us to better understand nature. Though it provides many answers, it also continues to open up even deeper puzzles. To address these, scientists keep expanding and improving their theories and experiments, and have occasionally stumbled upon major discoveries so unexpected that they…
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The Imaging of Viruses
You may not believe it the next time you come down with a cold, but viruses are small. In fact, at tens to hundreds of nanometers, they belong to the quantum realm. As a result, they typically push the limits of electron microscopes. That explains why only a small fraction of the large variety of…
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The Smoke Detector
While you probably do not have a scanning tunneling microscope installed in your kitchen, chances are you do have another device that is equally dependent on the effect of quantum tunneling. At the heart of your average smoke detector is an ionization source used to detect the presence of smoke particles. The source is typically…
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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…