Physics in a New Era An Overview (2001) / Chapter Skim
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1. Quantum Manipulation and New Materials
1. Quantum Manipulation and New Materials
Pages 17-36
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Part I Physics Frontiers
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Atomic physicists have begun to study ancl control the new quantum properties that emerge in large collections of atoms, a traditional theme in condensed matter physics. At the same time, condensed matter physicists have begun to learn how to shrink the materials they study to sizes in which discrete quantum excitations (the traditional province of atomic physics)
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But the revolution in quantum mechanics of the early 20th century began a new era in microscopes: Particles such as electrons can also act like waves but can have far smaller wavelengths than visible light ancl hence can be used to make more powerful microscopes. Moclern electron microscopes have resolution 10,000 times finer than conventional optical microscopes ancl can see the individual atoms inside a diamond crystal.
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The figure shows a "quantum corral" consisting of an elliptical ring of 34 cobalt atoms placed on a copper surface. Quantum electron waves traveling along the copper surface are reflected by the corral atoms and trapped inside.
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Strange new quantum states can be created, providing arenas in which to test basic quantum mechanics and novel methods of quantum information processing. The most widespread advances have come from using laser radiation to slow, and hence cool, a sample of atoms.
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Thus, in a technique called contrast variation, scientists can highlight different types of molecules, such as a nucleic acid or a protein in a chromosome, and glean independent information on each component within a large biomolecule. We see below a model of two insulin molecules containing zinc ions (white balls)
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The laser trap provides a simple ancl inexpensive source of very cold trapped atoms ancl is seeing wiclespreacl use in the research laboratory as well as in novel applications for improving atomic clocks ancl lithography. Achieving and Using the Quantum Regime Novel cooling ancl confinement techniques allow atoms to be sufficiently cooled so that they no longer act as a group of indistinguishable particles but rather as waves corresponding to a single coherent quantum state.
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A special case has been the atomic clock, a device using the structure of the atom to define the second precisely (see sidebar "Atomic Clocks". The world's most precise clocks now use cesium fountains, in which samples of ultracold cesium atoms are launched upward.
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The second is now defined in terms of the separation of the two lowest energy states in the cesium atom. Atomic clocks provide the basis for precise navigation, including the global positioning system.
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BEC has opened up opportunities to explore quantum behavior in a novel regime as well as allowed manipulation of atomic samples with a precision limited only by the uncertainty principle of quantum mechanics. Experiments on condensate behavior involving dissipation and coupling between the quantum state and the environment have provided many surprises and challenges to theoretical understanding.
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Another practical use of the novel behavior of atoms in intense laser fields has been the creation of brighter sources of light in the far-infrared, ultraviolet, and x-ray spectral regions with shorter pulses. Pulsed x rays produced in this interaction between atoms and intense light will make it possible to study problems in surface science, such as catalysis, chemistry, atomic physics, and biological imaging, with unprecedented temporal and spatial resolution.
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In cuprates, however, the electron distribution is less symmetric, as illustrated by the fourfold symmetry in the figure below. Today's high-temperature superconductors are finding growing use in filters for the wireless communications industry, as magnetic field sensors in medical scanning applications and in _ _ .
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Many of the materials advances listed in Table 1.1 aciciressecl a technological neecl, such as information storage and transfer. Others were ciriven TABLE 1.1 Some New Materials of the Past 15 Years Advance Driver Nature of Advance New compounds/materials High-temperature superconductors Science Unexpected Organic superconductors Science Unexpected Rare-earth optical amplifiers Technology Evolutionary High-field magnets Technology Evolutionary Organicelectronic materials Technology Evolutionary Magneto-optical recording materials Technology Evolutionary Amorphous metals Technology Evolutionary New structures of known materials Quasicrystals Science Unexpected Buckyballs and related structures Science Unexpected Nanoclusters Science Evolutionary Metallic hydrogen Science Evolutionary Bose-Einstein condensates Science Evolutionary Giant magnetoresistance materials Technology Unexpected Diamond films Technology Evolutionary Quantum dots Technology Evolutionary Foams/gels Technology Evolutionary New properties of known materials Gallium nitride Technology Unexpected Silicon-germanium Technology Evolutionary
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The fractional quantum Hall effect was first observed in high-mobility semiconductor structures now used in high-frequency applications. Many of the advances listed in Table 1.1, such as the development of giant magnetoresistance materials, have driven the technology of the information age.
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Biology and physics will overlap even more in the future as physicists imitate nature for improved nanostructural control and as artificial nanostructures are used in biomedical applications.
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A related and important new direction for the coming decade can be called "molecular electronics." Using methods made possible by advances in lithographic fabrication and scanning tunneling microscopy, physicists are beginning to study the transport of electrons through a single molecule. In the future it may be possible to identify DNA sequences from their electrical properties.
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Using combinations of laser light and radio waves to manipulate the trapped atoms, rudimentary computational operations have been performed on qubits. Quantum engineering methods can be extended from a single atom to entangled states of many atoms using a suitable coupling mechanism.
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these technologies to learn what may or may not be feasible for practical applications. Although practical quantum computers are not likely to exist in the near future, more modest uses for multi-atom entangled states, such as improvements in atomic spectroscopy and atomic clocks, appear to be with i n reach.
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From page 36... ...
36 PHYSICS IN ~ NEW ERA We are in the midst of an exciting revolution in the ability to observe and manipulate material at the quantum leveL The next few decades are certain to lead to new insights into the strange world of quantum physics and to dramatic advances in technology/ as the geld of quantum englneer.
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