Controlling the Quantum World The Science of Atoms, Molecules, and Photons (2007) / Chapter Skim
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2 AMO Science and the Basic Laws of Nature
2 AMO Science and the Basic Laws of Nature
Pages 30-52
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From page 30... ...
In addition to being used to measure α to unprecedented precision as a test of quantum electrodynamics, techniques from AMO science can be used to place limits on the variation of α over cosmological timescales. And laser-based gravitational-wave detectors will characterize gravitational waves and unravel information about their violent origins and about the nature of gravity.
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From page 31... ...
FIGURE 2-1-1 Silver atoms vaporized in an oven are shaped into a beam by the slit, and the beam is passed through a nonuniform magnetic field. The beam splits in two components that contain atoms with up and down spin.
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From page 32... ...
Such spin resonance frequency measurements may provide our best opportunity to detect these tiniest effects of new fundamental forces that cannot yet be seen in experiments at high-energy accelerators. Atomic physics is taking up this challenge by creating ultrasharp spin resonances associated with long spin stability (hundreds to thousands of seconds in the case of nuclear spins in atomic gases or vapors)
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From page 33... ...
. At the same time, such sensitivity to spins and to the effect of magnetic fields on spins is opening up new applications in medical research and diagnosis.
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Indeed, in much of atomic phys ics we can consider bound atomic electrons as point charges interacting with the electric and magnetic fields of the other charges in the atom. Close to an electron, however, there is a lot more happening.
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that is due to the trade-off between the aligning force exerted on the magnetic moments of the atoms by a strong magnetic field and the randomizing force the molecules exert on
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it remains now for other atomic experiments, discussed in the subsection "Fine Structure constant," to measure α to equal precision; then it will be known whether or not the theory of quantum electrodynamics agrees with experiment to such unprecedented accuracy. in a more speculative vein, atomic experiments are so sensitive to the very fabric of space and time that they can measure its underlying symmetries as embodied in the principle of Lorentz invariance.
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From page 37... ...
By comparing the spectral energies of antihydrogen atoms and ordinary hydrogen atoms, one can search for effects due to cPt violation. bi FIGURE 2-4 If there is a preferred direction bi in space in the vicinity of Earth, sensitive spin experiments will show a diurnal effect on Earth as it rotates.
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From page 38... ...
in particular, advances in AMo science have led to ever more accurate atomic clocks. Likewise, improvements in clocks have enabled revolutions in technology, starting with the determination of longitude in the 17th century and leading to the development of the modern global positioning satellite (see Figure 2-5 for one such system)
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From page 39... ...
Knowing the time and the speed of light, the distance can be calculated. The time comes from four atomic clocks on each satellite.
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Cold atom physics continues to bear fruit: Major research pro grams on precision inertial naviga tion systems are under way in the United States and abroad; quantum degenerate Bose and Fermi atomic gases are modeling condensed mat ter systems of interest for both basic science and practical devices (Chap ter 3) ; and ions and atoms are being developed as the qubits for the new science of quantum information (see Chapter 7)
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From page 41... ...
, this improvement is substantial. the recipe for operating an atomic clock in the Heisenberg limit is to create a collective quantum state of all of the atoms, sometimes called a "superatom," that effectively speeds up the atomic clock by a factor of N
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From page 42... ...
,1 known as the fine structure constant α. Although gravity was long thought – to be truly constant over the lifetime of the universe, recent theories unifying it with the other physical interactions suggest the possibility of spatial and temporal variations of α and other physical "constants." Atomic physics comes into this picture because different atomic transitions depend differently on α so that comparing the rates of different atomic clocks over long periods of time allows one to put bounds on the local change of α with – – 1thisformulation of the fine constant uses the term h, which is called h-cross or h-bar.
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From page 43... ...
New instruments based on this technique are expected to revolutionize the fields of inertial navigation and gravitational anomaly detection. there is also a remarkable application of matter-wave interferometry to measuring the fine structure constant α, which could help test the fundamental quantum theory of electricity and magnetism to unprecedented accuracy.
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From page 44... ...
Gravitational waves are predicted to be tiny ripples in the otherwise smooth fabric of spacetime produced by violent events in the distant universe -- for example, by the merging of two neutron stars or two black holes, or in the cores of supernova explosions. they have never been observed directly, but their influence on the orbital motion of the corotating binary pulsar PSR1913+16 has been confirmed by direct measurement.
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SOURCE: LIGO Laboratory. ultrastable laser beams that bounce back and forth millions of times between two freely hanging test masses fitted with mirrors, one at each free end of an arm.
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Development of interferometer configurations that mitigate sensitivity to platform motion while sustaining or improving sensor performance remains a significant scientific challenge. the current generation of atomic sensors is based on laser-cooled ensembles of cold atoms in free space and pulses of laser light.
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From page 47... ...
this principle also renders fermionic interferometry somewhat analogous to white-light interferometry in conventional optics. Fine Structure Constant Matter-wave interference experiments can be used to make precision measurements of the value of the fine structure constant, α.
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Gravity, the least understood of the four fundamental forces in nature, can be investigated with astrophysical observations, specifically in its strong-field regime, where it dramatically affects the nature of space and time. For instance, looking at the exotic environment of a massive black hole or a neutron star and using the spectra of highly ionized atoms of iron and other abundant elements as precision clocks can test the predictions of einstein's theory of general relativity in quantita tive detail (see Figure 2-8)
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the challenges are being addressed with laboratory astrophysics experiments that use high-intensity lasers and/or particle accelerators to simulate such high-energy-density conditions. While the understanding of atomic physics under these conditions is still in its infancy, laser experiments can produce intense field regimes for short durations, as described in chapter 4, which may be useful in this context.
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With increasing spectral resolution of x-ray telescopes in the future, coupled with further detailed calculations and measurements of charge transfer by atomic physicists, cometary x rays can be used as detailed diagnostics of the solar wind composition. 1The solar wind is a dilute plasma composed of protons, electrons, and a variety of atomic ions in many different ionization states.
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amo science B a s i c l aw s n at u r e and the of FIGURE 2-4-1 An x-ray image of the comet LINEAR taken by the Chandra X-Ray Observatory.
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in astrophysics many spectral lines are observed from species that are difficult to produce in the laboratory. Atomic and molecular theory provides critically important input to the models used in the interpretation of these astronomical observations.
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