Quantum Theory Tugged, And All of Physics Unraveled
Published: December 12, 2000
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''There is no other theory of what is happening,'' he said. The world is much bigger than it looks, a realization that he thinks will have a psychological impact equivalent to the first photographs of atoms. Indeed, for Dr. Deutsch there seems to be a deep connection between physics and computation. The structure of the quantum computer, he says, consists of many things going on at once, lots or parallel computations. ''Any physical process in quantum mechanics,'' he said. ''consists of classical computations going on in parallel.''
''The quantum theory of computation is quantum theory,'' he said.
The Roots of Weirdness
Quantum mechanics is the language in which physicists describe all the phenomena of nature save one, namely gravity, which is explained by Einstein's general theory of relativity. The two theories -- one describing a discontinuous ''quantized'' reality and the other a smoothly curving space-time continuum -- are mathematically incompatible, but physicists look to their eventual marriage, a so-called quantum gravity.
''There are different views as to whether quantum theory will encompass gravity or whether both quantum theory and general relativity will have to be modified,'' said Lee Smolin, a theorist at Penn State.
Some groundwork was laid as far back as the 1960's by Dr. Wheeler, 89, who has argued quantum theory with both Einstein and Bohr. Even space and time, Dr. Wheeler has pointed out, must ultimately pay their dues to the uncertainty principle and become discontinuous, breaking down at very small distances or in the compressed throes of the big bang into a space-time ''foam.''
Most physicists today put their hope for such a theory in superstrings, an ongoing and mathematically dense effort to understand nature as consisting of tiny strings vibrating in 10-dimensional space.
In a sort of missive from the front, Edward Witten of the Institute for Advanced Study in Princeton, N.J., said recently that so far quantum mechanics appeared to hold up in string land exactly as it was described in textbooks. But, he said in an e-mail message, ''Quantum mechanics is somehow integrated with geometry in a way that we don't really understand yet.''
The quantum is mysterious, he went on, because it goes against intuition. ''I am one of those who believes that the quantum will remain mysterious in the sense that if the future brings any changes in the basic formulation of quantum mechanics, I suspect our ordinary intuition will be left even farther behind.''
Intuition notwithstanding, some thinkers wonder whether or not quantum weirdness might, in fact, be the simplest way to make a universe. After all, without the uncertainty principle to fuzz the locations of its buzzing inhabitants, the atom would collapse in an electromagnetic heap. Without quantum fluctuations to roil the unholy smoothness of the big bang, there would be no galaxies, stars or friendly warm planets. Without the uncertainty principle to forbid nothingness, there might not even be a universe.
''We will first recognize how simple the universe is,'' Dr. Wheeler has often said, ''when we recognize how strange it is.'' Einstein often said that the question that really consumed him was whether God had any choice in creating the world. It may be in the end that we find out that for God, the only game in town was a dice game.
Photos: Erwin Schrodinger -- Wave mechanics; Louis de Broglie -- Matter waves; Wolfgang Pauli -- Exclusion principle; Werner Heisenberg -- Uncertainty principle; Max Planck -- Quantum energy; Paul Dirac -- Quantum field theory; Albert Einstein -- Light quantum; Max Born -- Probability wave; Niels Bohr -- Atomic model (Institut International de Physique Solvay, courtesy AIP Emilio Segre Visual Archives)(pg. F1); In 1927, scientists discussed quantum theory at the fifth in a series of meetings begun by Ernest Solvay, an industrialist. Front row, from left to right: Irving Langmuir, Max Planck, Marie Curie, Hendrik Lorentz, Albert Einstein, Paul Langevin, Charles Eugene Guye, Charles Wilson, Owen Richardson. Second row: Petrus Debye, Martin Knudsen, William Lawrence Bragg, Hendrik Kramers, Paul Dirac, Arthur H. Compton, Louis de Broglie, Max Born, Niels Bohr. Back row: Auguste Piccard, E. Henriot, Paul Ehrenfest, Edouard Herzen, Theophile De Donder, Erwin Schrodinger, J. E. Verschaffelt, Wolfgang Pauli, Werner Heisenberg, Ralph Howard Fowler, Leon Brillouin. (Institut International de Physique Solvay, courtesy AIP Emilio Segre Visual Archives); Erwin Schrodinger, whose cat was both dead and alive. (Photo Researchers); For Werner Heisenberg, uncertainty was the only sure thing. (Associated Press)(pg. F4); (Tim Charles/East Carolina University); (Michael W. Davidson/Photo Researchers); (University of Wisconsin); (Steve Duenes/The New York Times)(pg. F1) Chart: ''Celebrating a Century of Confusion and Triumph'' Quantum theory ignited a scientific revolution 100 years ago, giving rise to paradoxical notions of lumpy light, wavelike particles and the disconnection of cause and effect. Leading physicists were among those who debated the theory at a 1927 congress in Brussels. The discussion continues in Berlin this week. 1900 -- Max Planck proposes that atoms emit energy in discrete amounts, called quanta, rather than in continuous waves. 1905 -- Albert Einstein explains the photoelectric effect (light strikes an atom and dislodges an electron) by suggesting that light is made of little energy bundles, which are later called photons. Compact disc players work when the light (photons) from a laser strikes a sensor (photodiode) to generate electrical current (electron release). 1913 -- Niels Bohr proposes a planetary model of the atom in which electrons orbit the nucleus and jump between orbits as the atom absorbs or emits energy. 1924 -- Louis de Broglie develops the idea that matter, like light, can behave as waves. According to de Broglie's formula, the wavelength of an electron is only about one-10,000th the wavelength of a photon of light. In electron microscopes, beams of matter, electron beams, explore spaces far smaller than those accessible to light. At right, the mouth of the common housefly. 1924 -- Einstein and Satyendra Nath Bose develop a set of statistics recognizing a class of particles, called bosons, which can collectively exist in the same state of energy. Photons are bosons, so they can collectively occupy a single state, allowing them to coalesce as an intense laser beam. 1925 -- Wolfgang Pauli develops the exclusion principle, stating that no two electrons in an atom can occupy the same state of energy simultaneously. This explains the movement of electrons into successive orbits around the nucleus of an atom. 1926 -- Erwin Schrodinger proposes that an electron is best described by the mathematical function of all its possible energy states, a wave. Max Born later proposes that this wave is not the particle itself, but the probability of finding the particle in a particular place. 1926 -- Enrico Fermi and Paul Dirac describe the statistical properties of particles that obey the Pauli exclusion principle. Fermions, as they are known, include protons, neutrons and electrons and are distinct from particles that obey Bose-Einstein statistics. Atoms in certain solids, semiconductors, will collectively fill out their energy orbits with electrons. When excited from a burst of energy, these electrons can move about. Semiconductors are at the heart of the circuits in microprocessors. 1927 -- Werner Heisenberg arrives at his uncertainty principle, theorizing that it is impossible to measure both the position and momentum of a particle at the same time. An act of measurement, like shining light, will disturb a particle's values. 1928 -- Paul Dirac predicts antimatter by proposing that fermions, including electrons, can inhabit states of negative energy. When matter and antimatter collide, they annihilate each other and release energy. Positron emission tomography relies on collisions between electrons and their anti-particles, positrons, that occur in chemical compounds injected into the body. At right, a PET scan of the brain. (Sources: Science, ''Ultimate Visual Dictionary of Science,''Dorling Kindersley)(pg. F1)