ISSN:0031-9228    

DOI:10.1063/1.2806716

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.881939

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.881951

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

At the Symposium on Quantum Fluids and Solids in Paris this past July, Richard Packard of the University of California, Berkeley, entertained the audience by playing a brief recording: The sound on the tape began as a high‐pitched whistle and slid down the frequency scale over a period of a few seconds. What people were hearing was the sound of a superfluid surging rapidly back and forth through the holes in a membrane1 in response to a pressure difference applied across the membrane. This phenomenon is the superfluid analog of the AC Josephson effect for superconductors, according to which a supercurrent will oscillate across a thin tunnel junction under an applied voltage. (A French group had earlier reported evidence of this phenomenon.) In addition to recording the sounds of the mass oscillations, Packard and Seamus Davis and their respective groups at Berkeley found that the measured frequencies agreed with those predicted by the Josephson equations.

ISSN:0031-9228    

DOI:10.1063/1.881974

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The elementary particle of information used by modern digital computers is the bit—a register or memory element that can be in one of two distinct states, 0 or 1. But we live in a quantum world, and one can design computers in which each elementary unit of information is a quantum bit, or qubit, which can be in any superposition of two quantum states, |0⟩ and |1⟩. A quantum computer built withnsuch components could itself be in a superposition of2ndistinct states, each splinter of the superposition performing its own computation in parallel with all the rest.

ISSN:0031-9228    

DOI:10.1063/1.881969

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Organic chemists have long been challenged to find an easy way to break apart, or activate, the single bonds in methane so that they could use this very abundant compound as a building block to synthesize organic compounds. But methane is stubbornly unreactive. Recently, Dudley Herschbach and his colleagues at Harvard University found that they could use a catalytic supersonic nozzle to produce high yields of more reactive intermediaries starting with ethane—a cousin of methane. The new method is tantalizing, although it has not yet worked with methane—and even if it were to, it would have to be scaled up from producing thimblefuls to churning out millions of barrels of hydrocarbons before it would be of interest to the petroleum industry. Short of that, the catalytic supersonic nozzle is of 1nterest as a way to do nonequilibrium chemisty.

ISSN:0031-9228    

DOI:10.1063/1.881983

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

As early as about 1830 electrical discharges in gases were intriguing a number of experimental physicists in Europe. In 1881, at the Cavendish Laboratory at the University of Cambridge, J. J. Thomson began experimenting with gaseous discharges, and continued to do so for the next 50 years.

ISSN:0031-9228    

DOI:10.1063/1.881961

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Discussing the existence of electrons, philosopher of science Ian Hacking has written, “So far as I'm concerned, if you can spray them, then they are real.” He went on to elaborate this view: “We are completely convinced of the reality of electrons when we set out to build—and often enough succeed in building—new kinds of device that use various well‐understood causal properties of electrons to interfere in other more hypothetical parts of nature.”

ISSN:0031-9228    

DOI:10.1063/1.881975

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Over the course of a century, six leptons have been discovered in the universe of elementary particles. Three—the electron, muon and tau—each have one unit of electric charge; the other three—the neutrinos—have no charge.

ISSN:0031-9228    

DOI:10.1063/1.881960

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

It is ironic that, in the year when we celebrate the centenary of the discovery of the electron, the most exciting developments in the theory of electrons in solids have to do with the “fractionalization” of the electron—the discovery of particles that behave as though the electron had broken apart into three or five or more pieces each containing one‐third or one‐fifth of its charge, or into separate particles, one containing its charge and one its spin. (See figure 1.) No longer is the quantum theory of solids confined to the boring old electron; we now have a remarkable variety of fractional parts of electrons: composite fermions, composite bosons, spinons and holons, in addition to the heavy electrons, quasiparticles and small polarons of older stages of condensed matter theory.

ISSN:0031-9228    

DOI:10.1063/1.881959

出版商:AIP    

年代:1997

数据来源: AIP