New amplifier created for exploring space and quantum world

Researchers at the California Institute of Technology (Caltech) and NASA’s Jet Propulsion Laboratory (JPL) have developed a new type of amplifier for boosting electrical signals.

Last Updated: Jul 16, 2012, 09:02 AM IST

Washington: Researchers at the California Institute of Technology (Caltech) and NASA’s Jet Propulsion Laboratory (JPL) have developed a new type of amplifier for boosting electrical signals.
An amplifier is a device that increases the strength of a weak signal.

The device can be used for everything from studying stars, galaxies, and black holes to exploring the quantum world and developing quantum computers.

“This amplifier will redefine what it is possible to measure,” said Jonas Zmuidzinas, Caltech’s Merle Kingsley Professor of Physics, the chief technologist at JPL, and a member of the research team.

“Amplifiers play a basic role in a wide range of scientific measurements and in electronics in general. For many tasks, current amplifiers are good enough. But for the most demanding applications, the shortcomings of the available technologies limit us,” noted Peter Day, a visiting associate in physics at Caltech and a principal scientist at JPL.

Conventional transistor amplifiers -- like the ones that power your car speakers -- work for a large span of frequencies. They can also boost signals ranging from the faint to the strong, and this so-called dynamic range enables your speakers to play both the quiet and loud parts of a song.

But when an extremely sensitive amplifier is needed -- for example, to boost the faint, high-frequency radio waves from distant galaxies -- transistor amplifiers tend to introduce too much noise, resulting in a signal that is more powerful but less clear.

One type of highly sensitive amplifier is a parametric amplifier, which boosts a weak input signal by using a strong signal called the pump signal. As both signals travel through the instrument, the pump signal injects energy into the weak signal, therefore amplifying it.

About 50 years ago, Amnon Yariv, Caltech’s Martin and Eileen Summerfield Professor of Applied Physics and Electrical Engineering, showed that this type of amplifier produces as little noise as possible: the only noise it must produce is the unavoidable noise caused by the jiggling of atoms and waves according to the laws of quantum mechanics. The problem with many parametric amplifiers and sensitive devices like it, however, is that they can only amplify a narrow frequency range and often have a poor dynamic range.

But the Caltech and JPL researchers said that their new amplifier, which is a type of parametric amplifier, combines only the best features of other amplifiers. It operates over a frequency range more than ten times wider than other comparably sensitive amplifiers, can amplify strong signals without distortion, and introduces nearly the lowest amount of unavoidable noise.

In principle, the researchers said, design improvements should be able to reduce that noise to the absolute minimum. Versions of the amplifier can be designed to work at frequencies ranging from a few gigahertz to a terahertz (1,000 GHz). For comparison, a gigahertz is about 10 times greater than commercial FM radio signals in the U.S., which range from about 88 to 108 megahertz (1 GHz is 1,000 MHz).

“Our new amplifier has it all. You get to have your cake and eat it too,” Zmuidzinas says.

One of the key features of the new parametric amplifier is that it incorporates superconductors -- materials that allow an electric current to flow with zero resistance when lowered to certain temperatures. For their amplifier, the researchers are using titanium nitride (TiN) and niobium titanium nitride (NbTiN), which have just the right properties to allow the pump signal to amplify the weak signal.

Although the amplifier has a host of potential applications, the reason the researchers built the device was to help them study the universe. The team built the instrument to boost microwave signals, but the new design can be used to build amplifiers that help astronomers observe in a wide range of wavelengths, from radio waves to X rays.

The team has already begun working to produce such devices for Caltech’s Owens Valley Radio Observatory (OVRO) near Bishop, California, about 250 miles north of Los Angeles.

These amplifiers, Zmuidzinas noted, could be incorporated into telescope arrays like the Combined Array for Research in Millimeter-wave Astronomy at OVRO, of which Caltech is a consortium member, and the Atacama Large Millimeter/submillimeter Array in Chile.

Because the instrument is so sensitive and introduces minimal noise, it can also be used to explore the quantum world.

The team recently described the new instrument in the journal Nature Physics.