'Radio Wave Cooling' Offers New Twist on Laser Cooling

September 14, 2007
'Radio Wave Cooling' Offers New Twist on Laser Cooling
NIST physicists used radio waves to cool this silicon micro-cantilever, the narrow orange strip across the middle of this colorized micrograph. The cantilever, created by ion etching through a silicon wafer, lies parallel to a silicon radio-frequency electrode. Credit: J. Britton/ NIST

Visible and ultraviolet laser light has been used for years to cool trapped atoms—and more recently larger objects—by reducing the extent of their thermal motion. Now, applying a different form of radiation for a similar purpose, physicists at the National Institute of Standards and Technology have used radio waves to dampen the motion of a miniature mechanical oscillator containing more than a quadrillion atoms, a cooling technique that may open a new window into the quantum world using smaller and simpler equipment.

Described in a forthcoming issue of Physical Review Letters, this demonstration of radio-frequency (RF) cooling of a relatively large object may offer a new tool for exploring the elusive boundary where the familiar rules of the everyday, macroscale world give way to the bizarre quantum behavior seen in the smallest particles of matter and light. There may be technology applications as well: the RF circuit could be made small enough to be incorporated on a chip with tiny oscillators, a focus of intensive research for use in sensors to detect, for example, molecular forces.

The NIST experiments used an RF circuit to cool a 200 x 14 x 1,500 micrometer silicon cantilever—a tiny diving board affixed at one end to a chip and similar to the tuning forks used in quartz crystal watches—vibrating at 7,000 cycles per second, its natural “resonant” frequency. Scientists cooled it from room temperature (about 23 degrees C, or 73 degrees F) to -228 C (-379 F).

Other research groups have used optical techniques to chill micro-cantilevers to lower temperatures, but the RF technique may be more practical in some cases, because the equipment is smaller and easier to fabricate and integrate into cryogenic systems. By extending the RF method to higher frequencies at cryogenic temperatures, scientists hope eventually to cool a cantilever to its “ground state” near absolute zero (-273 C or -460 F) , where it would be essentially motionless and quantum behavior should emerge.

Laser cooling is akin to using the kinetic energy of millions of ping-pong balls (particles of light) striking a rolling bowling ball (such as an atom) to slow it down. The RF cooling technique, lead author Kenton Brown says, is more like pushing a child on a swing slightly out of synch with its back-and-forth motion to reduce its arc.

In the NIST experiments, the cantilever’s mechanical motion is reduced by the force created between two electrically charged plates, one of which is the cantilever, which store energy like electrical capacitors. In the absence of any movement, the force would be stable, but in this case, it is modulated by the cantilever vibrations. The stored energy takes some time to change in response to the cantilever’s movement, and this delay pushes the cantilever slightly out of synch, damping its motion.

Citation: K.R. Brown, J. Britton, R.J. Epstein, J. Chiaverini, D. Leibfried, and D.J. Wineland. 2007. Passive cooling of a micromechanical oscillator with a resonant electric circuit. Physical Review Letters. [Forthcoming].

Source: National Institute of Standards and Technology

Explore further: Changing temperature powers sensors in hard-to-reach places

Related Stories

New views at the nanoscale

April 27, 2010

(PhysOrg.com) -- Magnetic resonance imaging, first developed in the early 1970s, has become a standard diagnostic tool for cancer, cardiovascular disease and neurological disorders, among others. MRI is ideally suited to ...

Measuring tiny forces with light

August 25, 2016

Photons are bizarre: They have no mass, but they do have momentum. And that allows researchers to do counterintuitive things with photons, such as using light to push matter around.

Recommended for you

Quantum data takes a ride on sound waves

September 22, 2017

Yale scientists have created a simple-to-produce device that uses sound waves to store quantum information and convert it from one form to another, all inside a single, integrated chip.

A way to measure and control phonons

September 22, 2017

(Phys.org)—A team of researchers with the University of Vienna in Austria and Delft University of Technology in the Netherlands has developed a technique using photons for controlling and measuring phonons. In their paper ...

Gravitational waves may oscillate, just like neutrinos

September 21, 2017

(Phys.org)—Using data from the first-ever gravitational waves detected last year, along with a theoretical analysis, physicists have shown that gravitational waves may oscillate between two different forms called "g" and ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.