Time reversal findings may open doors to the future
Using a time-reversal technique, the team has discovered how to transmit power, sound or images to a nonlinear object without knowing the object’s exact location and without affecting objects around it. Their work, “Nonlinear Time Reversal in a Wave Chaotic System,” was published in the Feb. 7 issue of the Physical Review Letters journal. “That’s the magic of time reversal,” says Steven Anlage, a university physics professor involved in the project. “When you reverse the waveform’s direction in space and time, it follows the same path it took coming out and finds its way exactly back to the source.”
When a signal travels through the air, its waveforms scatter before an antenna picks it up. Recording the received signal and transmitting it backwards reverses the scatter and sends it back as a focused beam in space and time.
“If you go toward a secure building, they won’t let you take cell phones,” Frazier says, “So instead of checking everyone, they could detect the cell phone and send a lot of energy to to jam it.”
What differentiates this research from other time-reversal projects, such as underwater communication, is that it focuses on nonlinear objects such as a cellphone, diode or even a rusty piece of metal. When the altered, nonlinear frequency of nonlinear objects is recorded, time-reversed and retransmitted, it creates a private communication channel, because other objects cannot understand the signal.
“Time reversal has been around for 10 to 20 years but it requires some pretty sophisticated technology to make it work,” Anlage says. “Technology is now catching up to where we are able to use it in some new and interesting ways.”