A long-standing quest for science and technology has been to develop electronics and information processing that operate near the fastest timescales allowed by the laws of nature. A promising way to achieve this goal involves using laser light to guide the motion of electrons in matter, and then using this control to develop electronic circuit elements—a concept known as lightwave electronics.
Remarkably, lasers currently allow us to generate bursts of electricity on femtosecond timescales—that is, in a millionth of a billionth of a second. Yet our ability to process information in these ultrafast timescales has remained elusive.
Now, researchers at the University of Rochester and the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have made a decisive step in this direction by demonstrating a logic gate—the building block of computation and information processing—that operates at femtosecond timescales. The feat, reported in the journal Nature, was accomplished by harnessing and independently controlling, for the first time, the real and virtual charge carriers that compose these ultrafast bursts of electricity.
The researchers' advances have opened the door to information processing at the petahertz limit, where one quadrillion computational operations can be processed per second. That is almost a million times faster than today's computers operating with gigahertz clock rates, where 1 petahertz is 1 million gigahertz.
"This is a great example of how fundamental science can lead to new technologies," says Ignacio Franco, an associate professor of chemistry and physics at Rochester who [...] performed the theoretical studies that lead to this discovery.
In recent years, scientists have learned how to exploit laser pulses that last a few femtoseconds to generate ultrafast bursts of electrical currents. This is done, for example, by illuminating tiny graphene-based wires connecting two gold metals. The ultrashort laser pulse sets in motion, or "excites," the electrons in graphene and, importantly, sends them in a particular direction—thus generating a net electrical current.
Laser pulses can produce electricity far faster than any traditional method—and do so in the absence of applied voltage. Further, the direction and magnitude of the current can be controlled simply by varying the shape of the laser pulse (that is, by changing its phase).
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