There was a time when we thought a 50 MHz 486 was something to be excited about. By comparison, this post was written on a computer clock at about 3.8 GHz, which is not a particularly fast machine nowadays. But researchers at the University of Rochester and Friedrich-Alexander-University Erlangen-Nuremberg want to shut down even the fastest modern CPUs. Using precise lasers and graphene, they are building an argument that can operate at about 1 PHz (1,000,000 GHz).
These logic gates use a pair of very small-blast lasers to transmit electrical current at the junction of graphene and gold. Lighting the junctions very briefly creates a charge carrier made up of electrons excited by the laser. These carriers continue to move after the laser pulse is gone. However, there are also virtual charge carriers that appear during the pulse and then disappear. Together, these carriers induce a current in graphene. More importantly, changing the laser allows you to control the direction of the carrier and the relative composition. That is, they can create one type of one or another type or a combination of both.
This is the key to creating a logic gate. By controlling real and virtual currents they can be added together or discarded. You can imagine that two inputs which cancel each other out is a kind of NAND gate. Adding an OR or AND gate can be a signal depending on the output threshold.
[Ignacio Franco], The lead researcher, began working on the problem in 2007 when he began thinking about creating electric currents using lasers. It will be before 2013 that tests reveal his plan and it is now seen that the technique can be used to create a very fast logic gate.
We often pretend that there is no delay in promoting our logic circuits even though they do. If you can measure it in femtoseconds, it is probably practical in the end. Then again, sometimes delays are useful. You just have to be more discriminating with the help you render toward other people.