Lightwave valleytronics might be the key to quantum computing
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Lightwave valleytronics might be the key to quantum computing


A major challenge in quantum computing has
been designing a system that can operate at room temperature. Lightwave valleytronics, which uses intense
lightwaves and the momentum of electrons to process logic, could be a solution. It starts with a 2-dimensional semiconductor
— a single-atom-thick material that has unique conduction properties. In this type of semiconducting material, the
electrons happen to favor one of two specific momenta. These two preferred momenta are often referred
to as valleys. And it takes a lot of energy to get the electrons
out of one valley and into the next. To get the unexcited electrons into either
valley, energy must be introduced with circularly polarized light. And as it turns out, a pulse of clockwise
circularly polarized light will excite the electrons into one valley, but counterclockwise
light will excite the electrons into the opposite valley. The resulting valley state is easily observed
because the spin of the light emitted by the electrons depends on which valley they’re
in. But the electrons will only remain excited
in either valley for a few femtoseconds before the material returns to its normal, unexcited
state. In order to build a conventional computer,
there needs to be a way to represent a bit of information with two possible values, zero
or one, or in this case, valley 1 or 2. But that bit must also be able to switch between
zero and one to perform logic operations. This is done with a high intensity, linearly
polarized pulse of light to force the electrons to change momentum and hop from one valley
to the other, which opens the door to incredibly fast valleytronic logic. If this system is scaled up to build a conventional
computer, it would be millions of times faster than what exists today. And better still, these valley states can
exist in quantum superpositions of one another, meaning that the electrons are in both states
at the same time. The bit is both a zero and a one. This could make it possible to build a quantum
computer that works at room temperature. [music]

5 Comments

  • Kaushal Timilsina

    If we consider the valley energy states, is it like this: if you give enough energy for a particle to go to another valley it will return, unless you take away certain energy so that it can no longer return-with a quantum correspondence of that. But if you take away the energy you'd have to supply the energy again, which is much difficult to do in specific sites without disturbing other energy states. So what we can do is use that circulate that energy around in particles nearby, which contain no information and then take the energy back when we need to change the energy state of that. In materials like graphene, it is much easier to store such energy elsewhere and get it back allowing for better controlled computational power. Is that something that makes sense?

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