= Trapped ion quantum computer
{wiki}
TODO understand.
\Video[https://www.youtube.com/watch?v=j1SKprQIkyE]
{title=Trapping Ions for Quantum Computing by Diana Craik (2019)}
{description=
A basic introduction, but very concrete, with only a bit of math it might be amazing:
* https://youtu.be/j1SKprQIkyE?t=217 you need <ultra-high vacuum>
* https://youtu.be/j1SKprQIkyE?t=257 you put the <Calcium> on a "calcium oven", heat it up, and make it evaporates a little bit
* https://youtu.be/j1SKprQIkyE?t=289 you need <lasers>. You shine the laser on the calcium atom to eject one of the two valence electrons from it. Though e.g. <Universal Quantum> is trying to do away with them, because alignment for thousands or millions of particles would be difficult.
* https://youtu.be/j1SKprQIkyE?t=518 keeping all surrounding electrodes positive would be unstable. So they instead alternate electrode quickly between plus and minus
* https://youtu.be/j1SKprQIkyE?t=643 talks about the alternative, of doing it just with electrodes on a chip, which is easier to manufacture. They fly at about 100 microns above the trap. And you can have multiple ions per chip.
* https://youtu.be/j1SKprQIkyE?t=1165 using <microwaves> you can flip the <spin> of the <electron>, or put it into a superposition. From more reading, we understand that she is talking about a <hyperfine transition>, which often happen in the <microwave> area.
* https://youtu.be/j1SKprQIkyE?t=1210 talks about making <quantum gates>. You have to put the ions into a <magnetic field> at one of the two <resonance frequencies> of the system. Presumably what is meant is an inhomogenous magnetic field as in the <Stern-Gerlach experiment>.
This is the hard and interesting part. It is not clear why the atoms become coupled in any way. Is it due to electric repulsion?
She is presumably describing the <Cirac–Zoller CNOT gate>.
Sounds complicated, several technologies need to work together for that to work! Videos of ions moving are from https://www.physics.ox.ac.uk/research/group/ion-trap-quantum-computing[].
A major flaw of this presentation is not explaining the <readout (quantum computing)> process.
}
\Video[https://www.youtube.com/watch?v=LR_aNOcnH0Q]
{title=How To Trap Particles in a Particle Accelerator by the <Royal Institution> (2016)}
{description=Demonstrates trapping pollen particles in an alternating field.}
\Video[https://www.youtube.com/watch?v=lJOuPmI--5c]
{title=Ion trapping and quantum gates by Wolfgang Ketterle (2013)}
{description=
* https://youtu.be/lJOuPmI--5c?t=1601 <Cirac–Zoller CNOT gate> was the first 2 qubit gate. Explains it more or less.
}
\Video[https://www.youtube.com/watch?v=W3l0QPEnaq0]
{title=Introduction to quantum optics by Peter Zoller (2018)}
{description=
THE Zoller from <Cirac–Zoller CNOT gate> talks about his gate.
* https://www.youtube.com/watch?v=W3l0QPEnaq0&t=427s shows that the state is split between two options: center of mass mode (ions move in same direction), and strechmode (atoms move in opposite directions)
* https://youtu.be/W3l0QPEnaq0?t=658 shows a schematic of the experiment
}
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