Ions and Ion traps
A quantum computer must be able to perform all the necesary functions required for a computer: perform calculations, store data, and transfer information. All of these processes can be done by manipulating the qubits. We use ions as the qubits in a quantum computer.
An ion is an atom that is charged. Atoms are made up from neutons (no charge), protons (positive charge), and electrons (negative charge). Atoms are generally uncharged, as there are usually an equal number of protons and neutrons. However when an atom has an uneven number of protons and electrons, it is said to become charged, i.e an ion.
By manipulating these ions, a quantum computer can be made. However this manipulation can only be achieved under the correct conditions, these conditions are made avaliable by using structures called “Ion Traps”.
Although ion traps have very different forms, they all perform the same function: they all generate an oscillating electric field, which allows for containment and control of the ions. To avoid any unwanted interaction from the enviroment, ions also have to be housed in ulta-high vacuum systems, in which the vacuum is better than that of outer space!
By using lithographic techniques, which are methods used to carve tiny features into materials, and standard electrical materials, ion traps can be created which are only a few millionth of a millimetre in size! These structures are not just built for trapping the ions, they are designed to mimic components of a computer, e.g with regions for calculations (CPU), and for ion storage and memory, as well as being able to transfer ions between these these regions. This fuffils the necessary operations of data manipulation, storage and transportation.
Traps are also designed for scalability, as by increasing the total number of trappable ions, the total computational power improves easily.
As stated, a quantum computer cannot just be created from just trapping ions, it is necessary to move the information (the ions) between different locations in a trap, for example between calculation and storage regions.
Our group has developed a method which allows the means to confidently control the motion of individual ions and shuttle an ion to any position in a ion trap microchip.
By developing traps that generate complex electrical fields, it is possible to push and pull the ions by varying the strength of these fields, making it posible to manipulate single ions around corners!
Right now, we are in the process of developing full scale architectures that contain all the neccesary features for a full scale quantum computer.
Quantum Gate Operations
The final ingredient for the quantum computer is the actual processing part where quantum gate operations are implemented. For this purpose we develop methods where we implement quantum gates using microwave radiation. For this purpose we shine microwave radiation onto the trapped atoms. Using very sophisticated control methods, we are able to imprint quantum gate operations on individual atoms. Our approach is fully scalable and will eventuall allow quantum processing of millions of atoms leading to unprescedented quantum processing power.