So how do we create such a computer? One of the current efforts to create a quantum computer uses the outer most electron in a phosphorus atom as a qubit. The spin of the electron has a magnetic dipole, which can be read as up or down. The phosphorus is embedded in a body of silicon atoms. In order to measure the spin of the electron it is placed inside of a strong magnetic field. The at room temperature there would be a lot of energy in the electron so it could switch between up and down spin. So the system is cooled to near absolute zero so that the electron will align with the magnetic field and will remain as a down spin. To write information to the electron we need to shoot it with a burst of microwaves. The frequency of the waves depends on the strength of the magnetic field. We can read the state of the electron with a transistor. The transistor lets electrons flow through it creating a current. Only if the electron is in the up spin position will it have enough potential to overcome the voltage needed to enter the transistor. This will be seen as a spike in the electric potential.

Besides the electron, the nucleus of the atom also has a spin up and a spin down. The spin of the nucleus is much weaker than that of the electron but it can still be written to using microwaves. Why use the nucleus of the atom than? The nucleus is much more isolated from outside interference than the electron. Using the nucleus as a qubit will last for a much longer time because the energy in it is so small and it is so isolated from the outside world. To read the state of the nucleus we use the electron. The nucleus creates a small magnetic field that will alter the frequency that the electron will react to. So depending on the spin of the nucleus, the electron will react to a different frequency of microwave. To be able to detect these small changes in nuclear spin the silicon that the phosphorus is embedded in must have no spin. Silicone 28 has no spin to it so it is used as a natural body to hold the phosphorus.