Research indicates that making qubits is also possible with cmos transistor
Scientists have succeeded in proving that it should be possible to make qubits with a practically ‘normal’ cmos circuit. This can be done by making cmos transistors so small that undesired quantum effects normally occur.
For the experiment at temperatures below 20K, the researchers from different institutes used a cmos transistor with a gate that encloses the channel on three sides, creating two right angles. The electric field in the corners is stronger than elsewhere on the nanowire, so that the corners function as electrostatic quantum traps, also known as ‘quantum dots’. At the extremely low temperatures, it is possible to isolate a single electron moving back and forth between the two quantum dots.
Schematic representation of cmos with silicon nanowire and gate with the two quantum dots. Source: ACS
Depending on how the electron is ‘distributed’ between both angles, two different quantum states can exist that are similar to a 1 and a 0 of the qubit. The trapped electron can also be superimposed of both states by a fast voltage pulse at the gate. That quantum state can exist for a duration of one hundred picoseconds, the researchers report in their paper in Nano Letters of the American Chemical Society.
To measure the difference in capacitance of the double quantum dots, the researchers used an oscillator at 355MHz. By measuring interferences, the state of the quantum dots could then be determined. Interference plays an important role in quantum mechanics. In interference, waves interact, in this case electromagnetic waves of electrons.
With this, the researchers show that it will probably be possible to read the quantum state in a controlled manner. This requires a longer lifespan of the quantum state, around the nanosecond. That is a factor of ten more than is currently the case.
More research is being done on obtaining qubits with ‘normal’ hardware, if cooling to near absolute zero is disregarded for a while. Recently, researchers from the Australian Center for Quantum Computation & Communication Technology in Nature Natotechnology showed that entanglement could be obtained on a silicon chip.