In their attempt to create a silicon quantum computer chip, a team of researchers from the Center of Excellence for Computing and Quantum Communication Technology (CQC2T) from the UNSW in Sydney has successfully demonstrated how to adjust the frequency of control of a qubit. And the way they did it was to engineer its atomic composition.
The work, which was published in Scientific progress, researchers involved in the construction of two qubits. One was a constructed molecule composed of two phosphorus atoms and only one electron, while the other consisted of a single phosphorus atom and a single electron. Both were placed in a silicon chip, only 16 nanometers away. The qubits were exposed to frequencies of about 40 GHz by a perfectly aligned microwave antenna that was above them.
The results of the study showed that when the frequency of the signal that was used to control the spin of the electron changed, the single atom had a completely different control frequency from that of the molecule containing two phosphorus atoms. The researchers turned to the experts at Purdue University for a little help in understanding how the positioning of atoms influenced the electron control frequencies.
"Addressing each qubit individually when they are so close is difficult," notes Scientology's UNSW professor Michelle Simmons, co-author of the paper and director of CQC2T. "The research confirms the ability to fine-tune the neighboring qubits in resonance without impacting one on the other".
The creation of engineered phosphor molecules that have different separations between atoms allows assemblies for qubit groups with variable control frequencies. "We can tune in on this or that molecule – a little like tuning into different radio stations," says the studio's co-lead author, Sam Hilde, UNSW's Research Fellow. "It creates an integrated address that will provide significant benefits for the creation of a silicon quantum computer."
The optimization of the qubits in this way is only the beginning of the demonstration of the entangled states that are necessary for a quantum computer to function as it should and to perform complex calculations. By designing these qubit atoms inside a silicon chip, the molecules can be developed with different resonance frequencies. Essentially what it means is that the control or manipulation of one will not affect another and that it is something that is a vital component of quantum computing.