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Australian scientists have taken a new step in their approach to creating a silicon quantum computer chip, demonstrating their ability to adjust the frequency of control of a qubit by developing its atomic configuration
Image caption: Frequency spectrum of a modified molecule. The three peaks represent three different configurations of spins in the atomic nuclei, and the distance between the peaks depends on the exact distance between the atoms forming the molecule. Photo: Dr. Sam Hile
A team of researchers from the Center of Excellence for Quantum Computing and Communication Technology (CQC2T) at UNSW Sydney has successfully implemented an atomic engineering strategy to address the close spin qubits in silicon.
The researchers constructed two qubits – an artificial molecule composed of two phosphorus atoms with a single electron and the other a single atom of phosphorus with a single electron – and placed them only 16 nanometers in a microchip of silicon.
By configuring a microwave antenna over qubits with precision alignment, qubits were exposed at frequencies of about 40GHz. The results showed that when modifying the signal frequency used to control the electron spin, the single atom had a radically different control frequency compared to the electron spin in the molecule of two phosphorus atoms.
UNSW researchers collaborated closely with experts from Purdue University, who used powerful computing tools to model atomic interactions and understand how the position of the atoms influenced the control frequencies of each electron. move atoms as little as one nanometer.
"Sending individually to each qubit when they are so close is difficult," says Michelle Simmons, UNSW's Scientific Director, Director of CQC2T and co-author of the paper.
"The research confirms the ability to tune neighboring qubits into resonance without touching each other."
The creation of modified phosphorus molecules with different separations between the atoms of the molecule allows families of qubits with different control frequencies. Each molecule can be used individually by selecting the frequency that controls its electronic spin.
"We can tune into a particular molecule – a bit like connecting to different radio stations," says Sam Hile, co-lead author of the paper and researcher at UNSW.
"It creates an integrated address that will provide significant benefits for the construction of a quantum silicon computer."
The adjustment and individual control of qubits in a 2-bit system is a precursor to demonstrate the entangled states required for a quantum computer to function and perform complex calculations.
These results show how the team – led by Professor Simmons – has relied on their unique Australian approach to creating quantum bits from individual atoms accurately positioned in silicon.
By designing the atomic placement of atoms in the qubits in the silicon chip, the molecules can be created with different resonant frequencies. This means that the spin control of a qubit will not affect the spin of the neighboring qubit, which will lead to fewer errors – an essential requirement for the development of a quantum computer at large scale.
"The ability to generate the number of atoms in qubits makes it possible to selectively address one qubit to another, which translates into lower error rates, even if it is not possible. they are very close, "says Professor Simmons.
"These results highlight the continuing benefits of atomic qubits in silicon."
This last advance in rotation control results from recent research by the team on controllable interactions between two qubits.
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