Scientists are struggling to translate the conflicting discoveries of the quantum field of the past century into the technology of the future. The cornerstone of these technologies is the quantum bit, or qubit. Different types are produced, including those that use dots in the symmetric shape of diamond and silicon. They could one day revolutionize computers, speed up drug discovery, create seamless networks and more. In collaboration with researchers from different universities, scientists from the US Department of Energy’s (DOE) Argonne National Laboratory have discovered a way to introduce electrons as (A new twist on quantum bits) qubits into nanomaterial structures.
Their test results showed a record integration time – a key property of any useful qubit because it defines the number of calculations that can be performed during the qubit’s lifetime. Electrons have a similar spin, with one important difference. When the surface turns on the dots, they can turn to the right or to the left.
Electrons can act as if they are spinning in both directions at the same time. This is a quantum feature called superposition. Being in two states at the same time makes electrons ideal candidates for switching qubits. Spin qubits need the right materials to support, control and detect them, as well as to read the information they contain. With this in mind, the team chose to study a nanomaterial composed of only carbon, hollow tubular in shape and only about one nanometer thick, or one billionth of a meter, about 100,000 thinner than wide of human hair.
“These carbon nanotubes are usually a few micrometers long,” Xuedan Ma said.
He is a scientist at the Center for Nanoscale Materials (CNM) at Argonne, a DOE Office of Science. He also holds appointments at the Pritzker School of Molecular Engineering at the University of Chicago and the Northwestern-Argonne Institute of Science and Engineering at Northwestern University.
The problem the team faced was that the carbon nanotubes themselves could not hold electrons in place. It moves in nanotubes. Early researchers placed electrodes nanometers apart to prevent electrons from bouncing between them. But this arrangement is large, expensive and difficult to develop.
Current teams have devised ways to eliminate the need for electrodes or other nanoscale devices to block electrons. Instead, they use chemicals to change the atomic structure of the carbon nanotube in such a way that the electron traps rotate in one direction.
Jia-Shiang Chen, a chemist, said: “To our great satisfaction, our chemical modification process creates a very strong bond in the carbon nanotube. Chen is a CNM member and postdoctoral researcher at the Center for Molecular Quantum Transduction at Northwestern University.
The team’s test results showed a record switching time compared to systems made by other methods – 10 microseconds.
Given their small size, spin qubit platforms can easily be incorporated into quantum devices and allow for many possible ways to read quantum information. In addition, the carbon tubes are very flexible and their sound can be used to store information from the qubit.
“There’s a long way to go from turning our qubits and carbon nanotubes into a practical technology, but it’s a big step in that direction,” Ma said.
The group’s findings were reported in Nature Communications.
Source: Argonne National Laboratory
