Researchers extend coherence of qubits

University of Pittsburgh and Delft University of Technology researchers have developed a method that better preserves the coherence of quantum bits (qubits). “Single electron spins in semiconductor quantum dots are a versatile platform for quantum information processing,” the researchers note in the February 17 online issue of Nature Nanotechnology, “but controlling decoherence remains a considerable challenge.”

The researchers report that their approach employs hole spins to keep quantum bits in the same physical state up to 10 times longer than methods relying on electron spins.

“Previously, our group and others have used electron spins, but the problem was that they interacted with spins of nuclei, and therefore it was difficult to preserve the alignment and control of electron spins,” said Sergey Frolov, assistant professor in the Department of Physics and Astronomy within Pitt’s Kenneth P. Dietrich School of Arts and Sciences, in a press release. Frolov did the work as a postdoctoral fellow at Delft University of Technology in the Netherlands.

They note that the development of hole-spin-based electronic devices has been limited by fabrication challenges, but they successfully made use of gate-tunable hole quantum dots formed in InSb (indium antimonide) nanowires.

“Our vision for a quantum computer is to connect thousands of spins, and now we know how to control a single spin,” said Frolov. “In the future, we’d like to scale up this concept to include multiple qubits.”

Coauthors of the paper include Leo Kouwenhoven, Stevan Nadj-Perge, Vlad Pribiag, Johan van den Berg, and Ilse van Weperen of Delft University of Technology and Sebastien Plissard and Erik Bakkers from Eindhoven University of Technology in the Netherlands.

You can visit the University of Pittsburgh Website to read a summary of the research here or purchase a copy of the Nature Nanotechnology article here.

A related article on the realization of a practical quantum computer describes how scientists working at Princeton and the Joint Quantum Institute (JQI) have shown how a major hurdle in transferring information from one quantum bit, or qubit, to another might be overcome. Their so-called “quantum bus” provides the link that would enable quantum processors to perform complex computations.