Researchers in the US and the Netherlands have discovered a way of using silicon to more easily manipulate quantum bits, or qubits, for devices in quantum computing.
Developed by scientists at Purdue University, the University of Wisconsin-Madison, and the Technological University of Delft in the Netherlands, the breakthrough takes advantage of an "enhanced spin-orbit interaction" in silicon, which they found can alter qubits using electric fields, without the need for any artificial agents.
The push behind the research is that a silicon quantum computer chip has the potential to hold millions of qubits for much faster information processing than with the bits of today's computers. If made possible, it would mean much higher-speed database searches, better cybersecurity and more efficient simulation of materials and chemical processes.
"Qubits encoded in the spins of electrons are especially long-lived in silicon, but they are difficult to control by electric fields," explained research assistant professor in Purdue's School of Electrical and Computer Engineering, Rajib Rahman.
"Spin-orbit interaction is an important knob for the design of qubits that was thought to be small in this material, traditionally."
The researchers found more prominent spin-orbit interaction than usual at the surface of silicon where qubits are located in the form of so-called quantum dots (electrons confined in three dimensions).
Rahman's lab identified that this spin-orbit interaction is anisotropic in nature, meaning it's dependent on the angle of an external magnetic field, and strongly affected by atomic details of the surface.
"If there is a strong spin-orbit interaction, the qubit's lifetime is shorter but you can manipulate it more easily. The opposite happens with a weak spin-orbit interaction: The qubit's lifetime is longer, but manipulation is more difficult," added Rahman.
While the Wisconsin-Madison team were the ones to make the silicon device, the Delft team performed the experiments and the Purdue team led the theoretical investigation of the experimental observations.
The full study has been published in Nature Partner Journals.
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