The future of quantum electronics might depend on some intriguing “kinks.”
A team of researchers at Penn State, led by physics professor Jun Zhu, has discovered a way to control these kinks, which are crucial for building advanced devices like sensors and lasers.
They have created a switch that can turn on and off these kink states, which are pathways for electrical conduction at the edge of semiconducting materials.
By controlling these kink states, scientists can regulate the flow of electrons in a quantum system.
“We see these kink states as the backbone for a quantum interconnect network,” said Zhu. “Such a network could carry quantum information over long distances on a chip, something classical copper wires can’t do because they have resistance and can’t maintain quantum coherence.”
The research, published in the journal Science, provides a foundation for further studies into kink states and their use in quantum devices and computers.
Unlike conventional switches that regulate current through a gate like traffic through a toll plaza, this new switch removes and rebuilds the road itself.
Kink states exist in a material called Bernal bilayer graphene, which consists of two layers of atomically thin carbon stacked together with a slight misalignment.
This setup, combined with an electric field, results in unusual electronic properties, including the quantum valley Hall effect.
This effect means that electrons occupy different “valley” states and move in opposite directions without colliding, which is key for using kink states as quantum wires to transmit information.
“The amazing thing about our devices is that electrons moving in opposite directions don’t collide, even though they share the same pathways,” said Ke Huang, a graduate student at Penn State and the study’s first author.
“This allows us to observe a ‘quantized’ resistance value, crucial for using kink states to transmit quantum information.”
The team improved the electronic cleanness of their devices by using a clean graphite/hexagonal boron nitride stack as a global gate. Graphite is a good conductor of electricity, while hexagonal boron nitride is an insulator.
This combination helps contain electrons to the kink states and control their flow.
“The use of this material was key to our success,” Huang said. “It eliminated electron backscattering, which occurs when electrons moving in opposite directions collide.”
The researchers found that the quantization of kink states remains even at temperatures of several tens of Kelvin, higher than typical cryogenic temperatures where quantum effects usually survive.
“The higher the temperature we can make this work, the more likely it can be used in practical applications,” Zhu said.
The team tested their switch and found it could quickly and repeatedly control current flow. This adds to their collection of kink state-based quantum electronics tools that help control and direct electrons.
“We’ve developed a quantum highway system that can carry electrons without collision and direct current flow, laying a strong foundation for future studies,” Zhu said. “Our next goal is to show how electrons behave like coherent waves on these kink state highways.”
The researchers believe this is a significant step towards realizing a quantum interconnect system, though there is still much work to be done.
