Long-distance quantum communications seek to provide privacy and mitigate transmission losses through use of entanglement swapping quantum repeaters. The last several years have seen rapid development in solid state quantum repeaters that combine long-lived quantum memories with a source of indistinguishable single photons.
Son et al. provided an overview of the current work in optically active spin qubits made with silicon carbide as well as discussion of the challenges and possible solutions for using the material in future quantum repeaters.
“The pace of innovation in this field during the last few years has been staggering,” said author David Awschalom. “What began as some unexpected experimental discoveries and fundamental quantum physics demonstrations are now evolving to become one of the great technological advances of the century.”
Silicon carbide is already produced at wafer scales for commercial electronics. Such scalability, along with color centers that combine quantum memories with a photonic interface in a semiconductor material, make them promising for building quantum nodes in communications.
Another upcoming development is multi-qubit nodes using nuclear memories to enable small-scale computing and quantum error correction protocols. They expect demonstrations of entanglement spanning more than 100 kilometers using established fiber networks as a quantum communication testbed.
Point-to-point quantum communication channels, however, are expected to be limited to the order of tens to a few hundred kilometers. This will require improvements in cryogenics and more scalable integration of qubits with photonic devices to fabricate the necessary high volume of multiple repeater nodes.
The group looks to explore new defect symmetries to achieve long-lived quantum states by using isotope engineering of silicon carbide.
Source: “Developing silicon carbide for quantum spintronics,” by Nguyen T. Son, Christopher P. Anderson, Alexandre Bourassa, Kevin C Miao, Charles Babin, Matthias Widmann, Matthias Niethammer, Jawad Ul Hassan, Naoya Marioka, Ivan G. Ivanov, Florian Kaiser, Joerg Wrachtrup, and David D. Awschalom, Applied Physics Letters (2020). The article can be accessed at https://doi.org/10.1063/5.0004454.
