KIT researchers block 96% of light with tin-vacancy qubits in diamond

[Rogue Di]

Researchers in Germany have shown a strong link between light and tin vacancy qubits in diamond. Quantum Zeitgeist reports on work led by Kerim Köster at the Karlsruhe Institute of Technology, with partners in Stuttgart, Ulm and a Fraunhofer institute

Tin vacancy centres are defects in diamond that act as qubits and can interact with single photons. The team placed them in a tunable Fabry-Pérot microcavity and found they blocked about 96 percent of transmitted light, while operating at temperatures up to 1 kelvin

The cavity enhanced the emission by a Purcell factor of 4.1 in a diamond like mode, compared with 1.85 in an air like mode. The team reached a cooperativity of 4.0 and spin selective contrast of 0.91, meaning the light response depended strongly on the qubit's spin state

The authors describe this as a promising platform for efficient spin photon interfaces for quantum networks. The linewidth was about twice the theoretical minimum because of charge noise, an ideal cooperativity of 8.0 is only a projection, and the summary article contains some formatting errors

Near total light extinction depending on the spin state is exactly what quantum network nodes need, because it lets photons carry information about the qubit. Working at up to 1 kelvin is also helpful, since that is easier to reach than the millikelvin temperatures many systems require. Tin vacancies are looking more and more attractive

Are tin vacancies the best diamond defect for quantum networks? And how close are practical quantum network nodes?

Researchers See Almost Total Light Extinction With Tin-vacancy Qubits In Diamondquantumzeitgeist.com