According to the authors of this latest paper, the microwave grape trick also shows their promise as alternative microwave resonators for quantum sensing applications. These applications include satellite technology, masers, microwave photon detection, the hunt for axions (a candidate for dark matter) and various quantum systems, and driving spin in superconducting qubits for quantum computers.
Prior research had specifically examined the electric fields behind the plasma effect. “We showed that grape pairs can also amplify magnetic fields that are crucial for quantum sensing applications,” said co-author Ali Fawaz, a graduate student at Macquarie University.
Fawaz and co-authors used specially prepared nanodiamonds for their experiments. Unlike pure diamonds, which are colorless, some of the carbon atoms in the nanodiamonds were replaced, creating tiny defect centers that act like tiny magnets, making them ideal for quantum detection. Sapphires are typically used for this purpose, but Fawaz et al. realized that water conducts microwave energy better than sapphires – and that grapes are mostly water.
So the team placed a nanodiamond on top of a thin fiberglass and placed it between two grapes. She then shone green laser light through the fiber, causing the defect centers to glow red. Measuring the brightness told them the strength of the magnetic field around the grapes, which turned out to be twice as strong with grapes as without.
The size and shape of the grapes used in the experiments proved crucial; they need to be about 27 millimeters long to get concentrated microwave energy at just the right frequency for the quantum sensor. The biggest pitfall is that the use of the grapes turned out to be less stable with more energy loss. Future research can identify more reliable potential materials to achieve a similar effect.
DOI: Physical Review Applied, 2024. 10.1103/PhysRevApplied.22.064078 (About DOIs).
