  The development of highly sensitive and rapid biosensing tools targeted to
the highly contagious virus SARS-CoV-2 is critical to tackling the COVID-19
pandemic. Quantum sensors can play an important role, thanks to their superior
sensitivity and fast improvements in recent years. Here we propose a molecular
transducer designed for nitrogen-vacancy (NV) centers in nanodiamonds,
translating the presence of SARS-CoV-2 RNA into an unambiguous magnetic noise
signal that can be optically read out. We evaluate the performance of the
hybrid sensor, including its sensitivity and false negative rate, and compare
it to widespread diagnostic methods. The proposed method is fast and promises
to reach a sensitivity down to a few hundreds of RNA copies with false negative
rate less than 1%. The proposed hybrid sensor can be further implemented with
different solid-state defects and substrates, generalized to diagnose other RNA
viruses, and integrated with CRISPR technology.
