Magnetic field mediated temperature sensing with a solid-state spin qubit: a proposal for hybrid quantum thermometry with a permanent magnet

Diamond nitrogen-vacancy (NV) centers are promising thermal sensors with versatile applications, from electronic devices to biomedical systems. However, conventional thermometry relies on the intrinsic property of the NV center, temperature dependence of the zero-field splitting, which is small and significantly reduces at low temperatures (<150 K). Here, we propose a hybrid quantum thermometry combining diamond NV centers with a permanent magnet with a high reversible temperature coefficient. This method converts temperature variations into magnetic field signals, detected by NV centers through magnetometry protocols like Ramsey interferometry. Our calculations show that this approach enhances thermal sensitivity by a factor of 10 to 10⁴ compared to conventional thermometry, including thermal echo and thermal Carr-Purcell-Meiboom-Gill (TCPMG). Moreover, it operates across a wide temperature range, down to 20 K, making it suitable for cryogenic quantum thermometry. This proposal offers significant advancement over current NV thermometry, enabling highly sensitive, low-temperature measurements.