Quantum sensing using superconducting circuits

Superconducting qubits are one of the most promising components for future quantum information technologies. There are several types of qubits currently known and used. Transmons for example are insensitive to external noise and show the longest coherence time among them. Therefore, they are intensively studied as building blocks of a quantum computer. On the other hand, flux qubits show long coherence time although they are sensitive to an external magnetic field. A sensitivity of 3.3 pT/Hz1/2 was recently reported [1]. Here we utilize flux qubits as a sensitive magnetic field sensor to detect local electron spin
resonances (ESR).