Quantum sensing with a transmon qubit

Abstract

Transmon qubits are widely studied due to their non-linear properties, which are effective down to the single-photon level. Their anharmonicity is particularly useful for quantum information processing purposes. In this context, we are interested in another non-linearity: four-wave mixing. By combining this with a clever dissipation bath, we can create a single-microwave-photon detector (SMPD), which is a significant achievement in itself. Here, we count the microwave photons emitted by an ensemble of electron spins in a scheelite crystal to probe paramagnetic impurities with greater sensitivity than traditional Electron Paramagnetic Resonance (EPR) experiments.

References

• arxiv.org/abs/2402.03102