Nanoscale probing of magnetic noise near conducting surfaces with single-spin qubits
Noise emanating from conductors and their surfaces can limit the coherence times and relaxation rates of many promising quantum information systems, from superconducting qubits and gate-defined quantum dots to atoms and ions on chips. Here we present experimental results demonstrating the use of single electronic spin qubits in diamond to probe the spectral, spatial, and temperature dependent properties of magnetic noise near conductors. Using individual nitrogen vacancy (NV) centers implanted close to the diamond surface, we investigate magnetic Johnson noise at distances down to 10 nm from the metal surface, a length scale not currently achievable in other systems, over a wide range of temperatures, from 6 to 295 K. We observe a significant deviation from the predictions of the Drude model and Ohm’s law arising from the ballistic motion of electrons in the metal, and show that the observed behavior is well described by the introduction of a nonlocal dielectric function. Our approach holds considerable promise for the investigation of more complex condensed matter systems, and we will discuss some potential applications and extensions of this work.