Ohmic and step noise from a single trapping center hybridized with a Fermi sea

TL;DR

This paper demonstrates how single electron tunneling devices can detect and analyze noise from individual trapping centers hybridized with a Fermi sea, revealing their energetic properties through spectral features.

Contribution

It introduces a method to identify and characterize individual trapping centers by analyzing their noise spectra in quantum devices.

Findings

Noise spectrum is Ohmic when linewidth exceeds thermal energy.

Lorentzian noise spectrum appears when linewidth is below thermal energy.

Steps in noise spectrum can reveal trap energetics.

Abstract

We show that single electron tunneling devices such as the Cooper-pair box or double quantum dot can be sensitive to the zero-point fluctuation of a single trapping center hybridized with a Fermi sea. If the trap energy level is close to the Fermi sea and has line-width \gamma > k_B T, its noise spectrum has an Ohmic Johnson-Nyquist form, whereas for \gamma < k_B T the noise has a Lorentzian form expected from the semiclassical limit. Trap levels above the Fermi level are shown to lead to steps in the noise spectrum that can be used to probe their energetics, allowing the identification of individual trapping centers coupled to the device.