Squeezed noise due to two-level system defects in superconducting resonator circuits

Abstract

Motivated by recent surprising experimental results for the noise output of superconducting microfabricated resonators used in quantum computing applications and astronomy, we develop a fully quantum theoretical model to describe quantum dynamics of these circuits. Building on theoretical techniques from quantum optics, we calculate the noise in the output voltage due to two-level system (TLS) defects. The theory predicts squeezing for the noise in the amplitude quadrature with respect to the input noise, which qualitatively reproduces the noise ellipse observed in experiment. We show that noise enhancement along the phase direction persists for pump frequencies away from resonance. Our results also suggest that intrinsic TLS fluctuations must be incorporated in the model in order to describe the experimentally observed dependence of the phase noise on input power.

4 pages, 4 figures

References in corpus (4)

• A semi-empirical model for two-level system noise in superconducting microresonators
• Generation of squeezed states of microwave radiation in a superconducting resonant circuit
• Saturation of Two Level Systems and Charge Noise in Josephson Junction Qubits
• Strongly quadrature-dependent noise in superconducting micro-resonators measured at the vacuum-noise limit

Cited by in corpus (1)

• Towards understanding two-level-systems in amorphous solids -- Insights from quantum circuits