Accession Number:

ADA624057

Title:

Decoherence from 1/f Flux Noise

Descriptive Note:

Final rept. 1 Oct 2010-30 Sep 2014

Corporate Author:

CALIFORNIA UNIV SANTA BARBARA

Report Date:

2014-12-30

Pagination or Media Count:

11.0

Abstract:

Qubit dephasing is governed by low-frequency noise in the bias parameters that control the energy separation between the qubit states. It has been shown that dephasing in phase and flux qubits is dominated by an excess low frequency magnetic flux noise with a 1f power spectrum and magnitude at 1 Hz of order 1 microPhi0sqrtHz. Recent experiments by McDermott et al. provide clear evidence for the existence of unpaired magnetic states on the surfaces of superconducting thin film devices it is now believed that fluctuations of these surface spin states are the source of the ubiquitous 1f flux noise. However, the microscopic mechanism that drives fluctuations of these spins is not understood moreover, there is no clear path to reducing the flux noise magnitude. This program is devoted to a systematic investigation of magnetic surface defects in SQUIDs and phase qubits. Measurements of surface spin susceptibility and susceptibility noise will yield valuable clues about the microscopic nature of the magnetic fluctuators, and shed light on interactions between defects. The role of qubit loop geometry on flux noise magnitude and dephasing will be explored in detail. The experiments will guide theoretical efforts to develop improved models for flux noise.

Subject Categories:

  • Physical Chemistry
  • Electrical and Electronic Equipment
  • Atomic and Molecular Physics and Spectroscopy
  • Quantum Theory and Relativity

Distribution Statement:

APPROVED FOR PUBLIC RELEASE