Measurement of the noise spectrum using a multiple-pulse sequence.

Area of Science:

• Quantum physics
• Quantum information science
• Quantum computing

Background:

• Quantum systems, such as qubits, are susceptible to decoherence caused by environmental noise.
• Understanding the noise spectrum is crucial for mitigating decoherence and improving quantum computations.
• Existing methods for characterizing noise often require complex experimental setups or theoretical assumptions.

Purpose of the Study:

• To propose a direct method for obtaining the noise spectrum responsible for qubit phase decoherence.
• To establish a straightforward relationship between the noise spectrum and qubit coherence time.
• To validate the applicability of this method across diverse noise environments.

Main Methods:

• Deriving a direct relationship between the noise spectrum and the coherence time of a qubit under a π pulse sequence.
• Utilizing experimentally available data for spectrum extraction.
• Applying the derived relationship to different types of noise baths.

Main Results:

• A simple and direct method for obtaining the noise spectrum from experimental data is established.
• The derived relationship between the noise spectrum and coherence time is shown to be universally applicable.
• The method is validated for qubits interacting with classical noise, bosonic baths, and spin baths.

Conclusions:

• The proposed method offers a practical approach to characterize noise affecting qubit coherence.
• This technique simplifies the study of quantum decoherence across various physical systems.
• The findings contribute to the development of more robust quantum information processing technologies.