Single-electron spin resonance detection by microwave photon counting.

Area of Science:

• Quantum Physics
• Spectroscopy
• Materials Science

Background:

• Electron spin resonance (ESR) spectroscopy is vital for characterizing paramagnetic impurities but provides only ensemble-averaged data due to low signal-to-noise.
• Existing single-spin detection methods are often system-specific or limited to very small detection volumes, posing a challenge for practical applications.

Purpose of the Study:

• To demonstrate a novel method for single-electron magnetic resonance detection.
• To overcome the limitations of traditional ESR and existing single-spin techniques.

Main Methods:

• Utilized spin fluorescence detection with a microwave photon counter at millikelvin temperatures.
• Coupled individual paramagnetic erbium ions in a scheelite crystal to a high-quality-factor planar superconducting resonator to enhance radiative decay rates.

Main Results:

• Achieved single-electron magnetic resonance with a signal-to-noise ratio of 1.9 in one second integration time.
• Observed fluorescence signal anti-bunching, confirming detection of individual emitters.
• Measured coherence times up to 3 milliseconds, limited by spin radiative lifetime.

Conclusions:

• The developed method enables single-spin detection with potential applications in magnetic resonance and quantum computing.
• This technique allows for single-spin detection in a significantly larger volume (approx. 10 μm³) compared to existing methods.
• The approach is adaptable to various paramagnetic species with suitable relaxation times.