Nanoscale magnetic imaging of a single electron spin under ambient conditions (1209.0203v1)

Abstract: The detection of ensembles of spins under ambient conditions has revolutionized the biological, chemical, and physical sciences through magnetic resonance imaging and nuclear magnetic resonance. Pushing sensing capabilities to the individual-spin level would enable unprecedented applications such as single molecule structural imaging; however, the weak magnetic fields from single spins are undetectable by conventional far-field resonance techniques. In recent years, there has been a considerable effort to develop nanoscale scanning magnetometers, which are able to measure fewer spins by bringing the sensor in close proximity to its target. The most sensitive of these magnetometers generally require low temperatures for operation, but measuring under ambient conditions (standard temperature and pressure) is critical for many imaging applications, particularly in biological systems. Here we demonstrate detection and nanoscale imaging of the magnetic field from a single electron spin under ambient conditions using a scanning nitrogen-vacancy (NV) magnetometer. Real-space, quantitative magnetic-field images are obtained by deterministically scanning our NV magnetometer 50 nanometers above a target electron spin, while measuring the local magnetic field using dynamically decoupled magnetometry protocols. This single-spin detection capability could enable single-spin magnetic resonance imaging of electron spins on the nano- and atomic scales and opens the door for unique applications such as mechanical quantum state transfer.

• The paper introduces a novel scanning NV magnetometer technique to image a single electron spin at room temperature.
• It employs integrated confocal microscopy and AFM with diamond nanopillars to achieve sensitivities around 96 nT/√Hz.
• This breakthrough paves the way for advanced quantum sensing applications in quantum computing and high-resolution biological imaging.

Nanoscale Magnetic Imaging of a Single Electron Spin Under Ambient Conditions

The paper "Nanoscale Magnetic Imaging of a Single Electron Spin under Ambient Conditions" presents a significant advancement in the field of quantum sensing and magnetic resonance imaging by demonstrating the detection and imaging of single electron spins using a scanning nitrogen-vacancy (NV) magnetometer while maintaining ambient conditions. The work is a crucial step forward in overcoming the limitations associated with previous methodologies that required ultralow temperatures and high vacuum conditions.

Summary of the Approach

The authors employ a scanning technique utilizing NV centers in diamond to achieve single-spin detection. NV centers are advantageous due to their ability to be optically initialized and read out, possessing long coherence times even at room temperature. This paper leverages recent advances in diamond nanofabrication to position NV centers within approximately 25 nm of scanning probe tips, thereby enhancing magnetic resolution.

The experimental setup consists of a combined confocal and atomic force microscope (AFM) which hosts an NV center in a diamond nanopillar. The sensor NV's spin state undergoes initialization and readout through optical means, with its positioning controlled by atomic force feedback. For magnetic sensing, the authors measure the NV spin's optically detected electron spin resonance (ESR), employing both continuous and pulsed manipulative schemes. The detection relies on the changes in precession of the NV spin induced by the local magnetic field of the target spin.

Numerical and Experimental Outcomes

The paper reports successful imaging of a single target NV spin, verified by comparing the magnetically measured and optically determined locations, achieving magnetic field imaging centered on the target. Notably, the sensor's NV magnetic field sensitivity is reported to be approximately 96 nT/$\sqrt{\rm Hz}$ at a closest approach distance of about 50 nm from the target.

A series of intricate protocols, such as dynamic decoupling, are meticulously applied to enhance the coherence of the sensor NV spin. These achieved a peak magnetic sensitivity of roughly 18 nT/$\sqrt{\rm Hz}$ using advanced XY8 pulsing sequences. This technique permitted magnetic field imaging with a signal-to-noise ratio above four after substantial integration times, showcasing the potential for real-world applications despite the current time limitations.

Implications and Future Prospects

The implications of this research are profound for both theoretical understanding and practical applications. The possibility of ambient-condition nanoscale magnetic imaging opens avenues in diverse fields, such as single molecule structural imaging and biological system exploration at unprecedented resolutions. Given these results, further reductions in sensor-to-target distance, and optimization of spin initialization, could improve signal quality significantly, enabling faster imaging and higher resolution.

Future advancements could explore enhancing phase evolution times or leveraging mechanical quantum state transfer. The potential for quantum information applications is noteworthy, particularly in entangling sensor-target pairs and transferring quantum states—an endeavor that may revolutionize quantum computing interfaces.

Conclusion

In summary, the paper articulates a robust methodology for the magnetic imaging of single electron spins at nanoscale dimensions under ambient conditions. The intersection of cutting-edge quantum technologies with ambient-condition operations exemplifies an exciting direction for future research, promising substantial advancements in numerous scientific domains. The demonstrated techniques lay foundational work for further developments in spin-based sensing technologies and their applications in quantum information science.