Dynamic strain-mediated coupling of a single diamond spin to a mechanical resonator (1403.4173v3)

Abstract: The development of hybrid quantum systems is central to the advancement of emerging quantum technologies, including quantum information science and quantum-assisted sensing. The recent demonstration of high quality single-crystal diamond resonators has led to significant interest in a hybrid system consisting of nitrogen-vacancy center spins that interact with the resonant phonon modes of a macroscopic mechanical resonator through crystal strain. However, the nitrogen-vacancy spin-strain interaction has not been well characterized. Here, we demonstrate dynamic, strain-mediated coupling of the mechanical motion of a diamond cantilever to the spin of an embedded nitrogen-vacancy center. Via quantum control of the spin, we quantitatively characterize the axial and transverse strain sensitivities of the nitrogen-vacancy ground state spin. The nitrogen-vacancy center is an atomic scale sensor and we demonstrate spin-based strain imaging with a strain sensitivity of 3 10^-6 strain Hz^-1/2. Finally, we show how this spin-resonator system could enable coherent spin-phonon interactions in the quantum regime.

• The paper quantitatively characterizes strain-induced interactions in diamond NV centers using high-quality mechanical resonators.
• It employs coherent quantum control and spin-based imaging to measure both axial and transverse strain sensitivities with precise metrics.
• The findings establish a foundation for scalable quantum systems and advanced nanoscale sensing applications through strain engineering.

Overview of Dynamic Strain-Mediated Coupling of a Single Diamond Spin to a Mechanical Resonator

The paper "Dynamic strain-mediated coupling of a single diamond spin to a mechanical resonator" represents a significant contribution to the field of hybrid quantum systems, particularly those utilizing nitrogen-vacancy (NV) centers in diamond. The research demonstrates dynamical coupling between the mechanical motion of diamond cantilevers and the electronic spin states of embedded NV centers through strain, a result with implications for both quantum information processing and nanoscale sensing.

Key Contributions and Findings

The paper's primary contribution is the quantitative characterization of strain-induced interactions within NV center spin states. Using high-quality single-crystal diamond cantilevers, the researchers explored both axial and transverse strain sensitivities. They achieved a strain sensitivity of approximately $$3 \times 10^{-6} \, \text{strain} \cdot \text{Hz}^{-1/2}$$ through spin-based imaging techniques. These findings were procured by leveraging coherent quantum control to detect spin-level shifts induced by phonon modes of the resonator.

Experimental Insight

The experiment featured a finely-tuned setup where an NV center in a diamond host was subject to dynamic strain from a mechanical resonator under controlled conditions. The cantilevers, resonant at their fundamental mechanical mode, were systematically strained through a piezoelectric transducer while maintaining measurements at pressures below $10^{-5}$ torr. Spin control and detection were carried out using microwave pulses, and the coupling strengths were derived from the cantilever's zero-point motion and controlled displacements.

Discussion on Strain Coupling Mechanisms

The paper demonstrates that both axial and transverse strain coupling can be described effectively within an electric-field induced model. The axial strain sensitivity parameter, labeled as $\gamma_{\parallel}$, was extracted as $13.4 \pm 0.8 \, \text{GHz/strain}$, which aligns with theoretical expectations and other empirical measurements. Notably, the transverse susceptibility, here higher than anticipated at $21.5 \pm 1.2 \, \text{GHz/strain}$, elucidates discrepancies with existing predictions and necessitates refined theoretical attention.

Implications for Quantum Technologies

The dynamic strain-mediated coupling outlined in this work underscores the potential for NV centers as pivotal elements in quantum hybrid systems. The high stability and coherence of NV centers make them attractive candidates for exploiting strain as a means to induce coherent interactions within quantum systems. As the paper suggests, scaling down resonator dimensions can enhance strain coupling to enter the quantum regime, enabling applications such as quantum state preparation and manipulation in macroscopic resonators.

Future Directions

The findings invite further exploration into miniaturized resonators designed to maximize zero-point motion coupling while minimizing mechanical losses. Additionally, leveraging the NV-spin interaction with both axial and transverse strains opens avenues for advanced quantum sensing technologies. Future work could also address the full potential of shear strain interactions, which were not significant in this paper but hold promise in alternative configurations or applications.

In conclusion, this research provides substantial evidence supporting the feasibility of integrating and controlling strain-mediated NV center interactions within hybrid quantum frameworks. As we look forward, the promising experimental techniques and insightful characterizations presented offer a robust foundation for evolving quantum systems and sensing apparatus rooted in NV center technologies.