Quantum Interference of Single Photons from Remote Nitrogen-Vacancy Centers in Diamond
This paper presents a rigorous examination of quantum interference between single photons emitted by two spatially separated nitrogen-vacancy (NV) centers in diamond, an advancement in quantum information science with considerable implications for quantum network technology. The authors demonstrate this phenomenon over a 2-meter separation, marking a step forward in the entanglement of remote solid-state qubits.
Experimental Findings and Methodology
The central experiment involves creating indistinguishable photons from two NV centers located in separate diamond samples. To maximize photon collection efficiency, macroscopic solid immersion lenses (SILs) are employed. Through the measurement of a second-order cross-correlation function, the authors achieve g(2)(0)=0.35±0.04, indicating successful quantum interference. This value, notably less than 0.5, is indicative of photon indistinguishability, a crucial component for entangling remotely separated quantum systems.
The paper deploys sophisticated optical techniques to mitigate spectral inhomogeneity, arising primarily from local environmental variations around the NV centers. By adjusting the optical transition frequencies of the NV centers via external electric fields, the authors enhance photon indistinguishability, an essential requirement for demonstrating Hong-Ou-Mandel (HOM) interference in solid-state systems.
Technological Implications
Nitrogen-vacancy centers in diamond, with robust electron and nuclear spin features, are potential candidates for quantum information processing implementations. The realizations achieved in this paper underscore the potential for scalable quantum networks using solid-state qubits. By overcoming the intrinsic challenges of variance in emitter environments, this research supports the architecture needed for reliable, indistinguishable single-photon sources.
Theoretical and Practical Considerations
The paper bridges a significant gap between atomic and solid-state quantum systems, traditionally operated under disparate conditions. It invokes the potential extension of atomic system methodologies to solid-state devices, a topic that has garnered attention for its practicality and scalability. Considering the demonstrated ability to produce indistinguishable photons in NV centers, further development could align with improving entanglement fidelity and minimization of photon loss.
Future Developments
Future research can leverage the demonstrated enhancement in photon collection efficiency and frequency tuning to increase the rate of entanglement between distant NV centers. The paper speculates that advanced photon collection techniques and further improvements in the external control of NV centers will be pivotal in evolving quantum network architectures. Additionally, the limitations experienced with external fields and collection efficiencies serve as targets for technological progress.
In conclusion, the research presents substantial experimental results that further the understanding of photon interference in solid-state systems, positing NV centers as credible elements for future large-scale quantum networks. Such systems could fundamentally alter the landscape of computational and communication methodologies, contingent on continued advancements in photon indistinguishability and qubit entanglement fidelity.