arXiv subjects

Ou Wang

Publications and source records attributed to Ou Wang.

3 recordsLinked to original sources

arXiv2026

High-cooperativity coupling and spin-resolved extinction of tin-vacancy centers in a diamond-like microcavity

The tin-vacancy (SnV) center in diamond is a promising spin-photon interface for quantum networks, combining favorable optical properties with spin coherence above 1K. Unfolding the full potential requires cavity enhancement to increase photon-emitter coupling efficiency. Here, we demonstrate cavity-enhanced light-matter coupling of SnV centers in a fully tunable Fabry-P\'erot microcavity operating at temperatures down to 1K with in-situ magnetic field control. We access the diamond-like regime of hybrid cavity modes through integration of low-roughness diamond membranes, where the field is concentrated inside the diamond and Purcell enhancement is maximized. Diamond-like modes deliver a more than two-fold increase in the effective Purcell factor over air-like modes, reaching $C_0 = 4.1(1)$ compared to $C_0 = 1.85(5)$ in the air-like case, while simultaneously relaxing mechanical stability requirements. Resonant probing reveals coherent cavity-emitter coupling with 96% extinction contrast and a coherent cooperativity of $C = 4.0(14)$. By applying a magnetic field, we further achieve spin-resolved cavity extinction, observing spin-selective optical transitions with a contrast of ${\cal C}_{\rm spin} = 0.91$. These results establish SnV centers in diamond coupled to open Fabry-P\'erot microcavities as a promising platform for efficient spin-photon interfaces.

quant-ph↗

arXiv2019

Unidirectional single-photon emission from germanium-vacancy zero-phonon lines: Deterministic emitter-waveguide interfacing at plasmonic hot spots

Striving for nanometer-sized solid-state single-photon sources, we investigate atom-like quantum emitters based on single germanium vacancy (GeV) centers isolated in crystalline nanodiamonds (NDs). Cryogenic characterization indicated symmetry-protected and bright (> 10^6 counts/s with off-resonance excitation) zero-phonon optical transitions with up to 6-fold enhancement in energy splitting of their ground states as compared to that found for GeV centers in bulk diamonds (i.e., up to 870 GHz in highly strained NDs vs 150 GHz in bulk). Utilizing lithographic alignment techniques, we demonstrate an integrated nanophotonic platform for deterministic interfacing plasmonic waveguides with isolated GeV centers in NDs that enables 10-fold enhancement of single-photon decay rates along with the emission direction control by judiciously designing and positioning a Bragg reflector. This approach allows one to realize the unidirectional emission from single-photon dipolar sources introducing a novel method that is alternative to the propagation-direction-dependent techniques based on chiral interactions or topological protection. The developed plasmon-based nanophotonic platform opens thereby new perspectives for quantum nanophotonics in general and for realizing entanglement between single photons and spin qubits, in particular.

physics.app-ph↗

arXiv2018

Single SiV$^-$ centers in low-strain nanodiamonds with bulk-like spectral properties and nano-manipulation capabilities

We report on the isolation of single SiV$^-$ centers in nanodiamonds. We observe the fine-structure of single SiV$^-$ center with improved inhomogeneous ensemble linewidth below the excited state splitting, stable optical transitions, good polarization contrast and excellent spectral stability under resonant excitation. Based on our experimental results we elaborate an analytical strain model where we extract the ratio between strain coefficients of excited and ground states as well the intrinsic zero-strain spin-orbit splittings. The observed strain values are as low as best values in low-strain bulk diamond. We achieve our results by means of H-plasma treatment of the diamond surface and in combination with resonant and off-resonant excitation. Our work paves the way for indistinguishable, single photon emission. Furthermore, we demonstrate controlled nano-manipulation via atomic force microscope cantilever of 1D- and 2D-alignments with a so-far unreached accuracy of about 10nm, as well as new tools including dipole rotation and cluster decomposition. Combined, our results show the potential to utilize SiV$^-$ centers in nanodiamonds for the controlled interfacing via optical coupling of individually well-isolated atoms for bottom-up assemblies of complex quantum systems.

cond-mat.mes-hall↗