Diamond Color Centers Achieve 0.3nm Linewidth with Strong Broadband Phonon Decoupling for Stable Emission

Single-photon emitters represent a crucial technology for advances in information processing and secure communication, yet their performance is often limited by unwanted interactions with vibrations within their material environment. Now, Swetapadma Sahoo from the University of Illinois at Urbana-Champaign, Péter Udvarhelyi from the University of California Los Angeles, and Jaden Li, also from the University of Illinois at Urbana-Champaign, and their colleagues report a significant breakthrough in creating remarkably stable and efficient single-photon emitters. The team engineered color centers within nanodiamonds that exhibit comprehensive decoupling from the surrounding vibrational environment, achieving record-narrow emission linewidths and exceeding 10 million counts per second in saturation at room temperature. This achievement, characterized by almost complete suppression of unwanted vibrational sidebands, points to a novel mechanism for phonon decoupling in wide-gap materials and promises to unlock qualitatively higher performance for quantum networks and nanoscale devices, while also opening avenues for exploring new physical resources associated with vibrational states.

Silicon-Vacancy Centers in Nanodiamonds for Quantum Emission

This research explores silicon-vacancy (SiV) centers within nanodiamonds, investigating their potential as stable and efficient sources of single photons for quantum technologies. SiV centers, defects in the diamond structure created by silicon and missing carbon atoms, exhibit fluorescence suitable for these applications. Scientists focus on creating high-quality nanodiamonds and thoroughly characterizing their properties to optimize SiV center performance. Researchers investigate how temperature affects the fluorescence characteristics of SiV centers, aiming to achieve stable and bright single-photon emission.

They combine experimental investigation with theoretical modeling, using advanced calculations to understand the electronic structure of these defects and predict their behavior. This combined approach provides a comprehensive understanding of SiV centers in nanodiamonds. The research utilizes techniques to characterize the nanodiamonds and their embedded SiV centers. Nanodiamonds are synthesized using controlled processes, and their structure is verified using micro-Raman spectroscopy and transmission electron microscopy. Energy-dispersive X-ray spectroscopy confirms elemental composition, while photoluminescence spectroscopy studies the fluorescence of the SiV centers at various temperatures.

Further analysis includes fluorescence lifetime measurements and polarization analysis to confirm single-photon emission. Researchers successfully synthesized nanodiamonds with controlled size and a relatively high concentration of SiV centers. They observed that the fluorescence spectrum of the SiV centers shifts with temperature, indicating changes in the defect’s electronic structure. Evidence suggests these SiV centers can emit single photons, a crucial requirement for quantum applications. Polarization analysis provides information about the orientation of the SiV centers within the nanodiamonds.

Nanodiamonds Host Isolated Single-Photon Emitters

Scientists have developed a method for creating bright, isolated single-photon emitters by embedding color centers within nanodiamonds. This approach decouples the emitters from disruptive environmental vibrations, enhancing their performance for quantum technologies. The team synthesized nanoscale diamond particles using a high-pressure, high-temperature process, resulting in particles with an average size of 43 nanometers. Raman spectroscopy confirmed the diamond structure, and energy-dispersive X-ray spectroscopy verified the carbon-dominated composition. Researchers employed photoluminescence mapping to identify isolated emitters hosted within the nanodiamonds.

These emitters exhibited single-photon emission, confirmed through second-order correlation measurements. A key innovation involved characterizing the unique spectral signature of these emitters, consistently observing four narrow, nearly harmonically spaced emission lines accompanied by PL antibunching, establishing them as spectral fingerprints of newly discovered IL1 centers. Notably, the zero-phonon line exhibited a record-narrow linewidth of 0. 31 nanometers at 547. 5 nanometers, exceeding the performance of known color centers.

Detailed investigation of a single IL1 center revealed exceptionally bright emission, reaching saturation intensities of 12. 5 Mcps after background correction, and remarkably stable output with no observable blinking down to the millisecond timescale. Time-resolved measurements established an excited-state lifetime of 2. 4 nanoseconds, and calculations determined a quantum yield of 92% in the two-level approximation. Polarization analysis demonstrated a high degree of linear polarization, with visibility reaching up to 91% for some emitters, indicating emission originating from a single linearly polarized dipole transition. This combination of characteristics positions these nanodiamond-hosted color centers as promising candidates for advanced quantum technologies.

Stable Nanodiamonds Emit Record Bright Single Photons

This work presents a breakthrough in creating remarkably stable and bright single-photon emitters, achieved through the development of novel color centers within nanodiamonds. Scientists successfully decoupled these color centers from interactions with the surrounding diamond structure, dramatically improving their performance for potential applications in quantum technologies. The research demonstrates record-narrow linewidths of 0. 31 nanometers at room temperature, a significant improvement over previously known color centers. These centers exhibit stable, bright emission, reaching saturation intensities of up to 12.

5 Mcps after background correction. The team verified the nanoscale nature of the diamond particles using transmission electron microscopy, observing linear sizes of 43 ±7 nanometers. Raman spectroscopy confirmed the presence of the diamond lattice, and energy-dispersive X-ray spectroscopy verified the carbon-dominated composition. Photoluminescence intensity maps revealed isolated emitters hosted by these nanodiamonds, confirmed to be single-photon emitters through second-order correlation measurements. A key characteristic of these emitters is a spectrum featuring four sharp, nearly harmonically spaced emission lines, consistently accompanied by PL antibunching, establishing them as spectral fingerprints of single IL1 centers.

Detailed analysis of a single IL1 center revealed an excited-state lifetime of 2. 4 ±0. 1 nanoseconds, and a remarkably high quantum yield of 92% in the two-level approximation. This high quantum yield, coupled with the absence of significant “bunching” behavior, indicates a strong radiative component to the excited state decay. Polarization measurements demonstrate a high degree of linear polarization, with visibility reaching up to 91% for some emitters, indicating emission originating from a single linearly polarized dipole transition. The suppression of bulk phonon sidebands, and the observation of a single localized vibrational mode responsible for the four-peak vibronic spectrum, represent a unique mechanism for phonon decoupling in wide-gap materials.

Vibrational Decoupling Enhances Nanodiamond Photon Emission

This research demonstrates the creation of single-photon emitters within nanodiamonds that exhibit significantly enhanced coherence and controllability, overcoming limitations imposed by interactions with surrounding vibrations. Scientists achieved this by strongly decoupling the color centers from the bulk vibrational environment, resulting in remarkably narrow emission linewidths and stable, bright single-photon emission at room temperature. The team’s observations reveal a unique mechanism involving a radiative orbital transition coupled to a localized vibrational mode, effectively isolating the emitter from disruptive external vibrations. These findings represent a substantial advance in the field of quantum photonics, enabling qualitatively improved performance in applications such as quantum networks and nanoscale sensing. The suppression of unwanted vibrational interactions unlocks the potential to explore and utilize the vibrational states themselves as physical resources for quantum technologies. While this work focuses on demonstrating the decoupling mechanism and characterizing the resulting emitters, further investigation is needed to fully understand the temperature dependence of the spectral lines and to optimize the nanodiamond fabrication process for consistent emitter performance.