arXiv subjects

Valery A. Davydov

Publications and source records attributed to Valery A. Davydov.

At least 19 recordsLinked to original sources

arXiv2026

Chip-integrated metasurface-enabled single-photon skyrmion sources

Skyrmions, topologically stable field configurations, have recently emerged in classical optics as structured light for high-density data applications. Achieving controllable on-chip generation of single-photon skyrmions, while being highly desirable for quantum information technologies, remains challenging due to the nanoscale confinement of quantum emitters (QEs). Here we demonstrate a metasurface-integrated quantum emitter (metaQE) platform enabling room-temperature on-chip generation of single-photon skyrmions. Near-field coupling between QEs and propitiously designed surface arrays of meta-atoms mediates spin-orbit interaction, transforming nanoscale-localized dipole emission into free-propagating topologically structured photonic modes. By exploiting this approach for structuring quantum emission from different color centers in nanodiamonds, we realize diverse skyrmionic states, including high-order anti-skyrmions and skyrmionium, and thereby demonstrate its universality across QEs. Our work establishes a unified framework for on-chip structured quantum light sources, offering versatile control of high-dimensional topological states, such as skyrmions, and advancing scalable quantum photonic technologies.

physics.optics↗

arXiv2025

Ultranarrow Bright Single-Photon Emitters in Diamond with Strong Broadband Phonon Decoupling

Single-photon emitters are fundamental building blocks for quantum information processing, communication and sensing. However, unwanted interactions with bulk phonons in their host environment strongly limit their coherence and controllability. We report single color centers in nanodiamonds that are strongly and comprehensively decoupled from the bulk phononic environment. The color centers feature record-narrow linewidths down to 0.3 nm at room temperature and stable, bright emission, exceeding 10 Mcps in saturation. Notably, the bulk phonon sideband is almost entirely suppressed, revealing the presence of a single localized vibrational mode outside the diamond phonon band. Our observations and simulations point towards a unique mechanism for phonon decoupling in common wide-gap materials, based on a strongly radiative orbital transition coupled to a localized vibrational mode. The new color center enables qualitatively higher performance for applications in quantum networks and nanoscale sensing, and the exploration of new physical resources associated with vibrational states.

quant-ph↗

arXiv2023

Ultracompact single-photon sources of linearly polarized vortex beams

Ultracompact chip-integrated single-photon sources of collimated beams with polarizationencoded states are crucial for integrated quantum technologies. However, most of currently available single-photon sources rely on external bulky optical components to shape the polarization and phase front of emitted photon beams. Efficient integration of quantum emitters with beam shaping and polarization encoding functionalities remains so far elusive. Here, we present ultracompact single-photon sources of linearly polarized vortex beams based on chip-integrated quantum emitter-coupled metasurfaces, which are meticulously designed by fully exploiting the potential of nanobrick arrayed metasurfaces. We first demonstrate on-chip single-photon generation of high-purity linearly polarized vortex beams with prescribed topological charges of -1, 0, and +1. We further realize multiplexing of single-photon emission channels with orthogonal linear polarizations carrying different topological charges and demonstrate their entanglement. Our work illustrates the potential and feasibility of ultracompact quantum emitter-coupled metasurfaces as a new quantum optics platform for realizing chip-integrated high-dimensional single-photon sources.

physics.optics↗

arXiv2023

Scattering holography designed metasurfaces for channeling single-photon emission

Channelling single-photon emission in multiple well-defined directions and simultaneously controlling its polarization characteristics is highly desirable for numerous quantum technology applications. We show that this can be achieved by using quantum emitters (QEs) nonradiatively coupled to surface plasmon polaritons (SPPs), which are scattered into outgoing free-propagating waves by appropriately designed metasurfaces. The QE-coupled metasurface design is based on the scattering holography approach with radially diverging SPPs as reference waves. Using holographic metasurfaces fabricated around nanodiamonds with single Ge vacancy centers, we experimentally demonstrate on-chip integrated efficient generation of two well-collimated single-photon beams propagating along different 15-degree off-normal directions with orthogonal linear polarizations.

physics.optics↗

arXiv2023

Sub-to-super-Poissonian photon statistics in cathodoluminescence of color center ensembles in isolated diamond crystals

Impurity-vacancy centers in diamond offer a new class of robust photon sources with versatile quantum properties. While individual color centers commonly act as single-photon sources, their ensembles have been theoretically predicted to have tunable photon-emission statistics. Importantly, the particular type of excitation affects the emission properties of a color center ensemble within a diamond crystal. While optical excitation favors non-synchronized excitation of color centers within an ensemble, electron-beam excitation can synchronize the emitters and thereby provides a control of the second-order correlation function $g_2(0)$. In this letter, we demonstrate experimentally that the photon stream from an ensemble of color centers can exhibit $g_2(0)$ both above and below unity. Such a photon source based on an ensemble of few color centers in a diamond crystal provides a highly tunable platform for informational technologies operating at room temperature.

cond-mat.mes-hall↗

arXiv2021

Prolonged orbital relaxation by locally modified phonon density of states for SiV$^-$ center in nanodiamonds

Coherent quantum systems are a key resource for emerging quantum technology. Solid-state spin systems are of particular importance for compact and scalable devices. However, interaction with the solid-state host degrades the coherence properties. The negatively-charged silicon vacancy center in diamond is such an example. While spectral properties are outstanding, with optical coherence protected by the defects symmetry, the spin coherence is susceptible to rapid orbital relaxation limiting the spin dephasing time. A prolongation of the orbital relaxation time is therefore of utmost urgency and has been tackled by operating at very low temperatures or by introducing large strain. However, both methods have significant drawbacks, the former requires use of dilution refrigerators and the latter affects intrinsic symmetries. Here, a novel method is presented to prolong the orbital relaxation with a locally modified phonon density of states in the relevant frequency range, by restricting the diamond host to below 100 nm. The method works at liquid Helium temperatures of few Kelvin and in the low-strain regime.

quant-ph↗

arXiv2021

A Robust Coherent Single-Photon Interface for Moderate- NA Optics Based on SiV Center in Nanodiamonds and a Plasmonic Bullseye Antenna

Coherent exchange of single photons is at the heart of applied Quantum Optics. The negatively-charged silicon vacancy center in diamond is among most promising sources for coherent single photons. Its large Debye-Waller factor, short lifetime and extraordinary spectral stability is unique in the field of solid-state single photon sources. However, the excitation and detection of individual centers requires high numerical aperture optics which, combined with the need for cryogenic temperatures, puts technical overhead on experimental realizations. Here, we investigate a hybrid quantum photonics platform based on silicon-vacancy center in nanodiamonds and metallic bullseye antenna to realize a coherent single-photon interface that operates efficiently down to low numerical aperture optics with an inherent resistance to misalignment.

physics.optics↗

arXiv2021

Hybrid quantum photonics based on artificial atoms placed inside one hole of a photonic crystal cavity

Spin-based quantum photonics promise to realize distributed quantum computing and quantum networks. The performance depends on efficient entanglement distribution, where the efficiency can be boosted by means of cavity quantum electrodynamics. The central challenge is the development of compact devices with large spin-photon coupling rates and high operation bandwidth. Photonic crystal cavities comprise strong field confinement but put high demands on accurate positioning of an atomic system in the mode field maximum. Color center in diamond, and in particular the negatively-charged Silicon-Vacancy center, emerged as a promising atom-like systems. Large spectral stability and access to long-lived, nuclear spin memories enabled elementary demonstrations of quantum network nodes including memory-enhanced quantum communication. In a hybrid approach, we deterministically place SiV$^-$-containing nanodiamonds inside one hole of a one-dimensional, free-standing, Si$_3$N$_4$-based photonic crystal cavity and coherently couple individual optical transitions to the cavity mode. We optimize the light-matter coupling by utilizing two-mode composition, waveguiding, Purcell-enhancement and cavity resonance tuning. The resulting photon flux is increased by more than a factor of 14 as compared to free-space. The corresponding lifetime shortening to below 460 ps puts the potential operation bandwidth beyond GHz rates. Our results mark an important step to realize quantum network nodes based on hybrid quantum photonics with SiV$^-$- center in nanodiamonds.

cond-mat.mtrl-sci↗

arXiv2020

Purcell-Enhanced Emission from Individual SiV$^-$ Center in Nanodiamonds Coupled to a Si$_3$N$_4$-Based, Photonic Crystal Cavity

Hybrid quantum photonics combines classical photonics with quantum emitters in a postprocessing step. It facilitates to link ideal quantum light sources to optimized photonic platforms. Optical cavities enable to harness the Purcell-effect boosting the device efficiency. Here, we postprocess a free-standing, crossed-waveguide photonic crystal cavity based on Si$_3$N$_4$ with SiV$^-$ center in nanodiamonds. We develop a routine that holds the capability to optimize all degrees of freedom of the evanescent coupling term utilizing AFM nanomanipulation. After a few optimization cycles we resolve the fine-structure of individual SiV$^-$ centers and achieve a Purcell enhancement of more than 4 on individual optical transitions, meaning that four out of five spontaneously emitted photons are channeled into the photonic device. Our work opens up new avenues to construct efficient quantum photonic devices.

cond-mat.mtrl-sci↗

arXiv2019

Preparing single SiV$^{-}$ center in nanodiamonds for external, optical coupling with access to all degrees of freedom

Optical coupling enables intermediate- and long-range interactions between distant quantum emitters. Such interaction may be the basic element in bottom-up approaches of coupled spin systems or for integrated quantum photonics and quantum plasmonics. Here, we prepare nanodiamonds carrying single, negatively-charged silicon-vacancy centers for evanescent optical coupling with access to all degrees of freedom by means of atomic force nanomanipulation. The color centers feature excellent optical properties, comparable to silicon-vacancy centers in bulk diamond, resulting in a resolvable fine structure splitting, a linewidth close to the Fourier-Transform limit under resonant excitation and a good polarization contrast. We determine the orbital relaxation time $T_{1}$ of the orbitally split ground states and show that all optical properties are conserved during translational nanomanipulation. Furthermore, we demonstrate the rotation of the nanodiamonds. In contrast to the translational operation, the rotation leads to a change in polarization contrast. We utilize the change in polarization contrast before and after nanomanipulation to determine the rotation angle. Finally, we evaluate the likelihood for indistinguishable, single photon emission of silicon-vacancy centers located in different nanodiamonds. Our work enables ideal evanescent, optical coupling of distant nanodiamonds containing silicon-vacancy centers with applications in the realization of quantum networks, quantum repeaters or complex quantum systems.

cond-mat.mtrl-sci↗

arXiv2019

Silicon-vacancy color centers in Si- and Si,P-doped nanodiamonds: thermal susceptibilities of photo luminescence band at 740 nm

We have characterized thermal susceptibilities of the spectral band at 740 nm of silicon-vacancy (SiV) centers in Si- and Si,P-doped nanodiamonds over a temperature range from 295 K to 350 K, which is of interest for thermometry in biological systems. Si-doped crystals reveal linear dependence of the SiV zero-phonon line position, width and relative amplitude with susceptibilities of 0.0126(4) nm/K, 0.062(2) nm/K and $-0.037(2)$ K$^{-1}$, respectively. Si,P-doped nanodiamonds show significantly smaller (up to 35 % for the width) susceptibilities and prove control of SiV properties with additional chemical doping. It is argued that a significant contribution to the heating of the nanodiamonds induced by laser light can be intrinsic due to a high concentration and low luminescence quantum yield of SiV centers.

cond-mat.mes-hall↗

arXiv2019

Single Silicon Vacancy Centers in 10-Nanometer Diamonds for Quantum Information Applications

Ultra-small, low-strain, artificially produced diamonds with an internal, active color center have substantial potential for quantum information processing and biomedical applications. Thus, it is of great importance to be able to artificially produce such diamonds. Here, we report on the high-pressure, high-temperature synthesis of such nanodiamonds about 10 nm in size and containing an optically active, single silicon-vacancy color center. Using special sample preparation technique, we were able to prepare samples containing single nanodiamonds on the surface. By correlating atomic-force microscope images and confocal optical images we verified presents of optically active color centers in single nanocrystals, and using second-order correlation measurements proved single-photon emission statistics of this nanodiamonds. This color centers have non-blinking, spectrally narrow emission with narrow distribution of spectral width and positions of zero-phonon line thus proving high quality of the nanodiamonds produced

physics.app-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↗

arXiv2019

Ultrasensitive all-optical thermometry using nanodiamonds with high concentration of silicon-vacancy centres and multiparametric data analysis

Nanoscale thermometry is paramount to study primary processes of heat transfer in solids and is a subject of hot debate in cell biology. Here we report ultrafast temperature sensing using all-optical thermometry exploiting synthetic nanodiamonds with silicon-vacancy (SiV) centres embedded at a high concentration. Using multi-parametric analysis of photoluminescence (PL) of these centres, we have achieved an intrinsic noise floor of about 10 mK Hz$^{-1/2}$, which is a thousand-fold increase in the readout speed in comparison to the current record values demonstrated with all-optical methods of comparable spatial-resolution and precision. Our thermometers are smaller than 250-nm across but can detect a 0.4$^\circ$C change of temperature in a measurement taking only 0.001 second. The exceptional sensitivity and simplicity of these thermometers enable a wide range of applications such as temperature monitoring and mapping within intracellular regions and in state-of-the-art solid-state electronic nanodevices.

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↗

arXiv2018

On-chip excitation of single germanium-vacancies in nanodiamonds embedded in plasmonic waveguides

Monolithic integration of quantum emitters in nanoscale plasmonic circuitry requires low-loss plasmonic configurations capable of confining light well below the diffraction limit. We demonstrate on-chip remote excitation of nanodiamond-embedded single quantum emitters by plasmonic modes of dielectric ridges atop colloidal silver crystals. The nanodiamonds are produced to incorporate single germanium-vacancy (GeV) centers, providing bright, spectrally narrow and stable single-photon sources suitable for highly integrated circuits. Using electron-beam lithography with hydrogen silsesquioxane (HSQ) resist, dielectric-loaded surface plasmon polariton waveguides (DLSPPWs) are fabricated on single crystalline silver plates so as to contain those of spin-casted nanodiamonds that are found to feature appropriate single GeV centers. The low-loss plasmonic configuration enabled the 532 nm pump laser light to propagate on-chip in the DLSPPW and reach to an embedded nanodiamond where a single GeV center is incorporated. The remote GeV emitter is thereby excited and coupled to spatially confined DLSPPW modes with an outstanding figure-of-merit of 180 due to a ~6-fold Purcell enhancement, ~56% coupling efficiency and ~33 μm transmission length, revealing the potential of our approach for on-chip realization of nanoscale functional quantum devices.

cond-mat.mes-hall↗

arXiv2017

Varying temperature and silicon content in nanodiamond growth: effects on silicon-vacancy centers

Nanodiamonds containing color centers open up many applications in quantum information processing, metrology, and quantum sensing. In particular, silicon vacancy (SiV) centers are prominent candidates as quantum emitters due to their beneficial optical qualities. Here we characterize nanodiamonds produced by a high-pressure high-temperature method without catalyst metals, focusing on two samples with clear SiV signatures. Different growth temperatures and relative content of silicon in the initial compound between the samples altered their nanodiamond size distributions and abundance of SiV centers. Our results show that nanodiamond growth can be controlled and optimized for different applications.

cond-mat.mtrl-sci↗

arXiv2017

All-optical nanoscale thermometry with silicon-vacancy centers in diamond

We demonstrate an all-optical thermometer based on an ensemble of silicon-vacancy centers (SiVs) in diamond by utilizing a temperature dependent shift of the SiV optical zero-phonon line transition frequency, $Δλ/ΔT= 6.8\,\mathrm{GHz/K}$. Using SiVs in bulk diamond, we achieve $70\,\mathrm{mK}$ precision at room temperature with a sensitivity of $360\,\mathrm{mK/\sqrt{Hz}}$. Finally, we use SiVs in $200\,\mathrm{nm}$ nanodiamonds as local temperature probes with $521\,\mathrm{ mK/\sqrt{Hz}}$ sensitivity. These results open up new possibilities for nanoscale thermometry in biology, chemistry, and physics, paving the way for control of complex nanoscale systems.

quant-ph↗