Color centres in diamond represent a very interesting system for realizing single photon emitters, even at room temperature, in particular are attracting an ever-growing interest in quantum optics, quantum information and quantum sensing, due to their appealing photo-physical properties combined with ease of access and manipulation in a solid state system characterized by high transparency and structural stability. Literally hundreds of optically active color centers can be created and controlled in the diamond matrix, to be employed either as bright and stable single-photon sources or individual spin systems with optical readout, with record performances even at room temperature. In concurrence with the remarkable results obtained at the state of the art on the exploitation of the unique properties of the negatively-charged nitrogen-vacancy complex (NV), new and appealing color centers are continuously being discovered and characterized. In the present contribution, the most recent results obtained by a collaboration among the Italian National Institutes of Metrologic Research (INRiM), the University of Torino and the Italian National Institutes of Nuclear Physics (INFN) will be overviewed and critically assessed in their future perspectives.
Properties of quantum light represent a tool for overcoming limits of classical optics. Several experiments have demonstrated this advantage ranging from quantum enhanced imaging to quantum illumination. In this work, experimental demonstration of quantum-enhanced resolution in confocal fluorescence microscopy will be presented. This is achieved by exploiting the non-classical photon statistics of fluorescence emission of single nitrogen-vacancy (NV) color centers in diamond. By developing a general model of super-resolution based on the direct sampling of the kth-order autocorrelation function of the photoluminescence signal, we show the possibility to resolve, in principle, arbitrarily close emitting centers. Finally, possible applications of NV-based fluorescent nanodiamonds in biosensing and future developments will be presented.
Diamond’s nitrogen-vacancy (NV) centers show great promise in sensing applications and quantum computing due to their long electron spin coherence time and their ability to be located, manipulated and read out using light. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532- nm laser light, even at room temperature. The NV's states are isolated from environmental perturbations making their spin coherence comparable to trapped ions. An important breakthrough would be in connecting, using waveguides, multiple diamond NVs together optically. However, the inertness of diamond is a significant hurdle for the fabrication of integrated optics similar to those that revolutionized silicon photonics. In this work we show the possibility of buried waveguide fabrication in diamond, enabled by focused femtosecond high repetition rate laser pulses. We use μRaman spectroscopy to gain better insight into the structure and refractive index profile of the optical waveguides.
We present two recent results achieved in INRIM laboratories paving the way for next future commercial use of quantum imaging techniques. The first exploits non-classical photon statistics of single nitrogen-vacancy color centers in diamond for realising super-resolution. A little more in detail we demonstrate that the measurement of high order correlation functions allows overcoming Abbe limit. The second exploits ghost imaging in a specific case of practical interest, i.e. in measuring magnetic structures in garnets.
Single-photon sources (SPS) play a key-role in many applications, spanning from quantum metrology, to quantum information and to the foundations of quantum mechanics. Even if an ideal SPS (i. e. emitting indistinguishable, ”on-demand” single photons, at an arbitrarily fast repetition rate) is far to be realized due to real-world deviations from the ideality, much effort is currently devoted to improving the performance of real sources. With regards to the emission probability, it appears natural to employ sources that are in principle deterministic in the single- photon emission (single quantum emitters such as single atoms, ions, molecules, quantum dots, or color centers in diamond) as opposed to probabilistic ones (usually heralded SPS based on parametric down-conversion). We present an overview of our latest results concerning a work-in-progress NIR pulsed single photon source based on single quantum emitters (color centers in diamond) exploiting recently reported centers. They are particularly interesting because of the narrow emission line (tipically less than 5 nm), the shorter excited state lifetime with respect to NV centres (1 - 2 ns compared to 12 ns, allowing a ten-fold photon emission rate upon saturation) and the polarized emission.
In this proceedings we will present a research project financed by Piedmont regional government (Italy) and finalized to
the realization and commercialization of functional devices for cellular bio-sensing based on diamond. Partners of the
project are: Crisel Instruments, Torino University, Torino Polytechnic, INRIM, Politronica, Bionica Tech, Ulm
Here the main features of the final devices will be briefly summarized.
We envisage an active diamond-based cellular substrate that can simultaneously stimulate and detect a variety of signals
(chemical, optical, electrical) to and from neuroendocrine cells, in a fully biocompatible environment for the cellular
system under test. Such a device can be realized by fully exploiting the peculiar properties of diamond: optical
transparency, biocompatibility, chemical inertness, accessibility to a conductive graphite-like phase; properties that will
be further explored and tested during the project.
Manufacturing of miniaturized photonic devices based on diamond technology is possible by implanting the pristine
material with highly energetic particles. Here we report on the spectral characterization of the optical constants of
proton-irradiated diamond. Absorption of the irradiated zones was estimated in the UV-vis-NIR from direct
transmittance measurement using a dedicated setup with enhanced spatial resolution. The OPD data providing an
estimation of the thickness of the damaged area and its depth profile, have allowed then evaluation of the extinction
coefficient from the transmission measurements. Simultaneous variation of dispersive optical constants makes the
modeling significantly more complicated compared to the above cited monochromatic study.
Mono and polycrystalline Chemical Vapor Deposited (CVD) diamond is a promising material for several
advanced topics: microchips substrate, biological applications, UV and particle detection. Commercial CVD
diamonds are available in small square size, commonly 3-5 millimeters side and 0.5-1.5 millimeters thickness.
To improve diamond reliability for described applications, it is important to have a quality control on
diamond samples, not only for electrical constants but also for optical characteristics and surface roughness.
In this paper we present an optical characterization method based on interferometric instruments, to measure
surface structure and internal homogeneity of mono ad polycrystalline commercial CVD diamonds, with
Nitrogen-vacancy centers in diamond typically have spin-conserving optical transitions, a feature which allows
for optical detection of the long-lived electronic spin states through fluorescence detection. However, by applying
stress to a sample it is possible to obtain spin-nonconserving transitions in which a single excited state couples to
multiple ground states. Here we describe two-frequency optical spectroscopy on single nitrogen-vacancy centers
in a high-purity diamond sample at low temperature. When stress is applied to the sample it is possible to
observe coherent population trapping with a single center. By adjusting the stress it is possible to obtain a
situation in which all of the transitions from the three ground sublevels to a common excited state are strongly
allowed. These results show that all-optical spin manipulation is possible for this system, and we propose that
that by coupling single centers to optical microcavities, a scalable quantum network could be realized for photonic
quantum information processing.
We describe how a quantum non-demolition device based on electromagnetically-induced transparency in solidstate atom-like systems could be realized. Such a resource, requiring only weak optical nonlinearities, could potentially enable photonic quantum information processing (QIP) that is much more efficient than QIP based on linear optics alone. As an example, we show how a parity gate could be constructed. A particularly interesting physical system for constructing devices is the nitrogen-vacancy defect in diamond, but the excited-state structure for this system is unclear in the existing literature. We include some of our latest spectroscopic results that indicate that the optical transitions are generally not spin-preserving, even at zero magnetic field, which allows the realization of a Λ-type system.
In the last decade, the synthesis and characterization of nanometer sized carbon clusters have attracted growing interest within the scientific community. This is due to both scientific interest in the process of diamond nucleation and growth, and to the promising technological applications in nanoelectronics and quantum communications and computing. Our research group has demonstrated that MeV carbon ion implantation in fused silica followed by thermal annealing in the presence of hydrogen leads to the formation of nanocrystalline diamond, with cluster size ranging from 5 to 40 nm. In the present paper, we report the synthesis of carbon nanoclusters by the implantation into fused silica of keV carbon ions using the Plasma Immersion Ion Implantation (PIII) technique, followed by thermal annealing in forming gas (4% <sup>2</sup>H in Ar). The present study is aimed at evaluating this implantation technique that has the advantage of allowing high fluence-rates on large substrates. The carbon nanostructures have been characterized with optical absorption and Raman spectroscopies, cross sectional Transmission Electron Microscopy (TEM), and Parallel Electron Energy Loss Spectroscopy (PEELS). Nuclear Reaction Analysis (NRA) has been employed to evaluate the deuterium incorporation during the annealing process, as a key mechanism to stabilize the formation of the clusters.