Realization of novel quantum technologies requires a control over their fundamental constituent- a single photon emitter. In this work we will present a comparative study of single photon emitters based on color centers in diamond which deliver performance comparable with decoy state implementation with weak coherent sources, and are most suitable for practical applications. In particular we will present the photo-physical properties of a novel family of single photon emitters, originated from Cr impurities in the diamond lattice, which exhibit a typical emission lines in the range of 740-760 nm, and a count rate in the range of 0.8-3.2 106 counts/s. We will highlight future directions to optimize these sources and present simulations of their performance in practical devices.
Realization of novel quantum technologies requires a control over their fundamental constituent- a single photon emitter. In this work we will present a comparative study of single photon emitters based on color centers in diamond which deliver performance comparable with decoy state implementation with weak coherent sources, and are most suitable for practical applications. In particular we will present the photo-physical properties of a novel family of single photon emitters, originated from Cr impurities in the diamond lattice, which exhibit a typical emission lines in the range of 740-760 nm, and a count rate in the range of 0.8-3.2 106 counts/s. We will highlight future directions to optimize these sources and present simulations of their performance in practical devices.
Quantum communication and quantum metrology established a demand for an accessible solid state systems which can generate a stream of single photons on demand [1]. Although single photon emission has been demonstrated from quantum dots (QD)[1,2], single molecules [3] and nanowires [4], their practical operation is limited by the temperature or photostability. Diamond crystals, however, are the most promising platform for generation of robust, photo-stable, single photons at room temperature [5,6]. Nevertheless, out of more than 500 existing optical centers in diamond only three known centers demonstrated a clear single photon emission: the nitrogen-vacancy complex [6,7], the silicon-vacancy complex [8] and the nickel-nitrogen complex [9,10]. Recent progress in materials science and fabrication techniques of diamond color centers unveiled novel quantum emitters with photo-physical properties surpassing the current mainstream [11,12,13]. Consequently, the versatility of the diamond lattice to host various impurities which give luminescence signals lead to a dramatic discovery of ultra bright single photon emitters operating in the MHz regime [14]. These new centers, comparable with QD in terms of brightness [1], but have the tremendous advantage of their room temperature operation and photo-stability. Furthermore, it opened a new avenue to investigate essentially an unknown group of single photon emitters. A brief description of the fabrication methods and a detailed quantum optical characterization of this class of diamond emitters is the subject of this presentation. In particular we will present the photo-physical properties of a novel family of single photon emitters, most likely originated from Cr impurities within the chemical vapor deposition grown nano-diamond crystals. We concentrate on the typical emission lines in the range of 740 - 790 nm, which exhibit single photon emission with count rate in the range of 0.8-3.2 106 counts/s at the limit of infinite optical excitation power, and life time as short as 1 ns. Even more, some of the emitters exhibit a photon statistics without any photon bunching, indicating a two-level system with unitary quantum efficiency. We will also show preliminary results of a resonant excitation at 4 K. We will highlight future directions to optimize these sources and avenues to investigate the fundamental properties of these centers.
Single photon emitters are core components of quantum technologies. In this work new family of emitters based on chromium impurities in diamond is presented. The emitters can be fabricated by ion implantation of chromium into bulk diamond or incorporated during the growth of diamond nanocrystals. The remarkable photo‐physical properties of these emitters include room temperature operation, narrow photoluminescence (PL) in the near infra red and ultra bright, fully polarized photon emission with count rate of 3.2×106 counts/s. These photo physical properties make the Cr centers ideal for quantum information processing, metrology, and cellular bio markers applications.
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.
Sources of single photons are integral to a number of applications in the emerging field of quantum technologies. For any practical implementation of single-photon sources, a variety of different properties and an overall comprehensive characterization of the sources are required. Color centers in hBN and group IV color centers in diamond are promising candidate sources due to their favorable properties and rich internal level structure. Both of these candidates, however, also present some serious challenges. Although bright and spectrally narrow, defects in hBN suffer from emission instabilities. Furthermore, limited knowledge about their atomic composition leads to behaviour, which is often unpredictable. Meanwhile, Group IV centers generally exhibit low extraction efficiencies due to total internal reflection inside the high-index diamond host material. In this thesis, several large-scale series of experiments are conducted to investigate both types of emitters in a confocal fluorescence microscope at room temperature. The excitation characteristics of a large number of single-photon emitters in hBN from a narrow spectral window are investigated using a fully automated procedure. The results are compared to theoretical predictions for several carbon defects from the literature to gain further knowledge of the atomic nature of the underlying defects. Based on this approach, the CB, CN, CBVN, and CNVB centers are confidently ruled out as possible origins of the observed emission. Some uncertainty remains about the assignment of the carbon trimer C2CN as well as carbon-based donor-acceptor pairs. In a separate series of experiments, emission instabilities of hBN emitters from the same spectral region are studied. The detected fluctuations in brightness were conclusively attributed to spectral diffusion of the emission. Furthermore, optical stabilization of these effects via short-wavelength irradiation favors an explanation of the observed behavior via nearby charge carriers and the resulting Stark effect. Tin-vacancies, as representatives of group IV centers, are studied in a novel type of diamond waveguide structure for light collection enhancement. A center with sharp zero-phonon emission around 619 nm, a g(2)(0) value of 0.32, and simultaneous stable count rate of 3.4 Mcps was found. By restricting the collection to the zero-phonon line, g(2)(0) = 0.1 could be achieved. In a widespread characterization of the sample, it was found that most structures contain more than one negatively charged SnV center, which leaves an opportunity to improve the implantation parameters. In additional experiments on single tin-vacancy centers, a possible transition to a higher excited state as well as the charge-state transitions of the defects were probed. The results of these measurements contribute to the growing body of research on tin-vacancies and other group IV centers.
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.
A detailed study of the photophysical properties of several chromium-related color centers produced within chemical vapor deposition diamond is presented. These emitters show narrow luminescence lines in the range of $740\ensuremath{-}770$ nm. Single-photon emission was verified with continuous and pulsed excitation with detected emission rates at saturation in the range of ($2\ensuremath{-}3$) $\ifmmode\times\else\texttimes\fi{}$ 106 counts/s, while direct lifetime measurements reveal excited state lifetimes for the distinct centers ranging $1\ensuremath{-}14$ ns. In addition, a number of quantum emitters demonstrate two-level behavior with no bunching present in the second-order correlation function. The three-level systems revealed typically photoluminescence lines with width half-maximum of 4 nm while the two-level emitters have full width half-maximum of 10 nm at room temperature. In addition, the quantum efficiency of the two-level system was measured to be four times higher than that of the three-level system.