[Show abstract][Hide abstract]ABSTRACT: Spin impurities in diamond can be versatile tools for a wide range of
solid-state-based quantum technologies, but finding spin impurities which offer
sufficient quality in both photonic and spin properties remains a challenge for
this pursuit. The silicon-vacancy center has recently attracted a lot of
interest due to its spin-accessible optical transitions and the quality of its
optical spectrum. Complementing these properties, spin coherence is essential
for the suitability of this center as a spin-photon quantum interface. Here, we
report all-optical generation of coherent superpositions of spin states in the
ground state of a negatively charged silicon-vacancy center using coherent
population trapping. Our measurements reveal a characteristic spin coherence
time, T2*, exceeding 250 nanoseconds at 4 K. We further investigate the role of
phonon-mediated coupling between orbital states as a source of irreversible
decoherence. Our results indicate the feasibility of all-optical coherent
control of silicon-vacancy spins using ultrafast laser pulses.
[Show abstract][Hide abstract]ABSTRACT: The spin state of the silicon-vacancy centre in diamond and its optical accessibility have so far remained elusive. We here evidence spin-tagged fluorescence through resonant optical access to the electronic spin 1/2 of the centre.
[Show abstract][Hide abstract]ABSTRACT: The spin state of the silicon-vacancy centre in diamond and its optical accessibility have so far remained elusive. We here evidence spin-tagged fluorescence through resonant optical access to the electronic spin ½ of the centre.
[Show abstract][Hide abstract]ABSTRACT: Colour centres in diamond have emerged as versatile tools for solid-state quantum technologies ranging from quantum information to metrology, where the nitrogen-vacancy centre is the most studied to date. Recently, this toolbox has expanded to include novel colour centres to realize more efficient spin-photon quantum interfaces. Of these, the silicon-vacancy centre stands out with highly desirable photonic properties. The challenge for utilizing this centre is to realize the hitherto elusive optical access to its electronic spin. Here we report spin-tagged resonance fluorescence from the negatively charged silicon-vacancy centre. Our measurements reveal a spin-state purity approaching unity in the excited state, highlighting the potential of the centre as an efficient spin-photon quantum interface.
Full-text · Article · Feb 2014 · Nature Communications
[Show abstract][Hide abstract]ABSTRACT: The negatively charged silicon vacancy (SiV) color center in diamond has recently proven its suitability for bright and stable single photon emission. However, its electronic structure so far has remained elusive. We here explore the electronic structure by exposing single SiV defects to a magnetic field where the Zeeman effect lifts the degeneracy of magnetic sublevels. The similar responses of single centers and a SiV ensemble in a low strain reference sample prove our ability to fabricate almost perfect single SiVs, revealing the true nature of the defect's electronic properties. We model the electronic states using a group-theoretical approach yielding a good agreement with the experimental observations. Furthermore, the model correctly predicts polarization measurements on single SiV centers and explains recently discovered spin selective excitation of SiV defects.
Full-text · Article · Jan 2014 · Physical Review Letters
[Show abstract][Hide abstract]ABSTRACT: We demonstrate a quantum key distribution (QKD) testbed for room temperature
single photon sources based on defect centres in diamond. A BB84 protocol over
a short free-space transmission line is implemented. The performance of
nitrogen-vacancy (NV) as well as silicon-vacancy defect (SiV) centres is
evaluated and an extrapolation for next-generation sources with enhanced
efficiency is discussed.
Full-text · Article · Oct 2013 · New Journal of Physics
[Show abstract][Hide abstract]ABSTRACT: The work demonstrates frequency downconversion of single photons from a quantum dot and prove the preservation of the single photon character. The authors were able to translate the frequency of single photons of a semiconductor quantum dot from the red spectral range to the telecom O-band. It was proven that this conversion process leaves the quantum properties of the photons untouched. The high over-all efficiency of 32% for this conversion interface makes it well suited for an application in long-range quantum transmission links.
[Show abstract][Hide abstract]ABSTRACT: We study single silicon vacancy (SiV) centres in chemical vapour deposition
(CVD) nanodiamonds on iridium as well as an ensemble of SiV centres in a high
quality, low stress CVD diamond film by using temperature dependent
luminescence spectroscopy in the temperature range 5-295 K. We investigate in
detail the temperature dependent fine structure of the zero-phonon-line (ZPL)
of the SiV centres. The ZPL transition is affected by inhomogeneous as well as
temperature dependent homogeneous broadening and blue shifts by about 20 cm-1
upon cooling from room temperature to 5 K. We employ excitation power dependent
g(2) measurements to explore the temperature dependent internal population
dynamics of single SiV centres and infer almost temperature independent
Full-text · Article · Oct 2012 · New Journal of Physics
[Show abstract][Hide abstract]ABSTRACT: We demonstrate efficient (>30%) quantum frequency conversion of visible single photons (711 nm) emitted by a quantum dot to a telecom wavelength (1313 nm). Analysis of the first- and second-order coherence before and after wavelength conversion clearly proves that pivotal properties, such as the coherence time and photon antibunching, are fully conserved during the frequency translation process. Our findings underline the great potential of single photon sources on demand in combination with quantum frequency conversion as a promising technique that may pave the way for a number of new applications in quantum technology.
Full-text · Article · Oct 2012 · Physical Review Letters
[Show abstract][Hide abstract]ABSTRACT: We report the frequency downconversion of single photons from a quantum dot (710nm) to the telecommunications O-band with over-all conversion efficiency of 33%. We show the conservation of nonclassical statistics and coherence properties during conversion.
[Show abstract][Hide abstract]ABSTRACT: We fabricate photonic crystal microcavities in a single crystal diamond membrane and actively tune the cavity modes into resonance with the emission line of color centers in diamond to enhance the emission rate.
[Show abstract][Hide abstract]ABSTRACT: Diamond is an attractive material for photonic quantum technologies because its colour centres have a number of outstanding properties, including bright single photon emission and long spin coherence times. To take advantage of these properties it is favourable to directly fabricate optical microcavities in high-quality diamond samples. Such microcavities could be used to control the photons emitted by the colour centres or to couple widely separated spins. Here, we present a method for the fabrication of one- and two-dimensional photonic crystal microcavities with quality factors of up to 700 in single crystal diamond. Using a post-processing etching technique, we tune the cavity modes into resonance with the zero phonon line of an ensemble of silicon-vacancy colour centres, and we measure an intensity enhancement factor of 2.8. The controlled coupling of colour centres to photonic crystal microcavities could pave the way to larger-scale photonic quantum devices based on single crystal diamond.
Full-text · Article · Nov 2011 · Nature Nanotechnology
[Show abstract][Hide abstract]ABSTRACT: We report on the production of nanodiamonds (NDs) with 70-80 nm size via bead
assisted sonic disintegration (BASD) of a polycrystalline chemical vapor
deposition (CVD) film. The NDs display high crystalline quality as well as
intense narrowband (7 nm) room temperature luminescence at 738 nm due to in
situ incorporated silicon vacancy (SiV) centers. The fluorescence properties at
room and cryogenic temperatures indicate that the NDs are, depending on
preparation, applicable as single photon sources or as fluorescence labels.
Full-text · Article · Jun 2011 · Applied Physics Letters
[Show abstract][Hide abstract]ABSTRACT: In this paper, we report the first realization of photonic crystal cavities in quasi-single crystal diamond of high optical quality. As initial material, we use heteroepitaxial diamond films with a thickness of about 10 μm grown by chemical vapor deposition on Si(001) substrates via iridium/yttria-stabilized zirconia buffer layers. In a first step, we fabricate a free standing membrane by removing the silicon substrate. Afterwards, the diamond film is thinned out to a thickness of 300 nm using dry etching techniques, yielding very smooth surface roughness of 5 nm rms. In a second step, the photonic crystal structure is milled into the diamond film by a focused beam of Ga+-ions at an energy of 30 keV. We fabricate ID "nanobeam" cavities in a free standing waveguide as well as 2D photonic crystal structures with several missing holes.
[Show abstract][Hide abstract]ABSTRACT: Color centers in diamond are very promising candidates among the possible realizations for practical single-photon sources because of their long-time stable emission at room temperature. The popular nitrogen-vacancy center shows single-photon emission, but within a large, phonon-broadened spectrum (~100nm), which strongly limits its applicability for quantum communication. By contrast, Ni-related centers exhibit narrow emission lines at room temperature. We present investigations on single color centers consisting of Ni and Si created by ion implantation into single crystalline IIa diamond. We use systematic variations of ion doses between 10^8/cm^2 and 10^14/cm^2 and energies between 30keV and 1.8MeV. The Ni-related centers show emission in the near infrared spectral range (~770nm to 787nm) with a small line-width (~3nm FWHM). A measurement of the intensity correlation function proves single-photon emission. Saturation measurements yield a rather high saturation count rate of 77.9 kcounts/s. Polarization dependent measurements indicate the presence of two orthogonal dipoles. Comment: 8 pages, published in conference proceedings of SPIE Photonics Europe 2010
Full-text · Article · Mar 2010 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract]ABSTRACT: Microcavities in diamond-based photonic crystals are being considered as an attractive architecture to manipulate and control atom-photon coupling. Here we consider a photonic crystal structure consisting of a triangular lattice of air holes etched into a thin free-standing membrane of diamond. By introducing point defects into the periodic structure, light can be localized in three dimensions within a volume smaller than one cubic wavelength. Our work is focused on the "Zero missing hole waveguide-section cavity (M0)" cavity, where the defect is created by shifting two neighboring holes outwards. The field distribution as well as the resonant frequency and the Q-factor of the cavity mode are calculated by FDTD simulations.