Quantum control of hybrid nuclear-electronic qubits

Pulsed magnetic resonance is a wide-reaching technology allowing the quantum state of electronic and nuclear spins to be controlled on the timescale of nanoseconds and microseconds respectively. The time required to flip either dilute electronic or nuclear spins is orders of magnitude shorter than their decoherence times, leading to several schemes for quantum information processing with spin qubits. We investigate instead the novel regime where the eigenstates approximate 50:50 superpositions of the electronic and nuclear spin states forming "hybrid nuclear-electronic" qubits. Here we demonstrate quantum control of these states for the first time, using bismuth-doped silicon, in just 32 ns: this is orders of magnitude faster than previous experiments where pure nuclear states were used. The coherence times of our states are five orders of magnitude longer, reaching 4 ms, and are limited by the naturally-occurring 29Si nuclear spin impurities. There is quantitative agreement between our experiments and no-free-parameter analytical theory for the resonance positions, as well as their relative intensities and relative Rabi oscillation frequencies. In experiments where the slow manipulation of some of the qubits is the rate limiting step, quantum computations would benefit from faster operation in the hybrid regime.Comment: 20 pages, 8 figures, new data and simulation

Ultrafast entangling gates between nuclear spins using photo-excited triplet states

The representation of information within the spins of electrons and nuclei has been powerful in the ongoing development of quantum computers. Although nuclear spins are advantageous as quantum bits (qubits) due to their long coherence lifetimes (exceeding seconds), they exhibit very slow spin interactions and have weak polarisation. A coupled electron spin can be used to polarise the nuclear spin and create fast single-qubit gates, however, the permanent presence of electron spins is a source of nuclear decoherence. Here we show how a transient electron spin, arising from the optically excited triplet state of C60, can be used to hyperpolarise, manipulate and measure two nearby nuclear spins. Implementing a scheme which uses the spinor nature of the electron, we performed an entangling gate in hundreds of nanoseconds: five orders of magnitude faster than the liquid-state J coupling. This approach can be widely applied to systems comprising an electron spin coupled to multiple nuclear spins, such as NV centres, while the successful use of a transient electron spin motivates the design of new molecules able to exploit photo-excited triplet states.Comment: 5 pages, 3 figure

cw and pulsed EPR study of lithium irradiated n-type 21R SiC

The impact of light and medium mass ions in crystals in the MeV range is of particular interest in high energy implantations. In the present work, extensive continuous wave (cw) and pulsed electron paramagnetic resonance (EPR) studies of a 21R SiC Lely platelet, after irradiation with 8 MeV 7Li2+ ions in the random direction, up to a maximum dose of approximately 1 × 1016 particles/cm2 are presented. The existence of new types of defects induced in the end-of-range region of impinging ions is discussed and analyzed. Due to the complexity of the induced structure, the technique of progressive annealing was utilized, revealing interesting features in the experimental spectra. The results are compared to known literature and an attempt is made to explain the occurring similarities. Furthermore, a new paramagnetic defect was isolated and analyzed, persisting up to 1100 °C during the annealing procedure

Synthesis, characterization and evaluation of multi sensitive nanocarriers by using the layer by layer method

Hypothesis: Nowadays nanomedicine appears to be the most promising field in the area of nanotechnology. Diseases such as cancer, which lack of early diagnosis and therapy, are now able to be faced up via small nanoscale objects characterized by unique physicochemical characteristics. Nanocarriers have been investigated in the last years as a result of their ability to selectively target the diseased area. The present work deals with multi-sensitive hollow polymeric nanoformulations with well-tuned size, shape and cargo loading. Experiments: The synthetic route of biocompatible polymeric drug delivery systems consists of five steps. In the first step the core of methacrylic acid (MAA) was fabricated and then in the second step the first temperature-sensitive layer was added. An additional layer, the pH sensitive, was synthesized in the third step and last, in the fourth step the redox sensitive shell was fabricated. The layers were synthesized by distillation precipitation co-polymerization via layer by layer methodology. In the final step, the core-shell structures were modified in order to encapsulate chemotherapeutic agents, such as daunorubicin (DNR) and Cisplatin. The loading capacity (% L.C.) and encapsulation efficiency (% E.E.) percentages were measured by the standard curve methodology. Furthermore, the releasing properties of the multi responsive nanocarriers were investigated, applying the above already mentioned approach. Finally, cell migration and cell viability studies were performed in human breast epithelial cancer MCF-7 and normal human keratinocyte NCTC 2544 cell lines both in the presence and absence of reactive oxygen species (ROS) by using scavenging agents in order to evaluate the cell proliferation efficiency along with the apoptotic effect induced by these multi-sensitive drug delivery systems. Findings: To this end, the hollow nanospheres presented an excellent release behaviour with DNR and Cisplatin under acidic environment, high temperature as well as in the presence of glutathione. Moreover, the cell proliferation assay in conjunction to the wound-healing assays indicated that the hollow NCs are non-toxic both in healthy and cancer cells in contrary to the loaded ones. © 201

Bulk nanobubbles: Production and investigation of their formation/stability mechanism

Nanobubbles (ΝΒs) have attracted concentrated scientific attention due to their unique physicochemical properties and large number of potential applications. In this study, a novel nanobubble generator with low energy demand, operating continuously, is presented. Air and oxygen bulk nanobubbles (NBs@air and NBs@O2) with narrow size distribution and outstanding stability were prepared in water solution. The bulk NBs’ behavior was evaluated taking into consideration the hydrodynamic diameter and ζ-potential as a function of processing time, gas type, pH value and NaCl concentration. According to the results the optimum processing time was 30 min, whereas the effect of water salinity was stronger in NBs@O2 than NBs@air. In order to investigate further the NBs properties, Electron Paramagnetic Resonance (EPR) spectroscopy was applied for quantitative analysis of free radicals following the spin trapping methodology. The mechanism of bulk NBs’ generation and their extremely long-time stability can be attributed mainly to the hydrogen bonding interactions. The formation of a diffusion layer, by absorption of OH− due to electrostatic interaction, contributing to negative surface charge, whereas the interaction of ions with the surface hydroxylic groups provide the equilibrium between the protonation and deprotonation of water and finally the formation of a stable interface layer. A remarkable highlight of this work is the long-time stability of generated bulk NBs which is up to three months. © 2019 Elsevier Inc

Unusual ³¹P Hyperfine Strain Effects in a Conformationally Flexible Cu(II) Complex Revealed by Two-Dimensional Pulse EPR Spectroscopy

Strain effects on g and metal hyperfine coupling tensors, A, are often manifested in Electron Paramagnetic Resonance (EPR) spectra of transition metal complexes, as a result of their intrinsic and/or solvent-mediated structural variations. Although distributions of these tensors are quite common and well understood in continuous-wave (cw) EPR spectroscopy, reported strain effects on ligand hyperfine coupling constants are rather scarce. Here we explore the case of a conformationally flexible Cu(II) complex, [Cu{Ph2P(O)NP(O)Ph2-κ2O,O′}2], bearing P atoms in its second coordination sphere and exhibiting two structurally distinct CuO4 coordination spheres, namely a square planar and a tetrahedrally distorted one, as revealed by X-ray crystallography. The Hyperfine Sublevel Correlation (HYSCORE) spectra of this complex exhibit 31P correlation ridges that have unusual inverse or so-called “boomerang” shapes and features that cannot be reproduced by standard simulation procedures assuming only one set of magnetic parameters. Our work shows that a distribution of isotropic hyperfine coupling constants (hfc) spanning a range between negative and positive values is necessary in order to describe in detail the unusual shapes of HYSCORE spectra. By employing DFT calculations we show that these hfc correspond to molecules showing variable distortions from square planar to tetrahedral geometry, and we demonstrate that line shape analysis of such HYSCORE spectra provides new insight into the conformation-dependent spectroscopic response of the spin system under investigation

Unusual 31P Hyperfine Strain Effects in a Conformationally Flexible Cu(II) Complex Revealed by Two-Dimensional Pulse EPR Spectroscopy

Strain effects on g and metal hyperfine coupling tensors, A, are often manifested in Electron Paramagnetic Resonance (EPR) spectra of transition metal complexes, as a result of their intrinsic and/or solvent-mediated structural variations. Although distributions of these tensors are quite common and well understood in continuous-wave (cw) EPR spectroscopy, reported strain effects on ligand hyperfine coupling constants are rather scarce. Here we explore the case of a conformationally flexible Cu(II) complex, [Cu{Ph2P(O)NP(O)Ph2-κ2O,O′}2], bearing P atoms in its second coordination sphere and exhibiting two structurally distinct CuO4 coordination spheres, namely a square planar and a tetrahedrally distorted one, as revealed by X-ray crystallography. The Hyperfine Sublevel Correlation (HYSCORE) spectra of this complex exhibit 31P correlation ridges that have unusual inverse or so-called "boomerang" shapes and features that cannot be reproduced by standard simulation procedures assuming only one set of magnetic parameters. Our work shows that a distribution of isotropic hyperfine coupling constants (hfc) spanning a range between negative and positive values is necessary in order to describe in detail the unusual shapes of HYSCORE spectra. By employing DFT calculations we show that these hfc correspond to molecules showing variable distortions from square planar to tetrahedral geometry, and we demonstrate that line shape analysis of such HYSCORE spectra provides new insight into the conformation-dependent spectroscopic response of the spin system under investigation. © 2020 American Chemical Society