NanoSQUID magnetometry of individual cobalt nanoparticles grown by focused electron beam induced deposition

We demonstrate the operation of low-noise nano superconducting quantum interference devices (SQUIDs) based on the high critical field and high critical temperature superconductor YBa$_2$Cu$_3$O$_7$ (YBCO) as ultra-sensitive magnetometers for single magnetic nanoparticles (MNPs). The nanoSQUIDs exploit the Josephson behavior of YBCO grain boundaries and have been patterned by focused ion beam milling. This allows to precisely define the lateral dimensions of the SQUIDs so as to achieve large magnetic coupling between the nanoloop and individual MNPs. By means of focused electron beam induced deposition, cobalt MNPs with typical size of several tens of nm have been grown directly on the surface of the sensors with nanometric spatial resolution. Remarkably, the nanoSQUIDs are operative over extremely broad ranges of applied magnetic field (-1 T $< \mu_0 H <$ 1 T) and temperature (0.3 K $< T<$ 80 K). All these features together have allowed us to perform magnetization measurements under different ambient conditions and to detect the magnetization reversal of individual Co MNPs with magnetic moments (1 - 30) $\times 10^6\,\mu_{\rm B}$. Depending on the dimensions and shape of the particles we have distinguished between two different magnetic states yielding different reversal mechanisms. The magnetization reversal is thermally activated over an energy barrier, which has been quantified for the (quasi) single-domain particles. Our measurements serve to show not only the high sensitivity achievable with YBCO nanoSQUIDs, but also demonstrate that these sensors are exceptional magnetometers for the investigation of the properties of individual nanomagnets

Strong Coupling of a Single Photon to a Magnetic Vortex

Strong light-matter coupling means that cavity photons and other types of matter excitations are coherently exchanged. It is used to couple different qubits (matter) via a quantum bus (photons) or to communicate different types of excitations, e.g., transducing light into phonons or magnons. A, so far, unexplored interface is the coupling between light and topologically protected particle-like excitations as magnetic domain walls, skyrmions, or vortices. Here, we show theoretically that a single photon living in a superconducting cavity can be strongly coupled to the gyrotropic mode of a magnetic vortex in a nanodisc. We combine numerical and analytical calculations for a superconducting coplanar waveguide resonator and different realizations of the nanodisc (materials and sizes). We show that, for enhancing the coupling, constrictions fabricated in the resonator are crucial, allowing to reach strong coupling in CoFe discs of radius 200-400 nm having resonance frequencies of a few GHz. The strong coupling regime permits coherently exchanging a single photon and quanta of vortex gyration. Thus, our calculations show that the device proposed here serves as a transducer between photons and gyrating vortices, opening the way to complement superconducting qubits with topologically protected spin-excitations such as vortices or skyrmions. We finish by discussing potential applications in quantum data processing based on the exploitation of the vortex as a short-wavelength magnon emitter

Coupling single molecule magnets to quantum circuits

In this work we study theoretically the coupling of single molecule magnets (SMMs) to a variety of quantum circuits, including microwave resonators with and without constrictions and flux qubits. The main results of this study is that it is possible to achieve strong and ultrastrong coupling regimes between SMM crystals and the superconducting circuit, with strong hints that such a coupling could also be reached for individual molecules close to constrictions. Building on the resulting coupling strengths and the typical coherence times of these molecules (of the order of microseconds), we conclude that SMMs can be used for coherent storage and manipulation of quantum information, either in the context of quantum computing or in quantum simulations. Throughout the work we also discuss in detail the family of molecules that are most suitable for such operations, based not only on the coupling strength, but also on the typical energy gaps and the simplicity with which they can be tuned and oriented. Finally, we also discuss practical advantages of SMMs, such as the possibility to fabricate the SMMs ensembles on the chip through the deposition of small droplets.Comment: 23 pages, 12 figure

Magnetized Strange Stars and Signals of Gravitational Waves

We study the emission of gravitational waves from spheroidal magnetized strange stars for both an isolated slowly rotating star and a binary system. In the first case, we compute the quadrupole moment and the amplitude of gravitational waves that may be emitted. For the binary system, the tidal deformability is obtained by solving simultaneously the system of spheroidal structure equations and the Love number equation. These results are compared with the data inferred from the GW170817 event which is also used to calculate the mass and tidal deformability of the companion star in the binary system. Our model supports binary systems formed by magnetized strange stars describing reasonable signals of gravitational waves contrasted with other models of binary systems composed of magnetized hadronic stars and non-magnetized quark stars

Preliminary study of the genetic differentiation between two variety of cuban creole pig

It is admitted an Iberian origin for the Cuban Creole Pig breed. Inside this breed there exist varieties morphologically very well defined, as the Unhaired and Middlehaired types. The existence of these types is traditionally admitted by Cuban producers, researchers and by the society in general. To confirmate the genetic differentiation of these two morphological types, we have analyzed 93 samples of the breed, with representation of the middlehaired (MD) type (58 animals) and unhaired (UH) type (35 animals) taken from several Cuba provinces. We have used a test of 20 microsatellites of the recommended by FAO/ISAG. The obtained values for the parameters GST (0.74 and 0.12 percent) are extremely low. All these results are showing a no existence of varieties inside the Cuban Creole Pig breed.Al cerdo Criollo Cubano (cCC) se le atribuye un origen ibérico. Dentro de este último existen variedades bien definidas, como la Lampiña y la Entrepelada, las cuales han tenido representación al menos morfológica dentro del cCC. La existencia de estos dos tipos es aceptada en Cuba por productores, investigadores y por la sociedad en general. Con el objetivo de determinar la existencia o no de diferenciación genética entre ellos, se analizaron 93 animales, de ellos, 58 entrepelados y 35 lampiños. Se emplearon 20 microsatélites recomendados por la FAO/ISAG (International Society of Animal Genetics) para estudios de biodiversidad porcina. Los microsatélites se amplificaron mediante la Reacción en Cadena de la Polimerasa (PCR) y los fragmentos amplificados se separaron mediante electroforesis en un secuenciador automático. Los valores que se obtienen en los parámetros GST, 0,74 p.100 y 0,12 p.100 son extremadamente bajos, lo que demuestra que dentro del cCC no existe subdivisión varietal