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The silicon vacancy (SiV) center in diamond is drawing much attention due to its optical and spin properties, attractive for quantum information processing and sensing. Comparatively little is known, however, about the dynamics governing SiV charge state interconversion mainly due to challenges associated with generating, stabilizing, and characterizing all possible charge states, particularly at room temperature. Here, we use multi-color confocal microscopy and density functional theory to examine photo-induced SiV recombination - from neutral, to single-, to double-negatively charged - over a broad spectral window in chemical-vapor-deposition diamond under ambient conditions. For the SiV0 to SiV- transition, we find a linear growth of the photo-recombination rate with laser power at all observed wavelengths, a hallmark of single photon dynamics. Laser excitation of SiV-, on the other hand, yields only fractional recombination into SiV2-, a finding we interpret in terms of a photo-activated electron tunneling process from proximal nitrogen atoms.

Recently it has been pointed out that an outstanding application of an IBM quantum computer is to reverse the arrow of time [Lesovik et al. Sci. Rep. 9, 1 (2019)]. The issue of the consequences of the reversal of the arrow of time on the execution of a CNOT gate by a quantum device is addressed. It is predicted that if the CNOT gate is executed towards the future then this was previously executed in the past. The above might confirm the paradigm that an event in the present time influences another event in the past time [2]. Such a physical phenomena is called retrocausality., Comment: 8 pages, 5 figures

GRBs are the most energetic electromagnetic events in the Universe. Those whose typical duration is longer than a few seconds are known as long GRBs and shorter than a few seconds are short GRBs. It is widely accepted that these events are associated with the collapse of a very massive star and the neutron star (NS) binary merger, respectively. A fast-spinning, strongly magnetized NS could be expected before a black hole (BH) in both scenarios. We allude to the thermal neutrinos' particular properties propagating inside the fireball for differentiating both scenarios in this work. We first derive the neutrino effective potential associated with each medium in a strong and weak magnetic field. We calculate the three-flavor oscillation probabilities, and finally, we get the expected neutrino rate in both scenarios. Given these observables' evolution, we can determine whether the progenitor could be associated with a strongly magnetized NS or a BH., Comment: Proceeding paper presented in the ICRC 2021 conference

Since neutrinos can escape from dense regions without being deflected, they are promising candidates to study the new physics at the sources that produce them. With the increasing development of more sensitive detectors in the coming years, we will infer several intrinsic properties from incident neutrinos. In particular, we centralise our study in those produced by thermal processes in short gamma-ray bursts (sGRBs) and their interactions within the central engine's anisotropic medium. On the one hand, we consider baryonic winds produced with a strong magnetic contribution, and on the other hand, we treat only neutrino-driven winds. First, we obtain the effective neutrino potential considering both baryonic density profiles around the central engine. Then, we get the three-flavour oscillation probabilities in this medium to finally calculate the expected neutrino ratios. We find a stronger angular dependence on the expected neutrino ratios, which, incidentally, contrast from the expected theoretical ratios without considering the winds' additional contribution. The joint analysis of this observable, together with the sGRB ejected jet angle, might lead to an effective mechanism to discriminate between the involved merger progenitors (black hole-neutron star or neutron star-neutron star), acting as an additional detection channel to gravitational waves., Comment: Accepted for publication in MNRAS

With the most recent multi-messenger detection, a new branch in modern astronomy has arisen. The GW170817 event together with the short gamma-ray burst GRB 170817A was the first-ever detection of the gravitational waves and an electromagnetic counterpart. These detections encourage us to think that in the following years we will detect a single event through three different channels: including the mentioned above plus neutrinos from multiple astrophysical sources, like those detected from SN1987A. It is believed that short GRBs are originated in the merger of a black-hole (BH) with a neutron star (NS) or NS-NS scenario. Particularly only in the latter case, several simulations suggest that the magnetic field can be amplified up to $10^{16}$ G. Considering this effect over created thermal neutrinos during the initial stage, we could differentiate short GRB progenitors through the neutrino expected flavor ratio and the opacity created by the baryon-loaded winds ejected in each scenario. Moreover, We find that it is more feasible to detect neutrinos from BH-NS than NS-NS systems. Finally, we also estimate the number of neutrino events expected on ground-based detectors, finding that it is possible to detect neutrinos from an energetic enough source located within a nearby vicinity with Hyper-Kamiokande detector., Comment: 14 pages, 6 figures

Recent X-ray observations in the central compact remnant of Puppis A and other young pulsars have provided convincing evidence about the anti-magnetar nature of the so-called central compact objects (CCOs). The measured period derivative, corrected by the proper movement, provides exceptionally low superficial magnetic fields for such sources. Using the dipole radiation canonical model, the superficial magnetic field of the CCO (RX J0822-4300) in Puppis A was estimated to be $B\simeq 2.9 \times 10^{10}$ G. In this paper, we present a numerical model to interpret the unusual magnetic-field behavior in RX J0822-4300. Using the magnetohydrodynamic simulations during the hypercritical accretion phase, we propose that a variety of MeV neutrinos is created given evidence about the submergence of the magnetic field in the pulsar. We investigate the production, propagation, oscillations, and detection of MeV neutrinos from this source. The detection of neutrino events with their flavor ratios would be a compelling signature of the decreasing evolution of the magnetic field not only in RX J0822-4300 but also in CCO candidates., Comment: 16 pages, 9 figures. Accepted for publication in PASP

The measurement of the period and period derivative, and the canonical model of dipole radiation have provided a method to estimate the low superficial magnetic fields in the so-called Central Compact Objects (CCOs). In the present work, a scenario is introduced in order to explain the magnetic behavior of such CCOs. Based on magnetohydrodynamic simulations of the post core-collapse supernova phase during the hypercritical accretion episode, we argue that the magnetic field of a newborn neutron star could have been early buried. During this phase, thermal neutrinos are created mainly by the pair annihilation, plasmon decay, photo-neutrino emission and other processes. We study the dynamics of these neutrinos in this environment and also estimate the number expected of the neutrino events with their flavor ratios on Earth. The neutrino burst is the only viable observable that could provide compelling evidence of the hypercritical phase and therefore, the hidden magnetic field mechanism as the most favorable scenario to explain the anomalous low magnetic fields estimated for CCOs., Comment: 18 pages, 7 figures and 4 tables. Accepted for publication in PRD. New reference was added

It is shown that three-dimensional nonparaxial beams are described by the oblate spheroidal exact solutions of the Helmholtz equation. For the first time, their beam behaviour is investigated and their corresponding parameters are defined. Using the fact that the beam width of the family of paraxial Gaussian beams is described by an hyperbola, the connection between the physical parameters of nonparaxial spheroidal beam solutions and those of paraxial beams is formally stablished. These results are also helpful to investigate the exact vector nonparaxial beams., Comment: 8 pages, 3 figures, accepted by Optics Letters