In this study, we report the first Cu-filled through silicon via (TSV) integrated ion trap. TSVs are placed directly underneath electrodes as vertical interconnections between ion trap and a glass interposer, facilitating the arbitrary geometry desig
n with increasing electrodes numbers and evolving complexity. The integration of TSVs reduces the form factor of ion trap by more than 80%, minimizing parasitic capacitance from 32 to 3 pF. A low RF dissipation is achieved in spite of the absence of ground screening layer. The entire fabrication process is on 12-inch wafer and compatible with established CMOS back end process. We demonstrate the basic functionality of the trap by loading and laser-cooling single 88Sr+ ions. It is found that both heating rate (17 quanta/ms for an axial frequency of 300 kHz) and lifetime (~30 minutes) are comparable with traps of similar dimensions. This work pioneers the development of TSV-integrated ion traps, enriching the toolbox for scalable quantum computing.
Data of the numerical solution of the time-dependent Schrodinger equation of a system containing one spin-1/2 particle interacting with a bath of up to 32 spin-1/2 particles is used to construct a Markovian quantum master equation describing the dyna
mics of the system spin. The procedure of obtaining this quantum master equation, which takes the form of a Bloch equation with time-independent coefficients, accounts for all non-Markovian effects in as much the general structure of the quantum master equation allows. Our simulation results show that, with a few rather exotic exceptions, the Bloch-type equation with time-independent coefficients provides a simple and accurate description of the dynamics of a spin-1/2 particle in contact with a thermal bath. A calculation of the coefficients that appear in the Redfield master equation in the Markovian limit shows that this perturbatively derived equation quantitatively differs from the numerically estimated Markovian master equation, the results of which agree very well with the solution of the time-dependent Schrodinger equation.
Magnetic skyrmions are promising for building next-generation magnetic memories and spintronic devices due to their stability, small size and the extremely low currents needed to move them. In particular, skyrmion-based racetrack memory is attractive
for information technology, where skyrmions are used to store information as data bits instead of traditional domain walls. Here we numerically demonstrate the impacts of skyrmion-skyrmion and skyrmion-edge repulsions on the feasibility of skyrmion-based racetrack memory. The reliable and practicable spacing between consecutive skyrmionic bits on the racetrack as well as the ability to adjust it are investigated. Clogging of skyrmionic bits is found at the end of the racetrack, leading to the reduction of skyrmion size. Further, we demonstrate an effective and simple method to avoid the clogging of skyrmionic bits, which ensures the elimination of skyrmionic bits beyond the reading element. Our results give guidance for the design and development of future skyrmion-based racetrack memory.
Tunneling spectra of near optimally doped, submicron Bi$_2$Sr$_2$CaCu$_2$O$_{8+delta}$ intrinsic Josephson junctions are presented, and examined in the region where the superconducting gap evolves into pseudogap. The spectra are analyzed using a self
-energy model, proposed by Norman {it et al.}, in which both quasiparticle scattering rate $Gamma$ and pair decay rate $Gamma_{Delta}$ are considered. The density of states derived from the model has the familiar Dynes form with a simple replacement of $Gamma$ by $gamma_+$ = ($Gamma$ + $Gamma_{Delta}$)/2. The $gamma_+$ parameter obtained from fitting the experimental spectra shows a roughly linear temperature dependence, which puts a strong constraint on the relation between $Gamma$ and $Gamma_{Delta}$. We discuss and compare the Fermi arc behavior in the pseudogap phase from the tunneling and angle-resolved photoemission spectroscopy experiments. Our results indicate an excellent agreement between the two experiments, which is in favor of the precursor pairing view of the pseudogap.
We report tunneling spectra of near optimally doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+delta}$ intrinsic Josephson junctions with area of 0.09 $mu$m$^2$, which avoid some fundamental difficulties in the previous tunneling experiments and allow a stable temper
ature-dependent measurement. A d-wave Eliashberg analysis shows that the spectrum at 4.2 K can be well fitted by considering electron couplings to a bosonic magnetic resonance mode and a broad high-energy continuum. Above $T_c$, the spectra show a clear pseudogap that persists up to 230 K, and a crossover can be seen indicating two different pseudogap phases existing above $T_c$. The intrinsic electron tunneling nature is discussed in the analysis.
White-light observations of the solar corona show that there are two characteristic types of Coronal Mass Ejections (CMEs) in terms of speed-height profiles: so-called fast CMEs that attain high speeds low in the corona and slow CMEs that gradually a
ccelerate from low initial speeds. Low and Zhang (2002) have recently proposed that fast and slow CMEs result from initial states with magnetic configurations characterized by normal prominences (NPs) and inverse prominences (IPs), respectively. To test their theory, we employed a two-dimensional, time-dependent, resistive magnetohydrodynamic code to simulate the expulsion of CMEs in these two different prominence environments. Our numerical simulations demonstrate that (i) a CME-like expulsion is more readily produced in an NP than in an IP environment, and, (ii) a CME originating from an NP environment tends to have a higher speed early in the event than one originating from an IP environment. Magnetic reconnection plays distinct roles in the two different field topologies of these two environments to produce their characteristic CME speed-height profiles. Our numerical simulations support the proposal of Low and Zhang (2002) although the reconnection development for the NP associated CME is different from the one sketched in their theory. Observational implications of our simulations are discussed.
