11,301 research outputs found
Non-adiabatic Arbitary Geometric Gates in 2-qubit NMR Model
We study a 2-qubit nuclear spin system for realizing an arbitrary geometric
quantum phase gate by means of non-adiabatic operation. A single magnetic pulse
with multi harmonic frequencies is applied to manipulate the quantum states of
2-qubit instantly. Using resonant transition approximation, the time dependent
Hamiltonian of two nuclear spins can be solved analytically. The time evolution
of the wave function is obtained without adiabatic approximation. The
parameters of magnetic pulse, such as the frequency, amplitude, phase of each
harmonic part as well as the time duration of the pulse, are determined for
achieving an arbitrary non-adiabatic geometric phase gate. The derivation of
non-adiabatic geometric controlled phase gates and A-A phase are also
addressed.Comment: 7 pages, 1 figur
Magnetic Catalysis in AdS4
We study the formation of fermion condensates in Anti de Sitter space. In
particular, we describe a novel version of magnetic catalysis that arises for
fermions in asymptotically AdS4 geometries which cap off in the infra-red with
a hard wall. We show that the presence of a magnetic field induces a fermion
condensate in the bulk that spontaneously breaks CP symmetry. From the
perspective of the dual boundary theory, this corresponds to a strongly coupled
version of magnetic catalysis in d=2+1.Comment: 22 pages, 4 figures. v2: References added, factors of 2 corrected,
extra comments added in appendix. v3: extra comments about fermion modes in a
hard wall background. v4: A final factor of
Enhancement and tunability of near-field radiative heat transfer mediated by surface plasmon polaritons in thin plasmonic films
The properties of thermal radiation exchange between hot and cold objects can
be strongly modified if they interact in the near field where electromagnetic
coupling occurs across gaps narrower than the dominant wavelength of thermal
radiation. Using a rigorous fluctuational electrodynamics approach, we predict
that ultra-thin films of plasmonic materials can be used to dramatically
enhance near-field heat transfer. The total spectrally integrated film-to-film
heat transfer is over an order of magnitude larger than between the same
materials in bulk form and also exceeds the levels achievable with polar
dielectrics such as SiC. We attribute this enhancement to the significant
spectral broadening of radiative heat transfer due to coupling between surface
plasmon polaritons (SPPs) on both sides of each thin film. We show that the
radiative heat flux spectrum can be further shaped by the choice of the
substrate onto which the thin film is deposited. In particular, substrates
supporting surface phonon polaritons (SPhP) strongly modify the heat flux
spectrum owing to the interactions between SPPs on thin films and SPhPs of the
substrate. The use of thin film phase change materials on polar dielectric
substrates allows for dynamic switching of the heat flux spectrum between
SPP-mediated and SPhP-mediated peaks.Comment: 25 pages, 11 figure
Electron Transfer in Donor-Acceptor Systems: Many-Particle Effects and Influence of Electronic Correlations
We investigate electron transfer processes in donor-acceptor systems with a
coupling of the electronic degrees of freedom to a common bosonic bath. The
model allows to study many-particle effects and the influence of the local
Coulomb interaction U between electrons on donor and acceptor sites. Using the
non-perturbative numerical renormalization group approach we find distinct
differences between the electron transfer characteristics in the single- and
two-particle subspaces. We calculate the critical electron-boson coupling
alpha_c as a function of and show results for density-density correlation
functions in the whole parameter space. The possibility of many-particle
(bipolaronic) and Coulomb-assisted transfer is discussed.Comment: 4 pages, 4 figure
SGXIO: Generic Trusted I/O Path for Intel SGX
Application security traditionally strongly relies upon security of the
underlying operating system. However, operating systems often fall victim to
software attacks, compromising security of applications as well. To overcome
this dependency, Intel introduced SGX, which allows to protect application code
against a subverted or malicious OS by running it in a hardware-protected
enclave. However, SGX lacks support for generic trusted I/O paths to protect
user input and output between enclaves and I/O devices.
This work presents SGXIO, a generic trusted path architecture for SGX,
allowing user applications to run securely on top of an untrusted OS, while at
the same time supporting trusted paths to generic I/O devices. To achieve this,
SGXIO combines the benefits of SGX's easy programming model with traditional
hypervisor-based trusted path architectures. Moreover, SGXIO can tweak insecure
debug enclaves to behave like secure production enclaves. SGXIO surpasses
traditional use cases in cloud computing and makes SGX technology usable for
protecting user-centric, local applications against kernel-level keyloggers and
likewise. It is compatible to unmodified operating systems and works on a
modern commodity notebook out of the box. Hence, SGXIO is particularly
promising for the broad x86 community to which SGX is readily available.Comment: To appear in CODASPY'1
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