103 research outputs found
Probing nonlinear adiabatic paths with a universal integrator
We apply a flexible numerical integrator to the simulation of adiabatic
quantum computation with nonlinear paths. We find that a nonlinear path may
significantly improve the performance of adiabatic algorithms versus the
conventional straight-line interpolations. The employed integrator is suitable
for solving the time-dependent Schr\"odinger equation for any qubit
Hamiltonian. Its flexible storage format significantly reduces cost for storage
and matrix-vector multiplication in comparison to common sparse matrix schemes.Comment: 8 pages, 6 figure
Transmission from reverse reaction coordinate mappings
We point out that the transport properties of non-interacting fermionic
chains tunnel-coupled to two reservoirs at their ends can be mapped to those of
a single quantum dot that is tunnel-coupled to two transformed reservoirs. The
parameters of the chain are mapped to additional structure in the spectral
densities of the transformed reservoirs. For example, this enables the
calculation of the transmission of quantum dot chains by evaluating the known
transmission of a single quantum dot together with structured spectral
densities. We exemplify this analytically for short chains, which allows to
optimize the transmission. In addition, we also demonstrate that the mapping
can be performed numerically by computing the transmission of a
Su-Schrieffer-Heeger chain.Comment: 9+5 pages, 9 figures, invited contribution to the special issue
"Non-linear and Complex Dynamics in Semiconductors and Related Materials"
with the motto ''Complex Systems Science meets Matter and Materials'' in EPJ
Stochastic thermodynamics for "Maxwell demon" feedbacks
We propose a way to incorporate the effect of a specific class of feedback
processes into stochastic thermodynamics. These "Maxwell demon" feedbacks do
not affect the system energetics but only the energy barriers between the
system states (in a way which depends on the system states). They are thus of a
purely informational nature. We show that the resulting formalism can be
applied to study the thermodynamic effect of a feedback process acting on
electron transfers through a junction.Comment: 3 figures, v2:accepted in EP
Table-top creation of entangled multi-keV photon pairs via the Unruh effect
Electrons moving in a strong periodic electromagnetic field (e.g., laser or
undulator) may convert quantum vacuum fluctuations into pairs of entangled
photons, which can be understood as a signature of the Unruh effect. Apart from
verifying this striking phenomenon, the considered effect may allow the
construction of a table-top source for entangled photons (``photon pair
laser'') and the associated quantum-optics applications in the multi-keV regime
with near-future facilities. 04.62.+v, 12.20.Fv, 41.60.-m, 42.50.Dv.Comment: 4 pages, 1 figur
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