160 research outputs found
High-intracavity-power thin-disk laser for the alignment of molecules
We propose a novel approach for strong alignment of gas-phase molecules for
experiments at arbitrary repetition rates. A high-intracavity-power
continuous-wave laser will provide the necessary ac electric field of
- . We demonstrate thin-disk lasers
based on Yb:YAG and Yb:LuO in a linear high-finesse resonator providing
intracavity power levels in excess of 100~kW at pump power levels on the order
of 50~W. The multi-longitudinal-mode operation of this laser avoids
spatial-hole burning even in a linear standing-wave resonator. The system will
be scaled up as in-vacuum system to allow for the generation of fields of
. This system will be directly applicable for
experiments at modern X-ray light sources, such as synchrotrons or
free-electron lasers, which operate at various very high repetition rates. This
would allow to record molecular movies through temporally resolved diffractive
imaging of fixed-in-space molecules, as well as the spectroscopic investigation
of combined X-ray-NIR strong-field effects of atomic and molecular systems
Secret Message Transmission over Quantum Channels under Adversarial Quantum Noise: Secrecy Capacity and Super-Activation
We determine the secrecy capacities of AVQCs (arbitrarily varying quantum
channels). Both secrecy capacity with average error probability and with
maximal error probability are derived. Both derivations are based on one common
code construction. The code we construct fulfills a stringent secrecy
requirement, which is called the strong code concept. We determine when the
secrecy capacity is a continuous function of the system parameters and
completely characterize its discontinuity points both for average error
criterion and for maximal error criterion. Furthermore, we prove the phenomenon
"super-activation" for secrecy capacities of AVQCs, i.e., two quantum channels
both with zero secrecy capacity, which, if used together, allow secure
transmission with positive capacity. We also discuss the relations between the
entanglement distillation capacity, the entanglement generating capacity, and
the strong subspace transmission capacity for AVQCs.Comment: arXiv admin note: text overlap with arXiv:1702.0348
The Multiple-Access Channel with Entangled Transmitters
Communication over a classical multiple-access channel (MAC) with
entanglement resources is considered, whereby two transmitters share
entanglement resources a priori before communication begins. Leditzki et al.
(2020) presented an example of a classical MAC, defined in terms of a pseudo
telepathy game, such that the sum rate with entangled transmitters is strictly
higher than the best achievable sum rate without such resources. Here, we
determine the capacity region for the general MAC with entangled transmitters,
and show that the previous result can be obtained as a special case.
Furthermore, it has long been known that the capacity region of the classical
MAC under a message-average error criterion can be strictly larger than with a
maximal error criterion (Dueck, 1978). We observe that given entanglement
resources, the regions coincide
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