Evidence for a chemical-thermal structure at base of mantle from sharp lateral P-wave variations beneath Central America

Compressional waves that sample the lowermost mantle west of Central America show a rapid change in travel times of up to 4 s over a sampling distance of 300 km and a change in waveforms. The differential travel times of the PKP waves (which traverse Earth's core) correlate remarkably well with predictions for S-wave tomography. Our modeling suggests a sharp transition in the lowermost mantle from a broad slow region to a broad fast region with a narrow zone of slowest anomaly next to the boundary beneath the Cocos Plate and the Caribbean Plate. The structure may be the result of ponding of ancient subducted Farallon slabs situated near the edge of a thermal and chemical upwelling

Entangling Power in the Deterministic Quantum Computation with One Qubit

The deterministic quantum computing with one qubit (DQC1) is a mixed-state quantum computation algorithm that evaluates the normalized trace of a unitary matrix and is more powerful than the classical counterpart. We find that the normalized trace of the unitary matrix can be directly described by the entangling power of the quantum circuit of the DQC1, so the nontrivial DQC1 is always accompanied with the non-vanishing entangling power. In addition, it is shown that the entangling power also determines the intrinsic complexity of this quantum computation algorithm, i.e., the larger entangling power corresponds to higher complexity. Besides, it is also shown that the non-vanishing entangling power does always exist in other similar tasks of DQC1.Comment: 6 pages and 1 figur