768,475 research outputs found
Ordering states with various coherence measures
Quantum coherence is one of the most significant theories in quantum physics.
Ordering states with various coherence measures is an intriguing task in
quantification theory of coherence. In this paper, we study this problem by use
of four important coherence measures -- the norm of coherence, the
relative entropy of coherence, the geometric measure of coherence and the
modified trace distance measure of coherence. We show that each pair of these
measures give a different ordering of qudit states when . However, for
single-qubit states, the norm of coherence and the geometric coherence
provide the same ordering. We also show that the relative entropy of coherence
and the geometric coherence give a different ordering for single-qubit states.
Then we partially answer the open question proposed in [Quantum Inf. Process.
15, 4189 (2016)] whether all the coherence measures give a different ordering
of states.Comment: 12 page
Topological Properties of Spatial Coherence Function
Topology of the spatial coherence function is considered in details. The
phase singularity (coherence vortices) structures of coherence function are
classified by Hopf index and Brouwer degree in topology. The coherence flux
quantization and the linking of the closed coherence vortices are also studied
from the topological properties of the spatial coherence function.Comment: 9 page
Dynamics of quantum coherence in Bell-diagonal states under Markovian channels
We study the curves of coherence for the Bell-diagonal states including
-norm of coherence and relative entropy of coherence under the Markovian
channels in the first subsystem once. For a special Bell-diagonal state under
bit-phase flip channel, we find frozen coherence under norm occurs, but
relative entropy of coherence decrease. It illustrates that the occurrence of
frozen coherence depends on the type of the measure of coherence. We study the
coherence evolution of Bell-diagonal states under Markovian channels in the
first subsystem times and find coherence under depolarizing channel
decreases initially then increases for small and tend to zero for large
. We discuss the dynamics of coherence of the Bell-diagonal state under two
independent same type local Markovian channels. We depict the dynamic behaviors
of relative entropy of coherence for Bell-diagonal state under the bi-side
different Markovian channel. We depict the dynamic behaviors of relative
entropy of coherence for Bell-diagonal state under the bi-side different
Markovian channel.Comment: 13 pages, 17 figure
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