13,204 research outputs found
Operational one-to-one mapping between coherence and entanglement measures
We establish a general operational one-to-one mapping between coherence
measures and entanglement measures: Any entanglement measure of bipartite pure
states is the minimum of a suitable coherence measure over product bases. Any
coherence measure of pure states, with extension to mixed states by convex
roof, is the maximum entanglement generated by incoherent operations acting on
the system and an incoherent ancilla. Remarkably, the generalized CNOT gate is
the universal optimal incoherent operation. In this way, all convex-roof
coherence measures, including the coherence of formation, are endowed with
(additional) operational interpretations. By virtue of this connection, many
results on entanglement can be translated to the coherence setting, and vice
versa. As applications, we provide tight observable lower bounds for
generalized entanglement concurrence and coherence concurrence, which enable
experimentalists to quantify entanglement and coherence of the maximal
dimension in real experiments.Comment: 14 pages, 1 figure, new results added, published in PR
Measuring coherence of quantum measurements
The superposition of quantum states lies at the heart of physics and has been
recently found to serve as a versatile resource for quantum information
protocols, defining the notion of quantum coherence. In this contribution, we
report on the implementation of its complementary concept, coherence from
quantum measurements. By devising an accessible criterion which holds true in
any classical statistical theory, we demonstrate that noncommutative quantum
measurements violate this constraint, rendering it possible to perform an
operational assessment of the measurement-based quantum coherence. In
particular, we verify that polarization measurements of a single photonic
qubit, an essential carrier of one unit of quantum information, are already
incompatible with classical, i.e., incoherent, models of a measurement
apparatus. Thus, we realize a method that enables us to quantitatively certify
which quantum measurements follow fundamentally different statistical laws than
expected from classical theories and, at the same time, quantify their
usefulness within the modern framework of resources for quantum information
technology.Comment: close to published versio
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