When an n-partite physical system is measured by n observers, the joint probabilities of outcomes conditioned on the observables chosen by the n parties form a nonnegative tensor, called an n-partite correlation tensor (CT). In this paper, we aim to establish some characterizations of nonsignaling and Bell locality of an n-partite CT, respectively. By placing CTs within the linear space of correlation-type tensors (CTTs), we prove that every n-partite nonsignaling CTT can be decomposed as a linear combination of all local deterministic CTs using single-value decomposition of matrices and mathematical induction. As a consequence, we prove that an n-partite CT is nonsignaling (resp. Bell local) if and only if it can be written as a quasi-convex (resp. convex) combination of the outer products of deterministic CTs, implying that an n-partite CT is nonsignaling if and only if it has a local hidden variable model governed by a quasi-probability distribution. As an application of these results, we prove that a CT is nonsignaling if and only if it can be written as a quasi-convex of two Bell local ones, revealing a close relationship between nonsignaling CTs and Bell local ones.

Quantum coherence is one of the most fundamental and striking features in quantum physics. Considered the standard coherence (SC), the partial coherence (PC) and the block coherence (BC) as variance of quantum states under some quantum channels (QCs) [Formula: see text], we propose the concept of channel-based coherence of quantum states, called [Formula: see text]-coherence for short, which contains the SC, PC and BC, but does not contain the positive operator-valued measure (POVM)-based coherence. By our definition, a state [Formula: see text] is said to be [Formula: see text]-incoherent if it is a fixed point of a QC [Formula: see text], otherwise, it is said to be [Formula: see text]-coherent. First, we find the set [Formula: see text] of all [Formula: see text]-incoherent states for some given channels [Formula: see text] and prove that the set [Formula: see text] forms a nonempty compact convex set for any channel [Formula: see text]. Second, we define [Formula: see text]-incoherent operations ([Formula: see text]-IOs) and prove that the set of all [Formula: see text]-IOs is a nonempty convex set. We also establish some characterizations of a [Formula: see text]-IO in terms of its Kraus operators. Lastly, we discuss the problem of quantifying [Formula: see text]-coherence and prove some related properties.

Motivated by the contributions [Sci. Rep. 6, 39063 (2016)] and [Phys. Rev. A 98, 052114 (2018)], we aim to establish a new method for theoretically checking Bell nonlocality of a bipartite state of systems  A ⊗  B for any finite dimensional Hilbert spaces  A and  B , provided that the operator space B( B ) has an orthonormal basis consisting of the identity operator and Hermitian unitary operators. Our main result induces a quantum channel Φ T, transforming a Bell local state AB as an unsteerable state Φ T, ( AB ) from A to B whenever the parameters T and satisfy the condition Θ(T, ) ≤ 1. Thus, when Θ(T, ) ≤ 1 and the image Φ T, ( AB ) is steerable from Ato B, the original state AB must be Bell nonlocal. Our result not only reveals a deep connection between EPR steerability and Bell nonlocality but also provides a feasible approach to theoretically prove difficultly verified Bell nonlocality by translating it into easily verified steerability.

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