Uncertainty relations for any multi observables

Uncertainty relations describe the lower bound of product of standard deviations of observables. By revealing a connection between standard deviations of quantum observables and numerical radius of operators, we establish a universal uncertainty relation for any $k$ observables, of which the formulation depends on the even or odd quality of $k$. This universal uncertainty relation is tight at least for the cases $k=2n$ and $k=3$. For two observables, the uncertainty relation is exactly a simpler reformulation of Schr\"odinger's uncertainty principle.Comment: 16 page

A variant of multitask n-vehicle exploration problem: maximizing every processor's average profit

We discuss a variant of multitask n-vehicle exploration problem. Instead of requiring an optimal permutation of vehicles in every group, the new problem asks all vehicles in a group to arrive at a same destination. It can also be viewed as to maximize every processor's average profit, given n tasks, and each task's consume-time and profit. Meanwhile, we propose a new kind of partition problem in fractional form, and analyze its computational complexity. Moreover, by regarding fractional partition as a special case, we prove that the maximizing average profit problem is NP-hard when the number of processors is fixed and it is strongly NP-hard in general. At last, a pseudo-polynomial time algorithm for the maximizing average profit problem and the fractional partition problem is presented, thanks to the idea of the pseudo-polynomial time algorithm for the classical partition problem.Comment: This work is part of what I did as a graduate student in the Academy of Mathematics and Systems Scienc

Optimality of a class of entanglement witnesses for 3⊗33\otimes 3 systems

Let $\Phi_{t,\pi}: M_3({\mathbb C}) \rightarrow M_3({\mathbb C})$ be a linear map defined by $\Phi_{t,\pi}(A)=(3-t)\sum_{i=1}^3E_{ii}AE_{ii}+t\sum_{i=1}^3E_{i,\pi(i)}AE_{i,\pi(i)}^\dag-A$, where $0\leq t\leq 3$ and $\pi$ is a permutation of $(1,2,3)$. We show that the Hermitian matrix $W_{\Phi_{t,\pi}}$ induced by $\Phi_{t,\pi}$ is an optimal entanglement witness if and only if $t=1$ and $\pi$ is cyclic.Comment: 12 page

Verifiable sufficient conditions for the error bound property of second-order cone complementarity problems

The error bound property for a solution set defined by a set-valued mapping refers to an inequality that bounds the distance between vectors closed to a solution of the given set by a residual function. The error bound property is a Lipschitz-like/calmness property of the perturbed solution mapping, or equivalently the metric subregularity of the underlining set-valued mapping. It has been proved to be extremely useful in analyzing the convergence of many algorithms for solving optimization problems, as well as serving as a constraint qualification for optimality conditions. In this paper, we study the error bound property for the solution set of a very general second-order cone complementarity problem (SOCCP). We derive some sufficient conditions for error bounds for SOCCP which is verifiable based on the initial problem data

Strong kk-commutativity preserving maps on 2×\times2 matrices

Let ${\mathcal M}_2(\mathbb F)$ be the algebra of 2$\times$2 matrices over the real or complex field $\mathbb F$. For a given positive integer $k\geq 1$, the $k$-commutator of $A$ and $B$ is defined by $[A,B]_k=[[A,B]_{k-1},B]$ with $[A,B]_0=A$ and $[A,B]_1=[A,B]=AB-BA$. The main result is shown that a map $\Phi: {\mathcal M}_2(\mathbb F)\to {\mathcal M}_2(\mathbb F)$ with range containing all rank one matrices satisfies that $[\Phi(A),\Phi(B)]_k = [A,B]_k$ for all $A, B\in{\mathcal M}_2(\mathbb F)$ if and only if there exist a functional $h :{\mathcal M}_2(\mathbb F) \rightarrow {\mathbb F}$ and a scalar $\lambda \in{\mathbb F}$ with $\lambda^{k+1} = 1$ such that $\Phi(A) = \lambda A + h(A)I$ for all $A \in{\mathcal M}_2(\mathbb F)$.Comment: 12 page

Strong 33-Commutativity Preserving Maps on Standard Operator Algebras

Let $X$ be a Banach space of dimension $\geq 2$ over the real or complex field ${\mathbb F}$ and ${\mathcal A}$ a standard operator algebra in ${\mathcal B}(X)$. A map $\Phi:{\mathcal A} \rightarrow {\mathcal A}$ is said to be strong $3$-commutativity preserving if $[\Phi(A),\Phi(B)]_3 = [A,B]_3$ for all $A, B\in{\mathcal A}$, where $[A,B]_3$ is the 3-commutator of $A,B$ defined by $[A,B]_3=[[[A,B],B],B]$. The main result in this paper is shown that, if $\Phi$ is a surjective map on ${\mathcal A}$, then $\Phi$ is strong $3$-commutativity preserving if and only if there exist a functional $h :{\mathcal A} \rightarrow {\mathbb F}$ and a scalar $\lambda \in{\mathbb F}$ with $\lambda^4 = 1$ such that $\Phi(A) = \lambda A + h(A)I$ for all $A \in{\mathcal A}$.Comment: 14 page

Criteria of positivity for linear maps constructed from permutation pairs

In this paper, we show that a $D$-type map $\Phi_D:M_n\rightarrow M_n$ with $D=(n-2)I_n+P_{\pi_1}+P_{\pi_2}$ induced by a pair $\{\pi_1,\pi_2\}$ of permutations of $(1,2,..., n)$ is positive if $\{\pi_1,\pi_2\}$ has property (C). The property (C) is characterized for $\{\pi_1,\pi_2\}$, and an easy criterion is given for the case that $\pi_1=\pi^p$ and $\pi_2=\pi^q$, where $\pi$ is the permutation defined by $\pi(i)=i+1$ mod $n$ and $1\leq p<q\leq n$

Non-linear maps on self-adjoint operators preserving numerical radius and numerical range of Lie product

Let $H$ be a complex separable Hilbert space of dimension $\geq 2$, ${\mathcal B}_s(H)$ the space of all self-adjoint operators on $H$. We give a complete classification of non-linear surjective maps on $\mathcal B_s(H)$ preserving respectively numerical radius and numerical range of Lie product.Comment: 22 page

Entanglement criterion independent on observables for multipartite Gaussian states based on uncertainty principle

The local uncertainty relation (LUR) criteria for quantum entanglement, which is dependent on chosen observables, is developed recent. In the paper, applying the uncertainty principle, an entanglement criteria for multipartite Gaussian states is given, which is implemented by a minimum optimization computer program and independent on observalbes.Comment: 9 page

Fidelity of states in infinite dimensional quantum systems

In this paper we discuss the fidelity of states in infinite dimensional systems, give an elementary proof of the infinite dimensional version of Uhlmann's theorem, and then, apply it to generalize several properties of the fidelity from finite dimensional case to infinite dimensional case. Some of them are somewhat different from those for finite dimensional case.Comment: 12 page