



01302nas a2200145   4500008004100000245011100041210006900152260001300221490000700234520073400241100001600975700001800991700002101009856012601030       2014                        eng d00aWhen the asymptotic limit offers no advantage in the local-operations-and-classical-communication paradigm0 aWhen the asymptotic limit offers no advantage in the localoperat  c5/9/20140 v893 a<p>We consider bipartite LOCC, the class of operations implementable by local quantum operations and classical communication between two parties. Surprisingly, there are operations that can be approximated to arbitrary precision but are impossible to implement exactly if only a finite number of messages are exchanged. This significantly complicates the analysis of what can or cannot be approximated with LOCC. Toward alleviating this problem, we exhibit two scenarios in which allowing vanishing error does not help. The first scenario is implementation of projective measurements with product measurement operators. The second scenario is the discrimination of unextendable product bases on two three-dimensional systems.</p>1 aFu, Honghao1 aLeung, Debbie1 aMancinska, Laura  uhttps://quics.umd.edu/publications/when-asymptotic-limit-offers-no-advantage-local-operations-and-classical-communication01336nas a2200169   4500008004100000245006500041210006300106260001300169300001600182490000800198520084400206100002301050700001801073700002101091700001701112856003701129       2013                        eng d00aA framework for bounding nonlocality of state discrimination0 aframework for bounding nonlocality of state discrimination  c2013/9/4  a1121 - 11530 v3233 a  We consider the class of protocols that can be implemented by local quantum
operations and classical communication (LOCC) between two parties. In
particular, we focus on the task of discriminating a known set of quantum
states by LOCC. Building on the work in the paper "Quantum nonlocality without
entanglement" [BDF+99], we provide a framework for bounding the amount of
nonlocality in a given set of bipartite quantum states in terms of a lower
bound on the probability of error in any LOCC discrimination protocol. We apply
our framework to an orthonormal product basis known as the domino states and
obtain an alternative and simplified proof that quantifies its nonlocality. We
generalize this result for similar bases in larger dimensions, as well as the
"rotated" domino states, resolving a long-standing open question [BDF+99].
1 aChilds, Andrew, M.1 aLeung, Debbie1 aMancinska, Laura1 aOzols, Maris  uhttp://arxiv.org/abs/1206.5822v100982nas a2200169   4500008004100000245008200041210006900123260001500192300001100207490000700218520047100225100002300696700001800719700002100737700001700758856003700775       2013                        eng d00aInterpolatability distinguishes LOCC from separable von Neumann  measurements0 aInterpolatability distinguishes LOCC from separable von Neumann   c2013/06/25  a1122040 v543 a  Local operations with classical communication (LOCC) and separable operations
are two classes of quantum operations that play key roles in the study of
quantum entanglement. Separable operations are strictly more powerful than
LOCC, but no simple explanation of this phenomenon is known. We show that, in
the case of von Neumann measurements, the ability to interpolate measurements
is an operational principle that sets apart LOCC and separable operations.
1 aChilds, Andrew, M.1 aLeung, Debbie1 aMancinska, Laura1 aOzols, Maris  uhttp://arxiv.org/abs/1306.5992v101458nas a2200145   4500008004100000245005700041210005600098260001500154520102700169100002301196700001801219700002101237700001701258856003701275       2010                        eng d00aCharacterization of universal two-qubit Hamiltonians0 aCharacterization of universal twoqubit Hamiltonians  c2010/04/093 a  Suppose we can apply a given 2-qubit Hamiltonian H to any (ordered) pair of
qubits. We say H is n-universal if it can be used to approximate any unitary
operation on n qubits. While it is well known that almost any 2-qubit
Hamiltonian is 2-universal (Deutsch, Barenco, Ekert 1995; Lloyd 1995), an
explicit characterization of the set of non-universal 2-qubit Hamiltonians has
been elusive. Our main result is a complete characterization of 2-non-universal
2-qubit Hamiltonians. In particular, there are three ways that a 2-qubit
Hamiltonian H can fail to be universal: (1) H shares an eigenvector with the
gate that swaps two qubits, (2) H acts on the two qubits independently (in any
of a certain family of bases), or (3) H has zero trace. A 2-non-universal
2-qubit Hamiltonian can still be n-universal for some n >= 3. We give some
partial results on 3-universality. Finally, we also show how our
characterization of 2-universal Hamiltonians implies the well-known result that
almost any 2-qubit unitary is universal.
1 aChilds, Andrew, M.1 aLeung, Debbie1 aMancinska, Laura1 aOzols, Maris  uhttp://arxiv.org/abs/1004.1645v2