1,369 research outputs found
General Monogamy Inequality for Bipartite Qubit Entanglement
We consider multipartite states of qubits and prove that their bipartite
quantum entanglement, as quantified by the concurrence, satisfies a monogamy
inequality conjectured by Coffman, Kundu, and Wootters. We relate this monogamy
inequality to the concept of frustration of correlations in quantum spin
systems.Comment: Fixed spelling mistake. Added references. Fixed error in
transformation law. Shorter and more explicit proof of capacity formula.
Reference added. Rewritten introduction and conclusion
Multipartite entanglement in 2 x 2 x n quantum systems
We classify multipartite entangled states in the 2 x 2 x n (n >= 4) quantum
system, for example the 4-qubit system distributed over 3 parties, under local
filtering operations. We show that there exist nine essentially different
classes of states, and they give rise to a five-graded partially ordered
structure, including the celebrated Greenberger-Horne-Zeilinger (GHZ) and W
classes of 3 qubits. In particular, all 2 x 2 x n-states can be
deterministically prepared from one maximally entangled state, and some
applications like entanglement swapping are discussed.Comment: 9 pages, 3 eps figure
Superpressure balloon flights from Christchurch, New Zealand, July 1968 - December 1969
Strain gages on superpressure balloon flights from Christchurch, New Zealand - Jul. 1968 to Dec. 196
Local permutations of products of Bell states and entanglement distillation
We present new algorithms for mixed-state multi-copy entanglement
distillation for pairs of qubits. Our algorithms perform significantly better
than the best known algorithms. Better algorithms can be derived that are tuned
for specific initial states. The new algorithms are based on a characterization
of the group of all locally realizable permutations of the 4^n possible tensor
products of n Bell states.Comment: 6 pages, 1 figur
Valence Bond Solids for Quantum Computation
Cluster states are entangled multipartite states which enable to do universal
quantum computation with local measurements only. We show that these states
have a very simple interpretation in terms of valence bond solids, which allows
to understand their entanglement properties in a transparent way. This allows
to bridge the gap between the differences of the measurement-based proposals
for quantum computing, and we will discuss several features and possible
extensions
Minimally Entangled Typical Thermal State Algorithms
We discuss a method based on sampling minimally entangled typical thermal
states (METTS) that can simulate finite temperature quantum systems with a
computational cost comparable to ground state DMRG. Detailed implementations of
each step of the method are presented, along with efficient algorithms for
working with matrix product states and matrix product operators. We furthermore
explore how properties of METTS can reveal characteristic order and excitations
of systems and discuss why METTS form an efficient basis for sampling. Finally,
we explore the extent to which the average entanglement of a METTS ensemble is
minimal.Comment: 18 pages, 14 figure
The Algebraic Bethe Ansatz and Tensor Networks
We describe the Algebraic Bethe Ansatz for the spin-1/2 XXX and XXZ
Heisenberg chains with open and periodic boundary conditions in terms of tensor
networks. These Bethe eigenstates have the structure of Matrix Product States
with a conserved number of down-spins. The tensor network formulation suggestes
possible extensions of the Algebraic Bethe Ansatz to two dimensions
A new family of matrix product states with Dzyaloshinski-Moriya interactions
We define a new family of matrix product states which are exact ground states
of spin 1/2 Hamiltonians on one dimensional lattices. This class of
Hamiltonians contain both Heisenberg and Dzyaloshinskii-Moriya interactions but
at specified and not arbitrary couplings. We also compute in closed forms the
one and two-point functions and the explicit form of the ground state. The
degeneracy structure of the ground state is also discussed.Comment: 15 pages, 1 figur
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