Selective entanglement breaking
Abstract
We discuss the cases where local decoherence selectively degrades one type of entanglement more than other types. A typical case is called state ordering change, in which two input states with different amounts of entanglement undergoes a local decoherence and the state with the larger entanglement results in an output state with less entanglement than the other output state. We are also interested in a special case where the state with the larger entanglement evolves to a separable state while the other output state is still entangled, which we call selective entanglement breaking. For threelevel or larger systems, it is easy to find examples of the state ordering change and the selective entanglement breaking, but for twolevel systems it is not trivial whether such situations exist. We present a general strategy to construct examples of twoqubit states exhibiting the selective entanglement breaking regardless of entanglement measure. We also give a more striking example of the selective entanglement breaking in which the less entangled input state has only an infinitesimal amount of entanglement.
 Authors:
 Division of Materials Physics, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 13 Machikaneyama, Toyonaka, Osaka 5608531 (Japan)
 (Japan)
 Publication Date:
 OSTI Identifier:
 20982253
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.75.032307; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; QUANTUM COMPUTERS; QUANTUM DECOHERENCE; QUANTUM ENTANGLEMENT; QUANTUM MECHANICS; QUBITS
Citation Formats
Kinoshita, Yuma, Namiki, Ryo, Yamamoto, Takashi, CREST Research Team for Photonic Quantum Information, 418 Honmachi, Kawaguchi, Saitama 3310012, Koashi, Masato, Imoto, Nobuyuki, CREST Research Team for Photonic Quantum Information, 418 Honmachi, Kawaguchi, Saitama 3310012, and SORST Research Team for Interacting Carrier Electronics, 418 Honmachi, Kawaguchi, Saitama 3310012. Selective entanglement breaking. United States: N. p., 2007.
Web. doi:10.1103/PHYSREVA.75.032307.
Kinoshita, Yuma, Namiki, Ryo, Yamamoto, Takashi, CREST Research Team for Photonic Quantum Information, 418 Honmachi, Kawaguchi, Saitama 3310012, Koashi, Masato, Imoto, Nobuyuki, CREST Research Team for Photonic Quantum Information, 418 Honmachi, Kawaguchi, Saitama 3310012, & SORST Research Team for Interacting Carrier Electronics, 418 Honmachi, Kawaguchi, Saitama 3310012. Selective entanglement breaking. United States. doi:10.1103/PHYSREVA.75.032307.
Kinoshita, Yuma, Namiki, Ryo, Yamamoto, Takashi, CREST Research Team for Photonic Quantum Information, 418 Honmachi, Kawaguchi, Saitama 3310012, Koashi, Masato, Imoto, Nobuyuki, CREST Research Team for Photonic Quantum Information, 418 Honmachi, Kawaguchi, Saitama 3310012, and SORST Research Team for Interacting Carrier Electronics, 418 Honmachi, Kawaguchi, Saitama 3310012. Thu .
"Selective entanglement breaking". United States.
doi:10.1103/PHYSREVA.75.032307.
@article{osti_20982253,
title = {Selective entanglement breaking},
author = {Kinoshita, Yuma and Namiki, Ryo and Yamamoto, Takashi and CREST Research Team for Photonic Quantum Information, 418 Honmachi, Kawaguchi, Saitama 3310012 and Koashi, Masato and Imoto, Nobuyuki and CREST Research Team for Photonic Quantum Information, 418 Honmachi, Kawaguchi, Saitama 3310012 and SORST Research Team for Interacting Carrier Electronics, 418 Honmachi, Kawaguchi, Saitama 3310012},
abstractNote = {We discuss the cases where local decoherence selectively degrades one type of entanglement more than other types. A typical case is called state ordering change, in which two input states with different amounts of entanglement undergoes a local decoherence and the state with the larger entanglement results in an output state with less entanglement than the other output state. We are also interested in a special case where the state with the larger entanglement evolves to a separable state while the other output state is still entangled, which we call selective entanglement breaking. For threelevel or larger systems, it is easy to find examples of the state ordering change and the selective entanglement breaking, but for twolevel systems it is not trivial whether such situations exist. We present a general strategy to construct examples of twoqubit states exhibiting the selective entanglement breaking regardless of entanglement measure. We also give a more striking example of the selective entanglement breaking in which the less entangled input state has only an infinitesimal amount of entanglement.},
doi = {10.1103/PHYSREVA.75.032307},
journal = {Physical Review. A},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}

We show the rather counterintuitive result that entangled input states can strictly enhance the distinguishability of two entanglementbreaking channels.

Entanglement and spontaneous symmetry breaking in quantum spin models
It is shown that spontaneous symmetry breaking does not modify the groundstate entanglement of two spins, as defined by the concurrence, in the XXZ chain and the transverse field Ising chain. Correlation function inequalities, valid in any dimensions for these models, are presented outlining the regimes where entanglement is unaffected by spontaneous symmetry breaking. 
Classical simulability, entanglement breaking, and quantum computation thresholds
We investigate the amount of noise required to turn a universal quantum gate set into one that can be efficiently modeled classically. This question is useful for providing upper bounds on faulttolerant thresholds, and for understanding the nature of the quantumclassical computational transition. We refine some previously known upper bounds using two different strategies. The first one involves the introduction of bientangling operations, a class of classically simulable machines that can generate at most bipartite entanglement. Using this class we show that it is possible to sharpen previously obtained upper bounds in certain cases. As an example, we show thatmore » 
Nonadditivity of quantum and classical capacities for entanglement breaking multipleaccess channels and the butterfly network
We analyze quantum network primitives which are entanglement breaking. We show superadditivity of quantum and classical capacity regions for quantum multipleaccess channels and the quantum butterfly network. Since the effects are especially visible at high noise they suggest that quantum information effects may be particularly helpful in the case of the networks with occasional high noise rates. The present effects provide a qualitative borderline between superadditivities of bipartite and multipartite systems. 
Entanglement–breaking indices
We study a set of new functionals (called entanglement–breaking indices) which characterize how many local iterations of a given (local) quantum channel are needed in order to completely destroy the entanglement between the system of interest over which the transformation is defined and an external ancilla. The possibility of contrasting the noisy effects introduced by the channel iterations via the action of intermediate (filtering) transformations is analyzed. We provide some examples in which our functionals can be exactly calculated. The differences between unitary and nonunitary filtering operations are analyzed showing that, at least for systems of dimension d larger thanmore »