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QUROPE - aggregated feeds in category PhysicsenPRA: Quantum information: One-step generation of continuous-variable quadripartite cluster states in a circuit QED system
http://link.aps.org/doi/10.1103/PhysRevA.96.012327
<p>Author(s): Zhi-peng Yang, Zhen Li, Sheng-li Ma, and Fu-li Li</p><p>We propose a dissipative scheme for one-step generation of continuous-variable quadripartite cluster states in a circuit QED setup consisting of four superconducting coplanar waveguide resonators and a gap-tunable superconducting flux qubit. With external driving fields to adjust the desired qubit-r...</p><br/><p>[Phys. Rev. A 96, 012327] Published Fri Jul 21, 2017</p>Fri, 21 Jul 2017 16:00:00 +0200arXiv.org: Quantum Physics: Rigorous free fermion entanglement renormalization from wavelet theory. (arXiv:1707.06243v1 [quant-ph])
http://arxiv.org/abs/1707.06243
<p>We construct entanglement renormalization schemes which provably approximate
the ground states of non-interacting fermion nearest-neighbor hopping
Hamiltonians on the one-dimensional discrete line and the two-dimensional
square lattice. These schemes give hierarchical quantum circuits which build up
the states from unentangled degrees of freedom. The circuits are based on pairs
of discrete wavelet transforms which are approximately related by a
"half-shift": translation by half a unit cell.<p><a href="http://arxiv.org/abs/1707.06243">read more</a></p>
Fri, 21 Jul 2017 14:08:30 +0200arXiv.org: Quantum Physics: Slowing Quantum Decoherence by Squeezing in Phase Space. (arXiv:1707.06244v1 [quant-ph])
http://arxiv.org/abs/1707.06244
<p>Non-Gaussian states, and specifically the paradigmatic Schr\"odinger cat
state, are well-known to be very sensitive to losses. When propagating through
damping channels, these states quickly loose their non-classical features.
However, by squeezing the superposition states, the decoherence process can be
qualitatively changed and substantially slowed down. Here, we experimentally
observe the reduced decoherence of squeezed optical coherent-state
superpositions through a lossy channel.<p><a href="http://arxiv.org/abs/1707.06244">read more</a></p>
Fri, 21 Jul 2017 14:08:30 +0200arXiv.org: Quantum Physics: Multi-parameter estimation in networked quantum sensors. (arXiv:1707.06252v1 [quant-ph])
http://arxiv.org/abs/1707.06252
<p>We introduce a general model for a network of quantum sensors, and we use
this model to consider the question: When can entanglement between the sensors,
and/or global measurements, enhance the precision with which the network can
measure a set of unknown parameters? We rigorously answer this question by
presenting precise theorems proving that for a broad class of problems there
is, at most, a very limited intrinsic advantage to using entangled states or
global measurements.<p><a href="http://arxiv.org/abs/1707.06252">read more</a></p>
Fri, 21 Jul 2017 14:08:30 +0200arXiv.org: Quantum Physics: Lindblad dynamics of the quantum spherical model. (arXiv:1707.06273v1 [quant-ph])
http://arxiv.org/abs/1707.06273
<p>The purely relaxational non-equilibrium dynamics of the quantum spherical
model as described through a Lindblad equation is analysed. It is shown that
the phenomenological requirements of reproducing the exact quantum equilibrium
state as stationary solution and the associated classical Langevin equation in
the classical limit $g\to 0$ fix the form of the Lindblad dissipators, up to an
overall time-scale.<p><a href="http://arxiv.org/abs/1707.06273">read more</a></p>
Fri, 21 Jul 2017 14:08:30 +0200arXiv.org: Quantum Physics: Convex geometry of quantum resource quantification. (arXiv:1707.06298v1 [quant-ph])
http://arxiv.org/abs/1707.06298
<p>We introduce a framework unifying the mathematical characterisation of
different measures of general quantum resources and allowing for a systematic
way to define a variety of faithful quantifiers for any given convex quantum
resource theory. The approach allows us to describe many commonly used measures
such as matrix norm-based quantifiers, robustness measures, convex roof-based
measures, and witness-based quantifiers together in a common formalism based on
the convex geometry of the underlying sets of resource-free states.<p><a href="http://arxiv.org/abs/1707.06298">read more</a></p>
Fri, 21 Jul 2017 14:08:30 +0200arXiv.org: Quantum Physics: An Ontology of Nature with Local Causality, Parallel Lives, and Many Relative Worlds. (arXiv:1707.06324v1 [quant-ph])
http://arxiv.org/abs/1707.06324
<p>Parallel Lives (PL) is an ontological model of nature in which quantum
mechanics and special relativity are unified in a single universe with a single
Minkowski space-time. Point-like objects called \emph{lives} are the only
fundamental objects in this space-time, and they propagate at or below $c$, and
interact with one another only locally at point-like events in space-time ---
not unlike relativistic billiard balls. Lives are the only causal agents in the
universe, and thus the causal structure of interaction events in space-time is
Lorentz invariant.<p><a href="http://arxiv.org/abs/1707.06324">read more</a></p>
Fri, 21 Jul 2017 14:08:30 +0200arXiv.org: Quantum Physics: Use of global interactions in efficient quantum circuit constructions. (arXiv:1707.06356v1 [quant-ph])
http://arxiv.org/abs/1707.06356
<p>In this paper we study the ways to use a global entangling operator to
efficiently implement circuitry common to a selection of important quantum
algorithms. In particular, we focus on the circuits composed with global Ising
entangling gates and arbitrary addressable single-qubit gates. We show that
under certain circumstances the use of global operations can substantially
improve the entangling gate count.
</p>Fri, 21 Jul 2017 14:08:30 +0200arXiv.org: Quantum Physics: Dirac states in armchair- and zigzag-edged graphene M\"obius strips. (arXiv:1707.06361v1 [cond-mat.mes-hall])
http://arxiv.org/abs/1707.06361
<p>Edge structure plays an essential role in the nature of electronic states in
graphene nanoribbons. By focusing on the interplay between this feature and
non-trivial topology in the domain of the Dirac confinement problem, this paper
proposes to examine how effects associated with edge shape manifest themselves
in conjunction with the topological signature typical of M\"{o}bius strips
within a low-energy regime.<p><a href="http://arxiv.org/abs/1707.06361">read more</a></p>
Fri, 21 Jul 2017 14:08:30 +0200arXiv.org: Quantum Physics: Quantum State Concentration and Classification of Multipartite Entanglement. (arXiv:1707.06371v1 [quant-ph])
http://arxiv.org/abs/1707.06371
<p>Entanglement is a unique nature of quantum theory referring to classical
ones, having tremendous potentials for application. Nevertheless, the
complexity of quantum entanglement grows exponentially with the increase of
entangled particles. Here we introduce a quantum state concentration scheme
which decomposes the multipartite entangled state into a series of bipartite
and tripartite entanglement. The scheme works by first introducing virtual
particles to the given multipartite state, and then rescaling the system by a
recursively use of the high order singular value decomposition.<p><a href="http://arxiv.org/abs/1707.06371">read more</a></p>
Fri, 21 Jul 2017 14:08:30 +0200