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Models of quantum systems on curved space-times lack sufficient experimental

verification. Some speculative theories suggest that quantum properties, such

as entanglement, may exhibit entirely different behavior to purely classical

systems. By measuring this effect or lack thereof, we can test the hypotheses

behind several such models. For instance, as predicted by Ralph and coworkers

[T C Ralph, G J Milburn, and T Downes, Phys. Rev. A, 79(2):22121, 2009; T C

Photon anti-bunching, measured via the Hanbury-Brown-Twiss experiment, is one

of the key signatures of quantum light and is tied to sub-Poissonian photon

number statistics. Recently, it has been reported that photon anti-bunching or

conditional sub-Poissonian photon number statistics can be obtained via

second-order interference of mutually incoherent weak lasers and heralding

based on photon counting. Here, we report theoretical analysis on the limits of

We study the tensor rank of the tensor corresponding to the algebra of

n-variate complex polynomials modulo the dth power of each variable. As a

result we find a sequence of tensors with a large gap between rank and border

rank, and thus a counterexample to a conjecture of Rhodes. At the same time we

obtain a new lower bound on the tensor rank of tensor powers of the generalised

W-state tensor. In addition, we exactly determine the tensor rank of the tensor

- Read more about A note on the gap between rank and border rank. (arXiv:1504.05597v2 [math.AC] UPDATED)
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It has been found that a model of extended electrons is more suited to

describe theoretical simulations and experimental results obtained via scanning

tunnelling microscopes, but while the dynamic properties are easily

incorporated, magnetic properties, and in particular electron spin properties

pose a problem due to their conceived isotropy in the absence of measurement.

The spin of an electron reacts with a magnetic field and thus has the

properties of a vector. However, electron spin is also isotropic, suggesting

- Read more about Spin in the extended electron model. (arXiv:1703.08076v1 [physics.gen-ph])
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We consider the problem of deciding if a set of quantum one-qudit gates

$\mathcal{S}=\{U_1,\ldots,U_n\}$ is universal. We provide the compact form

criteria leading to a simple algorithm that allows deciding universality of any

given set of gates in a finite number of steps. Moreover, for a non-universal

$\mathcal{S}$ our criteria indicate what type of gates can be added to

$\mathcal{S}$ to turn it into a universal set.

- Read more about Criteria for universality of quantum gates. (arXiv:1610.00547v5 [quant-ph] UPDATED)
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We show that dephasing of individual atoms destroys the superradiance

transition of the Dicke model, but that adding individual decay toward the spin

down state can restore this transition. To demonstrate this, we present a

method to give an exact solution for the $N$ atom problem with individual

dephasing which scales polynomially with $N$. By comparing finite size scaling

of our exact solution to a cumulant expansion, we confirm the destruction and

restoration of the superradiance transition holds in the thermodynamic limit.

New classical modalities of atomic force microscopy continue to emerge to

achieve higher spatial, spectral, and temporal resolution for nanometrology of

materials. Here, we introduce the concept of a quantum mechanical modality that

capitalizes on squeezed states of probe displacement. We show that such

squeezing is enabled nanomechanically when the probe enters the van der Waals

regime of interaction with a sample. The effect is studied in the non-contact

- Read more about Quantum state atomic force microscopy. (arXiv:1703.08077v1 [quant-ph])
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A dynamical estimate is given for the Boltzmann entropy of the Universe,

under the simplifying assumptions provided by Newtonian cosmology. We first

model the cosmological fluid as the probability fluid of a quantum-mechanical

system. Next, following current ideas about the emergence of spacetime, we

regard gravitational equipotentials as isoentropic surfaces. Therefore

gravitational entropy is proportional to the vacuum expectation value of the

gravitational potential in a certain quantum state describing the matter

- Read more about Boltzmann entropy of a Newtonian Universe. (arXiv:1703.08082v1 [quant-ph])
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Drawing on ideas from game theory and quantum physics, we investigate

nonlocal correlations from the point of view of equilibria in games of

incomplete information. These equilibria can be classified in decreasing power

as general communication equilibria, belief-invariant equilibria and correlated

equilibria, all of which contain the familiar Nash equilibria. The notion of

belief-invariant equilibrium has appeared in game theory before, in the 1990s.

However, the class of non-signalling correlations associated to

We study 't Hooft anomalies of discrete groups in the framework of

(1+1)-dimensional multiscale entanglement renormalization ansatz states on the

lattice. Using matrix product operators, general topological restrictions on

conformal data are derived. An ansatz class allowing for optimization of MERA

with an anomalous symmetry is introduced. We utilize this class to numerically

study a family of Hamiltonians with a symmetric critical line. Conformal data

is obtained for all irreducible projective representations of each anomalous

- Read more about Anomalies and entanglement renormalization. (arXiv:1703.07782v1 [quant-ph])
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