The Pusey-Barrett-Rudolph (PBR) no-go theorem provides an argument for the
reality of the quantum state by ruling out {\psi}-epistemic ontological
theories, in which the quantum state is of a statistical nature. It applies
under an assumption of preparation independence, the validity of which has been
subject to debate. We propose two plausible and less restrictive alternatives:
a weaker notion allowing for classical correlations, and an even weaker,
physically motivated notion of independence, which merely prohibits the

We study how correlations affect the performance of the simulator of a
Maxwell's demon demonstrated in a recent optical experiment [Vidrighin et al.,
Phys. Rev. Lett. 116, 050401 (2016)]. The power of the demon is found to be
enhanced or hindered, depending on the nature of the correlation, in close
analogy to the situation faced by a thermal demon.

We suggest an extension of the Hilbert Phase Space formalism, which appears
to be naturally suited for application to the dissipative (open) quantum
systems, such as those described by the non-stationary (time-dependent)
Hamiltonians $H(x,p,t)$. A notion of quantum differential is introduced,
highlighting the difference between the quantum and classical propagators. The
equation of quantum dynamics of the generalised Wigner function in the extended
Hilbert phase space is derived, as well as its classical limit, which serves as

We model recent experiments on living sulphur bacteria interacting with
quantised light, using the Dicke model. The strong coupling achieved between
the bacteria and the light indicates that during the experiment the bacteria
(treated as dipoles) and the quantized light are entangled. The vacuum Rabi
splitting, which was measured in the experiment for a range of different
parameters, can be used as an entanglement witness.

The concept of correlation is central to all approaches that attempt the
description of many-body effects in electronic systems. Multipartite
correlation is a quantum information theoretical property that is attributed to
quantum states independent of the underlying physics. In quantum chemistry,
however, the correlation energy (the energy not seized by the Hartree-Fock
ansatz) plays a more prominent role. We show that these two different
viewpoints on electron correlation are closely related. The key ingredient

Continuous variable Beam Splitter (BS) generated entanglement from single
mode optical states generated by single nonclassicality (NC) inducing operation
have been found of immense importance in several information processing tasks.
There exists a broader class of optical states, generated from successive
action of multiple different NC-inducing operations, which show many intriguing
nonclassical properties; however the BS conversion of the NC for such states

Environmental influences are typical in any practical situation which in turn
can have fatal effects on quantum resources. Bell nonlocality is such an
important resource. Some environmental interactions can lead to nonlocality
being lost. In such situations, it is vital to find possible prescriptions to
retrieve nonlocality. The present work lays down one such prescription.
Precisely, we have studied some well-known classes of states under the ambit of
the Bell-CHSH inequality in two qubits, where we start from a Bell-CHSH local

We consider the simultaneous and continuous measurement of qubit observables
$\sigma_z$ and $\sigma_z\cos\varphi + \sigma_x\sin\varphi$, focusing on the
temporal correlations of the two output signals. Using quantum Bayesian theory,
we derive analytical expressions for the correlators, which we find to be in
very good agreement with experimentally measured output signals. We further
discuss how the correlators can be applied to parameter estimation, and use

Objectivity constitutes one of the main features of the macroscopic classical
world. An important aspect of the quantum-to-classical transition issue is to
explain how such a property arises from the microscopic quantum world.
Recently, within the framework of open quantum systems, there has been proposed
such a mechanism in terms of the, so-called, Spectrum Broadcast Structures.
These are multipartite quantum states of the system of interest and a part of

Of course not, but if one believes that information cannot be destroyed in a
theory of quantum gravity, then we run into apparent contradictions with
quantum theory when we consider evaporating black holes. Namely that the
no-cloning theorem or the principle of entanglement monogamy is violated. Here,
we show that neither violation need hold, since, in arguing that black holes
lead to cloning or non-monogamy, one needs to assume a tensor product structure
between two points in space-time that could instead be viewed as causally