All

Our goal is to compare two unequivalent definitions of the Gell-Mann
channels. It turns out that both definitions coincide for qubits and qutrits.
In higher dimensions, there exist some constraints under which the channels
describe the same dynamics. Finally, we find the GKSL time-local generators for
a class of the Gell-Mann channels.

A qudit code is a subspace of the state space of a fixed number of qudits.
Such a code is permutation-invariant if it is unchanged under the swapping of
any pair of the underlying qudits. Prior permutation-invariant codes encode a
single qubit into $N$ qubits that correct $t$ arbitrary errors. We design
permutation-invariant codes encoding a $d$-level system into $N$ qudits that
correct $t$ arbitrary errors. The logical codewords in our
permutation-invariant qudits codes are linear combinations of Dicke states,

The coherent control of spin qubits forms the basis of many applications in
quantum information processing and nanoscale sensing, imaging and spectroscopy.
Such control is conventionally achieved by direct driving of the qubit
transition with a resonant global field, typically at microwave frequencies.
Here we introduce an approach that relies on the resonant driving of nearby
environment spins, whose localised magnetic field in turn drives the qubit when

We provide a scheme for inferring causal relations from uncontrolled
statistical data based on tools from computational algebraic geometry, in
particular, the computation of Groebner bases. We focus on causal structures
containing just two observed variables, each of which is binary. We consider
the consequences of imposing different restrictions on the number and
cardinality of latent variables and of assuming different functional
dependences of the observed variables on the latent ones (in particular, the

The transport of sound and heat, in the form of phonons, can be limited by
disorder-induced scattering. In electronic and optical settings the
introduction of chiral transport, in which carrier propagation exhibits parity
asymmetry, can remove elastic backscattering making carrier transport robust
against unwanted disorder. While chiral transport is also achievable for
phonons the suppression of disorder-induced scattering has never been
demonstrated in non-topological phononic systems. Here we experimentally

Here we show that, if we insert context dependent unitary evolutions (which
can be achieved via post selection) into spatial (i.e., normal) Bell-CHSH test,
then it is possible to violate space-time Bell-CHSH inequality maximally (i.e.,
up to $4$). However this does not contradict Tsirelson quantum bound
($2\sqrt{2}$), as the latter has been derived without taking into consideration
context dependent unitary evolutions and/or post selection. As an important

We demonstrate that temporal observables, which are sensitive to a system's
history (as opposed to its state), implicate entangled histories. We exemplify
protocols for measuring such observables, and algorithms for predicting the
(stochastic) outcomes of such measurements. Temporal observables allow us to
define, and potentially to measure, precise mathematical consequences of
intrinsically disjoint, yet mutually accessible, branches within the evolution
of a pure quantum state.

We consider a family of quantum channels characterized by the fact that
certain (in general nonorthogonal) Pure states at the channel entrance are
mapped to (tensor) Products of Pure states (PPP, hence "pcubed") at the
complementary outputs (the main output and the "environment") of the channel.
The pcubed construction, a reformulation of the twisted-diagonal procedure by
M. M Wolf and D. Perez-Garcia, [Phys. Rev. A 75, 012303 (2007)], can be used to
produce a large class of degradable quantum channels; degradable channels are

Instantaneous quantum computing is a sub-universal quantum complexity class,
whose circuits have proven to be hard to simulate classically in the
Discrete-Variable (DV) realm. We extend this proof to the Continuous-Variable
(CV) domain by using squeezed states and homodyne detection, and by exploring
the properties of post-selected circuits. In order to treat post-selection in
CVs we consider finitely-resolved homodyne detectors, corresponding to a
realistic scheme based on discrete probability distributions of the measurement

In the early days of quantum mechanics, it was believed that the time energy
uncertainty principle (TEUP) bounds the efficiency of energy measurements,
relating the duration ($\Delta t$) of the measurement, and its accuracy error
($\Delta E$) by $\Delta t\Delta E \ge$ 1/2. In 1961 Y. Aharonov and Bohm gave a
counterexample, whereas Aharonov, Massar and Popescu [2002] showed that under
certain conditions the principle holds. Can we classify when and to what extent
the TEUP is violated?