We propose a minimalistic model of quantum measurements within a finite
system that undergoes a regular unitary evolution. Based on information theory,
the measurement process requires a sacrifice of information entropy. This loss
in our model is represented by a single cubit being isolated from the rest of
the system. As a result of the partitioning, the classical domain emerges and
the measurement occurs. The effect of the measurement on the quantum state of

The complex collisional properties of atoms fundamentally limit
investigations into a range of processes in many-atom ensembles. In contrast,
the bottom-up assembly of few- and many-body systems from individual atoms
offers a controlled approach to isolating and studying such collisional
processes. Here, we use optical tweezers to individually assemble pairs of
trapped $^{85}$Rb atoms, and study the spin dynamics of the two-body system in
a thermal state. The spin-2 atoms show strong pair correlation between magnetic

Long-lived sub-levels of the electronic ground-state manifold of rare-earth
ions in crystals can be used as atomic population reservoirs for photon
echo-based quantum memories. We measure the dynamics of the Zeeman sub-levels
of erbium ions that are doped into a lithium niobate waveguide, finding
population lifetimes at cryogenic temperatures as long as seconds. Then, using
these levels, we prepare and characterize atomic frequency combs, which can
serve as a memory for quantum light at 1532 nm wavelength. The results allow

Motivated by the problem of classifying individuals with a disease versus
controls using functional genomic attributes as input, we encode the input as a
string of 1s (presence) or 0s (absence) of the genomic attribute across the
genome. Blocks of physical regions in the subdivided genome serve as the
feature dimensions, which takes full advantage of remaining in the
computational basis of a quantum computer. Given that a natural distance
between two binary strings is the Hamming distance and that this distance

Localization in one-dimensional disordered or quasiperiodic non-interacting
systems in presence of power-law hopping is very different from localization in
short-ranged systems. Power-law hopping leads to algebraic localization as
opposed to exponential localization in short-ranged systems. Exponential
localization is synonymous with insulating behavior in the thermodynamic limit.
Here we show that the same is not true for algebraic localization. We show, on

In quantum computation the target fidelity of the qubit gates is very high,
with the admissible error being in the range from $10^{-3}$ to $10^{-4}$ and
even less, depending on the protocol. The direct experimental determination of
such an extremely small error is very challenging by standard quantum-process
tomography. Instead, the method of randomized benchmarking, which uses a random
sequence of Clifford gates, has become a standard tool for determination of the

A classical stochastic formalism is presented and applied to the case of two
linearly coupled harmonic oscillators. It is shown that phenomena such as
state-swap, quadrature squeezing, entanglement and violation of entanglement
inequalities naturally occur in a stochastic framework, as a consequence of the
interaction. Based on these results, it is discussed how these effects arise in
fully classical systems, such as cholesteric liquid crystals in the presence of
a magnetic field.

Given two pairs of quantum states, we want to decide if there exists a
quantum channel that transforms one pair into the other. The theory of quantum
statistical comparison and quantum relative majorization provides necessary and
sufficient conditions for such a transformation to exist, but such conditions
are typically difficult to check in practice. Here, by building upon work by
Matsumoto, we relax the problem by allowing for small errors in one of the

Pure state entanglement transformations have been thought of as irreversible,
with reversible transformations generally only possible in the limit of many
copies. Here, we show that reversible entanglement transformations do not
require processing on the many copy level, but can instead be undertaken on
individual systems, provided the amount of entanglement which is produced or
consumed is allowed to fluctuate. We derive necessary and sufficient conditions

We study the large-time behaviour of a sample $\mathcal{S}$ consisting of an
ensemble of fermionic walkers on a graph interacting with a structured infinite
reservoir of fermions $\mathcal{E}$ through an exchange of particles in
preferred states. We describe the asymptotic state of $\mathcal{S}$ in terms
the initial state of $\mathcal{E}$, with especially simple formulae in the
limit of small coupling strength. We also study the particle fluxes into the
different parts of the reservoir.