Tracking the behaviour of stochastic systems is a crucial task in the
statistical sciences. It has recently been shown that quantum models can
faithfully simulate such processes whilst retaining less information about the
past behaviour of the system than the optimal classical models. We extend these
results to general temporal and symbolic dynamics. Our systematic protocol for
quantum model construction relies only on an elementary description of the
dynamics of the process. This circumvents restrictions on corresponding

In previous work we proved that, for categories of free finite-dimensional
modules over a commutative semiring, linear compact-closed symmetric monoidal
structure is a property, rather than a structure. That is, if there is such a
structure, then it is uniquely defined (up to monoidal equivalence). Here we
provide a novel unifying category-theoretic notion of symmetric monoidal
structure with local character, which we prove to be a property for a much
broader spectrum of categorical examples, including the infinite-dimensional

The observations the dc voltage on asymmetric superconducting ring testify
that one of the ring segments is a dc power source. The persistent current
flows against the total electric field in this segment. This paradoxical
phenomenon is observed when the ring or its segments are switched between
superconducting and normal state by non-equilibrium noises. We demonstrate that
the dc voltage and the power increase with the number of the identical rings
connected in series. Large voltage and power sufficient for practical

We test the principles of classical modal logic in fully quantum settings.
Modal logic models our reasoning in multi-agent problems, and allows us to
solve puzzles like the muddy children paradox. The Frauchiger-Renner thought
experiment highlighted fundamental problems in applying classical reasoning
when quantum agents are involved; we take it as a guiding example to test the
axioms of classical modal logic. In doing so, we find a problem in the original
formulation of the Frauchiger-Renner theorem: a missing assumption about

Quantum self-testing addresses the following question: is it possible to
verify the existence of a multipartite state even when one's measurement
devices are completely untrusted? This problem has seen abundant activity in
the last few years, particularly with the advent of parallel self-testing
(i.e., testing several copies of a state at once), which has applications not
only to quantum cryptography but also quantum computing. In this work we give
the first error-tolerant parallel self-test in a three-party (rather than

Physical systems in the time domain may exhibit analogous phenomena in real
space, such as time crystals, time-domain Fresnel lenses, and modulational
interference in a qubit. Here we report the experimental realization of
time-domain grating using a superconducting qutrit in periodically modulated
probe and control fields via two schemes: Simultaneous modulation and
complementary modulation. Both experimental and numerical results exhibit
modulated Autler-Townes (AT) and modulation-induced diffraction (MID) effects.

A notion of morphism that is suitable for the sheaf-theoretic approach to
contextuality is developed, resulting in a resource theory for contextuality.
The key features involve using an underlying relation rather than a function
between measurement scenarios, and allowing for stochastic mappings of outcomes
to outcomes. This formalizes an intuitive idea of using one empirical model to
simulate another one with the help of pre-shared classical randomness. This

A method for the implementation of a universal set of fault-tolerant logical
gates is presented using homological product codes. In particular, it is shown
that one can fault-tolerantly map between different encoded representations of
a given logical state, enabling the application of different classes of
transversal gates belonging to the underlying quantum codes. This allows for
the circumvention of no-go results pertaining to universal sets of transversal

We employ a quasirandom methodology, recently developed by Martin Roberts, to
estimate the separability probabilities, with respect to the Bures (minimal
monotone/statistical distinguishability) measure, of generic two-qubit and
two-rebit states. This procedure, based on generalized properties of the golden
ratio, yielded, in the course of almost fifteen billion iterations, two-qubit
estimates repeatedly agreeing to close to nine decimal places with
$\frac{25}{341} =\frac{5^2}{11 \cdot 31} \approx 0.07331378299$. The

We review the physical foundations of Landauer's Principle, which relates the
loss of information from a computational process to an increase in
thermodynamic entropy. Despite the long history of the Principle, its
fundamental rationale and proper interpretation remain frequently
misunderstood. Contrary to some misinterpretations of the Principle, the mere
transfer of entropy between computational and non-computational subsystems can
occur in a thermodynamically reversible way without increasing total entropy.