Macroscopic fields like electromagnetic, MHD, acoustic or gravitational waves
are usually described by classical wave equations with possible additional
damping terms and coherent sources. The aim of this paper is to develop a
complete macroscopic formalism including random/thermal sources, dissipation
and random scattering of waves by environment. The proposed reduced state of
field (RSF) combines averaged field with the two-point correlation function
called single-particle density matrix. The evolution equations for RSF is

At zero energy the Dirac equation has interesting behaviour. The asymmetry in
the number of spin up and spin down modes is determined by the topology of both
space and the gauge field in which the system sits. An analogous phenomenon
also occurs in electromagnetism. Writing Maxwell's equations in a Dirac-like
form, we identify cases where a material parameter plays the role of energy. At
zero energy we thus find electromagnetic modes that are indifferent to local

We consider a protocol for sharing quantum states using continuous variable
systems. Specifically we introduce an encoding procedure where bosonic modes in
arbitrary secret states are mixed with several ancillary squeezed modes through
a passive interferometer. We derive simple conditions on the interferometer for
this encoding to define a secret sharing protocol and we prove that they are
satisfied by almost any interferometer. This implies that, if the

We demonstrate how the dissipative interaction between a superconducting
qubit and a microwave photonic crystal can be used for quantum bath
engineering. The photonic crystal is created with a step-impedance transmission
line which suppresses and enhances the quantum spectral density of states,
influencing decay transitions of a transmon circuit. The qubit interacts with
the transmission line indirectly via dispersive coupling to a cavity. We
characterize the photonic crystal density of states from both the unitary and

Quantum tomography is currently ubiquitous for testing any implementation of
a quantum information processing device. Various sophisticated procedures for
state and process reconstruction from measured data are well developed and
benefit from precise knowledge of the model describing state preparation and
the measurement apparatus. However, physical models suffer from intrinsic
limitations as actual measurement operators and trial states cannot be known

The electron and positron magnetic moments are the most precise prediction of
the standard model of particle physics. The most accurate measurement of a
property of an elementary particle has been made to test this result. A new
experimental method is now being employed in an attempt to improve the
measurement accuracy by an order of magnitude. Positrons from a "student
source" now suffice for the experiment. Progress toward a new measurement is

Solid-state experimental realizations of Majorana bound states are based on
materials with strong intrinsic spin-orbit interactions. In this work, we
explore an alternative approach where spin-orbit coupling is induced
artificially through a non-uniform magnetic field that originates from an array
of micromagnets. Using a recently developed optimization algorithm, we find
suitable micromagnet geometries for the emergence of topological
superconductivity in a one-dimensional wire without intrinsic spin-orbit

We introduce two methods for estimating the density matrix for a quantum
system: Quantum Maximum Likelihood and Quantum Variational Inference. In these
methods, we construct a variational family to model the density matrix of a
mixed quantum state. We also introduce quantum flows, the quantum analog of
normalizing flows, which can be used to increase the expressivity of this
variational family. The eigenstates and eigenvalues of interest are then
derived by optimizing an appropriate loss function. The approach is

The Ehrenfest theorem and the Robertson uncertainty relation are well-known
basic equations in quantum mechanics. In both equations a commutator of two
operators occurs, where for the Ehrenfest theorem one of these two operators is
the Hamiltonian. For the correctness of the derivation of the Ehrenfest
theorem, there arise problems if we use the azimuthal angle in polar or
spherical coordinates as the other operator in this commutator. In addition,
similar problems may occur for the derivation of the Robertson uncertainty

We evaluate the rates of energy and phase relaxation of a superconducting
qubit caused by stray photons with energy exceeding the threshold for breaking
a Cooper pair. All channels of relaxation within this mechanism are associated
with the change in the charge parity of the qubit, enabling the separation of
the photon-assisted processes from other contributions to the relaxation rates.
Among the signatures of the new mechanism is the same order of rates of the
transitions in which a qubit looses or gains energy.