In order to elucidate the role of spontaneous symmetry breaking in condensed
matter systems, we explicitly construct the ground state wave function for a
nonrelativistic theory of a two-fluid system of bosons. This can model either
superconductivity or superfluidity, depending on whether we assign a charge to
the particles or not. Since each nonrelativistic field $\Psi_j$ ($j=1,2$)
carries a phase $\theta_j$ and the Lagrangian is formally invariant under
shifts $\theta_j\to\theta_j+\alpha_j$ for independent $\alpha_j$, one can

The study of critical properties of systems with long-range interactions has
attracted in the last decades a continuing interest and motivated the
development of several analytical and numerical techniques, in particular in
connection with spin models. From the point of view of the investigation of
their criticality, a special role is played by systems in which the
interactions are long-range enough that their universality class is different
from the short-range case and, nevertheless, they maintain the extensivity of

A weakness which has previously seemed unavoidable in particle
interpretations of quantum mechanics (such as in the de Broglie-Bohm model) is
addressed here and a resolution proposed. The weakness in question is the lack
of action and reaction occurring between the model's field (or "pilot wave")
and the particle. Although the field acts on the particle, the particle does
not act back on the field. It is shown here that this rather artificial feature
is, in fact, not necessary and can be fully eliminated while remaining

The success of quantum physics in description of various physical interaction
phenomena relies primarily on the accuracy of analytical methods used. In
quantum mechanics, many of such interactions such as those found in quantum
optomechanics and quantum computing have a highly nonlinear nature, which makes
their analysis extraordinarily difficult using classical schemes. Typically,
modern quantum systems of interest nowadays come with four basic properties:

Quantum sensing exploits fundamental features of quantum mechanics and
quantum control to realise sensing devices with potential applications in a
broad range of scientific fields ranging from basic science to applied
technology. The ultimate goal are devices that combine unprecedented
sensitivity with excellent spatial resolution. Here, we propose a new platform
for all-electric nanoscale quantum sensing based on a carbon nanotube double
quantum dot. Our analysis demonstrates that the platform can achieve

Coherence is a basic notion for quantum states. Instead of quantum states, in
this work, We establish a resource theory for quantifying the coherence of
Gaussian channels. To do this, we propose the definitions of incoherent
Gaussian channels and incoherent Gaussian superchannels.

Spin-exchange collisions in alkali vapors have been at the basis of several
fundamental and applied investigations, like nuclear structure studies and
tests of fundamental symmetries, ultra-sensitive atomic magnetometers, magnetic
resonance and bio-magnetic imaging. Spin-exchange collisions cause loss of spin
coherence, and concomittantly produce spin noise, both phenomena being central
to quantum metrology. We here develop the quantum trajectory picture of
spin-exchange collisions, consistent with their long-standing ensemble

Coherence distillation is one of the central problems in the resource theory
of coherence. In this Letter, we complete the deterministic distillation of
quantum coherence for a finite number of coherent states under strictly
incoherent operations. Specifically, we find the necessary and sufficient
condition for the transformation from a mixed coherent state into a pure state
via strictly incoherent operations, which recovers a connection between the
resource theory of coherence and the algebraic theory of majorization lattice.

Driving an open spin system by two strong, nearly degenerate fields enables
addressing populations of individual spin states, characterisation of their
interaction with thermal bath, and measurements of their relaxation/decoherence
rates. With such addressing we observe nested magnetic resonances having
nontrivial dependence on microwave field intensity: while the width of one of
the resonances undergoes a strong power broadening, the other one exhibits a

Privacy is under threat from artificial intelligence revolution fueled by
unprecedented abundance of data. Differential privacy, an established candidate
for privacy protection, is susceptible to adversarial attacks, acts
conservatively, and leads to miss-implementations because of lacking systematic
methods for setting its parameters (known as the privacy budget). An
alternative is information-theoretic privacy using entropy with the drawback of
requiring prior distribution of the private data. Here, by using the Fisher