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

# All

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