Dynamical quantum phase transitions (DQPTs) are manifested by time-domain
nonanalytic behaviors of many-body systems.Introducing a quench is so far
understood as a typical scenario to induce DQPTs.In this work, we discover a
novel type of DQPTs, termed "Floquet DQPTs", as intrinsic features of systems
with periodic time modulation.Floquet DQPTs occur within each period of
continuous driving, without the need for any quenches.In particular, in a
harmonically driven spin chain model, we find analytically the existence of

Understanding the distribution of quantum entanglement over many parties is a
fundamental challenge of quantum physics and is of practical relevance for
several applications in the field of quantum information. Here we use methods
from quantum metrology to microscopically characterize the entanglement
structure of multimode continuous-variable states in all possible
multi-partitions and in all reduced distributions. From experimentally measured
covariance matrices of Gaussian states with 2, 3, and 4 photonic modes with

A discrete time crystal is a recently discovered non-equilibrium phase of
matter that has been shown to exist in disordered, periodically driven Ising
spin chains. In this phase, if the system is initially prepared in one of a
certain class of pure multispin product states, it periodically returns to this
state over very long time scales despite the presence of interactions,
disorder, and pulse imperfections. Here, we show that this phase occurs in GaAs

Studied in this article is non-Markovian open quantum systems parametrized by
Hamiltonian H, coupling operator L, and memory kernel function {\gamma}, which
is a proper candidate for describing the dynamics of various solid-state
quantum information processing devices. We look into the subspace stabilization
problem of the system from the perspective of dynamical systems and control.
The problem translates itself into finding analytic conditions that
characterize invariant and attractive subspaces. Necessary and sufficient

We present a protocol for designing appropriately extended $\pi$ pulses that
achieves tunable, thus selective, electron-nuclear spin interactions with
low-driving radiation power. Our method is general since it can be applied to
different quantum sensor devices such as nitrogen vacancy centers or silicon
vacancy centers. Furthermore, it can be directly incorporated in commonly used
stroboscopic dynamical decoupling techniques to achieve enhanced nuclear
selectivity and control, which demonstrates its flexibility.

We establish the nonclassicality of continuous-variable states as a resource
for quantum metrology. Based on the quantum Fisher information of multimode
quadratures, we introduce the metrological power as a measure of
nonclassicality with a concrete operational meaning of displacement sensitivity
beyond the classical limit. This measure belongs to the resource theory of
nonclassicality, which is nonincreasing under linear optical elements. Our
Letter reveals that a single copy, highly nonclassical quantum state is

We present a general theory for laser-free entangling gates with trapped-ion
hyperfine qubits, using either static or oscillating magnetic-field gradients
combined with a pair of uniform microwave fields symmetrically detuned about
the qubit frequency. By transforming into a `bichromatic' interaction picture,
we show that either ${\hat{\sigma}_{\phi}\otimes\hat{\sigma}_{\phi}}$ or
${\hat{\sigma}_{z}\otimes\hat{\sigma}_{z}}$ geometric phase gates can be
performed. The gate basis is determined by selecting the microwave detuning.

Homodyne X-ray diffraction signals produced by classical light and classical
detectors are given by the modulus square of the charge density in momentum
space $\left|\sigma(\mathbf{q})\right|^{2}$, missing its phase which is
required in order to invert the signal to real space. We show that quantum
detection of the radiation field yields a linear diffraction pattern that
reveals $\sigma(\mathbf{q})$ itself, including the phase. We further show that
repeated diffraction measurements with variable delays constitute a novel

Many-body eigenstates beyond the gaussian approximation can be constructed in
terms of local integrals of motion (IOM), although their actual computation has
been until now a daunting task. We present a new practical computation of IOMS
based on displacement transformations. It represents a general and systematic
way to extend Hartree-Fock and configuration interaction theories to higher
order. Our method combines minimization of energy and energy variance of a

Recently a complete set of entropic conditions has been derived for the
interconversion structure of states under quantum operations that respect a
specified symmetry action, however the core structure of these conditions is
still only partially understood. Here we develop a coarse-grained description
with the aim of shedding light on both the structure and the complexity of this
general problem. Specifically, we consider the degree to which one can
associate a basic `shape' property to a quantum state or channel that captures