Squeezed states of light have received renewed attention due to their
applicability to quantum-enhanced sensing. To take full advantage of their
reduced noise properties to enhance atomic-based sensors, it is necessary to
generate narrowband near or on atomic resonance single-mode squeezed states of
light. We have previously generated bright two-mode squeezed states of light,
or twin beams, that can be tuned to resonance with the D1 line of $^{87}$Rb
with a non-degenerate four-wave mixing (FWM) process in a double-lambda

We looked into the algorithm for calculating Betti numbers presented by
Lloyd, Garnerone, and Zanardi (LGZ). We present a new algorithm in the same
spirit as LGZ with the intent of clarifying quantum algorithms for computing
Betti numbers. Our algorithm is simpler and slightly more efficient than that
presented by LGZ. We present a thorough analysis of our algorithm, pointing out
reasons that both our algorithm and that presented by LGZ do not run in
polynomial time for most inputs. However, the algorithms do run in polynomial

Hybrid quantum-classical systems make it possible to utilize existing quantum
computers to their fullest extent. Within this framework, parameterized quantum
circuits can be thought of as machine learning models with remarkable
expressive power. This Review presents components of these models and discusses
their application to a variety of data-driven tasks such as supervised learning
and generative modeling. With experimental demonstrations carried out on actual

Out-of-time-order correlators (OTOCs) have been proposed as a probe of chaos
in quantum mechanics, on the basis of their short-time exponential growth found
in some particular set-ups. However, it has been seen that this behavior is not
universal. Therefore, we query other quantum chaos manifestations arising from
the OTOCs and we thus study their long-time behavior in systems of completely
different nature: quantum maps, which are the simplest chaotic one-body system

History dependent discrete time quantum walks (QWs) are often studied for
their lattice traversal properties. A particular model in the literature uses
the state of a memory qubit at each site to record visits and to control the
dynamics of the walk. We generalize this model to the neighborhood-history
quantum walk (NHQW), in which the walk dynamics and the state of the memory
qubits in a neighborhood of the particle's position are interdependent. To
demonstrate it, we construct an NHQW on a one-dimensional lattice, with a

We derive the full linear-response theory for non-relativistic quantum
electrodynamics in the long wavelength limit, show quantum modifications of the
well-known Maxwell's equation in matter and provide a practical framework to
solve the resulting equations by using quantum-electrodynamical
density-functional theory. We highlight how the coupling between quantized
light and matter changes the usual response functions and introduces new types
of cross-correlated light-matter response functions. These cross-correlation

It is well known that the notions of spatial locality are often lost in
quantum systems with long-range interactions, as exhibited by the emergence of
phases with exotic long-range order and faster propagation of quantum
correlations. We demonstrate here that such induced ``quasinonlocal" effects do
not necessarily translate to growth of global entanglement in the quantum
system. By investigating the ground and quenched states of the variable-range,
spin-1/2 Heisenberg Hamiltonian, we observe that the genuine multiparty

Quantum memories are an important building block for quantum information
processing. Ideally, these memories preserve the quantum properties of the
input. We present general criteria for measures to evaluate the quality of
quantum memories. Then, we introduce a quality measure based on coherence
satisfying these criteria, which we characterize in detail for the qubit case.
The measure can be estimated from sparse experimental data and may be
generalized to characterize other building blocks, such as quantum gates and

Alkali-metal-vapor magnetometers, using coherent precession of polarized
atomic spins for magnetic field measurement, have become one of the most
sensitive magnetic field detectors. Their application areas range from
practical uses such as detections of NMR signals to fundamental physics
research such as searches for permanent electric dipole moments. One of the
main noise sources of atomic magnetometers comes from the light shift that
depends on the frequency of the pump laser. In this work, we theoretically

Many-body localization is shown to suppress imaginary parts of complex
eigenenergies for general non-Hermitian Hamiltonians having time-reversal
symmetry. We demonstrate that a real-complex transition, which we conjecture
occurs upon many-body localization, profoundly affects the dynamical stability
of non-Hermitian interacting systems with asymmetric hopping that respect
time-reversal symmetry. Moreover, the real-complex transition is shown to be
absent in non-Hermitian many-body systems with gain and/or loss that breaks