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We present new techniques for inertial-sensing atom interferometers which
produce multiple phase measurements per experimental cycle. With these
techniques, we realize two types of multiport measurements, namely quadrature
phase detection and real-time systematic phase cancellation, which address
challenges in operating high-sensitivity cold-atom sensors in mobile and field
applications. We confirm experimentally the increase in sensitivity due to
quadrature phase detection in the presence of large phase uncertainty, and

Defects in solids are in many ways analogous to trapped atoms or molecules.
They can serve as long-lived quantum memories and efficient light-matter
interfaces. As such, they are leading building blocks for long-distance quantum
networks and distributed quantum computers. This chapter describes the
quantum-mechanical coupling between atom-like spin states and light, using the
diamond nitrogen-vacancy (NV) center as a paradigm. We present an overview of
the NV center's electronic structure, derive a general picture of coherent

Decades ago, Aharonov and Bohm showed that electrons are affected by
electromagnetic potentials in the absence of forces due to fields. Zeilinger's
theorem describes this absence of classical force in quantum terms as the
"dispersionless" nature of the Aharonov-Bohm effect. Shelankov predicted the
presence of a quantum "force" for the same Aharonov-Bohm physical system as
elucidated by Berry. Here, we report an experiment designed to test Shelankov's
prediction and we provide a theoretical analysis that is intended to elucidate

While equilibrium phase transitions are well described by a free-energy
landscape, there are few tools to describe general features of their
non-equilibrium counterparts. On the other hand, near-equilibrium free-energies
are easily accessible but their full geometry is only explored in
non-equilibrium, e.g. after a quench. In the particular case of a
non-stationary system, however, the concepts of an order parameter and free
energy become ill-defined, and a comprehensive understanding of non-stationary

We accomplish studies of properly quantifying eavesdropper's information gain
in individual attacks on the BB84 system of quantum key distribution. A
noticeable sensitivity of conclusions to the choice of information measures is
brightly revealed, when generalized state discrimination is used at the last
stage. To realize her aims, Eve intrudes into the communication channel with
some entangling probe. The Fuchs-Peres-Brandt (FPB) probe is known as a
powerful individual attack on the BB84 protocol. In the simplest formulation,

In miniaturising electrical devices down to nanoscales, heat transfer has
turned into a serious obstacle but also potential resource for future
developments, both for conventional and quantum computing architectures.
Controlling heat transport in superconducting circuits has thus received
increasing attention in engineering microwave environments for circuit quantum
electrodynamics (cQED) and circuit quantum thermodynamics experiments (cQTD).
While theoretical proposals for cQTD devices are numerous, the experimental

Proposing an optomechanical cavity modulated periodically, we study the
modulation synchronization of mechanical modes of the mirrors. A periodic
modulation is applied to one of the mirrors, where the second mirror has the
capability of oscillation, without any modulation for that. As a result, we
find a phase-locking synchronization between the mechanical modes of the
mirrors and enhancement of quantum synchronization by having the periodic
modulation. Using the fact that, periodic modulation can make the squeezed

In classical two-party computation, a trusted initializer who prepares
certain initial correlations can help make the bipartite computation secure. We
propose two bipartite quantum protocols with possible aborts for approximately
generating such bipartite classical correlations with varying degrees of
privacy, without introducing a third party. The two parties are assumed to be
weakly cooperating and one of them needs to be modestly honest so that the

It has recently been shown that vacuum expectation values and Feynman path
integrals can be regularized using Fourier integral operator $\zeta$-function,
yet the physical meaning of these $\zeta$-regularized objects was unknown.

Measuring time is central to all sciences. Currently, the most accurate and
stable clocks are based on optical interrogation of either a single ion or an
ensemble of neutral atoms confined in an optical lattice. Here we demonstrate a
new optical clock system based on a trapped atomic array that is read out at
the single particle level, merging many of the benefits of ion and lattice
clocks as well as creating a bridge to recently developed techniques in quantum

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