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Quantum secure signature schemes have a lot of attention recently, in
particular because of the NIST call to standardize quantum safe cryptography.
However, only few signature schemes can have concrete quantum security because
of technical difficulties associated with the Quantum Random Oracle Model
(QROM). In this paper, we show that code-based signature schemes based on the
full domain hash paradigm can behave very well in the QROM i.e. that we can
have tight security reductions. We also study quantum algorithms related to the

The fundamental physical description of Nature is based on two mutually
incompatible theories: Quantum Mechanics and General Relativity. Their
unification in a theory of Quantum Gravity (QG) remains one of the main
challenges of theoretical physics. Quantum Gravity Phenomenology (QGP) studies
QG effects in low-energy systems. The basis of one such phenomenological model
is the Generalized Uncertainty Principle (GUP), which is a modified Heisenberg
uncertainty relation and predicts a deformed canon ical commutator. In this

We present a new optical scheme for BB84 protocol quantum key distribution
(QKD). The proposed setup consists of a compact all-fiber polarization encoding
optical scheme based on LiNbO3 phase modulators, single laser source and two
single-photon detectors. Optical scheme consists of standard telecommunication
components and is suitable for both fiber and free-space quantum communication
channels. Low losses (~2dB) in Bob's device increase both the key generation

We study the underlying mechanism in the implementation of unitary control on
a system with an experimental apparatus. We regard the unitary time-evolution
in the system as a physical phenomenon that results from the interaction
between the system and the apparatus. We model this situation using the setup
of the system and an external system that represents the apparatus. We consider
the conditions required to approximate the dynamics of the reduced density

Fundamental questions in chemistry and physics may never be answered due to
the exponential complexity of the underlying quantum phenomena. A desire to
overcome this challenge has sparked a new industry of quantum technologies with
the promise that engineered quantum systems can address these hard problems. A
key step towards demonstrating such a system will be performing a computation
beyond the capabilities of any classical computer, achieving so-called quantum

A strong electromagnetic field interacting with an electron system generates
both the Rabi oscillations and the Stark splitting of the electron density.
Changing of the electron density gives rise to nonadiabatic effects due to
existence of the electron-vibrational interaction in a dissipative system. In
this Letter, the mechanism of energy transfer between the electron system and
the phonon reservoir is presented. This mechanism is based on establishment of

What are the conditions for adiabatic quantum computation (AQC) to outperform
classical computation? Although there exist several quantum adiabatic
algorithms achieving the strong quantum speedup, the essential keys to their
speedups are still unclear. Here, we investigate the connection between
superpositions of macroscopically distinct states and known examples of the
speedup in AQC. To formalize this notion we consider an index $p$ that
quantifies a superposition of macroscopically distinct states from the

We investigate the electric quadrupole interaction of an alkali-metal atom
with guided light in the fundamental and higher-order modes of a vacuum-clad
ultrathin optical fiber. We calculate the quadrupole Rabi frequency, the
quadrupole oscillator strength, and their enhancement factors. In the example
of a rubidium-87 atom, we study the dependencies of the quadrupole Rabi
frequency on the quantum numbers of the transition, the mode type, the phase
circulation direction, the propagation direction, the orientation of the

Quantum bits based on individual trapped atomic ions constitute a promising
technology for building a quantum computer, with all the elementary operations
having been achieved with the necessary precision. However, the essential
two-qubit logic gate used for generating quantum entanglement has hitherto
always been performed in an adiabatic regime, where the gate is slow compared
with the characteristic motional frequencies of ions in the trap, giving logic

We introduce and analyze graph-associated entanglement cost, a generalization
of the entanglement cost of quantum states to multipartite settings. We
identify a necessary and sufficient condition for any multipartite entangled
state to be constructible when quantum communication between the multiple
parties is restricted to a quantum network represented by a tree. The condition
for exact state construction is expressed in terms of the Schmidt ranks of the
state defined with respect to edges of the tree. We also study approximate