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We investigate photoinduced proton-coupled electron transfer (PI-PCET)
reaction through a recently devel- oped quasi-diabatic (QD) quantum dynamics
propagation scheme. This scheme enables interfacing accurate diabatic-based
quantum dynamics approaches with adiabatic electronic structure calculations
for on-the-fly simulations. Here, we use the QD scheme to directly propagate
PI-PCET quantum dynamics with the di- abatic Partial Linearized Density Matrix

The goal of entanglement distillation is to turn a large number of weakly
entangled states into a smaller number of highly entangled ones. Practical
entanglement distillation schemes offer a tradeoff between the fidelity to the
target state, and the probability of successful distillation. Exploiting such
tradeoffs is of interest in the design of quantum repeater protocols. Here, we
present a number of methods to assess and optimise entanglement distillation

We investigate the modified trace distance measure of coherence recently
introduced in [Phys. Rev. A 94, 060302(R) (2016)]. We show that for any
single-qubit state, the modified trace norm of coherence is equal to the
$l_{1}$-norm of coherence. For any $d$-dimensional quantum system, an
analytical formula of this measure for a class of maximally coherent mixed
states is provided. The trade-off relation between the coherence quantified by
the new measure and the mixedness quantified by the trace norm is also

We investigate the performance of discrimination strategy in the comparison
task of known quantum states. In the discrimination strategy, one infers
whether or not two quantum systems are in the same state on the basis of the
outcomes of separate discrimination measurements on each system. In some cases
with more than two possible states, the optimal strategy in minimum-error
comparison is that one should infer the two systems are in different states
without any measurement, implying that the discrimination strategy performs

We map the density matrix of the qubit (spin-1/2) state associated with the
Bloch sphere and given in the tomographic probability representation onto
vertices of a triangle determining Triada of Malevich's squares. The three
triangle vertices are located on three sides of another equilateral triangle
with the sides equal to $\sqrt 2$. We demonstrate that the triangle vertices
are in one-to-one correspondence with the points inside the Bloch sphere and
show that the uncertainty relation for the three probabilities of spin

The prospect of computational hardware with quantum advantage relies
critically on the quality of quantum gate operations. Imperfect two-qubit gates
is a major bottleneck for achieving scalable quantum information processors.
Here, we propose a generalizable and extensible scheme for a two-qubit coupler
switch that controls the qubit-qubit coupling by modulating the coupler
frequency. Two-qubit gate operations can be implemented by operating the
coupler in the dispersive regime, which is non-invasive to the qubit states. We

A reliable, triggered photon source is required for many aspects of quantum
technology. Organic molecules are attractive for this application because they
can have high quantum yield and can be photostable, even at room temperature.
For the trigger pulse to generate a photon with high probability, it must
excite the molecule efficiently. We develop a simple model for that efficiency
and discuss how to optimise it. We demonstrate the validity of our model
through experiments on a single dibenzoterrylene (DBT) molecule in an

Quantum violation of Bell inequalities is now used in many quantum
information applications and it is important to analyze it both quantitatively
and conceptually. In the present paper, we analyze violation of multipartite
Bell inequalities via the local probability model - the LqHV (local quasi
hidden variable) model [Loubenets, J. Math. Phys. 53, 022201 (2012)],
incorporating the LHV model only as a particular case and correctly reproducing
the probabilistic description of every quantum correlation scenario, more

By simultaneously coupling multiple two-level artificial atoms to two
superconducting resonators, we design a quantum switch that tunes the
resonator-resonator coupling strength from zero to a large value proportional
to the number of qubits. This process is implemented by engineering the qubits
into different subradiant states, where the microwave photons decay from
different qubits destructively interfere with each other such that the
resonator-resonator coupling strength keeps stable in an open environment.

Strong quantum nonlinearity gives rise to many interesting quantum effects
and has wide applications in quantum physics. Herewe investigate the quantum
nonlinear effect of an optomechanical system (OMS) consisting of both linear
and quadratic coupling. Interestingly, a controllable optomechanical
nonlinearity is obtained by applying a driving laser into the cavity. This
controllable optomechanical nonlinearity can be enhanced into a strong coupling
regime, even if the system is initially in the weak-coupling regime. Moreover,