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Although it may seem The Delayed Choice experiments contradict causality and
one could construct an experiment which could possibly affect the past, using
Many World interpretation we prove it is not possible. We also find a
mathematical background to Which-path information and show why its
obtainability prevents system from interfering. We find a system which exhibit
both interference and correlation and show why one-particle interference and
correlations are complementary. Better visible interference pattern leads to

An initial coherent state is propagated exactly by a kicked quantum
Hamiltonian and its associated classical stroboscopic map. The classical
trajectories within the initial state are regular for low kicking strengths,
then bifurcate and become mainly chaotic as the kicking parameter is increased.
Time-evolution is tracked using classical, quantum and semiclassical Wigner
functions, obtained via the Herman-Kluk propagator. Quantitative comparisons
are also included and carried out from probability marginals and

There is a remarkable characteristic of photosynthesis in nature, that is,
the energy transfer efficiency is close to 100%. Recently, due to the rapid
progress made in the experimental techniques, quantum coherent effects have
been experimentally demonstrated. Traditionally, the incoherent theories are
capable of calculating the energy transfer efficiency, e.g., (generalized)
F\"orster theory and modified Redfield theory. However, in order to describe

Quantum simulation of chemical systems is one of the most promising near-term
applications of quantum computers. The variational quantum eigensolver, a
leading algorithm for molecular simulations on quantum hardware, has a serious
limitation in that it typically relies on a pre-selected wavefunction ansatz
that results in approximate wavefunctions and energies. Here we present an
arbitrarily accurate variational algorithm that instead of fixing an ansatz

Implementing high-fidelity two-qubit gates in single-electron spin qubits in
silicon double quantum dots is still a major challenge. In this work, we employ
analytical methods to design control pulses that generate high-fidelity
entangling gates for quantum computers based on this platform. Using realistic
parameters and initially assuming a noise-free environment, we present simple
control pulses that generate CNOT, CPHASE, and CZ gates with average fidelities

We theoretically study the quantum interference induced photon blockade
phenomenon in atom cavity QED system, where the destructive interference
between two different transition pathways prohibits the two-photon excitation.
Here, we first explore the single atom cavity QED system via an atom or cavity
drive. We show that the cavity-driven case will lead to the quantum
interference induced photon blockade under a specific condition, but the atom
driven case can't result in such interference induced photon blockade. Then, we

This paper develops the resource theory of asymmetric distinguishability for
quantum channels, generalizing the related resource theory for states
[arXiv:1006.0302, arXiv:1905.11629]. The key constituents of the channel
resource theory are quantum channel boxes, consisting of a pair of quantum
channels, which can be manipulated for free by means of an arbitrary quantum
superchannel (the most general physical transformation of a quantum channel).

Quantum vision is currently emerging as an interdisciplinary field
synthesizing the physiology of human vision with modern quantum optics. We
recently proposed a biometric scheme based on the human visual system's ability
to perform photon counting. We here present a light stimulus source that can
provide for the requirements of this biometric scheme, namely a laser light
beam having a cross section consisting of discrete pixels, allowing for an
arbitrary pattern of illuminated pixels, each having a photon number per unit

We prove that the classical capacity of an arbitrary quantum channel assisted
by a free classical feedback channel is bounded from above by the maximum
average output entropy of the quantum channel. As a consequence of this bound,
we conclude that a classical feedback channel does not improve the classical
capacity of a quantum erasure channel, and by taking into account energy
constraints, we conclude the same for a pure-loss bosonic channel. The method
for establishing the aforementioned entropy bound involves identifying an

We propose a brand-new protocol called machine learning continuous-variable
quantum key distribution (ML-CVQKD), aiming to break the limitation of
traditional pattern in CVQKD and establish a cross research platform between
CVQKD and machine learning. ML-CVQKD divides the whole system into state
learning process and state prediction process. The former is used for training
and estimating quantum classifier, and the latter is used for predicting
unlabeled signal states. Meanwhile, a quantum multi-label classification (QMLC)

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