# All

## Experimental Ultra-small Longitudinal Phase Estimation via Weak Measurement Amplification. (arXiv:1803.07746v1 [quant-ph])

Weak value amplification has been applied to various small physical
quantities estimation, however there still lacks a practical feasible protocol
to amplify ultra-small longitudinal phase, which is of importance in high
precision measurement. Very recently, a different amplification protocol within
the framework of weak measurements is proposed to solve this problem, which is
capable of measuring any ultra-small longitudinal phase signal that
conventional interferometry tries to do. Here we experimentally demonstrate

## More Nonlocality with Less Entanglement in CHSH Experiments. (arXiv:1803.07747v1 [quant-ph])

It is well-known that in certain scenarios, weakly entangled states can
generate stronger nonlocal effects than their maximally entangled counterparts.
In this paper, we consider violations of the CHSH Inequality when one party has
inefficient detectors. We show that violations can occur if and only if the
detection efficiency is above $50\%$. We derive a simple upper bound on the
entanglement needed to violate the inequality and show that it goes to zero as

## Lightlike shell solitons of extremal space-time film. (arXiv:1506.09137v7 [hep-th] UPDATED)

New exact solution class of Born -- Infeld type nonlinear scalar field model
is obtained. The variational principle of this model has a specific form which
is characteristic for extremal four-dimensional hypersurface or hyper-film in
five-dimensional space-time. Obtained solutions are singular solitons
propagating with speed of light and having energy, momentum, and angular
momentum which can be calculated for explicit conditions. Such solitons will be
called the lightlike ones. The soliton singularity has a form of moving

## Ultrabright narrow-band telecom two-photon source for long-distance quantum communication. (arXiv:1803.07749v1 [quant-ph])

We demonstrate an ultrabright narrow-band two-photon source at the 1.5 -\mu m
telecom wavelength for long-distance quantum communication. By utilizing a
bow-tie cavity, we obtain a cavity enhancement factor of $4.06\times 10^4$. Our
measurement of the second-order correlation function $G^{(2)} ({\tau})$ reveals
that the linewidth of $2.4$ MHz has been hitherto unachieved in the 1.5 -\mu m
telecom band. This two-photon source is useful for obtaining a high absorption

## Field extension of real values of physical observables in classical theory can help attain quantum results. (arXiv:1612.02211v2 [quant-ph] UPDATED)

Physical quantities are assumed to take real values, which stems from the
fact that an usual measuring instrument that measures a physical observable
always yields a real number. Here we consider the question of what will happen
if physical observables are allowed to take complex values. In this paper, we
show that by allowing observables in the Bell inequality to take complex
values, a classical physical theory can actually get the same upper bound of

## Snow Queen is Evil and Beautiful: Experimental Evidence for Probabilistic Contextuality in Human Choices. (arXiv:1711.00418v8 [q-bio.NC] UPDATED)

We present unambiguous experimental evidence for (quantum-like) probabilistic
contextuality in psychology. All previous attempts to find contextuality in a
psychological experiment were unsuccessful because of the gross violations of
marginal selectivity in behavioral data, making the traditional mathematical
tests developed in quantum mechanics inapplicable. In our crowdsourcing
experiment respondents were making two simple choices: of one of two characters

## Enhanced communication with the assistance of indefinite causal order. (arXiv:1711.10165v2 [quant-ph] UPDATED)

In quantum Shannon theory, the way information is encoded and decoded takes
advantage of the laws of quantum mechanics, while the way communication
channels are interlinked is assumed to be classical. In this Letter we relax
the assumption that quantum channels are combined classically, showing that a
quantum communication network where quantum channels are combined in a
superposition of different orders can achieve tasks that are impossible in
conventional quantum Shannon theory. In particular, we show that two identical

## Probing microscopic models for system-bath interactions via parametric driving. (arXiv:1803.07785v1 [physics.atom-ph])

We show that strong parametric driving of a quantum harmonic oscillator
coupled to a thermal bath allows one to distinguish between different
microscopic models for the oscillator-bath coupling. We consider a bath with an
Ohmic spectral density and a model where the system-bath interaction can be
tuned continuously between position and momentum coupling via the coupling
angle $\alpha$. We derive a master equation for the reduced density operator of
the oscillator in Born-Markov approximation and investigate its quasi-steady

## Adiabatic elimination for multi-partite open quantum systems with non-trivial zero-order dynamics. (arXiv:1803.07810v1 [quant-ph])

We provide model reduction formulas for open quantum systems consisting of a
target component which weakly interacts with a strongly dissipative
environment. The time-scale separation between the uncoupled dynamics and the
interaction allows to employ tools from center manifold theory and geometric
singular perturbation theory to eliminate the variables associated to the
environment (adiabatic elimination) with high-order accuracy. An important
specificity is to preserve the quantum structure: reduced dynamics in

## Theory of barrier vs tilt exchange gate operations in spin-based quantum computing. (arXiv:1711.00595v2 [cond-mat.mes-hall] UPDATED)

We present a theory for understanding the exchange interaction between
electron spins in neighboring quantum dots, either by changing the detuning of
the two quantum dots or independently tuning the tunneling barrier between
quantum dots. The Hubbard model and a more realistic confining-potential model
are used to investigate how the tilting and barrier control affect the
effective exchange coupling and thus the gate fidelity in both the detuning and
symmetric regimes. We show that the exchange coupling is less sensitive to the