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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

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

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

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

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

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

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

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

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

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