# All

Banaszek, W\'odkiewicz and others

(\cite{Banaszek},\cite{Chen},\cite{Chen-Zhang}) made the surprising discovery

that Einstein-Bell locality inequalities can be violated by the two mode

squeezed vacuum by a factor $\sqrt{2}$, in spite of the fact that the state has

a positive Wigner function. I use here the more general Gleason-Kochen-Specker

assumption of non-contextuality \cite{Gleason} to express classicality. I then

derive non-contextuality Bell inequalities for correlations of $N$ pseudo spins

We investigate the performance of error mitigation via measurement of

conserved symmetries on near-term devices. We present two protocols to measure

conserved symmetries during the bulk of an experiment, and develop a zero-cost

post-processing protocol which is equivalent to a variant of the quantum

subspace expansion. We develop methods for inserting global and local symetries

into quantum algorithms, and for adjusting natural symmetries of the problem to

We investigate the relation between a refined version of Leggett and Garg

conditions for macrorealism, namely the no-signaling-in-time (NSIT) conditions,

and the quantum mechanical notion of nondisturbance, and obtain a compatibility

relation among an arbitrary number of observables based on their minimally

disturbing sequential implementation. We show that all NSIT conditions are

satisfied for any state preparation if and only if simple compatibility

criteria on the state-update rules relative to the observables, i.e. quantum

Topological phases in spinless non-Hermitian models have been widely studied

both theoretically and experimentally in some artificial materials using

photonics and photonics. In this work, we investigate the interplay between

non-Hermitian loss and gain and non-Abelian gauge potential realized in a

two-component superconducting circuit. In our model, the non-Hermiticity along

only gives rise to trivial gain and loss to the states; while the non-Abelian

gauge along gives rise to flying butterfly spectra and associated edge modes,

Integrated photonics is an attractive platform for generating photonic

quantum states with high brightness, high stability and scalability. Many

schemes for generating photon pairs in an on-chip setting produce photons at

different frequencies and therefore the photons are distinguishable, which

limits their further use in many quantum information applications. Here, we use

the `dual-pump' technique and a silicon nanophotonic waveguide to produce

frequency-degenerate multi-photon quantum states. Two-photon and four-photon

We develop a general theoretical framework for measurement protocols

employing statistical correlations of randomized measurements. We focus on

locally randomized measurements implemented with local random unitaries in

quantum lattice models. In particular, we discuss the theoretical details

underlying the recent measurement of the second R\'{e}nyi entropy of highly

mixed quantum states consisting of up to $10$ qubits in a trapped-ion quantum

We systematically report a rigorous theory of the inverse scattering

transforms (ISTs) for the derivative nonlinear Schrodinger (DNLS) equation with

both zero boundary condition (ZBC)/non-zero boundary conditions (NZBCs) at

infinity and double poles of analytical scattering coefficients. The scattering

theories for both ZBC and NZBCs are addressed. The direct problem establishes

the analyticity, symmetries and asymptotic behavior of the Jost solutions and

Among certification techniques, those based on the violation of Bell

inequalities are appealing because they do not require assumptions on the

underlying Hilbert space dimension and on the accuracy of calibration methods.

Such device-independent techniques have been proposed to certify the quality of

entangled states, unitary operations, projective measurements following von

Neumann's model, and rank-one positive-operator-valued measures (POVM). Here,

we show that they can be extended to the characterization of generalized

We realize a potential platform for an efficient spin-photon interface namely

negatively-charged silicon-vacancy centers in a diamond membrane coupled to the

mode of a fully-tunable, fiber-based, optical resonator. We demonstrate that

introducing the thin ($\sim 200 \, \text{nm}$), single crystal diamond membrane

into the mode of the resonator does not change the cavity properties, which is

one of the crucial points for an efficient spin-photon interface. In

By means of studying the evolution equation for the Wigner distributions of

quantum dissipative systems we derive the quantum corrections to the classical

Liouville dynamics, taking into account the standard quantum friction model.

The resulting evolution turns out to be the classical one plus fluctuations

that depend not only on the $\hbar$ size but also on the momentum and the

dissipation parameter (i.e. the coupling with the environment). On the other

hand, we extend our studies of a paradigmatic system based on the kicked