Based on a generic quantum open system model, we study the geometric nature

of decoherence by defining a complex-valued geometric phase through stochastic

pure states describing non-unitary, non-cyclic and non-adiabatic evolutions.

The ensemble average of the complex geometric phases for the pure stochastic

states yields a conventional geometric phase together with an amplitude factor.

We show that the decoherence process described by the decaying amplitude can be

# All

We present a general approach to the classical dynamical systems simulation.

This approach is based on classical systems extension to quantum states. The

proposed theory can be applied to analysis of multiple (including

non-Hamiltonian) dissipative dynamical systems. As examples, we consider the

logistic model, the Van der Pol oscillator, dynamical systems of Lorenz,

R\"ossler (including R\"ossler hyperchaos) and Rabinovich-Fabrikant. Developed

methods and algorithms integrated in quantum simulators will allow us to solve

In this report we present a general approach for estimating quantum circuits

by means of measurements. We apply the developed general approach for

estimating the quality of superconducting and optical quantum chips. Using the

methods of quantum states and processes tomography developed in our previous

works, we have defined the adequate models of the states and processes under

consideration.

We present rigorous and intuitive master equation models to study on-demand

single photon sources from pulse-excited quantum dots coupled to cavities. We

consider three methods of source excitation: resonant pi-pulse, off-resonant

phonon-assisted inversion, and two-photon excitation of a biexciton-exciton

cascade, and investigate the effect of the pulse excitation process on the

quantum indistinguishability, efficiency, and purity of emitted photons. By

Emission and absorption of light lie at the heart of light-matter

interaction. Although the emission and absorption rates are regarded as

intrinsic properties of atoms and molecules, various ways to modify these rates

have been sought in critical applications such as quantum information

processing, metrology and light-energy harvesting. One of the promising

approaches is to utilize collective behavior of emitters as in superradiance.

Although superradiance has been observed in diverse systems, its conceptual

We study quantum anomaly detection with density estimation and multivariate

Gaussian distribution. Both algorithms are constructed using the standard

gate-based model of quantum computing. Compared with the corresponding

classical algorithms, the resource complexities of our quantum algorithm are

logarithmic in the dimensionality of quantum states and the number of training

quantum states. We also present a quantum procedure for efficiently estimating

the determinant of any Hermitian operators $\mathcal{A}\in\mathcal{R}^{N\times

We probe electric-field noise in a surface ion trap for ion-surface distances

$d$ between 50 and 300 $\mu\mathrm{m}$ in the normal and planar directions. We

find the noise distance dependence to scale as $d^{-2.6}$ in our trap and a

frequency dependence which is consistent with $1/f$ noise. Simulations of the

electric-field noise specific to our trap geometry provide evidence that we are

not limited by technical noise sources. Our distance scaling data is consistent

Generalising the concept of Bell nonlocality to networks leads to novel forms

of correlations, the characterization of which is however challenging. Here we

investigate constraints on correlations in networks under the two natural

assumptions of no-signaling and independence of the sources. We consider the

``triangle network'', and derive strong constraints on correlations even though

the parties receive no input, i.e. each party performs a fixed measurement. We

Scalable integration of bright emitters in quantum photonic structures is an

important step in the broader quest to generate and manipulate single photons

via compact solid-state devices. Unfortunately, implementations relying on

material platforms that also serve as the emitter host often suffer from a

trade-off between the desired emitter properties and the photonic system

practicality and performance. Here, we demonstrate 'pick and place' integration

We suggest a near deterministic compact model of a photonic CNOT gate based

on a quantum dot trapped in a double sided optical microcavity and a universal

cloner. Our design surpasses the cloner optimal limit of 5/6 and we show that

it provides fidelity around 91 % in the weak coupling regime.