Many-body localization is shown to suppress imaginary parts of complex

eigenenergies for general non-Hermitian Hamiltonians having time-reversal

symmetry. We demonstrate that a real-complex transition, which we conjecture

occurs upon many-body localization, profoundly affects the dynamical stability

of non-Hermitian interacting systems with asymmetric hopping that respect

time-reversal symmetry. Moreover, the real-complex transition is shown to be

absent in non-Hermitian many-body systems with gain and/or loss that breaks

# All

The theory of quantum thermodynamics investigates how the concepts of heat,

work, and temperature can be carried over to the quantum realm, where

fluctuations and randomness are fundamentally unavoidable. Of particular

practical relevance is the investigation of quantum thermal machines: Machines

that use the flow of heat in order to perform some useful task. In this

lectures series, we give a brief introduction into how the laws of

thermodynamics arise from quantum theory and how thermal machines can be

Suppressing undesired nonunitary effects is a major challenge in quantum

computation and quantum control. In this work, by considering the adiabatic

dynamics in presence of a surrounding environment, we theoretically and

experimentally analyze the robustness of adiabaticity in open quantum systems.

More specifically, by considering a decohering scenario, we exploit the

validity conditions of the adiabatic approximation as well as its sensitiveness

to the resonance situation, which typically harm adiabaticity in closed

We cast diffraction-based interferometry in the framework of post-selected

unitary description towards enabling it as a platform for quantum information

processing. We express slit-diffraction as an infinite-dimensional

transformation and truncate it to a finite-dimensional transfer matrix by

post-selecting modes. Using such a framework with classical fields, a

customized double-slit setup is effectively a lossy beam splitter in a

post-selected sense. Diffraction optics provides a robust alternative to

Alkali-metal-vapor magnetometers, using coherent precession of polarized

atomic spins for magnetic field measurement, have become one of the most

sensitive magnetic field detectors. Their application areas range from

practical uses such as detections of NMR signals to fundamental physics

research such as searches for permanent electric dipole moments. One of the

main noise sources of atomic magnetometers comes from the light shift that

depends on the frequency of the pump laser. In this work, we theoretically

We derive an equation for the time evolution of the natural occupation

numbers for fermionic systems with more than two electrons. The evolution of

such numbers is connected with the symmetry-adapted generalized Pauli exclusion

principle, as well as with the evolution of the natural orbitals and a set of

many-body relative phases. We then relate the evolution of these phases to a

geometrical and a dynamical term, attached to each one of the Slater

determinants appearing in the configuration-interaction expansion of the wave

Bell's theorem implies that any completion of quantum mechanics which uses

hidden variables (that is, preexisting values of all observables) must be

nonlocal in the Einstein sense. This customarily indicates that knowledge of

the hidden variables would permit superluminal communication. Such superluminal

signaling, akin to the existence of a preferred reference frame, is to be

expected. However, here we provide a protocol that allows an observer with

knowledge of the hidden variables to communicate with her own causal past,

Topological edge states arise in parity-time ($\mathcal{PT}$)-symmetric

non-unitary quantum dynamics but have so far only been discussed in the

$\mathcal{PT}$-symmetry-unbroken regime. Here we report the experimental

detection of robust topological edge states in one-dimensional photonic quantum

walks with spontaneously broken $\mathcal{PT}$ symmetry, thus establishing the

existence of topological phenomena therein. We theoretically prove and

experimentally confirm that the global Berry phase in non-unitary quantum-walk

Motivated by recent developments in the realm of matter waves, we explore the

potential of creating solitary waves on the surface of a torus. This is an

intriguing perspective due to the role of curvature in the shape and dynamics

of the coherent structures. We find different families of bright solitary waves

for attractive nonlinearities including ones localized in both angular

directions, as well as waves localized in one direction and homogeneous in the

other. The waves localized in both angular directions have also been

We quantitatively assess the energetic cost of several well-known control

protocols that achieve a finite time adiabatic dynamics, namely counterdiabatic

and local counterdiabatic driving, optimal control, and inverse engineering. By

employing a cost measure based on the norm of the total driving Hamiltonian, we

show that a hierarchy of costs emerges that is dependent on the protocol

duration. As case studies we explore the Landau-Zener model, the quantum

harmonic oscillator, and the Jaynes-Cummings model and establish that