The efficient quantum state reconstruction algorithm described in [P. Six et

al., Phys. Rev. A 93, 012109 (2016)] is experimentally implemented on the

non-local state of two microwave cavities entangled by a circular Rydberg atom.

We use information provided by long sequences of measurements performed by

resonant and dispersive probe atoms over time scales involving the system

decoherence. Moreover, we benefit from the consolidation, in the same

reconstruction, of different measurement protocols providing complementary

# All

Demonstrating a quantum computational speedup is a crucial milestone for

near-term quantum technology. Recently, quantum simulation architectures have

been proposed that have the potential to show such a quantum advantage, based

on commonly made assumptions. The key challenge in the theoretical analysis of

this scheme - as of other comparable schemes such as boson sampling - is to

lessen the assumptions and close the theoretical loopholes, replacing them by

Stimulated emission and absorption are two fundamental processes of

light-matter interaction, and the coefficients of the two processes should be

equal in general. However, we will describe a generic method to realize

significant difference between the stimulated emission and absorption

coefficients of two nondegenerate energy levels, which we refer to as

nonreciprocal transition. As a simple implementation, a cyclic three-level atom

system, comprising two nondegenerate energy levels and one auxiliary energy

The study of memory effects in quantum channels helps in developing

characterization methods for open quantum systems and strategies for quantum

error correction. Two main sets of channels exist, corresponding to system

dynamics with no memory (Markovian) and with memory (non-Markovian).

Interestingly, these sets have a non-convex geometry, allowing one to form a

channel with memory from the addition of memoryless channels and vice-versa.

Here, we experimentally investigate this non-convexity in a photonic setup by

Arrays of atoms trapped in optical tweezers combine features of programmable

analog quantum simulators with atomic quantum sensors. Here we propose

variational quantum algorithms, tailored for tweezer arrays as programmable

quantum sensors, capable of generating entangled states on-demand for precision

metrology. The scheme is designed to generate metrological enhancement by

optimizing it in a feedback loop on the quantum device itself, thus preparing

the best entangled states given the available quantum resources. We apply our

We present a method to map the evolution of photonic random walks that is

compatible with nonclassical input light. Our approach leverages a newly

developed flexible waveguide platform to tune the jumping rate between spatial

modes, allowing the observation of a range of evolution times in a chip of

fixed length. In a proof-of-principle demonstration we reconstruct the

evolution of photons through a uniform array of coupled waveguides by

monitoring the end-face alone. This approach enables direct observation of mode

We derive some entanglement properties of the ground states of two classes of

quantum spin chains described by the Fredkin model, for half-integer spins, and

the Motzkin model, for integer ones. Since the ground states of the two models

are known analytically, we can calculate the entanglement entropy, the

negativity and the quantum mutual information exactly. We show, in particular,

that these systems exhibit long-distance entanglement, namely two disjoint

Normal mode dynamics are ubiquitous underlying the motions of diverse systems

from rotating stars to crystal structures. These behaviors are composed of

simple collective motions of particles which move with the same frequency and

phase, thus encapsulating many-body effects into simple dynamic motions. In

regimes such as the unitary regime for ultracold Fermi gases, a single

collective mode can dominate, leading to simple behavior as seen in

superfluidity. I investigate the evolution of collective motion as a function

We study spin-dipole oscillations of a binary fermionic mixture at nonzero

temperatures. We apply the atomic-orbital method combined with the Monte Carlo

technique based sampling to probe finite temperatures. Our results agree

quantitatively with recent experiment, G. Valtolina et al., Nat. Phys. 13, 704

(2017), showing the appearance of the ferromagnetic phase at stronger repulsion

between components when the temperature is increased.

Recently, it has been demonstrated that asymptotic states of open quantum

system can undergo qualitative changes resembling pitchfork, saddle-node, and

period doubling classical bifurcations. Here, making use of the periodically

modulated open quantum dimer model, we report and investigate a quantum

Neimark-Sacker bifurcation. Its classical counterpart is the birth of a torus

(an invariant curve in the Poincar\'{e} section) due to instability of a limit

cycle (fixed point of the Poincar\'{e} map). The quantum system exhibits a