Hybrid interfaces between distinct quantum systems play a major role in the

implementation of quantum networks. Quantum states have to be stored in

memories to synchronize the photon arrival times for entanglement swapping by

projective measurements in quantum repeaters or for entanglement purification.

Here, we analyze the distortion of a single photon wave packet propagating

through a dispersive and absorptive medium with high spectral resolution.

Single photons are generated from a single In(Ga)As quantum dot with its

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We consider a general model, describing a quantum impurity with degenerate

energy levels, interacting with a gas of itinerant electrons, derive the

scaling equation and analyse the connection between its explicit form and the

symmetry of interaction. On the basis of this analysis we write down explicitly

the scaling equation for the interaction acting on $su(3)$ Lie algebra and

having either $SU(2)\times U(1)$, or $SU(2)$ symmetry.

We design a series of quantum circuits that generate absolute maximally

entangled (AME) states to benchmark a quantum computer. A relation between

graph states and AME states can be exploited to optimize the structure of the

circuits and minimize their depth. Furthermore, we find that most of the

provided circuits obey majorization relations for every partition of the

system, and at every step of the quantum computation. The rational for our

approach is to benchmark quantum computers with maximal useful entanglement,

We look into the possibility of entanglement generation in a

parity(P)-time(T)-symmetric framework and demonstrate the non-violation of

non-signalling principle for the case of bipartite systems when at least one is

guided by PT-symmetric quantum mechanics. Our analysis is based on the use of

the CPT-inner product to construct the reduced density operators both before

and after the action of time evolution operator.

We theoretically investigate the possibility of performing high precision

estimation of an externally imposed acceleration using scalar bosons in a

single-well trap. We work at the level of a two-mode truncation, valid for weak

to intermediate two-body interaction couplings.The splitting process into two

modes is in our model entirely caused by the interaction between the

constituent bosons and is hence neither due to an externally imposed

double-well potential nor due to populating a spinor degree of freedom. The

We study the quasiparticle excitation and quench dynamics of the

one-dimensional transverse-field Ising model with power-law ($1/r^{\alpha}$)

interactions. We find that long-range interactions give rise to a confining

potential, which couples pairs of domain walls (kinks) into bound

quasiparticles, analogous to mesonic bound states in high-energy physics. We

show that these quasiparticles have signatures in the dynamics of order

parameters following a global quench and the Fourier spectrum of these order

Quantum memories for light are important components for future long distance

quantum networks. We present on-chip quantum storage of telecommunications band

light at the single photon level in an ensemble of erbium-167 ions in an

yttrium orthosilicate photonic crystal nanobeam resonator. Storage times of up

to 10 $\mu$s are demonstrated using an all-optical atomic frequency comb

protocol in a dilution refrigerator under a magnetic field of 380 mT. We show

this quantum storage platform to have high bandwidth, high fidelity, and

We realize the dynamical 1D spin-orbit-coupling (SOC) of a Bose-Einstein

condensate confined within an optical cavity. The SOC emerges through

spin-correlated momentum impulses delivered to the atoms via Raman transitions.

These are effected by classical pump fields acting in concert with the quantum

dynamical cavity field. Above a critical pump power, the Raman coupling emerges

as the atoms superradiantly populate the cavity mode with photons.

Concomitantly, these photons cause a back-action onto the atoms, forcing them

Topological pumping of edge states in finite crystals or quasicrystals with

non-trivial topological phases provides a powerful means for robust excitation

transfer. In most schemes of topological pumping, the edge states become

delocalized and immersed into the continuum during the adiabatic cycle,

requiring extremely slow evolution to avoid nonadiabatic effects. Here a scheme

of topological pumping based on adiabatic passage of edge and interface states

is proposed, which is more robust against nonadiabatic effects and avoids

In the original round-robin differential-phase-shift (RRDPS) quantum key

distribution and its improved method, the photon-number-resolving detectors are

must for the security. We present a RRDPS protocol with yes-no detectors only.

We get the upper bounds of mutual information of Alice and Eve, and Bob and

Eve, and the formula of key rate. Our main idea is to divide all counts into

two classes, the counts due to the odd number photons of incident detectors and