We investigate the entanglement measures of tripartite W-State and GHZ-state

in noninertial frame through the coordinate transformation between Minkowski

and Rindler. First it is shown that all three qubits undergo in a uniform

acceleration $a$ of W-State, we find that the one-tangle, two-tangle, and

$\pi$-tangle decrease when the acceleration parameter $r$ increases, and the

two-tangle cannot arrive to infinity of the acceleration. Next we show that the

# All

Much of modern metrology and communication technology encodes information in

electromagnetic waves, typically as an amplitude or phase. While current

hardware can perform near-ideal measurements of photon number or field

amplitude, to date no device exists that can even in principle perform an ideal

phase measurement. In this work, we implement a single-shot canonical phase

measurement on a one-photon wave packet, which surpasses the current standard

of heterodyne detection and is optimal for single-shot phase estimation. By

We analyze the dynamics of multiparticle discrete-time quantum walk on the

two-dimensional lattice, with an interaction inspired on a classical model for

gas collision, called HPP model. In this classical model, the direction of

motion changes only when the particles collide head-on, preserving momentum and

energy. In our quantum model, the dynamics is driven by the usual quantum-walk

evolution operator if the particles are on different nodes, and is driven by

Quantum annealing is a heuristic algorithm for solving combinatorial

optimization problems, and D-Wave Systems Inc. has developed hardware for

implementing this algorithm. The current version of the D-Wave quantum annealer

can solve unconstrained binary optimization problems with a limited number of

binary variables, although cost functions of many practical problems are

defined by a large number of integer variables. To solve these problems with

the quantum annealer, the integer variables are generally binarized with

We theoretically analyze the performance of the nuclear magnetic resonance

(NMR) spectroscopy with a superconducting flux qubit (FQ). Such NMR with the FQ

is attractive because of the possibility to detect the relatively small number

of nuclear spins in a local region ($\sim\mu$m) with low temperatures ($\sim$

mK) and low magnetic fields ($\sim$ mT), in which other types of quantum

sensing schemes cannot easily access. A sample containing nuclear spins is

We present a novel continuous-time control strategy to exponentially

stabilize an eigenstate of a Quantum Non-Demolition (QND) measurement operator.

In open-loop, the system converges to a random eigenstate of the measurement

operator. The role of the feedback is to prepare a prescribed QND eigenstate

with unit probability. To achieve this we introduce the use of Brownian motion

to drive the unitary control actions; the feedback loop just adapts the

amplitude of this Brownian noise input as a function of the system state.

Entanglement is a fundamental resource for quantum information science.

However, bipartite entanglement is destroyed when one particle is sharply

measured, which occurs in most applications. Here we experimentally show that,

if instead of sharp measurements, one performs many sequential unsharp

measurements on one particle which are suitably chosen depending on the

previous outcomes, then entanglement is preserved and can reveal quantum

correlations through measurements on the second particle. Specifically, we

We study the subradiant collective states of a periodic chain of two-level

atoms with either transversal or longitudinal transition dipole moments with

respect to the chain axis. We show that long-lived subradiant states can be

obtained for the transversal polarization by properly choosing the chain period

for a given number of atoms in the case of no open diffraction channels. These

highly subradiant states have a linewidth that decreases with the number of

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

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