# All

## How to detect qubit-environment entanglement generated during qubit dephasing

Author(s): Katarzyna Roszak, Damian Kwiatkowski, and Łukasz Cywiński
We propose a straightforward experimental protocol to test whether qubit-environment entanglement is generated during pure dephasing of a qubit. The protocol is implemented using only measurements and operations on the qubit—it does not involve the measurement of the system-environment state of inte...
[Phys. Rev. A 100, 022318] Published Fri Aug 16, 2019

## Critical Behavior and Fractality in Shallow One-Dimensional Quasiperiodic Potentials

Author(s): Hepeng Yao, Hakim Khoudli, Léa Bresque, and Laurent Sanchez-Palencia
Quasiperiodic systems offer an appealing intermediate between long-range ordered and genuine disordered systems, with unusual critical properties. One-dimensional models that break the so-called self-dual symmetry usually display a mobility edge, similarly as truly disordered systems in a dimension ...
[Phys. Rev. Lett. 123, 070405] Published Fri Aug 16, 2019

## Semiquantum key distribution with high quantum noise tolerance

Author(s): Omar Amer and Walter O. Krawec
Semiquantum key distribution protocols are designed to allow two parties to establish a shared secret key, secure against an all-powerful adversary, even when one of the users is restricted to measuring and preparing quantum states in one single basis. While interesting from a theoretical standpoint...
[Phys. Rev. A 100, 022319] Published Fri Aug 16, 2019

## Deterministic transformations of three-qubit entangled pure states

Author(s): Gökhan Torun and Ali Yildiz
The states of three-qubit systems split into two inequivalent types of genuine tripartite entanglement, namely, the Greenberger-Horne-Zeilinger (GHZ) type and the $W$ type. A state belonging to one of these classes can be stochastically transformed only into a state within the same class by local op...
[Phys. Rev. A 100, 022320] Published Fri Aug 16, 2019

## How to observe and quantify quantum-discord states via correlations

Author(s): Matthew A. Hunt, Igor V. Lerner, Igor V. Yurkevich, and Yuval Gefen
Quantum correlations between parts of a composite system most clearly reveal themselves through entanglement. Designing, maintaining, and controlling entangled systems is very demanding, which raises the stakes for understanding the efficacy of entanglement-free, yet quantum correlations, exemplifie...
[Phys. Rev. A 100, 022321] Published Fri Aug 16, 2019

## Orbital-Angular-Momentum Multiplexed Continuous-Variable Entanglement from Four-Wave Mixing in Hot Atomic Vapor

Author(s): Xiaozhou Pan, Sheng Yu, Yanfen Zhou, Kun Zhang, Kai Zhang, Shuchao Lv, Sijin Li, Wei Wang, and Jietai Jing
Multiplexing is crucial for the data-carrying capacity of information communication systems. Orbital angular momentum (OAM) with a topological charge $ℓ$ ($ℓ$ integer) provides a degree of freedom to realize multiplexing. In this Letter, we report an experimental implementation of OAM multiplexed co...
[Phys. Rev. Lett. 123, 070506] Published Fri Aug 16, 2019

## Towards Low Overhead Magic State Distillation

Author(s): Anirudh Krishna and Jean-Pierre Tillich
Magic-state distillation is a resource intensive subroutine for quantum computation. The ratio of noisy input states to output states with an error rate at most $ε$ scales as $O\mathbf{(}{\mathrm{log}}^{γ}(1/ε)\mathbf{)}$ [S. Bravyi and J. Haah, Magic-state distillation with low overhead, Phys. Rev....
[Phys. Rev. Lett. 123, 070507] Published Fri Aug 16, 2019

## Three-Photon Discrete-Energy-Entangled $W$ State in an Optical Fiber

Author(s): B. Fang, M. Menotti, M. Liscidini, J. E. Sipe, and V. O. Lorenz
We experimentally demonstrate the generation of a three-photon discrete-energy-entangled $W$ state using multiphoton-pair generation by spontaneous four-wave mixing in an optical fiber. We show that, by making use of prior information on the photon source, we can verify the state produced by this so...
[Phys. Rev. Lett. 123, 070508] Published Fri Aug 16, 2019

## Critical look at the time-energy uncertainty relations. (arXiv:1908.05273v1 [quant-ph])

The Heisenberg and Mandelstam-Tamm time-energy uncertainty relations are
analyzed. The conlusion resulting from this analysis is that within the Quantum
Mechanics of Schr\"{o}dinger and von Neumann, the status of these relations can
not be considered as the same as the status of the position-momentum
uncertainty relations, which are rigorous. The conclusion is that the
time--energy uncertainty relations can not be considered as universally valid.

## Entanglement distance for an arbitrary state of M qubits. (arXiv:1908.03117v2 [quant-ph] UPDATED)

We propose a measure of entanglement that can be computed for any pure state
of an $M$-qubit system. The entanglement measure has the form of a distance
that we derive from an adapted application of the Fubini-Study metric. This
measure is invariant under local unitary transformations and defined as trace
of a suitable metric that we derive, the entanglement metric $\tilde{g}$.
Furthermore, the analysis of the eigenvalues of $\tilde{g}$ gives information
about the robustness of entanglement.