Superconducting quantum circuits are potential candidates to realize a
large-scale quantum computer. The envisioned large density of integrated
components, however, requires a proper thermal management and control of
dissipation. To this end, it is advantageous to utilize tunable dissipation
channels and to exploit the optimized heat flow at exceptional points (EPs).
Here, we experimentally realize an EP in a superconducting microwave circuit
consisting of two resonators. The EP is a singularity point of the Hamiltonian,

The advantages of quantum information processing are in many cases obtained
as consequences of quantum interactions, especially for computational tasks
where two-qubit interactions are essential. In this work, we establish the
framework of analyzing and quantifying loss or gain of information on a quantum
system when the system interacts with its environment. We show that the
information flow, the theoretical method of characterizing (non-)Markovianity
of quantum dynamics, corresponds to the rate of the minimum uncertainty about

Author(s): Armin Tavakoli, Jędrzej Kaniewski, Tamás Vértesi, Denis Rosset, and Nicolas Brunner
The goal of self-testing is to characterize an a priori unknown quantum system based solely on measurement statistics, i.e., using an uncharacterized measurement device. Here we develop self-testing methods for quantum prepare-and-measure experiments, thus not necessarily relying on entanglement and...
[Phys. Rev. A 98, 062307] Published Thu Dec 06, 2018

Author(s): Tan Li, Wan-Su Bao, He-Liang Huang, Feng-Guang Li, Xiang-Qun Fu, Shuo Zhang, Chu Guo, Yu-Tao Du, Xiang Wang, and Jie Lin
Grover's algorithm achieves a quadratic speedup over classical algorithms, but it is considered necessary to know the value of $λ$ exactly [Phys. Rev. Lett. 95, 150501 (2005); Phys. Rev. Lett. 113, 210501 (2014)], where $λ$ is the fraction of target items in the database. In this paper, we find out ...

Author(s): A. Ramezanpour
The standard quantum annealing algorithm tries to approach the ground state of a classical system by slowly decreasing the hopping rates of a quantum random walk in the configuration space of the problem, where the on-site energies are provided by the classical energy function. In a quantum reinforc...
[Phys. Rev. A 98, 062309] Published Thu Dec 06, 2018

Author(s): Mikołaj Lasota and Piotr Kolenderski
Implementations of many quantum communication protocols require sources of photon pairs. However, optimization of the properties of these photons for specific applications is an open problem. We theoretically demonstrate the possibility of extending the maximal distance of secure quantum communicati...
[Phys. Rev. A 98, 062310] Published Thu Dec 06, 2018

Spectral statistics of quantum systems have been studied in detail using the nearest neighbour level
spacings, which for generic chaotic systems follows random matrix theory predictions. In this work,
the probability density of the ##IMG##
[] and ##IMG##

Author(s): Mao-Sheng Li and Yan-Ling Wang
Recently, Modi et al. [Phys. Rev. Lett. 120, 230501 (2018)] found that masking quantum information is impossible in a bipartite scenario. This adds another item to the no-go theorems. In this paper, we present some schemes different from error correction codes, which show that quantum states can be ...
[Phys. Rev. A 98, 062306] Published Wed Dec 05, 2018

Author(s): Mikołaj Czechlewski, Debashis Saha, Armin Tavakoli, and Marcin Pawłowski
Device-independent dimension witnesses (DWs) are a remarkable way to test the dimension of a quantum system in a prepare-and-measure scenario imposing minimal assumptions on the internal features of the devices. However, as the dimension increases, the major obstacle in the realization of DWs arises...
[Phys. Rev. A 98, 062305] Published Tue Dec 04, 2018