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Author(s): Jiangwei Shang, Ali Asadian, Huangjun Zhu, and Otfried Gühne

The challenges of entanglement detection lead to the development of several entanglement measures and criteria. Here a special type of measurement is used to attest entanglement in a stronger way, i.e. it catches forms that are missed by other criteria and is effective in a single-shot fashion.

[Phys. Rev. A 98, 022309] Published Fri Aug 10, 2018

Author(s): Laszlo Gyongyosi and Sandor Imre

Quantum repeater networks are a fundamental of any future quantum internet and long-distance quantum communications. The entangled quantum nodes can communicate through several different levels of entanglement, leading to a heterogeneous, multilevel network structure. The level of entanglement betwe...

[Phys. Rev. A 98, 022310] Published Fri Aug 10, 2018

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Author(s): Suchetana Goswami, Bihalan Bhattacharya, Debarshi Das, Souradeep Sasmal, C. Jebaratnam, and A. S. Majumdar

We consider the problem of one-sided device-independent self-testing of any pure entangled two-qubit state based on steering inequalities which certify the presence of quantum steering. In particular, we note that in the 2-2-2 steering scenario (involving two parties, two measurement settings per pa...

[Phys. Rev. A 98, 022311] Published Fri Aug 10, 2018

The quantum simulation of quantum chemistry is a promising application of

quantum computers. However, for N molecular orbitals, the $\mathcal{O}(N^4)$

gate complexity of performing Hamiltonian and unitary Coupled Cluster Trotter

steps makes simulation based on such primitives challenging. We substantially

reduce the gate complexity of such primitives through a two-step low-rank

factorization of the Hamiltonian and cluster operator, accompanied by

truncation of small terms. Using truncations that incur errors below chemical

We consider circuit complexity in certain interacting scalar quantum field

theories, mainly focusing on the $\phi^4$ theory. We work out the circuit

complexity for evolving from a nearly Gaussian unentangled reference state to

the entangled ground state of the theory. Our approach uses Nielsen's geometric

method, which translates into working out the geodesic equation arising from a

certain cost functional. We present a general method, making use of integral

We study the eigenstates of quantum systems with large Hilbert spaces, via

their distribution of wavefunction amplitudes in a real-space basis. For

single-particle 'quantum billiards', these real-space amplitudes are known to

have Gaussian distribution for chaotic systems. In this work, we formulate and

address the corresponding question for many-body lattice quantum systems. For

integrable many-body systems, we examine the deviation from Gaussianity and

provide evidence that the distribution generically tends toward power-law

Using the Wigner approach, we propose an inequality to test the macroscopic

realism concept. The proposed inequality is first derived for three distinct

moments of time and then for $n$ distinct moments of time. Using the latter one

we show that any unitary evolution of a quantum system contradicts the concept

of macroscopic realism. We also obtain an inequality for testing of the

hypothesis of realism. It is shown that this inequality is not identical to the

Wigner inequality.

We propose the use of a waveguide-like transmission line based on

direct-current superconducting quantum interference devices (dc-SQUID) and

study the sine-Gordon (SG) equation which characterises the dynamical behavior

of the superconducting phase in this transmission line. Guided by the duality

between black holes in Jackiw-Teitelboim (JT) dilaton gravity and solitons in

sine-Gordon field theory, we show how to, in our setup, realize 1 + 1

dimensional black holes as solitons of the sine-Gordon equation. We also study

We investigate a topological superconducting wire with balanced gain and loss

that is effectively described by the non-Hermitian Kitaev/Majorana chain with

parity-time symmetry. This system is shown to possess two distinct types of

unconventional edge modes, those with complex energies and nonorthogonal

Majorana zero modes. The latter edge modes cause nonlocal particle transport

with currents that are localized at the edges and absent in the bulk. This

anomalous particle transport results from the interplay between parity-time

We study some desirable properties of recently introduced measures of quantum

correlations based on the amount of non-commutativity quantified by the

Hilbert-Schmidt norm (Sci Rep 6:25241, 2016, and Quantum Inf. Process. 16:226,

2017). Specifically, we show that: 1) for any bipartite ($A+B$) state, the

measures of quantum correlations with respect to subsystem $A$ are

non-increasing under any Local Commutative Preserving Operation on subsystem

$A$, and 2) for Bell diagonal states, the measures are non-increasing under