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Author(s): A. Messinger, B. G. Taketani, and F. K. Wilhelm

Quantum simulation is a promising field where a controllable system is used to mimic another system of interest, whose properties one wants to investigate. One of the key issues for such simulation is the ability to control the environment the system couples to, be it to isolate the system or to eng...

[Phys. Rev. A 99, 032325] Published Mon Mar 18, 2019

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Author(s): Geng Chai, Zhengwen Cao, Weiqi Liu, Shiyu Wang, Peng Huang, and Guihua Zeng

Atmospheric effects are the chief threats to the quantum properties of propagating quantum signals and may degrade the performance of quantum key distribution seriously. As one of the most important parts of continuous-variable quantum key distribution (CVQKD), a parameter estimation method has not ...

[Phys. Rev. A 99, 032326] Published Mon Mar 18, 2019

Author(s): Ying Guo, Wei Ye, Hai Zhong, and Qin Liao

The non-Gaussian operation can be used not only to enhance and distill the entanglement between Gaussian entangled states, but also to improve the performance of quantum communications. In this paper, we propose a non-Gaussian continuous-variable quantum key distribution (CVQKD) by using quantum cat...

[Phys. Rev. A 99, 032327] Published Mon Mar 18, 2019

Author(s): Patrick P. Potts

We introduce an experimental test for ruling out classical explanations for the statistics obtained when measuring arbitrary observables at arbitrary times using individual detectors. This test requires some trust in the measurements, represented by a few natural assumptions on the detectors. In qua...

[Phys. Rev. Lett. 122, 110401] Published Mon Mar 18, 2019

For a local Hamiltonian $H=\sum_i c_i A_i$, with $A_i$s being local

operators, it is known that $H$ could be encoded in a single (non-degenerate)

eigenstate $|\psi\rangle$ in certain cases. One case is that the system

satisfies the Eigenstate Thermalization Hypothesis (ETH), where the local

reduced density matrix asymptotically become equal to the thermal reduced

density matrix [PRX \textbf{8}, 021026 (2018)]. In this case, one can reproduce

$H$ (i.e. $c_i$s) from local measurement results

Quantum annealing devices have been subject to various analyses in order to

classify their usefulness for practical applications. While it has been

successfully proven that such systems can in general be used for solving

combinatorial optimization problems, they have not been used to solve chemistry

applications. In this paper we apply a mapping, put forward by Xia et al. (The

Journal of Physical Chemistry B 122.13 (2017): 3384-3395.), from a quantum

chemistry Hamiltonian to an Ising spin glass formulation and find the ground

We formulate a discretization of sigma models suitable for simulation by

quantum computers. Space is substituted by a lattice, as usually done in

lattice field theory, while the target space (a sphere) is replaced by the

"fuzzy sphere", a construction well known from non-commutative geometry.

Contrary to more naive discretizations of the sphere, in this construction the

exact $O(3)$ symmetry is maintained, which suggests that the discretized model

is in the same universality class as the continuum model. That would allow for

We introduce and study a class of models of free fermions hopping between

neighbouring sites with random Brownian amplitudes. These simple models

describe stochastic, diffusive, quantum, unitary dynamics. We focus on periodic

boundary conditions and derive the complete stationary distribution of the

system. It is proven that the generating function of the latter is provided by

the Harish-Chandra-Itzykson-Zuber integral which allows us to access all

fluctuations of the system state. The steady state is characterized by non

We study a one-dimensional translation-invariant Floquet quantum circuit

model constrained to conserve a $U(1)$ charge and its dipole moment. We

demonstrate that the Floquet spectrum contains quantum many-body scars, a small

set of localized states in an otherwise thermalizing spectrum. These states are

directly experimentally relevant due to their high overlap with easily-prepared

product states. Moreover, the model is quite generic, since the Floquet

We study the Bloch-Messiah reduction of parametric downconversion of light in

the pulsed regime with a nondegenerate phase matching providing generation of

twin beams. We find that in this case every squeezing eigenvalue has

multiplicity at least two. We discuss the problem of ambiguity in the

definition of the squeezing eigenmodes in this case and develop two approaches

to unique determination of the latter. First, we show that the modal functions

of the squeezing eigenmodes can be tailored from the Schmidt modes of the