We address continuous-time quantum walks on graphs, and discuss whether and how quantum-limited
measurements on the walker may extract information on the tunnelling amplitude between the nodes of
the graphs. For a few remarkable families of graphs, we evaluate the ultimate quantum bound to
precision, i.e. we compute the quantum Fisher information (QFI), and assess the performances of
incomplete measurements, i.e. measurements performed on a subset of the graph’s nodes. We also

We propose a quadratic unconstrained binary optimization (QUBO) formulation
of rectified linear unit (ReLU) type functions. Different from the q-loss
function proposed by Denchev et al. (2012), a simple discussion based on the
Legendre duality is not sufficient to obtain the QUBO formulation of the
ReLU-type functions. In addition to the Legendre duality, we employ the Wolfe
duality, and the QUBO formulation of the ReLU-type is derived. The QUBO
formulation is available in Ising-type annealing methods, including quantum

Author(s): Yan-Ling Wang, Mao-Sheng Li, and Zong-Xing Xiong
In this paper, we study the distinguishability of arbitrary dimensional generalized Bell states under one-way local operations and classical communication (LOCC). We introduce an admissible solutions set and a nonadmissible solutions set for each set of generalized Bell states. Any element that exis...
[Phys. Rev. A 99, 022307] Published Fri Feb 08, 2019

Author(s): Mark Steudtner and Stephanie Wehner
Quantum simulation of fermionic systems is a promising application of quantum computers, but to program them, we need to map fermionic states and operators to qubit states and quantum gates. While quantum processors may be built as two-dimensional qubit networks with couplings between nearest neighb...
[Phys. Rev. A 99, 022308] Published Fri Feb 08, 2019

Author(s): A. Rutkowski, M. Banacki, and M. Marciniak
For multipartite states, we consider a notion of $D$ symmetry. For a system of $N$ qubits, it coincides with the usual permutational symmetry. In the case of $N$ qudits ($d≥3$), the $D$ symmetry is stronger than the permutational one. For the space of all $\mathrm{D}$-symmetric vectors in ${({\mathb...
[Phys. Rev. A 99, 022309] Published Fri Feb 08, 2019

Author(s): Fatemeh Mostafavi, Luqi Yuan, and Hamidreza Ramezani
We introduce a class of non-Hermitian Hamiltonians that offers a dynamical approach to a shortcut to adiabaticity (DASA). In particular, in our proposed $2×2$ Hamiltonians, one eigenvalue is absolutely real and the other one is complex. This specific form of eigenvalues helps us to exponentially dec...
[Phys. Rev. Lett. 122, 050404] Published Fri Feb 08, 2019

Author(s): Christine Maier, Tiff Brydges, Petar Jurcevic, Nils Trautmann, Cornelius Hempel, Ben P. Lanyon, Philipp Hauke, Rainer Blatt, and Christian F. Roos
The way in which energy is transported through an interacting system governs fundamental properties in nature such as thermal and electric conductivity or phase changes. Remarkably, environmental noise can enhance the transport, an effect known as environment-assisted quantum transport (ENAQT). In t...
[Phys. Rev. Lett. 122, 050501] Published Fri Feb 08, 2019

Author(s): Gesualdo Delfino, Walter Selke, and Alessio Squarcini
We study the spontaneously broken phase of the $XY$ model in three dimensions, with boundary conditions enforcing the presence of a vortex line. Comparing Monte Carlo and field-theoretic determinations of the magnetization and energy density profiles, we numerically determine the mass of the vortex ...
[Phys. Rev. Lett. 122, 050602] Published Fri Feb 08, 2019

The second order correlation function is traditionally used to characterize
the photon statistics and to distinguish between classical and quantum states
of light. In this article we study a simple setup offering the possibility to
generate strong anti-bunched light. This is achieved by mixing on a beam
splitter a coherent state with a state with a non-negative Wigner function,
such as squeezed states or weak Schr\"odinger cat states. We elucidate the
interference mechanism generating such strong antibunching and relate it to

The weak equivalence principle (WEP) in the quantum regime has been the
subject of many studies with a broad range of approach to the problem. Here we
tackle the problem anew through the time of arrival (TOA) operator approach by
constructing the time of arrival operator for a non-relativistic and
structureless particle that is projected upward in a uniform gravitational
field with an intended arrival point below the classical turning point. The
TOA-operator is constructed under the constraint that the inertial and