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Author(s): Dominic J. Williamson, Arpit Dua, and Meng Cheng
We demonstrate that linear combinations of subregion entropies with canceling boundary terms, commonly used to calculate the topological entanglement entropy, may suffer from spurious nontopological contributions even in models with zero correlation length. These spurious contributions are due to a ...
[Phys. Rev. Lett. 122, 140506] Published Fri Apr 12, 2019

Author(s): Daochen Wang, Oscar Higgott, and Stephen Brierley
The problem of finding the ground state energy of a Hamiltonian using a quantum computer is currently solved using either the quantum phase estimation (QPE) or variational quantum eigensolver (VQE) algorithms. For precision $ε$, QPE requires $O(1)$ repetitions of circuits with depth $O(1/ε)$, wherea...
[Phys. Rev. Lett. 122, 140504] Published Fri Apr 12, 2019

Author(s): Carmine Napoli, Samanta Piano, Richard Leach, Gerardo Adesso, and Tommaso Tufarelli
We investigate the localization of two incoherent point sources with arbitrary angular and axial separations in the paraxial approximation. By using quantum metrology techniques, we show that a simultaneous estimation of the two separations is achievable by a single quantum measurement, with a preci...
[Phys. Rev. Lett. 122, 140505] Published Fri Apr 12, 2019

Author(s): Piers Lillystone, Joel J. Wallman, and Joseph Emerson
Contextuality is a fundamental nonclassical property of quantum theory, which has recently been proven to be a key resource for achieving quantum speed-ups in some leading models of quantum computation. However, which of the forms of contextuality, and how much thereof, are required to obtain a spee...
[Phys. Rev. Lett. 122, 140405] Published Fri Apr 12, 2019

The standard definition of quantum fluctuating work is based on the
two-projective energy measurement, which however does not apply to systems with
initial quantum coherence because the first projective energy measurement
destroys the initial coherence, and affects the subsequent evolution of the
system. To address this issue, several alternative definitions, such as those
based on the full counting statistics and the Margenau-Hill distribution, have
been proposed recently. These definitions seem ad hoc because justifications

Pricing interest-rate financial derivatives is a major problem in finance, in
which it is crucial to accurately reproduce the time-evolution of interest
rates. Several stochastic dynamics have been proposed in the literature to
model either the instantaneous interest rate or the instantaneous forward rate.
A successful approach to model the latter is the celebrated Heath-Jarrow-Morton
framework, in which its dynamics is entirely specified by volatility factors.

We develop an extension of the variational quantum eigensolver (VQE)
algorithm - multistate, contracted VQE (MC-VQE) - that allows for the efficient
computation of the transition energies between the ground state and several
low-lying excited states of a molecule, as well as the oscillator strengths
associated with these transitions. We numerically simulate MC-VQE by computing
the absorption spectrum of an ab initio exciton model of an 18-chromophore
light-harvesting complex from purple photosynthetic bacteria.

Motivated by the next generation of gravitational wave (GW) detectors, we
study the wave mechanics of a twisted light beam in the GW perturbed spacetime.
We found a new gravitational dipole interaction of photons and gravitational
waves. Physically, this interaction is due to coupling between the angular
momentum of twisted light and the GW polarizations. We demonstrate that for the
higher-order Laguerre-Gauss (LG) modes, this coupling effect makes photons

Prediction of financial crashes in a complex financial network is known to be
an NP-hard problem, i.e., a problem which cannot be solved efficiently with a
classical computer. We experimentally explore a novel approach to this problem
by using a D-Wave quantum computer to obtain financial equilibrium more
efficiently. To be specific, the equilibrium condition of a nonlinear financial
model is embedded into a higher-order unconstrained binary optimization (HUBO)

The probability of success of quantum annealing can be improved significantly
by pausing the annealer during its dynamics, exploiting thermal relaxation in a
controlled fashion. In this paper, we investigate the effect of pausing the
quantum annealing of the fully-connected ferromagnetic $ p $-spin model. We
numerically show that i) the optimal pausing point is 60% longer than the
avoided crossing time for the analyzed instance, and ii) at the optimal pausing