Quantum

Paper

Logarithmic growth of local entropy and total correlations in many-body localized dynamics

Fabio Anza, Francesca Pietracaprina, and John Goold,

Quantum 4, 250 (2020).

The characterizing feature of a many-body localized phase is the existence of an extensive set of quasi-local conserved quantities with an exponentially localized support. This structure end…

Paper

Accessible coherence in open quantum system dynamics

María García Díaz, Benjamin Desef, Matteo Rosati, Dario Egloff, John Calsamiglia, Andrea Smirne, Michaelis Skotiniotis, and Susana F. Huelga,

Quantum 4, 249 (2020).

Quantum coherence generated in a physical process can only be cast as a potentially useful resource if its effects can be detected at a later time. Recently, the notion of non-coherence-gene…

Paper

Variational Quantum Fidelity Estimation

Marco Cerezo, Alexander Poremba, Lukasz Cincio, and Patrick J. Coles,

Quantum 4, 248 (2020).

Computing quantum state fidelity will be important to verify and characterize states prepared on a quantum computer. In this work, we propose novel lower and upper bounds for the fidelity…

Paper

Two-Qubit Circuit Depth and the Monodromy Polytope

Eric C. Peterson, Gavin E. Crooks, and Robert S. Smith,

Quantum 4, 247 (2020).

For a native gate set which includes all single-qubit gates, we apply results from symplectic geometry to analyze the spaces of two-qubit programs accessible within a fixed number of gates.…

Paper

What is the minimum CHSH score certifying that a state resembles the singlet?

Xavier Valcarce, Pavel Sekatski, Davide Orsucci, Enky Oudot, Jean-Daniel Bancal, and Nicolas Sangouard,

Quantum 4, 246 (2020).

A quantum state can be characterized from the violation of a Bell inequality. The well-known CHSH inequality for example can be used to quantify the fidelity (up to local isometries) of the…

Paper

Continuous groups of transversal gates for quantum error correcting codes from finite clock reference frames

Mischa P. Woods and Álvaro M. Alhambra,

Quantum 4, 245 (2020).

Following the introduction of the task of $\textit{reference frame error}$ $\textit{correction}$ [1], we show how, by using reference frame alignment with clocks, one can add a continuous Abelia…

Paper

Resource Preservability

Chung-Yun Hsieh,

Quantum 4, 244 (2020).

Resource theory is a general, model-independent approach aiming to understand the qualitative notion of resource quantitatively. In a given resource theory, free operations are physical proc…

Paper

Device-independent characterization of quantum instruments

Sebastian Wagner, Jean-Daniel Bancal, Nicolas Sangouard, and Pavel Sekatski,

Quantum 4, 243 (2020).

Among certification techniques, those based on the violation of Bell inequalities are appealing because they do not require assumptions on the underlying Hilbert space dimension and on the a…

Paper

$ψ$-epistemic interpretations of quantum theory have a measurement problem

Joshua B. Ruebeck, Piers Lillystone, and Joseph Emerson,

Quantum 4, 242 (2020).

$\psi$-epistemic interpretations of quantum theory maintain that quantum states only represent incomplete information about the physical states of the world. A major motivation for this view i…

Paper

Quantum Speedup Based on Classical Decision Trees

Salman Beigi and Leila Taghavi,

Quantum 4, 241 (2020).

Lin and Lin [16] have recently shown how starting with a classical query algorithm (decision tree) for a function, we may find upper bounds on its quantum query complexity. More precisely, t…

Paper

Thermodynamics of Quantum Causal Models: An Inclusive, Hamiltonian Approach

Philipp Strasberg,

Quantum 4, 240 (2020).

Operational quantum stochastic thermodynamics is a recently proposed theory to study the thermodynamics of open systems based on the rigorous notion of a quantum stochastic process or quantu…

Paper

Engineering Schrödinger cat states with a photonic even-parity detector

G. S. Thekkadath, B. A. Bell, I. A. Walmsley, and A. I. Lvovsky,

Quantum 4, 239 (2020).

When two equal photon-number states are combined on a balanced beam splitter, both output ports of the beam splitter contain only even numbers of photons. Consider the time-reversal of this…

Paper

How post-selection affects device-independent claims under the fair sampling assumption

Davide Orsucci, Jean-Daniel Bancal, Nicolas Sangouard, and Pavel Sekatski,

Quantum 4, 238 (2020).

Device-independent certifications employ Bell tests to guarantee the proper functioning of an apparatus from the sole knowledge of observed measurement statistics, i.e. without assumptions o…

Paper

Classical and Quantum Algorithms for Tensor Principal Component Analysis

Matthew B. Hastings,

Quantum 4, 237 (2020).

We present classical and quantum algorithms based on spectral methods for a problem in tensor principal component analysis. The quantum algorithm achieves a $quartic$ speedup while using expon…

Paper

Analysing causal structures in generalised probabilistic theories

Mirjam Weilenmann and Roger Colbeck,

Quantum 4, 236 (2020).

Causal structures give us a way to understand the origin of observed correlations. These were developed for classical scenarios, but quantum mechanical experiments necessitate their generali…

Paper

Compilation by stochastic Hamiltonian sparsification

Yingkai Ouyang, David R. White, and Earl T. Campbell,

Quantum 4, 235 (2020).

Simulation of quantum chemistry is expected to be a principal application of quantum computing. In quantum simulation, a complicated Hamiltonian describing the dynamics of a quantum system i…

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