Quantum

Paper

Symmetries and monotones in Markovian quantum dynamics

Georgios Styliaris and Paolo Zanardi,

Quantum 4, 261 (2020).

What can one infer about the dynamical evolution of quantum systems just by symmetry considerations? For Markovian dynamics in finite dimensions, we present a simple construction that assign…

Paper

Device-independent quantum key distribution with single-photon sources

Jan Kołodyński, Alejandro Máttar, Paul Skrzypczyk, Erik Woodhead, Daniel Cavalcanti, Konrad Banaszek, and Antonio Acín,

Quantum 4, 260 (2020).

$\textit{Device-independent quantum key distribution}$ protocols allow two honest users to establish a secret key with minimal levels of trust on the provider, as security is proven without an…

Paper

The first law of general quantum resource theories

Carlo Sparaciari, Lídia del Rio, Carlo Maria Scandolo, Philippe Faist, and Jonathan Oppenheim,

Quantum 4, 259 (2020).

We extend the tools of quantum resource theories to scenarios in which multiple quantities (or resources) are present, and their interplay governs the evolution of physical systems. We deriv…

Paper

Contextual advantage for state-dependent cloning

Matteo Lostaglio and Gabriel Senno,

Quantum 4, 258 (2020).

A number of noncontextual models exist which reproduce different subsets of quantum theory and admit a no-cloning theorem. Therefore, if one chooses noncontextuality as one's notion of class…

Paper

Mitigation of readout noise in near-term quantum devices by classical post-processing based on detector tomography

Filip B. Maciejewski, Zoltán Zimborás, and Michał Oszmaniec,

Quantum 4, 257 (2020).

We propose a simple scheme to reduce readout errors in experiments on quantum systems with finite number of measurement outcomes. Our method relies on performing classical post-processing wh…

Paper

Improving Variational Quantum Optimization using CVaR

Panagiotis Kl. Barkoutsos, Giacomo Nannicini, Anton Robert, Ivano Tavernelli, and Stefan Woerner,

Quantum 4, 256 (2020).

Hybrid quantum/classical variational algorithms can be implemented on noisy intermediate-scale quantum computers and can be used to find solutions for combinatorial optimization problems. Ap…

Paper

Kolmogorov extension theorem for (quantum) causal modelling and general probabilistic theories

Simon Milz, Fattah Sakuldee, Felix A. Pollock, and Kavan Modi,

Quantum 4, 255 (2020).

In classical physics, the Kolmogorov extension theorem lays the foundation for the theory of stochastic processes. It has been known for a long time that, in its original form, this theorem…

Paper

Time-dependent Hamiltonian simulation with $L^1$-norm scaling

Dominic W. Berry, Andrew M. Childs, Yuan Su, Xin Wang, and Nathan Wiebe,

Quantum 4, 254 (2020).

The difficulty of simulating quantum dynamics depends on the norm of the Hamiltonian. When the Hamiltonian varies with time, the simulation complexity should only depend on this quantity ins…

Paper

Detecting mixed-unitary quantum channels is NP-hard

Colin Do-Yan Lee and John Watrous,

Quantum 4, 253 (2020).

A quantum channel is said to be a $\textit{mixed-unitary}$ channel if it can be expressed as a convex combination of unitary channels. We prove that, given the Choi representation of a quantum…

Paper

Number-Theoretic Characterizations of Some Restricted Clifford+T Circuits

Matthew Amy, Andrew N. Glaudell, and Neil J. Ross,

Quantum 4, 252 (2020).

Kliuchnikov, Maslov, and Mosca proved in 2012 that a $2\times 2$ unitary matrix $V$ can be exactly represented by a single-qubit Clifford+$T$ circuit if and only if the entries of $V$ belong to the…

Paper

A Hierarchy of Anyon Models Realised by Twists in Stacked Surface Codes

T. R. Scruby and D. E. Browne,

Quantum 4, 251 (2020).

Braiding defects in topological stabiliser codes can be used to fault-tolerantly implement logical operations. Twists are defects corresponding to the end-points of domain walls and are asso…

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

Fixed-Depth Two-Qubit Circuits 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…

Category: Paper