Quantum

Paper

Operational, gauge-free quantum tomography

Olivia Di Matteo, John Gamble, Chris Granade, Kenneth Rudinger, and Nathan Wiebe,

Quantum 4, 364 (2020).

As increasingly impressive quantum information processors are realized in laboratories around the world, robust and reliable characterization of these devices is now more urgent than ever. T…

Paper

Information and disturbance in operational probabilistic theories

Giacomo Mauro D’Ariano, Paolo Perinotti, and Alessandro Tosini,

Quantum 4, 363 (2020).

Any measurement is intended to provide $information$ on a system, namely knowledge about its state. However, we learn from quantum theory that it is generally impossible to extract information…

Paper

A volumetric framework for quantum computer benchmarks

Robin Blume-Kohout and Kevin C. Young,

Quantum 4, 362 (2020).

We propose a very large family of benchmarks for probing the performance of quantum computers. We call them $\textit{volumetric benchmarks}$ (VBs) because they generalize IBM's benchmark for m…

Paper

Optimal polynomial based quantum eigenstate filtering with application to solving quantum linear systems

Lin Lin and Yu Tong,

Quantum 4, 361 (2020).

We present a quantum eigenstate filtering algorithm based on quantum signal processing (QSP) and minimax polynomials. The algorithm allows us to efficiently prepare a target eigenstate of a…

Paper

On the Alberti-Uhlmann Condition for Unital Channels

Sagnik Chakraborty, Dariusz Chruściński, Gniewomir Sarbicki, and Frederik vom Ende,

Quantum 4, 360 (2020).

We address the problem of existence of completely positive trace preserving (CPTP) maps between two sets of density matrices. We refine the result of Alberti and Uhlmann and derive a necessa…

Paper

Composites and Categories of Euclidean Jordan Algebras

Howard Barnum, Matthew A. Graydon, and Alexander Wilce,

Quantum 4, 359 (2020).

We consider possible non-signaling composites of probabilistic models based on euclidean Jordan algebras (EJAs), satisfying some reasonable additional constraints motivated by the desire to…

Paper

Always-On Quantum Error Tracking with Continuous Parity Measurements

Razieh Mohseninia, Jing Yang, Irfan Siddiqi, Andrew N. Jordan, and Justin Dressel,

Quantum 4, 358 (2020).

We investigate quantum error correction using continuous parity measurements to correct bit-flip errors with the three-qubit code. Continuous monitoring of errors brings the benefit of a con…

Paper

Playing Pool with $|ψ\rangle$: from Bouncing Billiards to Quantum Search

Adam R. Brown,

Quantum 4, 357 (2020).

In “Playing Pool with $\pi$'' [1], Galperin invented an extraordinary method to learn the digits of $\pi$ by counting the collisions of billiard balls. Here I demonstrate an exact isomorphism b…

Paper

Quantum linear network coding for entanglement distribution in restricted architectures

Niel de Beaudrap and Steven Herbert,

Quantum 4, 356 (2020).

In this paper we propose a technique for distributing entanglement in architectures in which interactions between pairs of qubits are constrained to a fixed network $G$. This allows for two-qu…

Paper

General Quantum Resource Theories: Distillation, Formation and Consistent Resource Measures

Kohdai Kuroiwa and Hayata Yamasaki,

Quantum 4, 355 (2020).

Quantum resource theories (QRTs) provide a unified theoretical framework for understanding inherent quantum-mechanical properties that serve as resources in quantum information processing, b…

Paper

Time Observables in a Timeless Universe

Tommaso Favalli and Augusto Smerzi,

Quantum 4, 354 (2020).

Time in quantum mechanics is peculiar: it is an observable that cannot be associated to an Hermitian operator. As a consequence it is impossible to explain dynamics in an isolated system wit…

Paper

Bell nonlocality with a single shot

Mateus Araújo, Flavien Hirsch, and Marco Túlio Quintino,

Quantum 4, 353 (2020).

In order to reject the local hidden variables hypothesis, the usefulness of a Bell inequality can be quantified by how small a $p$-value it will give for a physical experiment. Here we show th…

Paper

Optimization of the surface code design for Majorana-based qubits

Rui Chao, Michael E. Beverland, Nicolas Delfosse, and Jeongwan Haah,

Quantum 4, 352 (2020).

The surface code is a prominent topological error-correcting code exhibiting high fault-tolerance accuracy thresholds. Conventional schemes for error correction with the surface code place q…

Paper

Classical Simulations of Quantum Field Theory in Curved Spacetime I: Fermionic Hawking-Hartle Vacua from a Staggered Lattice Scheme

Adam G. M. Lewis and Guifré Vidal,

Quantum 4, 351 (2020).

We numerically compute renormalized expectation values of quadratic operators in a quantum field theory (QFT) of free Dirac fermions in curved two-dimensional (Lorentzian) spacetime. First,…

Paper

Emergence of the Born rule in quantum optics

Brian R. La Cour and Morgan C. Williamson,

Quantum 4, 350 (2020).

The Born rule provides a fundamental connection between theory and observation in quantum mechanics, yet its origin remains a mystery. We consider this problem within the context of quantum…

Paper

A three-player coherent state embezzlement game

Zhengfeng Ji, Debbie Leung, and Thomas Vidick,

Quantum 4, 349 (2020).

We introduce a three-player nonlocal game, with a finite number of classical questions and answers, such that the optimal success probability of $1$ in the game can only be achieved in the lim…

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