Quantum

Paper

Self-testing of a single quantum device under computational assumptions

Tony Metger and Thomas Vidick,

Quantum 5, 544 (2021).

Self-testing is a method to characterise an arbitrary quantum system based only on its classical input-output correlations, and plays an important role in device-independent quantum informat…

Paper

Quantum algorithms and approximating polynomials for composed functions with shared inputs

Mark Bun, Robin Kothari, and Justin Thaler,

Quantum 5, 543 (2021).

We give new quantum algorithms for evaluating composed functions whose inputs may be shared between bottom-level gates. Let $f$ be an $m$-bit Boolean function and consider an $n$-bit function $F$ ob…

Paper

Instance Independence of Single Layer Quantum Approximate Optimization Algorithm on Mixed-Spin Models at Infinite Size

Jahan Claes and Wim van Dam,

Quantum 5, 542 (2021).

This paper studies the application of the Quantum Approximate Optimization Algorithm (QAOA) to spin-glass models with random multi-body couplings in the limit of a large number of spins. We…

Paper

Computable Rényi mutual information: Area laws and correlations

Samuel O. Scalet, Álvaro M. Alhambra, Georgios Styliaris, and J. Ignacio Cirac,

Quantum 5, 541 (2021).

The mutual information is a measure of classical and quantum correlations of great interest in quantum information. It is also relevant in quantum many-body physics, by virtue of satisfying…

Paper

Explicit asymptotic secret key rate of continuous-variable quantum key distribution with an arbitrary modulation

Aurélie Denys, Peter Brown, and Anthony Leverrier,

Quantum 5, 540 (2021).

We establish an analytical lower bound on the asymptotic secret key rate of continuous-variable quantum key distribution with an arbitrary modulation of coherent states. Previously, such bou…

Paper

Fisher Information in Noisy Intermediate-Scale Quantum Applications

Johannes Jakob Meyer,

Quantum 5, 539 (2021).

The recent advent of noisy intermediate-scale quantum devices, especially near-term quantum computers, has sparked extensive research efforts concerned with their possible applications. At t…

Paper

Simple and maximally robust processes with no classical common-cause or direct-cause explanation

Marcello Nery, Marco Túlio Quintino, Philippe Allard Guérin, Thiago O. Maciel, and Reinaldo O. Vianna,

Quantum 5, 538 (2021).

Guided by the intuition of coherent superposition of causal relations, recent works presented quantum processes without classical common-cause and direct-cause explanation, that is, processe…

Paper

Policies for elementary links in a quantum network

Sumeet Khatri,

Quantum 5, 537 (2021).

Distributing entanglement over long distances is one of the central tasks in quantum networks. An important problem, especially for near-term quantum networks, is to develop optimal entangle…

Paper

On the experiment-friendly formulation of quantum backflow

Maximilien Barbier and Arseni Goussev,

Quantum 5, 536 (2021).

In its standard formulation, quantum backflow is a classically impossible phenomenon in which a free quantum particle in a positive-momentum state exhibits a negative probability current. Re…

Paper

Qubit-efficient entanglement spectroscopy using qubit resets

Justin Yirka and Yiğit Subaşı,

Quantum 5, 535 (2021).

One strategy to fit larger problems on NISQ devices is to exploit a tradeoff between circuit width and circuit depth. Unfortunately, this tradeoff still limits the size of tractable problems…

Paper

Exploiting anticommutation in Hamiltonian simulation

Qi Zhao and Xiao Yuan,

Quantum 5, 534 (2021).

Quantum computing can efficiently simulate Hamiltonian dynamics of many-body quantum physics, a task that is generally intractable with classical computers. The hardness lies at the ubiquito…

Paper

Quantum routing with fast reversals

Aniruddha Bapat, Andrew M. Childs, Alexey V. Gorshkov, Samuel King, Eddie Schoute, and Hrishee Shastri,

Quantum 5, 533 (2021).

We present methods for implementing arbitrary permutations of qubits under interaction constraints. Our protocols make use of previous methods for rapidly reversing the order of qubits along…

Paper

Reachability Deficits in Quantum Approximate Optimization of Graph Problems

V. Akshay, H. Philathong, I. Zacharov, and J. Biamonte,

Quantum 5, 532 (2021).

The quantum approximate optimization algorithm (QAOA) has become a cornerstone of contemporary quantum applications development. Here we show that the $density$ of problem constraints versus p…

Paper

Towards understanding the power of quantum kernels in the NISQ era

Xinbiao Wang, Yuxuan Du, Yong Luo, and Dacheng Tao,

Quantum 5, 531 (2021).

A key problem in the field of quantum computing is understanding whether quantum machine learning (QML) models implemented on noisy intermediate-scale quantum (NISQ) machines can achieve qua…

Paper

Quantum reference frame transformations as symmetries and the paradox of the third particle

Marius Krumm, Philipp A. Höhn, and Markus P. Müller,

Quantum 5, 530 (2021).

In a quantum world, reference frames are ultimately quantum systems too – but what does it mean to "jump into the perspective of a quantum particle"? In this work, we show that quantum refer…

Paper

Quantum algorithms for escaping from saddle points

Chenyi Zhang, Jiaqi Leng, and Tongyang Li,

Quantum 5, 529 (2021).

We initiate the study of quantum algorithms for escaping from saddle points with provable guarantee. Given a function $f\colon\mathbb{R}^{n}\to\mathbb{R}$, our quantum algorithm outputs an…

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