Tyler D. Ellison, Kohtaro Kato, Zi-Wen Liu, and Timothy H. Hsieh,

Quantum 5, 612 (2021).

We introduce the concepts of a symmetry-protected sign problem and symmetry-protected magic to study the complexity of symmetry-protected topological (SPT) phases of matter. In particular, w…

Seungbeom Chin, Yong-Su Kim, and Sangmin Lee,

Quantum 5, 611 (2021).

The indistinguishability of quantum particles is widely used as a resource for the generation of entanglement. Linear quantum networks (LQNs), in which identical particles linearly evolve to…

Joseph Tindall, Frank Schlawin, Michael Sentef, and Dieter Jaksch,

Quantum 5, 610 (2021).

Coherent driving has established itself as a powerful tool for guiding a many-body quantum system into a desirable, coherent non-equilibrium state. A thermodynamically large system will, how…

Arthur G. Rattew, Yue Sun, Pierre Minssen, and Marco Pistoia,

Quantum 5, 609 (2021).

The efficient preparation of input distributions is an important problem in obtaining quantum advantage in a wide range of domains. We propose a novel quantum algorithm for the efficient pre…

Marco Fanizza, Matteo Rosati, Michalis Skotiniotis, John Calsamiglia, and Vittorio Giovannetti,

Quantum 5, 608 (2021).

We study the problem of transmitting classical information using quantum Gaussian states on a family of phase-noise channels with a finite decoherence time, such that the phase-reference is…

Jordi Picó-Cortés and Gloria Platero,

Quantum 5, 607 (2021).

Quantum dot-based quantum computation employs extensively the exchange interaction between nearby electronic spins in order to manipulate and couple different qubits. The exchange interactio…

Craig Gidney, Michael Newman, Austin Fowler, and Michael Broughton,

Quantum 5, 605 (2021).

Recently, Hastings & Haah introduced a quantum memory defined on the honeycomb lattice. Remarkably, this honeycomb code assembles weight-six parity checks using only two-local measurements.…

Clement Delcamp and Norbert Schuch,

Quantum 5, 604 (2021).

We define two dual tensor network representations of the (3+1)d toric code ground state subspace. These two representations, which are obtained by initially imposing either family of stabili…

H. Weisbrich, M. Bestler, and W. Belzig,

Quantum 5, 601 (2021).

Topology in general but also topological objects such as monopoles are a central concept in physics. They are prime examples for the intriguing physics of gauge theories and topological stat…

Jiaqing Jiang, Kun Wang, and Xin Wang,

Quantum 5, 600 (2021).

Completely positive and trace-preserving maps characterize physically implementable quantum operations. On the other hand, general linear maps, such as positive but not completely positive m…

Aldo C. Martinez-Becerril, Gabriel Bussières, Davor Curic, Lambert Giner, Raphael A. Abrahao, and Jeff S. Lundeen,

Quantum 5, 599 (2021).

Incompatible observables underlie pillars of quantum physics such as contextuality and entanglement. The Heisenberg uncertainty principle is a fundamental limitation on the measurement of th…

Priya Batra, Anukriti Singh, and T. S. Mahesh,

Quantum 5, 598 (2021).

We demonstrate characterizing quantum evolutions via matrix factorization algorithm, a particular type of the recommender system (RS). A system undergoing a quantum evolution can be characte…

Y. Herasymenko and T.E. O’Brien,

Quantum 5, 596 (2021).

Variational quantum eigensolvers (VQEs) are a promising class of quantum algorithms for preparing approximate ground states in near-term quantum devices. Minimizing the error in such an appr…

Antoine Tilloy and Howard M. Wiseman,

Quantum 5, 594 (2021).

Spontaneous collapse models and Bohmian mechanics are two different solutions to the measurement problem plaguing orthodox quantum mechanics. They have, a priori nothing in common. At a form…

Juan Zurita, Charles Creffield, and Gloria Platero,

Quantum 5, 591 (2021).

We investigate the interplay between Aharonov-Bohm (AB) caging and topological protection in a family of quasi-one-dimensional topological insulators, which we term CSSH ladders. Hybrids of…

Roie Dann and Ronnie Kosloff,

Quantum 5, 590 (2021).

Quantum dynamics of driven open systems should be compatible with both quantum mechanic and thermodynamic principles. By formulating the thermodynamic principles in terms of a set of postula…

Victoria J Wright and Stefan Weigert,

Quantum 5, 588 (2021).

Gleason-type theorems for quantum theory allow one to recover the quantum state space by assuming that (i) states consistently assign probabilities to measurement outcomes and that (ii) ther…

Manuel Campos, German Sierra, and Esperanza Lopez,

Quantum 5, 586 (2021).

We present a new tensor network algorithm for calculating the partition function of interacting quantum field theories in 2 dimensions. It is based on the Tensor Renormalization Group (TRG)…

Pavel Panteleev and Gleb Kalachev,

Quantum 5, 585 (2021).

We study the performance of medium-length quantum LDPC (QLDPC) codes in the depolarizing channel. Only degenerate codes with the maximal stabilizer weight much smaller than their minimum dis…

Peter Groszkowski and Jens Koch,

Quantum 5, 583 (2021).

$\textbf{scqubits}$ is an open-source Python package for simulating and analyzing superconducting circuits. It provides convenient routines to obtain energy spectra of common superconducting q…

Matthias C. Caro, Elies Gil-Fuster, Johannes Jakob Meyer, Jens Eisert, and Ryan Sweke,

Quantum 5, 582 (2021).

A large body of recent work has begun to explore the potential of parametrized quantum circuits (PQCs) as machine learning models, within the framework of hybrid quantum-classical optimizati…

Pengfei Zhang, Shao-Kai Jian, Chunxiao Liu, and Xiao Chen,

Quantum 5, 579 (2021).

Recently, the steady states of non-unitary free fermion dynamics are found to exhibit novel critical phases with power-law squared correlations and a logarithmic subsystem entanglement. In t…

Ulysse Chabaud, Frédéric Grosshans, Elham Kashefi, and Damian Markham,

Quantum 5, 578 (2021).

The demonstration of quantum speedup, also known as quantum computational supremacy, that is the ability of quantum computers to outperform dramatically their classical counterparts, is an i…

Shouzhen Gu, Rolando D. Somma, and Burak Şahinoğlu,

Quantum 5, 577 (2021).

We investigate the problem of fast-forwarding quantum evolution, whereby the dynamics of certain quantum systems can be simulated with gate complexity that is sublinear in the evolution time…

Pawel Blasiak, Ewa Borsuk, and Marcin Markiewicz,

Quantum 5, 575 (2021).

Reasoning about Bell nonlocality from the correlations observed in post-selected data is always a matter of concern. This is because conditioning on the outcomes is a source of non-causal co…

Davide Orsucci and Vedran Dunjko,

Quantum 5, 573 (2021).

Quantum algorithms for solving the Quantum Linear System (QLS) problem are among the most investigated quantum algorithms of recent times, with potential applications including the solution…

Saad Yalouz, Bruno Senjean, Filippo Miatto, and Vedran Dunjko,

Quantum 5, 572 (2021).

Variational quantum algorithms (VQA) are considered as some of the most promising methods to determine the properties of complex strongly correlated quantum many-body systems, especially fro…

Kenneth Sharman, Faezeh Kimiaee Asadi, Stephen C Wein, and Christoph Simon,

Quantum 5, 570 (2021).

Inspired by recent developments in the control and manipulation of quantum dot nuclear spins, which allow for the transfer of an electron spin state to the surrounding nuclear-spin ensemble…

Tamal Guha, Mir Alimuddin, Sumit Rout, Amit Mukherjee, Some Sankar Bhattacharya, and Manik Banik,

Quantum 5, 569 (2021).

Sharing correlated random variables is a resource for a number of information theoretic tasks such as privacy amplification, simultaneous message passing, secret sharing and many more. In th…

Julien Gacon, Christa Zoufal, Giuseppe Carleo, and Stefan Woerner,

Quantum 5, 567 (2021).

The Quantum Fisher Information matrix (QFIM) is a central metric in promising algorithms, such as Quantum Natural Gradient Descent and Variational Quantum Imaginary Time Evolution. Computing…

Patrick Rall,

Quantum 5, 566 (2021).

We consider performing phase estimation under the following conditions: we are given only one copy of the input state, the input state does not have to be an eigenstate of the unitary, and t…

Cathryn P. Michaels, Jesús Arjona Martínez, Romain Debroux, Ryan A. Parker, Alexander M. Stramma, Luca I. Huber, Carola M. Purser, Mete Atatüre, and Dorian A. Gangloff,

Quantum 5, 565 (2021).

Photonic cluster states are a powerful resource for measurement-based quantum computing and loss-tolerant quantum communication. Proposals to generate multi-dimensional lattice cluster state…

E. R. Castro, Jorge Chávez-Carlos, I. Roditi, Lea F. Santos, and Jorge G. Hirsch,

Quantum 5, 563 (2021).

We study the quantum-classical correspondence of an experimentally accessible system of interacting bosons in a tilted triple-well potential. With the semiclassical analysis, we get a better…

Nithin Raveendran and Bane Vasić,

Quantum 5, 562 (2021).

Iterative decoders for finite length quantum low-density parity-check (QLDPC) codes are attractive because their hardware complexity scales only linearly with the number of physical qubits.…

Carlo Marconi, Albert Aloy, Jordi Tura, and Anna Sanpera,

Quantum 5, 561 (2021).

Entanglement in symmetric quantum states and the theory of copositive matrices are intimately related concepts. For the simplest symmetric states, i.e., the diagonal symmetric (DS) states, i…

Yasunari Suzuki, Yoshiaki Kawase, Yuya Masumura, Yuria Hiraga, Masahiro Nakadai, Jiabao Chen, Ken M. Nakanishi, Kosuke Mitarai, Ryosuke Imai, Shiro Tamiya, Takahiro Yamamoto, Tennin Yan, Toru Kawakubo, Yuya O. Nakagawa, Yohei Ibe, Youyuan Zhang, Hirotsugu Yamashita, Hikaru Yoshimura, Akihiro Hayashi, and Keisuke Fujii,

Quantum 5, 559 (2021).

To explore the possibilities of a near-term intermediate-scale quantum algorithm and long-term fault-tolerant quantum computing, a fast and versatile quantum circuit simulator is needed. Her…

Giovanni Cataldi, Ashkan Abedi, Giuseppe Magnifico, Simone Notarnicola, Nicola Dalla Pozza, Vittorio Giovannetti, and Simone Montangero,

Quantum 5, 556 (2021).

We present a novel mapping for studying 2D many-body quantum systems by solving an effective, one-dimensional long-range model in place of the original two-dimensional short-range one. In pa…

Xiao-Liang Qi and Daniel Ranard,

Quantum 5, 555 (2021).

In a quantum measurement process, classical information about the measured system spreads throughout the environment. Meanwhile, quantum information about the system becomes inaccessible to…

Xiao Xiao, J. K. Freericks, and A. F. Kemper,

Quantum 5, 553 (2021).

Topological protection is employed in fault-tolerant error correction and in developing quantum algorithms with topological qubits. But, topological protection…

Shin-Liang Chen, Huan-Yu Ku, Wenbin Zhou, Jordi Tura, and Yueh-Nan Chen,

Quantum 5, 552 (2021).

Given a Bell inequality, if its maximal quantum violation can be achieved only by a single set of measurements for each party or a single quantum state, up to local unitaries, one refers to…

Kyle E. C. Booth, Bryan O’Gorman, Jeffrey Marshall, Stuart Hadfield, and Eleanor Rieffel,

Quantum 5, 550 (2021).

Constraint programming (CP) is a paradigm used to model and solve constraint satisfaction and combinatorial optimization problems. In CP, problems are modeled with constraints that describe…

Steven T. Flammia and Ryan O’Donnell,

Quantum 5, 549 (2021).

Motivated by estimation of quantum noise models, we study the problem of learning a Pauli channel, or more generally the Pauli error rates of an arbitrary channel. By employing a novel reduc…

Zhenyu Cai,

Quantum 5, 548 (2021).

Even with the recent rapid developments in quantum hardware, noise remains the biggest challenge for the practical applications of any near-term quantum devices. Full quantum error correctio…

Ivan Henao and Raam Uzdin,

Quantum 5, 547 (2021).

The laws of thermodynamics are usually formulated under the assumption of infinitely large environments. While this idealization facilitates theoretical treatments, real physical systems are…

Rafael N. Alexander, Glen Evenbly, and Israel Klich,

Quantum 5, 546 (2021).

The study of low-dimensional quantum systems has proven to be a particularly fertile field for discovering novel types of quantum matter. When studied numerically, low-energy states of low-d…

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…

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…

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…

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…

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…

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…

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…

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…

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…

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…

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…

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…

Alberto Biella and Marco Schiró,

Quantum 5, 528 (2021).

It is well known that by repeatedly measuring a quantum system it is possible to completely freeze its dynamics into a well defined state, a signature of the quantum Zeno effect. Here we sho…

Mankei Tsang,

Quantum 5, 527 (2021).

By taking a Poisson limit for a sequence of rare quantum objects, I derive simple formulas for the Uhlmann fidelity, the quantum Chernoff quantity, the relative entropy, and the Helstrom inf…

Joaquin Medina Dueñas, Gabriel O’Ryan Pérez, Carla Hermann-Avigliano, and Luis E. F. Foa Torres,

Quantum 5, 526 (2021).

What is the role of topology in the propagation of quantum light in photonic lattices? We address this question by studying the propagation of squeezed states in a topological one-dimensiona…

Veronika Baumann, Flavio Del Santo, Alexander R. H. Smith, Flaminia Giacomini, Esteban Castro-Ruiz, and Caslav Brukner,

Quantum 5, 524 (2021).

The quantum measurement problem can be regarded as the tension between the two alternative dynamics prescribed by quantum mechanics: the unitary evolution of the wave function and the state-…

Bartosz Regula, Ryuji Takagi, and Mile Gu,

Quantum 5, 522 (2021).

Although quantum channels underlie the dynamics of quantum states, maps which are not physical channels — that is, not completely positive — can often be encountered in settings such as enta…

Sisi Zhou, Zi-Wen Liu, and Liang Jiang,

Quantum 5, 521 (2021).

Covariant codes are quantum codes such that a symmetry transformation on the logical system could be realized by a symmetry transformation on the physical system, usually with limited capabi…

Andrea Di Biagio, Pietro Donà, and Carlo Rovelli,

Quantum 5, 520 (2021).

The operational formulations of quantum theory are drastically time oriented. However, to the best of our knowledge, microscopic physics is time-symmetric. We address this tension by showing…

Satvik Singh and Ion Nechita,

Quantum 5, 519 (2021).

We analyze bipartite matrices and linear maps between matrix algebras, which are respectively, invariant and covariant, under the diagonal unitary and orthogonal groups' actions. By presenti…

J. C. Pearl and E. G. Cavalcanti,

Quantum 5, 518 (2021).

In a recent work, it was shown by one of us (EGC) that Bell-Kochen-Specker inequality violations in phenomena satisfying the no-disturbance condition (a generalisation of the no-signalling c…

Oscar Higgott, Matthew Wilson, James Hefford, James Dborin, Farhan Hanif, Simon Burton, and Dan E. Browne,

Quantum 5, 517 (2021).

The surface code is a leading candidate quantum error correcting code, owing to its high threshold, and compatibility with existing experimental architectures. Bravyi {et al.} [7] showed tha…

Wiktor Szadowiak, Sanjukta Kundu, Jerzy Szuniewicz, and Radek Lapkiewicz,

Quantum 5, 516 (2021).

Quantitative characterization of the spatial structure of single photons is essential for free-space quantum communication and quantum imaging. We introduce an interferometric technique that…

N. Slate, E. Matwiejew, S. Marsh, and J. B. Wang,

Quantum 5, 513 (2021).

This paper proposes a highly efficient quantum algorithm for portfolio optimisation targeted at near-term noisy intermediate-scale quantum computers. Recent work by Hodson et al. (2019) expl…

Stefano Barison, Filippo Vicentini, and Giuseppe Carleo,

Quantum 5, 512 (2021).

We introduce a novel hybrid algorithm to simulate the real-time evolution of quantum systems using parameterized quantum circuits. The method, named "projected – Variational Quantum Dynamics…

Robin Lorenz and Jonathan Barrett,

Quantum 5, 511 (2021).

The causal structure of a unitary transformation is the set of relations of possible influence between any input subsystem and any output subsystem. We study whether such causal structure ca…

Neha Pathania and Tabish Qureshi,

Quantum 5, 507 (2021).

There has been an intense debate on the question as to whether a quanton, passing through a double-slit, experiences a 'momentum kick' due to the act of which-way detection. There have been…

A. Kumar, T. Krisnanda, P. Arumugam, and T. Paterek,

Quantum 5, 506 (2021).

Rutherford scattering is usually described by treating the projectile either classically or as quantum mechanical plane waves. Here we treat them as wave packets and study their head-on coll…

Stefano Chessa and Vittorio Giovannetti,

Quantum 5, 504 (2021).

We introduce $\textit{Partially Coherent Direct Sum}$ (PCDS) quantum channels, as a generalization of the already known $\textit{Direct Sum}$ quantum channels. We derive necessary and sufficient…

Augustin Vanrietvelde, Hlér Kristjánsson, and Jonathan Barrett,

Quantum 5, 503 (2021).

We argue that the quantum-theoretical structures studied in several recent lines of research cannot be adequately described within the standard framework of quantum circuits. This is in part…

Benjamin Zanger, Christian B. Mendl, Martin Schulz, and Martin Schreiber,

Quantum 5, 502 (2021).

Identifying computational tasks suitable for (future) quantum computers is an active field of research. Here we explore utilizing quantum computers for the purpose of solving differential eq…

Titas Chanda, Rebecca Kraus, Giovanna Morigi, and Jakub Zakrzewski,

Quantum 5, 501 (2021).

Topological materials have potential applications for quantum technologies. Non-interacting topological materials, such as e.g., topological insulators and superconductors, are classified by…

Mark T. Mitchison, John Goold, and Javier Prior,

Quantum 5, 500 (2021).

Energy storage is a basic physical process with many applications. When considering this task at the quantum scale, it becomes important to optimise the non-equilibrium dynamics of energy tr…

Joseph Bowles, Flavien Hirsch, and Daniel Cavalcanti,

Quantum 5, 499 (2021).

Activation of Bell nonlocality refers to the phenomenon that some entangled mixed states that admit a local hidden variable model in the standard Bell scenario nevertheless reveal their nonl…

Cyril Elouard, Philippe Lewalle, Sreenath K. Manikandan, Spencer Rogers, Adam Frank, and Andrew N. Jordan,

Quantum 5, 498 (2021).

The Wigner's friend paradox concerns one of the most puzzling problems of quantum mechanics: the consistent description of multiple nested observers. Recently, a variation of Wigner's gedank…

Craig Gidney,

Quantum 5, 497 (2021).

This paper presents “Stim", a fast simulator for quantum stabilizer circuits. The paper explains how Stim works and compares it to existing tools. With no foreknowledge, Stim can analyze a d…

Ulysse Chabaud, Damian Markham, and Adel Sohbi,

Quantum 5, 496 (2021).

We study supervised learning algorithms in which a quantum device is used to perform a computational subroutine – either for prediction via probability estimation, or to compute a kernel via…

Mateusz Mazelanik, Adam Leszczyński, Michał Lipka, Wojciech Wasilewski, and Michał Parniak,

Quantum 5, 493 (2021).

Certification of nonlocality of quantum mechanics is an important fundamental test that typically requires prolonged data collection and is only revealed in an in-depth analysis. These featu…

Stefan H. Sack and Maksym Serbyn,

Quantum 5, 491 (2021).

The quantum approximate optimization algorithm (QAOA) is a prospective near-term quantum algorithm due to its modest circuit depth and promising benchmarks. However, an external parameter op…

Karol Gietka, Friederike Metz, Tim Keller, and Jing Li,

Quantum 5, 489 (2021).

We show that the quantum Fisher information attained in an adiabatic approach to critical quantum metrology cannot lead to the Heisenberg limit of precision and therefore $regular$ quantum met…

Martina Gschwendtner, Andreas Bluhm, and Andreas Winter,

Quantum 5, 488 (2021).

A programmable quantum processor uses the states of a program register to specify one element of a set of quantum channels which is applied to an input register. It is well-known that such a…

Pedro Parrado-Rodríguez, Ciarán Ryan-Anderson, Alejandro Bermudez, and Markus Müller,

Quantum 5, 487 (2021).

Physical qubits in experimental quantum information processors are inevitably exposed to different sources of noise and imperfections, which lead to errors that typically accumulate hinderin…

Thomás Fogarty, Miguel Ángel García-March, Lea F. Santos, and Nathan L. Harshman,

Quantum 5, 486 (2021).

Interacting quantum systems in the chaotic domain are at the core of various ongoing studies of many-body physics, ranging from the scrambling of quantum information to the onset of thermali…

Christopher Eltschka, Marcus Huber, Simon Morelli, and Jens Siewert,

Quantum 5, 485 (2021).

Geometric intuition is a crucial tool to obtain deeper insight into many concepts of physics. A paradigmatic example of its power is the Bloch ball, the geometrical representation for the st…

Anubhav Chaturvedi, Máté Farkas, and Victoria J Wright,

Quantum 5, 484 (2021).

The predictions of quantum theory resist generalised noncontextual explanations. In addition to the foundational relevance of this fact, the particular extent to which quantum theory violate…

Xin Wang, Zhixin Song, and Youle Wang,

Quantum 5, 483 (2021).

Singular value decomposition is central to many problems in engineering and scientific fields. Several quantum algorithms have been proposed to determine the singular values and their associ…

Hayata Yamasaki, Madhav Krishnan Vijayan, and Min-Hsiu Hsieh,

Quantum 5, 480 (2021).

Quantum resource theory under different classes of quantum operations advances multiperspective understandings of inherent quantum-mechanical properties, such as quantum coherence and quantu…

Daniel J. Egger, Jakub Mareček, and Stefan Woerner,

Quantum 5, 479 (2021).

There is an increasing interest in quantum algorithms for problems of integer programming and combinatorial optimization. Classical solvers for such problems employ relaxations, which replac…

Soham Pal, Priya Batra, Tanjung Krisnanda, Tomasz Paterek, and T. S. Mahesh,

Quantum 5, 478 (2021).

Quantum entanglement is a form of correlation between quantum particles that cannot be increased via local operations and classical communication. It has therefore been proposed that an incr…

Myrto Arapinis, Mahshid Delavar, Mina Doosti, and Elham Kashefi,

Quantum 5, 475 (2021).

A Physical Unclonable Function (PUF) is a device with unique behaviour that is hard to clone hence providing a secure fingerprint. A variety of PUF structures and PUF-based applications have…

Bo Peng and Karol Kowalski,

Quantum 5, 473 (2021).

Recently a new class of quantum algorithms that are based on the quantum computation of the connected moment expansion has been reported to find the ground and excited state energies. In par…

Ulysse Chabaud, Pierre-Emmanuel Emeriau, and Frédéric Grosshans,

Quantum 5, 471 (2021).

Negativity of the Wigner function is arguably one of the most striking non-classical features of quantum states. Beyond its fundamental relevance, it is also a necessary resource for quantum…

Ewout van den Berg,

Quantum 5, 469 (2021).

We describe an efficient implementation of Bayesian quantum phase estimation in the presence of noise and multiple eigenstates. The main contribution of this work is the dynamic switching be…

Matthew Buican, Linfeng Li, and Rajath Radhakrishnan,

Quantum 5, 468 (2021).

We study the implications of the anyon fusion equation $a\times b=c$ on global properties of $2+1$D topological quantum field theories (TQFTs). Here $a$ and $b$ are anyons that fuse together to give…

Marco A. Rodríguez-García, Isaac Pérez Castillo, and P. Barberis-Blostein,

Quantum 5, 467 (2021).

Estimating correctly the quantum phase of a physical system is a central problem in quantum parameter estimation theory due to its wide range of applications from quantum metrology to crypto…

Leonardo Novo, Juani Bermejo-Vega, and Raúl García-Patrón,

Quantum 5, 465 (2021).

The problem of sampling outputs of quantum circuits has been proposed as a candidate for demonstrating a quantum computational advantage (sometimes referred to as quantum "supremacy"). In th…

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

Quantum 5, 464 (2021).

Measurement noise is one of the main sources of errors in currently available quantum devices based on superconducting qubits. At the same time, the complexity of its characterization and mi…

Shouvanik Chakrabarti, Rajiv Krishnakumar, Guglielmo Mazzola, Nikitas Stamatopoulos, Stefan Woerner, and William J. Zeng,

Quantum 5, 463 (2021).

We give an upper bound on the resources required for valuable quantum advantage in pricing derivatives. To do so, we give the first complete resource estimates for useful quantum derivative…

Alessandro Ferreri, Matteo Santandrea, Michael Stefszky, Kai H. Luo, Harald Herrmann, Christine Silberhorn, and Polina R. Sharapova,

Quantum 5, 461 (2021).

Nonlinear SU(1,1) interferometers are fruitful and promising tools for spectral engineering and precise measurements with phase sensitivity below the classical bound. Such interferometers ha…

Thomas D. Galley and Lluis Masanes,

Quantum 5, 457 (2021).

We introduce a general framework for analysing general probabilistic theories, which emphasises the distinction between the dynamical and probabilistic structures of a system. The dynamical…

William M. Kirby, Andrew Tranter, and Peter J. Love,

Quantum 5, 456 (2021).

We describe the $\textit{contextual subspace variational quantum eigensolver}$ (CS-VQE), a hybrid quantum-classical algorithm for approximating the ground state energy of a Hamiltonian. The ap…

Piotr Deuar,

Quantum 5, 455 (2021).

A number of physically intuitive results for the calculation of multi-time correlations in phase-space representations of quantum mechanics are obtained. They relate time-dependent stochasti…

Benjamin Tan, Marc-Antoine Lemonde, Supanut Thanasilp, Jirawat Tangpanitanon, and Dimitris G. Angelakis,

Quantum 5, 454 (2021).

We propose and analyze a set of variational quantum algorithms for solving quadratic unconstrained binary optimization problems where a problem consisting of $n_c$ classical variables can be i…

Lorenzo Leone, Salvatore F. E. Oliviero, You Zhou, and Alioscia Hamma,

Quantum 5, 453 (2021).

It is well known that a quantum circuit on $N$ qubits composed of Clifford gates with the addition of $k$ non Clifford gates can be simulated on a classical computer by an algorithm scaling as…

Daiqin Su, Robert Israel, Kunal Sharma, Haoyu Qi, Ish Dhand, and Kamil Brádler,

Quantum 5, 452 (2021).

Photon loss is destructive to the performance of quantum photonic devices and therefore suppressing the effects of photon loss is paramount to photonic quantum technologies. We present two s…

Stefano Scali, Janet Anders, and Luis A. Correa,

Quantum 5, 451 (2021).

Master equations are a vital tool to model heat flow through nanoscale thermodynamic systems. Most practical devices are made up of interacting sub-system, and are often modelled using eithe…

Oskar Słowik, Adam Sawicki, and Tomasz Maciążek,

Quantum 5, 450 (2021).

One of the key ingredients of many LOCC protocols in quantum information is a multiparticle (locally) maximally entangled quantum state, aka a critical state, that possesses local symmetries…

Léonce Dupays and Aurélia Chenu,

Quantum 5, 449 (2021).

Squeezed state in harmonic systems can be generated through a variety of techniques, including varying the oscillator frequency or using nonlinear two-photon Raman interaction. We focus on t…

Zixin Huang, Peter P. Rohde, Dominic W. Berry, Pieter Kok, Jonathan P. Dowling, and Cosmo Lupo,

Quantum 5, 447 (2021).

Quantum data locking is a quantum phenomenon that allows us to encrypt a long message with a small secret key with information-theoretic security. This is in sharp contrast with classical in…

M. Perarnau-Llobet, D. Malz, and J. I. Cirac,

Quantum 5, 446 (2021).

We consider the estimation of a Hamiltonian parameter of a set of highly photosensitive samples, which are damaged after a few photons $N_{\rm abs}$ are absorbed, for a total time $T$. The sampl…

John H. Selby, Carlo Maria Scandolo, and Bob Coecke,

Quantum 5, 445 (2021).

A reconstruction of quantum theory refers to both a mathematical and a conceptual paradigm that allows one to derive the usual formulation of quantum theory from a set of primitive assumptio…

Pavel Sekatski, Jean-Daniel Bancal, Xavier Valcarce, Ernest Y.-Z. Tan, Renato Renner, and Nicolas Sangouard,

Quantum 5, 444 (2021).

Device-independent quantum key distribution aims at providing security guarantees even when using largely uncharacterised devices. In the simplest scenario, these guarantees are derived from…

Jakub Czartowski and Karol Życzkowski,

Quantum 5, 442 (2021).

We analyse orthogonal bases in a composite $N\times N$ Hilbert space describing a bipartite quantum system and look for a basis with optimal single-sided mutual state distinguishability. This…

Wataru Yokojima, Marco Túlio Quintino, Akihito Soeda, and Mio Murao,

Quantum 5, 441 (2021).

Similarly to quantum states, quantum operations can also be transformed by means of quantum superchannels, also known as process matrices. Quantum superchannels with multiple slots are deter…

Christina Giarmatzi and Fabio Costa,

Quantum 5, 440 (2021).

We present a method to detect quantum memory in a non-Markovian process. We call a process Markovian when the environment does not provide a memory that retains correlations across different…

Andrea Smirne, Nina Megier, and Bassano Vacchini,

Quantum 5, 439 (2021).

The exchange of information between an open quantum system and its environment allows us to discriminate among different kinds of dynamics, in particular detecting memory effects to characte…

Kunal Marwaha,

Quantum 5, 437 (2021).

The $p$-stage Quantum Approximate Optimization Algorithm (QAOA$_p$) is a promising approach for combinatorial optimization on noisy intermediate-scale quantum (NISQ) devices, but its theoretical…

Graeme D. Berk, Andrew J. P. Garner, Benjamin Yadin, Kavan Modi, and Felix A. Pollock,

Quantum 5, 435 (2021).

We investigate the conditions under which an uncontrollable background processes may be harnessed by an agent to perform a task that would otherwise be impossible within their operational fr…

Kouhei Nakaji and Naoki Yamamoto,

Quantum 5, 434 (2021).

The hybrid quantum-classical algorithm is actively examined as a technique applicable even to intermediate-scale quantum computers. To execute this algorithm, the hardware efficient ansatz i…

Antoine Grospellier, Lucien Grouès, Anirudh Krishna, and Anthony Leverrier,

Quantum 5, 432 (2021).

Hypergraph product codes are a class of constant-rate quantum low-density parity-check (LDPC) codes equipped with a linear-time decoder called small-set-flip (SSF). This decoder displays sub…

Juan José García-Ripoll,

Quantum 5, 431 (2021).

In this work we study the encoding of smooth, differentiable multivariate functions in quantum registers, using quantum computers or tensor-network representations. We show that a large fami…

Artur Barasiński, Antonín Černoch, Wiesław Laskowski, Karel Lemr, Tamás Vértesi, and Jan Soubusta,

Quantum 5, 430 (2021).

In this work, we study a recently proposed operational measure of nonlocality by Fonseca and Parisio [Phys. Rev. A 92, 030101(R) (2015)] which describes the probability of violation of local…

Austin Gilliam, Stefan Woerner, and Constantin Gonciulea,

Quantum 5, 428 (2021).

In this paper we discuss Grover Adaptive Search (GAS) for Constrained Polynomial Binary Optimization (CPBO) problems, and in particular, Quadratic Unconstrained Binary Optimization (QUBO) pr…

Zbigniew Puchała, Łukasz Pawela, Aleksandra Krawiec, Ryszard Kukulski, and Michał Oszmaniec,

Quantum 5, 425 (2021).

We present an in-depth study of the problem of multiple-shot discrimination of von Neumann measurements in finite-dimensional Hilbert spaces. Specifically, we consider two scenarios: minimum…

Nikolai Miklin and Michał Oszmaniec,

Quantum 5, 424 (2021).

We consider the problem of certification of arbitrary ensembles of pure states and projective measurements solely from the experimental statistics in the prepare-and-measure scenario assumin…

Valery Shchesnovich,

Quantum 5, 423 (2021).

Giving a convincing experimental evidence of the quantum supremacy over classical simulations is a challenging goal. Noise is considered to be the main problem in such a demonstration, hence…

Lena Funcke, Tobias Hartung, Karl Jansen, Stefan Kühn, and Paolo Stornati,

Quantum 5, 422 (2021).

Parametric quantum circuits play a crucial role in the performance of many variational quantum algorithms. To successfully implement such algorithms, one must design efficient quantum circui…

Miriam Backens, Hector Miller-Bakewell, Giovanni de Felice, Leo Lobski, and John van de Wetering,

Quantum 5, 421 (2021).

Translations between the quantum circuit model and the measurement-based one-way model are useful for verification and optimisation of quantum computations. They make crucial use of a proper…

Jakub Rembieliński and Paweł Caban,

Quantum 5, 420 (2021).

In this paper we consider deterministic nonlinear time evolutions satisfying so called convex quasi-linearity condition. Such evolutions preserve the equivalence of ensembles and therefore a…

David Schmid, Haoxing Du, Maryam Mudassar, Ghi Coulter-de Wit, Denis Rosset, and Matty J. Hoban,

Quantum 5, 419 (2021).

We define the type-independent resource theory of local operations and shared entanglement (LOSE). This allows us to formally quantify postquantumness in common-cause scenarios such as the B…

Ivan Šupić, Daniel Cavalcanti, and Joseph Bowles,

Quantum 5, 418 (2021).

Self-testing protocols are methods to determine the presence of shared entangled states in a device independent scenario, where no assumptions on the measurements involved in the protocol ar…

Ryan Sweke, Jean-Pierre Seifert, Dominik Hangleiter, and Jens Eisert,

Quantum 5, 417 (2021).

Here we study the comparative power of classical and quantum learners for generative modelling within the Probably Approximately Correct (PAC) framework. More specifically we consider the fo…

David Drahi, Demid V. Sychev, Khurram K. Pirov, Ekaterina A. Sazhina, Valeriy A. Novikov, Ian A. Walmsley, and A. I. Lvovsky,

Quantum 5, 416 (2021).

Today's most widely used method of encoding quantum information in optical qubits is the dual-rail basis, often carried out through the polarisation of a single photon. On the other hand, ma…

Daniel Mills, Seyon Sivarajah, Travis L. Scholten, and Ross Duncan,

Quantum 5, 415 (2021).

Quantum computing systems need to be benchmarked in terms of practical tasks they would be expected to do. Here, we propose 3 "application-motivated" circuit classes for benchmarking: deep (…

Seung-Woo Lee, Jaewan Kim, and Hyunchul Nha,

Quantum 5, 414 (2021).

Quantum measurement is a basic tool to manifest intrinsic quantum effects from fundamental tests to quantum information applications. While a measurement is typically performed to gain infor…

Emanuel Malvetti, Raban Iten, and Roger Colbeck,

Quantum 5, 412 (2021).

We consider the task of breaking down a quantum computation given as an isometry into C-NOTs and single-qubit gates, while keeping the number of C-NOT gates small. Although several decomposi…

Nikolaos Koukoulekidis, Rhea Alexander, Thomas Hebdige, and David Jennings,

Quantum 5, 411 (2021).

Passivity is a fundamental concept that constitutes a necessary condition for any quantum system to attain thermodynamic equilibrium, and for a notion of temperature to emerge. While extensi…

Johnnie Gray and Stefanos Kourtis,

Quantum 5, 410 (2021).

Tensor networks represent the state-of-the-art in computational methods across many disciplines, including the classical simulation of quantum many-body systems and quantum circuits. Several…

Selwyn Simsek and Florian Mintert,

Quantum 5, 409 (2021).

The framework of quantum invariants is an elegant generalization of adiabatic quantum control to control fields that do not need to change slowly. Due to the unavailability of invariants for…

Patryk Lipka-Bartosik, Paweł Mazurek, and Michał Horodecki,

Quantum 5, 408 (2021).

In stochastic thermodynamics work is a random variable whose average is bounded by the change in the free energy of the system. In most treatments, however, the work reservoir that absorbs t…

Roberto Salazar, Tanmoy Biswas, Jakub Czartowski, Karol Życzkowski, and Paweł Horodecki,

Quantum 5, 407 (2021).

The optimal allocation of resources is a crucial task for their efficient use in a wide range of practical applications in science and engineering. This paper investigates the optimal alloca…

Seok Hyung Lie, Hyukjoon Kwon, M. S. Kim, and Hyunseok Jeong,

Quantum 5, 405 (2021).

The commodity-based cryptography is an alternative approach to realize conventionally impossible cryptographic primitives such as unconditionally secure bit-commitment by consuming pre-estab…

Sebastian Horvat and Borivoje Dakić,

Quantum 5, 404 (2021).

The double slit experiment provides a clear demarcation between classical and quantum theory, while multi-slit experiments demarcate quantum and higher-order interference theories. In this w…

Daniel Copeland and Jamie Pommersheim,

Quantum 5, 403 (2021).

We study the query complexity of quantum learning problems in which the oracles form a group $G$ of unitary matrices. In the simplest case, one wishes to identify the oracle, and we find a des…

João F. Doriguello and Ashley Montanaro,

Quantum 5, 402 (2021).

An $n\overset{p}{\mapsto}m$ random access code (RAC) is an encoding of $n$ bits into $m$ bits such that any initial bit can be recovered with probability at least $p$, while in a quantum RAC (QRAC),…

Jean-Daniel Bancal, Kai Redeker, Pavel Sekatski, Wenjamin Rosenfeld, and Nicolas Sangouard,

Quantum 5, 401 (2021).

Self-testing is a method to certify devices from the result of a Bell test. Although examples of noise tolerant self-testing are known, it is not clear how to deal efficiently with a finite…

Nathan Ramusat and Vincenzo Savona,

Quantum 5, 399 (2021).

Simulating the dynamics and the non-equilibrium steady state of an open quantum system are hard computational tasks on conventional computers. For the simulation of the time evolution, sever…

Julio Carlos Magdalena de la Fuente, Nicolas Tarantino, and Jens Eisert,

Quantum 5, 398 (2021).

It has long been known that long-ranged entangled topological phases can be exploited to protect quantum information against unwanted local errors. Indeed, conditions for intrinsic topologic…

Paul Hilaire, Edwin Barnes, and Sophia E. Economou,

Quantum 5, 397 (2021).

Quantum communication technologies show great promise for applications ranging from the secure transmission of secret messages to distributed quantum computing. Due to fiber losses, long-dis…

Gary J. Mooney, Charles D. Hill, and Lloyd C. L. Hollenberg,

Quantum 5, 396 (2021).

For universal quantum computation, a major challenge to overcome for practical implementation is the large amount of resources required for fault-tolerant quantum information processing. An…

Elizabeth Crosson and Aram W. Harrow,

Quantum 5, 395 (2021).

Path integral quantum Monte Carlo (PIMC) is a method for estimating thermal equilibrium properties of stoquastic quantum spin systems by sampling from a classical Gibbs distribution using Ma…

Jan F. Haase, Luca Dellantonio, Alessio Celi, Danny Paulson, Angus Kan, Karl Jansen, and Christine A. Muschik,

Quantum 5, 393 (2021).

Gauge theories establish the standard model of particle physics, and lattice gauge theory (LGT) calculations employing Markov Chain Monte Carlo (MCMC) methods have been pivotal in our unders…

J. Eli Bourassa, Rafael N. Alexander, Michael Vasmer, Ashlesha Patil, Ilan Tzitrin, Takaya Matsuura, Daiqin Su, Ben Q. Baragiola, Saikat Guha, Guillaume Dauphinais, Krishna K. Sabapathy, Nicolas C. Menicucci, and Ish Dhand,

Quantum 5, 392 (2021).

Photonics is the platform of choice to build a modular, easy-to-network quantum computer operating at room temperature. However, no concrete architecture has been presented so far that explo…

Hamza Fawzi and Omar Fawzi,

Quantum 5, 387 (2021).

We introduce a new quantum Rényi divergence $D^{\#}_{\alpha}$ for $\alpha \in (1,\infty)$ defined in terms of a convex optimization program. This divergence has several desirable computational a…

Leonardo Banchi and Gavin E. Crooks,

Quantum 5, 386 (2021).

Hybrid quantum-classical optimization algorithms represent one of the most promising application for near-term quantum computers. In these algorithms the goal is to optimize an observable qu…

Ophelia Crawford, Barnaby van Straaten, Daochen Wang, Thomas Parks, Earl Campbell, and Stephen Brierley,

Quantum 5, 385 (2021).

Estimating the expectation value of an operator corresponding to an observable is a fundamental task in quantum computation. It is often impossible to obtain such estimates directly, as the…

Timothée Hoffreumon and Ognyan Oreshkov,

Quantum 5, 384 (2021).

We develop an extension of the process matrix (PM) framework for correlations between quantum operations with no causal order that allows multiple rounds of information exchange for each par…

Mischa P. Woods,

Quantum 5, 381 (2021).

There are many different types of time keeping devices. We use the phrase $\textit{ticking clock}$ to describe those which – simply put – “tick'' at approximately regular intervals. Various i…

Kianna Wan,

Quantum 5, 380 (2021).

We present a simple but general framework for constructing quantum circuits that implement the multiply-controlled unitary…