Quantum – the open journal for quantum science

Quantum has published 104 Papers in 2 Volumes, as well as 11 Views in Quantum Views.

Paper

Faster quantum mixing for slowly evolving sequences of Markov chains

Davide Orsucci, Hans J. Briegel, and Vedran Dunjko,

Quantum 2, 105 (2018). https://doi.org/10.22331/q-2018-11-09-105

Markov chain methods are remarkably successful in computational physics, machine learning, and combinatorial optimization. The cost of such methods often reduces to the mixing time, i.e., th…

Paper

Any modification of the Born rule leads to a violation of the purification and local tomography principles

Thomas D. Galley and Lluis Masanes,

Quantum 2, 104 (2018). https://doi.org/10.22331/q-2018-11-06-104

Using the existing classification of all alternatives to the measurement postulates of quantum theory we study the properties of bi-partite systems in these alternative theories. We prove th…

Paper

How to make unforgeable money in generalised probabilistic theories

John H. Selby and Jamie Sikora,

Quantum 2, 103 (2018). https://doi.org/10.22331/q-2018-11-02-103

We discuss the possibility of creating money that is physically impossible to counterfeit. Of course, "physically impossible" is dependent on the theory that is a faithful description of nat…

Paper

Multi-path Summation for Decoding 2D Topological Codes

Ben Criger and Imran Ashraf,

Quantum 2, 102 (2018). https://doi.org/10.22331/q-2018-10-19-102

Fault tolerance is a prerequisite for scalable quantum computing. Architectures based on 2D topological codes are effective for near-term implementations of fault tolerance. To obtain high p…

Paper

The boundaries and twist defects of the color code and their applications to topological quantum computation

Markus S. Kesselring, Fernando Pastawski, Jens Eisert, and Benjamin J. Brown,

Quantum 2, 101 (2018). https://doi.org/10.22331/q-2018-10-19-101

The color code is both an interesting example of an exactly solved topologically ordered phase of matter and also among the most promising candidate models to realize fault-tolerant quantum…

Paper

Using and reusing coherence to realize quantum processes

María García Díaz, Kun Fang, Xin Wang, Matteo Rosati, Michalis Skotiniotis, John Calsamiglia, and Andreas Winter,

Quantum 2, 100 (2018). https://doi.org/10.22331/q-2018-10-19-100

Coherent superposition is a key feature of quantum mechanics that underlies the advantage of quantum technologies over their classical counterparts. Recently, coherence has been recast as a…

Paper

On Formalisms and Interpretations

Veronika Baumann and Stefan Wolf,

Quantum 2, 99 (2018). https://doi.org/10.22331/q-2018-10-15-99

One of the reasons for the heated debates around the interpretations of quantum theory is a simple confusion between the notions of formalism $\textit{versus}$ interpretation. In this note,…

Paper

Time-reversal of rank-one quantum strategy functions

Yuan Su and John Watrous,

Quantum 2, 98 (2018). https://doi.org/10.22331/q-2018-10-04-98

The $\textit{quantum strategy}$ (or $\textit{quantum combs}$) framework is a useful tool for reasoning about interactions among entities that process and exchange quantum information over th…

Paper

Non-Markovian Quantum Optics with Three-Dimensional State-Dependent Optical Lattices

A. González-Tudela and J. I. Cirac,

Quantum 2, 97 (2018). https://doi.org/10.22331/q-2018-10-01-97

Quantum emitters coupled to structured photonic reservoirs experience unconventional individual and collective dynamics emerging from the interplay between dimensionality and non-trivial pho…

Paper

Distinguishability times and asymmetry monotone-based quantum speed limits in the Bloch ball

T.J. Volkoff and K.B. Whaley,

Quantum 2, 96 (2018). https://doi.org/10.22331/q-2018-10-01-96

For both unitary and open qubit dynamics, we compare asymmetry monotone-based bounds on the minimal time required for an initial qubit state to evolve to a final qubit state from which it is…

Paper

Complete homotopy invariants for translation invariant symmetric quantum walks on a chain

C. Cedzich, T. Geib, C. Stahl, L. Velázquez, A. H. Werner, and R. F. Werner,

Quantum 2, 95 (2018). https://doi.org/10.22331/q-2018-09-24-95

We provide a classification of translation invariant one-dimensional quantum walks with respect to continuous deformations preserving unitarity, locality, translation invariance, a gap condi…

Paper

Analysis and limitations of modified circuit-to-Hamiltonian constructions

Johannes Bausch and Elizabeth Crosson,

Quantum 2, 94 (2018). https://doi.org/10.22331/q-2018-09-19-94

Feynman's circuit-to-Hamiltonian construction connects quantum computation and ground states of many-body quantum systems. Kitaev applied this construction to demonstrate QMA-completeness of…

Paper

Quantum repeaters with individual rare-earth ions at telecommunication wavelengths

F. Kimiaee Asadi, N. Lauk, S. Wein, N. Sinclair, C. O’Brien, and C. Simon,

Quantum 2, 93 (2018). https://doi.org/10.22331/q-2018-09-13-93

We present a quantum repeater scheme that is based on individual erbium and europium ions. Erbium ions are attractive because they emit photons at telecommunication wavelength, while europiu…

Paper

Test for a large amount of entanglement, using few measurements

Rui Chao, Ben W. Reichardt, Chris Sutherland, and Thomas Vidick,

Quantum 2, 92 (2018). https://doi.org/10.22331/q-2018-09-03-92

Bell-inequality violations establish that two systems share some quantum entanglement. We give a simple test to certify that two systems share an asymptotically large amount of entanglement,…

Paper

Electro-mechanical Casimir effect

Mikel Sanz, Witlef Wieczorek, Simon Gröblacher, and Enrique Solano,

Quantum 2, 91 (2018). https://doi.org/10.22331/q-2018-09-03-91

The dynamical Casimir effect is an intriguing phenomenon in which photons are generated from vacuum due to a non-adiabatic change in some boundary conditions. In particular, it connects the…

Paper

Experimental quantification of spatial correlations in quantum dynamics

Lukas Postler, Ángel Rivas, Philipp Schindler, Alexander Erhard, Roman Stricker, Daniel Nigg, Thomas Monz, Rainer Blatt, and Markus Müller,

Quantum 2, 90 (2018). https://doi.org/10.22331/q-2018-09-03-90

Correlations between different partitions of quantum systems play a central role in a variety of many-body quantum systems, and they have been studied exhaustively in experimental and theore…

Paper

Fidelity of quantum strategies with applications to cryptography

Gus Gutoski, Ansis Rosmanis, and Jamie Sikora,

Quantum 2, 89 (2018). https://doi.org/10.22331/q-2018-09-03-89

We introduce a definition of the fidelity function for multi-round quantum strategies, which we call the $\textit{strategy fidelity}$, that is a generalization of the fidelity function for q…

Paper

Modeling noise and error correction for Majorana-based quantum computing

Christina Knapp, Michael Beverland, Dmitry I. Pikulin, and Torsten Karzig,

Quantum 2, 88 (2018). https://doi.org/10.22331/q-2018-09-03-88

Majorana-based quantum computing seeks to use the non-local nature of Majorana zero modes to store and manipulate quantum information in a topologically protected way. While noise is anticip…

Paper

Almost Quantum Correlations are Inconsistent with Specker’s Principle

Tomáš Gonda, Ravi Kunjwal, David Schmid, Elie Wolfe, and Ana Belén Sainz,

Quantum 2, 87 (2018). https://doi.org/10.22331/q-2018-08-27-87

Ernst Specker considered a particular feature of quantum theory to be especially fundamental, namely that pairwise joint measurability of sharp measurements implies their global joint measur…

Paper

Device-independent randomness generation with sublinear shared quantum resources

Cédric Bamps, Serge Massar, and Stefano Pironio,

Quantum 2, 86 (2018). https://doi.org/10.22331/q-2018-08-22-86

In quantum cryptography, device-independent (DI) protocols can be certified secure without requiring assumptions about the inner workings of the devices used to perform the protocol. In orde…

Paper

Real Randomized Benchmarking

A. K. Hashagen, S. T. Flammia, D. Gross, and J. J. Wallman,

Quantum 2, 85 (2018). https://doi.org/10.22331/q-2018-08-22-85

Randomized benchmarking provides a tool for obtaining precise quantitative estimates of the average error rate of a physical quantum channel. Here we define real randomized benchmarking, whi…

Paper

Quantum walking in curved spacetime: discrete metric

Pablo Arrighi, Giuseppe Di Molfetta, and Stefano Facchini,

Quantum 2, 84 (2018). https://doi.org/10.22331/q-2018-08-22-84

A discrete-time quantum walk (QW) is essentially a unitary operator driving the evolution of a single particle on the lattice. Some QWs have familiar physics PDEs as their continuum limit. S…

Paper

Measuring acceleration using the Purcell effect

Kacper Kożdoń, Ian T. Durham, and Andrzej Dragan,

Quantum 2, 83 (2018). https://doi.org/10.22331/q-2018-08-18-83

We show that a two-level atom resonantly coupled to one of the modes of a cavity field can be used as a sensitive tool to measure the proper acceleration of a combined atom-cavity system. To…

Paper

Randomness versus nonlocality in the Mermin-Bell experiment with three parties

Erik Woodhead, Boris Bourdoncle, and Antonio Acín,

Quantum 2, 82 (2018). https://doi.org/10.22331/q-2018-08-17-82

The detection of nonlocal correlations in a Bell experiment implies almost by definition some intrinsic randomness in the measurement outcomes. For given correlations, or for a given Bell vi…

News

Quantum preserved in CLOCKSS

All articles published in Quantum and their meta-data are now securely and permanently preserved in the CLOCKSS Archive. In addition to our own backup strategy, which involves off-site storage of …

Paper

Monogamy of entanglement without inequalities

Gilad Gour and Yu Guo,

Quantum 2, 81 (2018). https://doi.org/10.22331/q-2018-08-13-81

We provide a fine-grained definition for monogamous measure of entanglement that does not invoke any particular monogamy relation. Our definition is given in terms an equality, as oppose to…

Paper

In situ upgrade of quantum simulators to universal computers

Benjamin Dive, Alexander Pitchford, Florian Mintert, and Daniel Burgarth,

Quantum 2, 80 (2018). https://doi.org/10.22331/q-2018-08-08-80

Quantum simulators, machines that can replicate the dynamics of quantum systems, are being built as useful devices and are seen as a stepping stone to universal quantum computers. A key diff…

Paper

Quantum Computing in the NISQ era and beyond

John Preskill,

Quantum 2, 79 (2018). https://doi.org/10.22331/q-2018-08-06-79

Noisy Intermediate-Scale Quantum (NISQ) technology will be available in the near future. Quantum computers with 50-100 qubits may be able to perform tasks which surpass the capabilities of t…

News

Quantum receives donation from Xanadu

Xanadu becomes the first quantum computing startup to support fair open-access publishing in quantum science by supporting Quantum with a small yearly donation that will contribute to cover the operating …

Paper

A Short Path Quantum Algorithm for Exact Optimization

M. B. Hastings,

Quantum 2, 78 (2018). https://doi.org/10.22331/q-2018-07-26-78

We give a quantum algorithm to exactly solve certain problems in combinatorial optimization, including weighted MAX-2-SAT as well as problems where the objective function is a weighted sum o…