Quantum – the open journal for quantum science

Quantum has published 93 Papers in 2 Volumes, as well as 11 Views in Quantum Views.

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…

Paper

Reliable numerical key rates for quantum key distribution

Adam Winick, Norbert Lütkenhaus, and Patrick J. Coles,

Quantum 2, 77 (2018). https://doi.org/10.22331/q-2018-07-26-77

In this work, we present a reliable, efficient, and tight numerical method for calculating key rates for finite-dimensional quantum key distribution (QKD) protocols. We illustrate our approa…

News

New Quantum papers to your inbox

Want to keep track of the latest papers appearing in Quantum? Now you have a new option: starting on the 1st of August, Quantum offers a monthly digest (sign up …

Leap

Single-molecule spintronics, or how to measure the magnetic state of a single atomic nucleus

Joana T. Coutinho, Salvador Cardona-Serra, and Alejandro Gaita-Ariño,

Quantum Views 2, 11 (2018). https://doi.org/10.22331/qv-2018-07-17-11

What is “Spintronics”? Imagine that you could store all the human knowledge in a single USB flash drive. Now imagine that you could access and select all that information as fast as you thin…

Leap

Sensing magnetic fields with diamonds and green laser light

Louise F. Frellsen and Sepehr Ahmadi,

Quantum Views 2, 10 (2018). https://doi.org/10.22331/qv-2018-07-17-10

Nitrogen-Vacancy (NV) centres in diamonds have quantum properties that allow them to sense weak magnetic fields. This is relevant both for research and health care as diamond magnetom…

Leap

How to build internet for quantum computers

Ondřej Černotík,

Quantum Views 2, 9 (2018). https://doi.org/10.22331/qv-2018-07-11-9

I am sitting at my computer and writing an article. When I finish and decide to publish it, a chain of events will start. First, my computer will take the electric signals encoding the words…

Leap

A simple demonstration of incompatibility of measurements

Martin Plávala,

Quantum Views 2, 8 (2018). https://doi.org/10.22331/qv-2018-07-11-8

The incompatibility of measurements is a strange feature of Quantum theory that forbids us from performing two measurements at the same time. Usually presented in the form of Heisenberg’s un…

Paper

Tomographically reconstructed master equations for any open quantum dynamics

Felix A. Pollock and Kavan Modi,

Quantum 2, 76 (2018). https://doi.org/10.22331/q-2018-07-11-76

Memory effects in open quantum dynamics are often incorporated in the equation of motion through a superoperator known as the memory kernel, which encodes how past states affect future dynam…

Leap

Zooming into superconductors

Jayadev Vijayan,

Quantum Views 2, 7 (2018). https://doi.org/10.22331/qv-2018-07-11-7

The game: minimizing energy Imagine I give you six balls, three red and three blue, and ask you to arrange them in a line. The only rule is that whenever two balls of the same colour are nex…

Paper

Hamiltonians for one-way quantum repeaters

Filippo M. Miatto, Michael Epping, and Norbert Lütkenhaus,

Quantum 2, 75 (2018). https://doi.org/10.22331/q-2018-07-05-75

Quantum information degrades over distance due to the unavoidable imperfections of the transmission channels, with loss as the leading factor. This simple fact hinders quantum communication,…

Leap

Superpositions test if gravity pulls the same on two objects

Eric Copenhaver,

Quantum Views 2, 6 (2018). https://doi.org/10.22331/qv-2018-07-04-6

Rocks and waves I used to go camping with my family. We always chose to camp close to the water. I didn’t like reading when I was young, so I always got bored when my parents sat down to rea…

Paper

Halving the cost of quantum addition

Craig Gidney,

Quantum 2, 74 (2018). https://doi.org/10.22331/q-2018-06-18-74

We improve the number of T gates needed to perform an n-bit adder from $8n + O(1)$ to $4n + O(1)$. We do so via a "temporary logical-AND" construction which uses four T gates to store the lo…