Quantum – the open journal for quantum science

Quantum has published 80 Papers in 2 Volumes, as well as 11 Views in Quantum Views.

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…

Peer-review at Quantum – analyzing the data

Christian Gogolin,

Quantum Views 2, 5 (2018). https://doi.org/10.22331/qv-2018-06-18-5

Many of you asked: "How long does it take to get published in Quantum?" We at Quantum are equally curious, as we want to provide the community with the most efficient peer-review process tha…

The dawn of quantum programming

Julien Ross,

Quantum Views 2, 4 (2018). https://doi.org/10.22331/qv-2018-06-14-4

Seminal work in the field of quantum programming was done at the turn of the century but these investigations were often restricted to theoretical studies and toy programming languages [0,1]…

Paper

Heralded generation of maximal entanglement in any dimension via incoherent coupling to thermal baths

Armin Tavakoli, Géraldine Haack, Marcus Huber, Nicolas Brunner, and Jonatan Bohr Brask,

Quantum 2, 73 (2018). https://doi.org/10.22331/q-2018-06-13-73

We present a scheme for dissipatively generating maximal entanglement in a heralded manner. Our setup requires incoherent interactions with two thermal baths at different temperatures, but n…

Paper

Robust Bell inequalities from communication complexity

Sophie Laplante, Mathieu Laurière, Alexandre Nolin, Jérémie Roland, and Gabriel Senno,

Quantum 2, 72 (2018). https://doi.org/10.22331/q-2018-06-07-72

The question of how large Bell inequality violations can be, for quantum distributions, has been the object of much work in the past several years. We say that a Bell inequality is normalize…

Paper

Codes and Protocols for Distilling $T$, controlled-$S$, and Toffoli Gates

Jeongwan Haah and Matthew B. Hastings,

Quantum 2, 71 (2018). https://doi.org/10.22331/q-2018-06-07-71

We present several different codes and protocols to distill $T$, controlled-$S$, and Toffoli (or $CCZ$) gates. One construction is based on codes that generalize the triorthogonal codes, all…

Paper

Phonon-assisted relaxation and decoherence of singlet-triplet qubits in Si/SiGe quantum dots

Viktoriia Kornich, Christoph Kloeffel, and Daniel Loss,

Quantum 2, 70 (2018). https://doi.org/10.22331/q-2018-05-28-70

We study theoretically the phonon-induced relaxation and decoherence of spin states of two electrons in a lateral double quantum dot in a SiGe/Si/SiGe heterostructure. We consider two types…

Paper

Scattering into one-dimensional waveguides from a coherently-driven quantum-optical system

Kevin A. Fischer, Rahul Trivedi, Vinay Ramasesh, Irfan Siddiqi, and Jelena Vučković,

Quantum 2, 69 (2018). https://doi.org/10.22331/q-2018-05-28-69

We develop a new computational tool and framework for characterizing the scattering of photons by energy-nonconserving Hamiltonians into unidirectional (chiral) waveguides, for example, with…

Paper

Scalable Neural Network Decoders for Higher Dimensional Quantum Codes

Nikolas P. Breuckmann and Xiaotong Ni,

Quantum 2, 68 (2018). https://doi.org/10.22331/q-2018-05-24-68

Machine learning has the potential to become an important tool in quantum error correction as it allows the decoder to adapt to the error distribution of a quantum chip. An additional motiva…

Paper

Coarse-grained distinguishability of field interactions

Cédric Bény,

Quantum 2, 67 (2018). https://doi.org/10.22331/q-2018-05-24-67

Information-theoretical quantities such as statistical distinguishability typically result from optimisations over all conceivable observables. Physical theories, however, are not generally…

Paper

Fluctuation-dissipation theorem for non-equilibrium quantum systems

Mohammad Mehboudi, Anna Sanpera, and Juan M. R. Parrondo,

Quantum 2, 66 (2018). https://doi.org/10.22331/q-2018-05-24-66

The fluctuation-dissipation theorem (FDT) is a central result in statistical physics, both for classical and quantum systems. It establishes a relationship between the linear response of a s…

Paper

Anticoncentration theorems for schemes showing a quantum speedup

Dominik Hangleiter, Juan Bermejo-Vega, Martin Schwarz, and Jens Eisert,

Quantum 2, 65 (2018). https://doi.org/10.22331/q-2018-05-22-65

One of the main milestones in quantum information science is to realise quantum devices that exhibit an exponential computational advantage over classical ones without being universal quantu…

Paper

Distribution of entanglement and correlations in all finite dimensions

Christopher Eltschka and Jens Siewert,

Quantum 2, 64 (2018). https://doi.org/10.22331/q-2018-05-22-64

The physics of a many-particle system is determined by the correlations in its quantum state. Therefore, analyzing these correlations is the foremost task of many-body physics. Any 'a priori…

Paper

Causation does not explain contextuality

Sally Shrapnel and Fabio Costa,

Quantum 2, 63 (2018). https://doi.org/10.22331/q-2018-05-18-63

Realist interpretations of quantum mechanics presuppose the existence of elements of reality that are independent of the actions used to reveal them. Such a view is challenged by several no-…