Paper – Quantum

Paper

Experimental investigation of high-dimensional quantum key distribution protocols with twisted photons

Frédéric Bouchard, Khabat Heshami, Duncan England, Robert Fickler, Robert W. Boyd, Berthold-Georg Englert, Luis L. Sánchez-Soto, and Ebrahim Karimi,

Quantum 2, 111 (2018).

Quantum key distribution is on the verge of real world applications, where perfectly secure information can be distributed among multiple parties. Several quantum cryptographic protocols hav…

Paper

Restoring Heisenberg scaling in noisy quantum metrology by monitoring the environment

Francesco Albarelli, Matteo A. C. Rossi, Dario Tamascelli, and Marco G. Genoni,

Quantum 2, 110 (2018).

We study quantum frequency estimation for $N$ qubits subjected to independent Markovian noise, via strategies based on time-continuous monitoring of the environment. Both physical intuition…

Paper

Hallmarking quantum states: unified framework for coherence and correlations

Gian Luca Giorgi and Roberta Zambrini,

Quantum 2, 109 (2018).

Quantum coherence and distributed correlations among subparties are often considered as separate, although operationally linked to each other, properties of a quantum state. Here, we propose…

Paper

Beyond the thermodynamic limit: finite-size corrections to state interconversion rates

Christopher T. Chubb, Marco Tomamichel, and Kamil Korzekwa,

Quantum 2, 108 (2018).

Thermodynamics is traditionally constrained to the study of macroscopic systems whose energy fluctuations are negligible compared to their average energy. Here, we push beyond this thermodyn…

Paper

Bell correlations at finite temperature

Matteo Fadel and Jordi Tura,

Quantum 2, 107 (2018).

We show that spin systems with infinite-range interactions can violate at thermal equilibrium a multipartite Bell inequality, up to a finite critical temperature $T_c$. Our framework can be…

Paper

Merlin-Arthur with efficient quantum Merlin and quantum supremacy for the second level of the Fourier hierarchy

Tomoyuki Morimae, Yuki Takeuchi, and Harumichi Nishimura,

Quantum 2, 106 (2018).

We introduce a simple sub-universal quantum computing model, which we call the Hadamard-classical circuit with one-qubit (HC1Q) model. It consists of a classical reversible circuit sandwiche…

Paper

Faster quantum mixing for slowly evolving sequences of Markov chains

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

Quantum 2, 105 (2018).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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).

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…