Quantum

Paper

Bound entangled states fit for robust experimental verification

Gael Sentís, Johannes N. Greiner, Jiangwei Shang, Jens Siewert, and Matthias Kleinmann,

Quantum 2, 113 (2018).

Preparing and certifying bound entangled states in the laboratory is an intrinsically hard task, due to both the fact that they typically form narrow regions in state space, and that a certi…

Paper

Quantum Interference of Force

Raul Corrêa, Marina F. B. Cenni, and Pablo L. Saldanha,

Quantum 2, 112 (2018).

We show that a quantum particle subjected to a positive force in one path of a Mach-Zehnder interferometer and a null force in the other path may receive a negative average momentum transfer…

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…

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