Paper Concepts of work in autonomous quantum heat engines Wolfgang Niedenzu, Marcus Huber, and Erez Boukobza, Quantum 3, 195 (2019). One of the fundamental questions in quantum thermodynamics concerns the decomposition of energetic changes into heat and work. Contrary to classical engines, the entropy change of the piston…
Paper Anomalous Weak Values Without Post-Selection Alastair A. Abbott, Ralph Silva, Julian Wechs, Nicolas Brunner, and Cyril Branciard, Quantum 3, 194 (2019). A weak measurement performed on a pre- and post-selected quantum system can result in an average value that lies outside of the observable's spectrum. This effect, usually referred to as an…
Paper Pilot-assisted intradyne reception for high-speed continuous-variable quantum key distribution with true local oscillator Fabian Laudenbach, Bernhard Schrenk, Christoph Pacher, Michael Hentschel, Chi-Hang Fred Fung, Fotini Karinou, Andreas Poppe, Momtchil Peev, and Hannes Hübel, Quantum 3, 193 (2019). We present a pilot-assisted coherent intradyne reception methodology for CV-QKD with true local oscillator. An optically phase-locked reference tone, prepared using carrier-suppressed optica…
Paper Open quantum systems are harder to track than open classical systems Prahlad Warszawski and Howard M. Wiseman, Quantum 3, 192 (2019). For a Markovian (in the strongest sense) open quantum system it is possible, by continuously monitoring the environment, to perfectly track the system; that is, to know the stochastically ev…
Paper Theory of variational quantum simulation Xiao Yuan, Suguru Endo, Qi Zhao, Ying Li, and Simon C. Benjamin, Quantum 3, 191 (2019). The variational method is a versatile tool for classical simulation of a variety of quantum systems. Great efforts have recently been devoted to its extension to quantum computing for effici…
Paper Product Decomposition of Periodic Functions in Quantum Signal Processing Jeongwan Haah, Quantum 3, 190 (2019). We consider an algorithm to approximate complex-valued periodic functions $f(e^{i\theta})$ as a matrix element of a product of $SU(2)$-valued functions, which underlies so-called quantum sig…
Paper The complexity of simulating local measurements on quantum systems Sevag Gharibian and Justin Yirka, Quantum 3, 189 (2019). An important task in quantum physics is the estimation of local quantities for ground states of local Hamiltonians. Recently, [Ambainis, CCC 2014] defined the complexity class ${P}^{{QMA}[{log}]}$…
Paper Heat-Bath Algorithmic Cooling with optimal thermalization strategies Álvaro M. Alhambra, Matteo Lostaglio, and Christopher Perry, Quantum 3, 188 (2019). Heat-Bath Algorithmic Cooling is a set of techniques for producing highly pure quantum systems by utilizing a surrounding heat-bath and unitary interactions. These techniques originally used…
Paper Locally accurate MPS approximations for ground states of one-dimensional gapped local Hamiltonians Alexander M. Dalzell and Fernando G. S. L. Brandão, Quantum 3, 187 (2019). A key feature of ground states of gapped local 1D Hamiltonians is their relatively low entanglement — they are well approximated by matrix product states (MPS) with bond dimension scaling…
Paper Quantum violations in the Instrumental scenario and their relations to the Bell scenario Thomas Van Himbeeck, Jonatan Bohr Brask, Stefano Pironio, Ravishankar Ramanathan, Ana Belén Sainz, and Elie Wolfe, Quantum 3, 186 (2019). The causal structure of any experiment implies restrictions on the observable correlations between measurement outcomes, which are different for experiments exploiting classical, quantum, or…
Paper Two-Qubit Pure Entanglement as Optimal Social Welfare Resource in Bayesian Game Manik Banik, Some Sankar Bhattacharya, Nirman Ganguly, Tamal Guha, Amit Mukherjee, Ashutosh Rai, and Arup Roy, Quantum 3, 185 (2019). Entanglement is of paramount importance in quantum information theory. Its supremacy over classical correlations has been demonstrated in a numerous information theoretic protocols. Here we…
Paper Beyond the Cabello-Severini-Winter framework: Making sense of contextuality without sharpness of measurements Ravi Kunjwal, Quantum 3, 184 (2019). We develop a hypergraph-theoretic framework for Spekkens contextuality applied to Kochen-Specker (KS) type scenarios that goes beyond the Cabello-Severini-Winter (CSW) framework. To do this,…
Perspective How good is a positive map at detecting quantum entanglement? Ion Nechita, Quantum Views 3, 24 (2019). Since the dawn of quantum mechanics, entanglement has been a central notion of the theory [18], a very important body of work being dedicated to understanding, classifying, measuring, and ch…
Paper Quantum error correction for the toric code using deep reinforcement learning Philip Andreasson, Joel Johansson, Simon Liljestrand, and Mats Granath, Quantum 3, 183 (2019). We implement a quantum error correction algorithm for bit-flip errors on the topological toric code using deep reinforcement learning. An action-value Q-function encodes the discounted value…
Paper Faster quantum simulation by randomization Andrew M. Childs, Aaron Ostrander, and Yuan Su, Quantum 3, 182 (2019). Product formulas can be used to simulate Hamiltonian dynamics on a quantum computer by approximating the exponential of a sum of operators by a product of exponentials of the individual summ…
Paper Simulation of quantum circuits by low-rank stabilizer decompositions Sergey Bravyi, Dan Browne, Padraic Calpin, Earl Campbell, David Gosset, and Mark Howard, Quantum 3, 181 (2019). Recent work has explored using the stabilizer formalism to classically simulate quantum circuits containing a few non-Clifford gates. The computational cost of such methods is directly relat…
