Paper Fast and high-fidelity entangling gate through parametrically modulated longitudinal coupling Baptiste Royer, Arne L. Grimsmo, Nicolas Didier, and Alexandre Blais, Quantum 1, 11 (2017). https://doi.org/10.22331/q-2017-05-11-11 We investigate an approach to universal quantum computation based on the modulation of longitudinal qubit-oscillator coupling. We show how to realize a controlled-phase gate by simultaneousl…
Paper A purification postulate for quantum mechanics with indefinite causal order Mateus Araújo, Adrien Feix, Miguel Navascués, and Časlav Brukner, Quantum 1, 10 (2017). https://doi.org/10.22331/q-2017-04-26-10 To study which are the most general causal structures which are compatible with local quantum mechanics, Oreshkov et al. introduced the notion of a process: a resource shared between some pa…
Paper Finite-density phase diagram of a $(1+1)-d$ non-abelian lattice gauge theory with tensor networks Pietro Silvi, Enrique Rico, Marcello Dalmonte, Ferdinand Tschirsich, and Simone Montangero, Quantum 1, 9 (2017). https://doi.org/10.22331/q-2017-04-25-9 We investigate the finite-density phase diagram of a non-abelian $SU(2)$ lattice gauge theory in $(1+1)$-dimensions using tensor network methods. We numerically characterise the phase diagra…
Paper Achieving quantum supremacy with sparse and noisy commuting quantum computations Michael J. Bremner, Ashley Montanaro, and Dan J. Shepherd, Quantum 1, 8 (2017). https://doi.org/10.22331/q-2017-04-25-8 The class of commuting quantum circuits known as IQP (instantaneous quantum polynomial-time) has been shown to be hard to simulate classically, assuming certain complexity-theoretic conjectu…
Paper Proposal for witnessing non-classical light with the human eye A. Dodel, A. Mayinda, E. Oudot, A. Martin, P. Sekatski, J.-D. Bancal, and N. Sangouard, Quantum 1, 7 (2017). https://doi.org/10.22331/q-2017-04-25-7 We give a complete proposal showing how to detect the non-classical nature of photonic states with naked eyes as detectors. The enabling technology is a sub-Poissonian photonic state that is…
Paper Extremal eigenvalues of local Hamiltonians Aram W. Harrow and Ashley Montanaro, Quantum 1, 6 (2017). https://doi.org/10.22331/q-2017-04-25-6 We apply classical algorithms for approximately solving constraint satisfaction problems to find bounds on extremal eigenvalues of local Hamiltonians. We consider spin Hamiltonians for which…
Paper QInfer: Statistical inference software for quantum applications Christopher Granade, Christopher Ferrie, Ian Hincks, Steven Casagrande, Thomas Alexander, Jonathan Gross, Michal Kononenko, and Yuval Sanders, Quantum 1, 5 (2017). https://doi.org/10.22331/q-2017-04-25-5 Characterizing quantum systems through experimental data is critical to applications as diverse as metrology and quantum computing. Analyzing this experimental data in a robust and reproduci…
Paper Limits on the storage of quantum information in a volume of space Steven T. Flammia, Jeongwan Haah, Michael J. Kastoryano, and Isaac H. Kim, Quantum 1, 4 (2017). https://doi.org/10.22331/q-2017-04-25-4 We study the fundamental limits on the reliable storage of quantum information in lattices of qubits by deriving tradeoff bounds for approximate quantum error correcting codes. We introduce…
Paper Better local hidden variable models for two-qubit Werner states and an upper bound on the Grothendieck constant $K_G(3)$ Flavien Hirsch, Marco Túlio Quintino, Tamás Vértesi, Miguel Navascués, and Nicolas Brunner, Quantum 1, 3 (2017). https://doi.org/10.22331/q-2017-04-25-3 We consider the problem of reproducing the correlations obtained by arbitrary local projective measurements on the two-qubit Werner state $\rho = v |\psi_- \rangle \langle\psi_- | + (1- v ) \frac{1}{4}$…
Paper The surface code with a twist Theodore J. Yoder and Isaac H. Kim, Quantum 1, 2 (2017). https://doi.org/10.22331/q-2017-04-25-2 The surface code is one of the most successful approaches to topological quantum error-correction. It boasts the smallest known syndrome extraction circuits and correspondingly largest thres…
