Archives: Paper

Ross Duncan, Aleks Kissinger, Simon Perdrix, and John van de Wetering,

Quantum 4, 279 (2020).

We present a completely new approach to quantum circuit optimisation, based on the ZX-calculus. We first interpret quantum circuits as ZX-diagrams, which provide a flexible, lower-level lang…

Adrian Chapman and Steven T. Flammia,

Quantum 4, 278 (2020).

Exactly solvable models are essential in physics. For many-body spin-$\mathbf{\sf{1}/{2}}$ systems, an important class of such models consists of those that can be mapped to free fermions hopp…

Jacob C. Bridgeman and Daniel Barter,

Quantum 4, 277 (2020).

We demonstrate how to do many computations for doubled topological phases with defects. These defects may be 1-dimensional domain walls or 0-dimensional point defects. Using…

Zhang Jiang, Amir Kalev, Wojciech Mruczkiewicz, and Hartmut Neven,

Quantum 4, 276 (2020).

We introduce a fermion-to-qubit mapping defined on ternary trees, where any single Majorana operator on an $n$-mode fermionic system is mapped to a multi-qubit Pauli operator acting nontrivial…

Nikola Paunković and Marko Vojinović,

Quantum 4, 275 (2020).

We study the notion of causal orders for the cases of (classical and quantum) circuits and spacetime events. We show that every circuit can be immersed into a classical spacetime, preserving…

Daniel Nickelsen and Michael Kastner,

Quantum 4, 273 (2020).

We introduce structured random matrix ensembles, constructed to model many-body quantum systems with local interactions. These ensembles are employed to study equilibration of isolated many-…

Carlos Bravo-Prieto, Josep Lumbreras-Zarapico, Luca Tagliacozzo, and José I. Latorre,

Quantum 4, 272 (2020).

We benchmark the accuracy of a variational quantum eigensolver based on a finite-depth quantum circuit encoding ground state of local Hamiltonians. We show that in gapped phases, the accurac…

Christian Arenz, Denys I. Bondar, Daniel Burgarth, Cecilia Cormick, and Herschel Rabitz,

Quantum 4, 271 (2020).

Speeding up the dynamics of a quantum system is of paramount importance for quantum technologies. However, in finite dimensions and without full knowledge of the details of the system, it is…

Andreu Riera-Campeny, Maria Moreno-Cardoner, and Anna Sanpera,

Quantum 4, 270 (2020).

Time crystals are genuinely non-equilibrium quantum phases of matter that break time-translational symmetry. While in non-equilibrium closed systems time crystals have been experimentally re…

Marius Schulte, Victor J. Martínez-Lahuerta, Maja S. Scharnagl, and Klemens Hammerer,

Quantum 4, 268 (2020).

We consider a large class of Ramsey interferometry protocols which are enhanced by squeezing and un-squeezing operations before and after a phase signal is imprinted on the collective spin o…

Daniel Jost Brod and Michał Oszmaniec,

Quantum 4, 267 (2020).

We present a comprehensive study of the impact of non-uniform, i.e. path-dependent, photonic losses on the computational complexity of linear-optical processes. Our main result states that,…

Joris Kattemölle and Jasper van Wezel,

Quantum 4, 265 (2020).

Decoherence is the main obstacle to quantum computation. The decoherence rate per qubit is typically assumed to be constant. It is known, however, that quantum registers coupling to a single…