Quantum

Paper

Classification of phases for mixed states via fast dissipative evolution

Andrea Coser and David Pérez-García,

Quantum 3, 174 (2019).

We propose the following definition of topological quantum phases valid for mixed states: two states are in the same phase if there exists a time independent, fast and local Lindbladian evol…

Paper

A polar decomposition for quantum channels (with applications to bounding error propagation in quantum circuits)

Arnaud Carignan-Dugas, Matthew Alexander, and Joseph Emerson,

Quantum 3, 173 (2019).

Inevitably, assessing the overall performance of a quantum computer must rely on characterizing some of its elementary constituents and, from this information, formulate a broader statement…

Paper

The Non-m-Positive Dimension of a Positive Linear Map

Nathaniel Johnston, Benjamin Lovitz, and Daniel Puzzuoli,

Quantum 3, 172 (2019).

We introduce a property of a matrix-valued linear map $\Phi$ that we call its “non-m-positive dimension'' (or “non-mP dimension'' for short), which measures how large a subspace can be if…

Paper

Guaranteed recovery of quantum processes from few measurements

Martin Kliesch, Richard Kueng, Jens Eisert, and David Gross,

Quantum 3, 171 (2019).

Quantum process tomography is the task of reconstructing unknown quantum channels from measured data. In this work, we introduce compressed sensing-based methods that facilitate the reconstr…

Paper

Clifford recompilation for faster classical simulation of quantum circuits

Hammam Qassim, Joel J. Wallman, and Joseph Emerson,

Quantum 3, 170 (2019).

Simulating quantum circuits classically is an important area of research in quantum information, with applications in computational complexity and validation of quantum devices. One of the s…

Paper

Simulating boson sampling in lossy architectures

Raúl García-Patrón, Jelmer J. Renema, and Valery Shchesnovich,

Quantum 3, 169 (2019).

Photon losses are among the strongest imperfections affecting multi-photon interference. Despite their importance, little is known about their effect on boson sampling experiments. In this w…

Paper

Tight, robust, and feasible quantum speed limits for open dynamics

Francesco Campaioli, Felix A. Pollock, and Kavan Modi,

Quantum 3, 168 (2019).

Starting from a geometric perspective, we derive a quantum speed limit for arbitrary open quantum evolution, which could be Markovian or non-Markovian, providing a fundamental bound on the t…

Paper

Applying quantum algorithms to constraint satisfaction problems

Earl Campbell, Ankur Khurana, and Ashley Montanaro,

Quantum 3, 167 (2019).

Quantum algorithms can deliver asymptotic speedups over their classical counterparts. However, there are few cases where a substantial quantum speedup has been worked out in detail for reaso…

Paper

Single-shot energetic-based estimator for entanglement in a half-parity measurement setup

Cyril Elouard, Alexia Auffèves, and Géraldine Haack,

Quantum 3, 166 (2019).

Producing and certifying entanglement between distant qubits is a highly desirable skill for quantum information technologies. Here we propose a new strategy to monitor and characterize enta…

Paper

Minimal energy cost of entanglement extraction

Lucas Hackl and Robert H. Jonsson,

Quantum 3, 165 (2019).

We compute the minimal energy cost for extracting entanglement from the ground state of a bosonic or fermionic quadratic system. Specifically, we find the minimal energy increase in the syst…

Paper

Nonadaptive fault-tolerant verification of quantum supremacy with noise

Theodoros Kapourniotis and Animesh Datta,

Quantum 3, 164 (2019).

Quantum samplers are believed capable of sampling efficiently from distributions that are classically hard to sample from. We consider a sampler inspired by the classical Ising model. It is…

Paper

Hamiltonian Simulation by Qubitization

Guang Hao Low and Isaac L. Chuang,

Quantum 3, 163 (2019).

We present the problem of approximating the time-evolution operator $e^{-i\hat{H}t}$ to error $\epsilon$, where the Hamiltonian $\hat{H}=(\langle G|\otimes\hat{\mathcal{I}})\hat{U}(|G\rangle\otimes\hat{\mathcal{I}})$…

Paper

Approximation Algorithms for Complex-Valued Ising Models on Bounded Degree Graphs

Ryan L. Mann and Michael J. Bremner,

Quantum 3, 162 (2019).

We study the problem of approximating the Ising model partition function with complex parameters on bounded degree graphs. We establish a deterministic polynomial-time approximation scheme f…

Paper

Fundamental limits on low-temperature quantum thermometry with finite resolution

Patrick P. Potts, Jonatan Bohr Brask, and Nicolas Brunner,

Quantum 3, 161 (2019).

While the ability to measure low temperatures accurately in quantum systems is important in a wide range of experiments, the possibilities and the fundamental limits of quantum thermometry a…

Paper

Quantizing time: Interacting clocks and systems

Alexander R. H. Smith and Mehdi Ahmadi,

Quantum 3, 160 (2019).

This article generalizes the conditional probability interpretation of time in which time evolution is realized through entanglement between a clock and a system of interest. This formalism…

Paper

Determining a local Hamiltonian from a single eigenstate

Xiao-Liang Qi and Daniel Ranard,

Quantum 3, 159 (2019).

We ask whether the knowledge of a single eigenstate of a local Hamiltonian is sufficient to uniquely determine the Hamiltonian. We present evidence that the answer is “yes" for generic loca…

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