Quantum

Gauge invariant information concerning quantum channels

Łukasz Rudnicki, Zbigniew Puchała, and Karol Zyczkowski,

Quantum 2, 60 (2018). https://doi.org/10.22331/q-2018-04-11-60

Motivated by the gate set tomography we study quantum channels from the perspective of information which is invariant with respect to the gauge realized through similarity of matrices repres…

Paper

Additivity of entropic uncertainty relations

René Schwonnek,

Quantum 2, 59 (2018). https://doi.org/10.22331/q-2018-03-30-59

We consider the uncertainty between two pairs of local projective measurements performed on a multipartite system. We show that the optimal bound in any linear uncertainty relation, formulat…

Paper

Dissipative stabilization of entangled cat states using a driven Bose-Hubbard dimer

M. Mamaev, L. C. G. Govia, and A. A. Clerk,

Quantum 2, 58 (2018). https://doi.org/10.22331/q-2018-03-27-58

We analyze a modified Bose-Hubbard model, where two cavities having on-site Kerr interactions are subject to two-photon driving and correlated dissipation. We derive an exact solution for th…

Paper

Non-Shannon inequalities in the entropy vector approach to causal structures

Mirjam Weilenmann and Roger Colbeck,

Quantum 2, 57 (2018). https://doi.org/10.22331/q-2018-03-14-57

A causal structure is a relationship between observed variables that in general restricts the possible correlations between them. This relationship can be mediated by unobserved systems, mod…

Paper

Magic state parity-checker with pre-distilled components

Earl T. Campbell and Mark Howard,

Quantum 2, 56 (2018). https://doi.org/10.22331/q-2018-03-14-56

Magic states are eigenstates of non-Pauli operators. One way of suppressing errors present in magic states is to perform parity measurements in their non-Pauli eigenbasis and postselect on e…

Paper

Sandwiched Rényi Convergence for Quantum Evolutions

Alexander Müller-Hermes and Daniel Stilck Franca,

Quantum 2, 55 (2018). https://doi.org/10.22331/q-2018-02-27-55

We study the speed of convergence of a primitive quantum time evolution towards its fixed point in the distance of sandwiched Rényi divergences. For each of these distance measures the conve…

Paper

Quantum Horn’s lemma, finite heat baths, and the third law of thermodynamics

Jakob Scharlau and Markus P. Mueller,

Quantum 2, 54 (2018). https://doi.org/10.22331/q-2018-02-22-54

Interactions of quantum systems with their environment play a crucial role in resource-theoretic approaches to thermodynamics in the microscopic regime. Here, we analyze the possible state t…

Paper

Flag fault-tolerant error correction with arbitrary distance codes

Christopher Chamberland and Michael E. Beverland,

Quantum 2, 53 (2018). https://doi.org/10.22331/q-2018-02-08-53

In this paper we introduce a general fault-tolerant quantum error correction protocol using flag circuits for measuring stabilizers of arbitrary distance codes. In addition to extending flag…

Paper

Elementary Thermal Operations

Matteo Lostaglio, Álvaro M. Alhambra, and Christopher Perry,

Quantum 2, 52 (2018). https://doi.org/10.22331/q-2018-02-08-52

To what extent do thermodynamic resource theories capture physically relevant constraints? Inspired by quantum computation, we define a set of elementary thermodynamic gates that only act on…

Paper

Characterization of linear maps on $M_n$ whose multiplicity maps have maximal norm, with an application in quantum information

Daniel Puzzuoli,

Quantum 2, 51 (2018). https://doi.org/10.22331/q-2018-02-05-51

Given a linear map $\Phi : M_n \rightarrow M_m$, its multiplicity maps are defined as the family of linear maps $\Phi \otimes \textrm{id}_{k} : M_n \otimes M_k \rightarrow M_m \otimes M_k$,…

Paper

Bond dimension witnesses and the structure of homogeneous matrix product states

Miguel Navascues and Tamas Vertesi,

Quantum 2, 50 (2018). https://doi.org/10.22331/q-2018-01-31-50

For the past twenty years, Matrix Product States (MPS) have been widely used in solid state physics to approximate the ground state of one-dimensional spin chains. In this paper, we study ho…

Paper

ProjectQ: an open source software framework for quantum computing

Damian S. Steiger, Thomas Häner, and Matthias Troyer,

Quantum 2, 49 (2018). https://doi.org/10.22331/q-2018-01-31-49

We introduce ProjectQ, an open source software effort for quantum computing. The first release features a compiler framework capable of targeting various types of hardware, a high-performanc…

Paper

Machine-learning-assisted correction of correlated qubit errors in a topological code

Paul Baireuther, Thomas E. O’Brien, Brian Tarasinski, and Carlo W. J. Beenakker,

Quantum 2, 48 (2018). https://doi.org/10.22331/q-2018-01-29-48

A fault-tolerant quantum computation requires an efficient means to detect and correct errors that accumulate in encoded quantum information. In the context of machine learning, neural netwo…

Paper

Randomized benchmarking with gate-dependent noise

Joel J. Wallman,

Quantum 2, 47 (2018). https://doi.org/10.22331/q-2018-01-29-47

We analyze randomized benchmarking for arbitrary gate-dependent noise and prove that the exact impact of gate-dependent noise can be described by a single perturbation term that decays expon…

Paper

Vacuum source-field correlations and advanced waves in quantum optics

Adam Stokes,

Quantum 2, 46 (2018). https://doi.org/10.22331/q-2018-01-18-46

The solution to the wave equation as a Cauchy problem with prescribed fields at an initial time $t=0$ is purely retarded. Similarly, in the quantum theory of radiation the specification of H…

Paper

Separability of diagonal symmetric states: a quadratic conic optimization problem

Jordi Tura, Albert Aloy, Ruben Quesada, Maciej Lewenstein, and Anna Sanpera,

Quantum 2, 45 (2018). https://doi.org/10.22331/q-2018-01-12-45

We study the separability problem in mixtures of Dicke states i.e., the separability of the so-called Diagonal Symmetric (DS) states. First, we show that separability in the case of DS in $C^d\otimes C^d$…

Paper

BQP-completeness of scattering in scalar quantum field theory

Stephen P. Jordan, Hari Krovi, Keith S. M. Lee, and John Preskill,

Quantum 2, 44 (2018). https://doi.org/10.22331/q-2018-01-08-44

Recent work has shown that quantum computers can compute scattering probabilities in massive quantum field theories, with a run time that is polynomial in the number of particles, their ener…

Paper

Fault-tolerant quantum computing in the Pauli or Clifford frame with slow error diagnostics

Christopher Chamberland, Pavithran Iyer, and David Poulin,

Quantum 2, 43 (2018). https://doi.org/10.22331/q-2018-01-04-43

We consider the problem of fault-tolerant quantum computation in the presence of slow error diagnostics, either caused by measurement latencies or slow decoding algorithms. Our scheme offers…

Paper

Cavity assisted measurements of heat and work in optical lattices

Louis Villa and Gabriele De Chiara,

Quantum 2, 42 (2018). https://doi.org/10.22331/q-2018-01-04-42

We propose a method to experimentally measure the internal energy of a system of ultracold atoms trapped in optical lattices by coupling them to the fields of two optical cavities. We show t…

Paper

Zero-knowledge convincing protocol on quantum bit is impossible

Pawel Horodecki, Michal Horodecki, and Ryszard Horodecki,

Quantum 1, 41 (2017). https://doi.org/10.22331/q-2017-12-23-41

Consider two parties: Alice and Bob and suppose that Bob is given a qubit system in a quantum state $\phi$, unknown to him. Alice knows $\phi$ and she is supposed to convince Bob that she kn…

Paper

A nonequilibrium quantum phase transition in strongly coupled spin chains

Eduardo Mascarenhas, Giacomo Giudice, and Vincenzo Savona,

Quantum 1, 40 (2017). https://doi.org/10.22331/q-2017-12-20-40

We study spin transport in a boundary driven XXZ spin chain. Driving at the chain boundaries is modeled by two additional spin chains prepared in oppositely polarized states. Emergent behavi…

Paper

Genuinely multipartite noncausality

Alastair A. Abbott, Julian Wechs, Fabio Costa, and Cyril Branciard,

Quantum 1, 39 (2017). https://doi.org/10.22331/q-2017-12-14-39

The study of correlations with no definite causal order has revealed a rich structure emerging when more than two parties are involved. This motivates the consideration of multipartite "nonc…

Paper

Toolbox for reconstructing quantum theory from rules on information acquisition

Philipp Andres Höhn,

Quantum 1, 38 (2017). https://doi.org/10.22331/q-2017-12-14-38

We develop an operational approach for reconstructing the quantum theory of qubit systems from elementary rules on information acquisition. The focus lies on an observer $O$ interrogating a…

Paper

Quantum and classical dynamics of a three-mode absorption refrigerator

Stefan Nimmrichter, Jibo Dai, Alexandre Roulet, and Valerio Scarani,

Quantum 1, 37 (2017). https://doi.org/10.22331/q-2017-12-11-37

We study the quantum and classical evolution of a system of three harmonic modes interacting via a trilinear Hamiltonian. With the modes prepared in thermal states of different temperatures,…

Paper

Quantum gates between distant qubits via spin-independent scattering

Leonardo Banchi, Enrico Compagno, Vladimir Korepin, and Sougato Bose,

Quantum 1, 36 (2017). https://doi.org/10.22331/q-2017-11-30-36

We show how the spin independent scattering of two initially distant qubits, say, in distinct traps or in remote sites of a lattice, can be used to implement an entangling quantum gate betwe…

Paper

Probing the non-classicality of temporal correlations

Martin Ringbauer and Rafael Chaves,

Quantum 1, 35 (2017). https://doi.org/10.22331/q-2017-11-25-35

Correlations between spacelike separated measurements on entangled quantum systems are stronger than any classical correlations and are at the heart of numerous quantum technologies. In prac…

Paper

Macroscopic superpositions require tremendous measurement devices

Michalis Skotiniotis, Wolfgang Dür, and Pavel Sekatski,

Quantum 1, 34 (2017). https://doi.org/10.22331/q-2017-11-21-34

We consider fundamental limits on the detectable size of macroscopic quantum superpositions. We argue that a full quantum mechanical treatment of system plus measurement device is required,…

Paper

Semi-device-independent framework based on natural physical assumptions

Thomas Van Himbeeck, Erik Woodhead, Nicolas J. Cerf, Raúl García-Patrón, and Stefano Pironio,

Quantum 1, 33 (2017). https://doi.org/10.22331/q-2017-11-18-33

The semi-device-independent approach provides a framework for prepare-and-measure quantum protocols using devices whose behavior must not be characterized nor trusted, except for a single as…

Paper

Quasi-probability distributions for observables in dynamic systems

Patrick P. Hofer,

Quantum 1, 32 (2017). https://doi.org/10.22331/q-2017-10-12-32

We develop a general framework to investigate fluctuations of non-commuting observables. To this end, we consider the Keldysh quasi-probability distribution (KQPD). This distribution provide…

Paper

Magic state distillation with low space overhead and optimal asymptotic input count

Jeongwan Haah, Matthew B. Hastings, D. Poulin, and D. Wecker,

Quantum 1, 31 (2017). https://doi.org/10.22331/q-2017-10-03-31

We present an infinite family of protocols to distill magic states for $T$-gates that has a low space overhead and uses an asymptotic number of input magic states to achieve a given target e…

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