Archives: Paper

Benjamin Dive, Alexander Pitchford, Florian Mintert, and Daniel Burgarth,

Quantum 2, 80 (2018). https://doi.org/10.22331/q-2018-08-08-80

Quantum simulators, machines that can replicate the dynamics of quantum systems, are being built as useful devices and are seen as a stepping stone to universal quantum computers. A key diff…

Adam Winick, Norbert Lütkenhaus, and Patrick J. Coles,

Quantum 2, 77 (2018). https://doi.org/10.22331/q-2018-07-26-77

In this work, we present a reliable, efficient, and tight numerical method for calculating key rates for finite-dimensional quantum key distribution (QKD) protocols. We illustrate our approa…

Felix A. Pollock and Kavan Modi,

Quantum 2, 76 (2018). https://doi.org/10.22331/q-2018-07-11-76

Memory effects in open quantum dynamics are often incorporated in the equation of motion through a superoperator known as the memory kernel, which encodes how past states affect future dynam…

Filippo M. Miatto, Michael Epping, and Norbert Lütkenhaus,

Quantum 2, 75 (2018). https://doi.org/10.22331/q-2018-07-05-75

Quantum information degrades over distance due to the unavoidable imperfections of the transmission channels, with loss as the leading factor. This simple fact hinders quantum communication,…

Armin Tavakoli, Géraldine Haack, Marcus Huber, Nicolas Brunner, and Jonatan Bohr Brask,

Quantum 2, 73 (2018). https://doi.org/10.22331/q-2018-06-13-73

We present a scheme for dissipatively generating maximal entanglement in a heralded manner. Our setup requires incoherent interactions with two thermal baths at different temperatures, but n…

Sophie Laplante, Mathieu Laurière, Alexandre Nolin, Jérémie Roland, and Gabriel Senno,

Quantum 2, 72 (2018). https://doi.org/10.22331/q-2018-06-07-72

The question of how large Bell inequality violations can be, for quantum distributions, has been the object of much work in the past several years. We say that a Bell inequality is normalize…

Kevin A. Fischer, Rahul Trivedi, Vinay Ramasesh, Irfan Siddiqi, and Jelena Vučković,

Quantum 2, 69 (2018). https://doi.org/10.22331/q-2018-05-28-69

We develop a new computational tool and framework for characterizing the scattering of photons by energy-nonconserving Hamiltonians into unidirectional (chiral) waveguides, for example, with…

Nikolas P. Breuckmann and Xiaotong Ni,

Quantum 2, 68 (2018). https://doi.org/10.22331/q-2018-05-24-68

Machine learning has the potential to become an important tool in quantum error correction as it allows the decoder to adapt to the error distribution of a quantum chip. An additional motiva…

Cédric Bény,

Quantum 2, 67 (2018). https://doi.org/10.22331/q-2018-05-24-67

Information-theoretical quantities such as statistical distinguishability typically result from optimisations over all conceivable observables. Physical theories, however, are not generally…

Mohammad Mehboudi, Anna Sanpera, and Juan M. R. Parrondo,

Quantum 2, 66 (2018). https://doi.org/10.22331/q-2018-05-24-66

The fluctuation-dissipation theorem (FDT) is a central result in statistical physics, both for classical and quantum systems. It establishes a relationship between the linear response of a s…

Dominik Hangleiter, Juan Bermejo-Vega, Martin Schwarz, and Jens Eisert,

Quantum 2, 65 (2018). https://doi.org/10.22331/q-2018-05-22-65

One of the main milestones in quantum information science is to realise quantum devices that exhibit an exponential computational advantage over classical ones without being universal quantu…

Christopher Eltschka and Jens Siewert,

Quantum 2, 64 (2018). https://doi.org/10.22331/q-2018-05-22-64

The physics of a many-particle system is determined by the correlations in its quantum state. Therefore, analyzing these correlations is the foremost task of many-body physics. Any 'a priori…

Sally Shrapnel and Fabio Costa,

Quantum 2, 63 (2018). https://doi.org/10.22331/q-2018-05-18-63

Realist interpretations of quantum mechanics presuppose the existence of elements of reality that are independent of the actions used to reveal them. Such a view is challenged by several no-…

Daniel Litinski and Felix von Oppen,

Quantum 2, 62 (2018). https://doi.org/10.22331/q-2018-05-04-62

We present a planar surface-code-based scheme for fault-tolerant quantum computation which eliminates the time overhead of single-qubit Clifford gates, and implements long-range multi-target…

Nicolai Friis and Marcus Huber,

Quantum 2, 61 (2018). https://doi.org/10.22331/q-2018-04-23-61

One of the most fundamental tasks in quantum thermodynamics is extracting energy from one system and subsequently storing this energy in an appropriate battery. Both of these steps, work ext…

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…

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…

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…

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…

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…

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…