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Strong squeezing limit in quantum stochastic models. (arXiv:1708.09678v1 [math-ph])

In this paper we study quantum stochastic differential equations (QSDEs) that
are driven by strongly squeezed vacuum noise. We show that for strong squeezing
such a QSDE can be approximated (via a limit in the strong sense) by a QSDE
that is driven by a single commuting noise process. We find that the
approximation has an additional Hamiltonian term.

Objectivity in non-Markovian spin-boson model. (arXiv:1702.08427v2 [quant-ph] UPDATED)

Objectivity constitutes one of the main features of the macroscopic classical
world. An important aspect of the quantum-to-classical transition issue is to
explain how such a property arises from the microscopic quantum world.
Recently, within the framework of open quantum systems, there has been proposed
such a mechanism in terms of the, so-called, Spectrum Broadcast Structures.
These are multipartite quantum states of the system of interest and a part of

Emergence, evolution, and control of multistability in a hybrid topological quantum/classical system. (arXiv:1708.09413v1 [cond-mat.mes-hall])

We present a novel class of nonlinear dynamical systems - a hybrid of
relativistic quantum and classical systems, and demonstrate that multistability
is ubiquitous. A representative setting is coupled systems of a topological
insulator and an insulating ferromagnet, where the former possesses an
insulating bulk with topologically protected, dissipationless, and conducting
surface electronic states governed by the relativistic quantum Dirac
Hamiltonian and latter is described by the nonlinear classical evolution of its

Bounds on entanglement dimensions and quantum graph parameters via noncommutative polynomial optimization. (arXiv:1708.09696v1 [math.OC])

In this paper we study bipartite quantum correlations using techniques from
tracial polynomial optimization. We construct a hierarchy of semidefinite
programming lower bounds on the minimal entanglement dimension of a bipartite
correlation. This hierarchy converges to a new parameter: the minimal average
entanglement dimension, which measures the amount of entanglement needed to
reproduce a quantum correlation when access to shared randomness is free. For
synchronous correlations, we show a correspondence between the minimal

Extended pump-probe Faraday rotation spectroscopy of the submicrosecond electron spin dynamics in n-type GaAs. (arXiv:1608.00314v4 [cond-mat.mes-hall] UPDATED)

We develop an extended pump-probe Faraday rotation technique to study the
submicrosecond electron spin dynamics with picosecond time resolution in a wide
range of magnetic fields. The electron spin dephasing time $T_2^*$ and the
longitudinal spin relaxation time $T_1$, both approaching $250$ ns in weak
fields, are measured thereby in $n$-type bulk GaAs. By tailoring the pump pulse
train through increasing the contained number of pulses, the buildup of

Controlling Spectrally Indistinguishable Nuclear Spins for a Decoherence-Free Subspace. (arXiv:1708.09414v1 [quant-ph])

Close nuclear spins with identical precession frequencies have the remarkable
property of feeling the same magnetic noise, which makes them exceptional
candidates for constructing a decoherence-free subspace (DFS). However,
selective control of such nuclei is not possible with existing methods based on
spectroscopic discrimination. We overcome this obstacle and present a protocol
for storage and retrieval of quantum information from a DFS. We demonstrate the
efficacy of our protocol with detailed numerical simulations of a

Opportunities and challenges for quantum-assisted machine learning in near-term quantum computers. (arXiv:1708.09757v1 [quant-ph])

With quantum computing technologies nearing the era of commercialization and
quantum supremacy, machine learning (ML) appears as one of the promising
"killer" applications. Despite significant effort, there has been a disconnect
between most quantum machine learning proposals, the needs of ML practitioners,
and the capabilities of near-term quantum devices to demonstrate quantum
enhancement in the near future. In this contribution to the focus collection on
"What would you do with 1000 qubits?", we provide concrete examples of

Entanglement generation and photon redistribution in Hong-Ou-Mandel Experiment. (arXiv:1708.09436v1 [quant-ph])

Hong-Ou-Mandel (HOM) effect was long believed to be a two-photon interference
phenomenon. Two indistinguishable photons mixed at a beam splitter will bunch
together to one of the output modes. Using two trapped ions as photon source,
we explore a hidden scenario of the HOM effect, where entanglement can be
generated between the two ions when a single photon is detected by one of the
detectors. A second photon emitted by the entangled photon sources will be

Statistical study of stacked/coupled site-controlled pyramidal quantum dots and their excitonic properties. (arXiv:1708.09758v1 [cond-mat.mes-hall])

We report on stacked multiple quantum dots (QDs) formed inside inverted
pyramidal recesses, which allow for the precise positioning of the QDs
themselves. Specifically we fabricated double QDs with varying inter-dot
distance and ensembles with more than two nominally highly symmetric QDs. For
each, the effect of the interaction between QDs is studied by characterizing a
large number of QDs through photoluminescence spectroscopy. A clear red-shift
of the emission energy is observed together with a change in the orientation of

Peptides as versatile scaffolds for quantum computing. (arXiv:1708.09440v1 [cond-mat.mes-hall])

In this work we showcase the potential of peptides as versatile scaffolds for
quantum computing and molecular spintronics. In particular, we focus on
lanthanide-binding tags, developed in the field of biotechnology for the study
of protein structure and dynamics, exploring their potential as scalable single
molecule spin transistors for quantum information processing. Firstly, we
demonstrate quantum coherent oscillations in a Neodymium peptidic qubit. Then,