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Author(s): M. K. Olsen
We propose and analyze a nonlinear optical apparatus in which the direction of asymmetric steering is controllable within the apparatus, rather than by adding noise to measurements. Using a nondegenerate parametric oscillator with an injected signal field, we show how the directionality and extent o...
[Phys. Rev. Lett. 119, 160501] Published Wed Oct 18, 2017

Author(s): Yong Zeng, Peng Xu, Xiaodong He, Yangyang Liu, Min Liu, Jin Wang, D. J. Papoular, G. V. Shlyapnikov, and Mingsheng Zhan
We report on the first experimental realization of the controlled-not (cnot) quantum gate and entanglement for two individual atoms of different isotopes and demonstrate a negligible cross talk between two atom qubits. The experiment is based on a strong Rydberg blockade for $^{87}\mathrm{Rb}$ and $...
[Phys. Rev. Lett. 119, 160502] Published Wed Oct 18, 2017

Author(s): F. Motzoi, M. P. Kaicher, and F. K. Wilhelm
We develop a generalized framework for constructing many-body-interaction operations either in linear time or in logarithmic time with a linear number of ancilla qubits. Exact gate decompositions are given for Pauli strings, many-control Toffoli gates, number- and parity-conserving interactions, uni...
[Phys. Rev. Lett. 119, 160503] Published Wed Oct 18, 2017

Author(s): Massimiliano F. Sacchi
We consider the problem of optimally approximating an unavailable quantum state $ρ$ by the convex mixing of states drawn from a set of available states ${{ν}_{i}}$. The problem is recast to look for the least distinguishable state from $ρ$ among the convex set ${∑}_{i}{p}_{i}{ν}_{i}$, and the corres...
[Phys. Rev. A 96, 042325] Published Wed Oct 18, 2017

Author(s): Yu Xiang, Buqing Xu, Ladislav Mišta, Jr., Tommaso Tufarelli, Qiongyi He, and Gerardo Adesso
Einstein-Podolsky-Rosen (EPR) steering is an asymmetric form of correlations which is intermediate between quantum entanglement and Bell nonlocality, and can be exploited as a resource for quantum communication with one untrusted party. In particular, steering of continuous-variable Gaussian states ...
[Phys. Rev. A 96, 042326] Published Wed Oct 18, 2017

The realization of a high-efficiency microwave single photon detector is a
long-standing problem in the field of microwave quantum optics. Here we propose
a quantum non-demolition, high-efficiency photon detector that can readily be
implemented in present state-of-the-art circuit quantum electrodynamics. This
scheme works in a continuous fashion, gaining information about the arrival
time of the photon as well as about its presence. The key insight that allows

We consider the estimation of two-qubit interactions when initial states of
both qubit can be locally controlled, while the final state of only one qubit
can be measured. This amounts to realize a model of quantum channel
communication with environment assistance. In such a framework the unitaries'
parameters space results a tetrahedron in $\mathbb{R}^3$. On its edges the
problem, becoming of single parameter estimation, can be exactly solved and we
derive optimal probe states and estimators. Our results show that the

We take the perspective of open quantum systems and examine from their
nonequilibrium dynamics the conditions when the physical quantities, their
relations and the laws of thermodynamics become well defined and viable for
quantum many body systems. We first describe how an open system nonequilibrium
dynamics (ONEq) approach is different from the closed combined system +
environment in a global thermal state (CGTs) setup. Only after the open system
equilibrates will it be amenable to conventional thermodynamics descriptions,

We find a series of topological phase transitions of increasing order, beyond
the more standard second-order phase transition in a one-dimensional
topological superconductor. The jumps in the order of the transitions depend on
the range of the pairing interaction, which is parametrized by an algebraic
decay with exponent $\alpha$. Remarkably, in the limit $\alpha = 1$ the order
of the topological transition becomes infinite. We compute the critical
exponents for the series of higher-order transitions in exact form and find

The light propagating in a waveguide array or photonic lattice has become an
ideal platform to control light and to mimic quantum behaviors in classical
system. We here investigate the propagation of light in a coupled waveguide
array with one of the waveguide periodically modulated in its geometric
structure or refractive index. Within the framework of Floquet theory, it is
interesting to find that the propagation of light shows the dynamic
localization (DL) in the modulated waveguide as long as bound quasistationary