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Exceptional points (EPs) with a global collapse of pairs of eigenfunctions
are shown to arise in two locally-coupled and spatially-extended optical
structures with balanced gain and loss. Global collapse at the EP deeply
changes light propagation, which becomes very sensitive to small changes of
initial conditions or system parameters, similarly to what happens in models of
classical or quantum catastrophes. The implications of global collapse for
light behavior are illustrated by considering discrete beam diffraction and

Defects in crystals are leading candidates for photon-based quantum
technologies, but progress in developing practical devices critically depends
on improving defect optical and spin properties. Motivated by this need, we
study a new defect qubit candidate, the shallow donor in ZnO. We demonstrate
all-optical control of the electron spin state of the donor qubits and measure
the spin coherence properties. We find a longitudinal relaxation time T$_1$
exceeding 100 ms, an inhomogeneous dephasing time T$_2^*$ of $17\pm2$ ns, and a

Two-photon Rabi splitting in a cavity-dot system provides a basis for
multi-qubit coherent control in quantum photonic network. Here we report on
two-photon Rabi splitting in a strongly coupled cavity-dot system. The quantum
dot was grown intentionally large in size for large oscillation strength and
small biexciton binding energy. Both exciton and biexciton transitions couple
to a high quality factor photonic crystal cavity with large coupling strengths

Author(s): Thomas Iadecola and Timothy H. Hsieh
We show that time-reflection symmetry in periodically driven (Floquet) quantum systems enables an inherently nonequilibrium phenomenon structurally similar to quantum-mechanical supersymmetry. In particular, we find Floquet analogs of the Witten index that place lower bounds on the degeneracies of s...
[Phys. Rev. Lett. 120, 210603] Published Thu May 24, 2018

Author(s): Sudipto Singha Roy, Himadri Shekhar Dhar, Debraj Rakshit, Aditi Sen(De), and Ujjwal Sen
Quantum networks are an integral component in performing efficient computation and communication tasks that are not accessible using classical systems. A key aspect in designing an effective and scalable quantum network is generating entanglement between its nodes, which is robust against defects in...
[Phys. Rev. A 97, 052325] Published Thu May 24, 2018

Author(s): Ying Guo, Cailang Xie, Peng Huang, Jiawei Li, Ling Zhang, Duan Huang, and Guihua Zeng
This paper deals with a channel-parameter estimation for continuous-variable quantum key distribution (CV-QKD) over a satellite-to-submarine link. In particular, we focus on the channel transmittances and the excess noise which are affected by atmospheric turbulence, surface roughness, zenith angle ...
[Phys. Rev. A 97, 052326] Published Thu May 24, 2018

The concept of quantum integrability has been introduced recently for quantum systems with
explicitly time-dependent Hamiltonians (Sinitsyn et al 2018 Phys. Rev. Lett . 120 190402). Within
the multistate Landau–Zener (MLZ) theory, however, there has been a successful alternative approach
to identify and solve complex time-dependent models (Sinitsyn and Chernyak 2017 J. Phys. A: Math.
Theor . 50 255203). Here we compare both methods by applying them to a new class of exactly solvable

We analyse the n -dimensional superintegrable Kepler–Coulomb system with non-central terms. We find
a novel underlying chain structure of quadratic algebras formed by the integrals of motion. We
identify the elements for each sub-structure and obtain the algebra relations satisfied by them and
the corresponding Casimir operators. These quadratic sub-algebras are realized in terms of a chain
of deformed oscillators with factorized structure functions. We construct the finite-dimensional

Product formulas can be used to simulate Hamiltonian dynamics on a quantum
computer by approximating the exponential of a sum of operators by a product of
exponentials of the individual summands. This approach is both straightforward
and surprisingly efficient. We show that by simply randomizing how the summands
are ordered, one can prove stronger bounds on the quality of approximation and
thereby give more efficient simulations. Indeed, we show that these bounds can