QUROPE Quantum Information Processing and Communication in Europe

Author(s): Kunkun Wang, Xingze Qiu, Lei Xiao, Xiang Zhan, Zhihao Bian, Wei Yi, and Peng Xue

Signaled by nonanalyticities in the time evolution of physical observables, dynamic quantum phase transitions (DQPTs) emerge in quench dynamics of topological systems and possess an interesting geometric origin captured by dynamic topological order parameters (DTOPs). In this Letter, we report the e...

[Phys. Rev. Lett. 122, 020501] Published Wed Jan 16, 2019

Author(s): Yuval R. Sanders, Guang Hao Low, Artur Scherer, and Dominic W. Berry

A new algorithm for quantum state preparation uses fewer gates than existing ones, by two orders of magnitude.

[Phys. Rev. Lett. 122, 020502] Published Wed Jan 16, 2019

Author(s): Max McGinley, Andreas Nunnenkamp, and Johannes Knolle

We investigate how information spreads in three paradigmatic one-dimensional models with spatial disorder. The models we consider are unitarily related to a system of free fermions and, thus, are manifestly integrable. We demonstrate that out-of-time-order correlators can spread slowly beyond the si...

[Phys. Rev. Lett. 122, 020603] Published Wed Jan 16, 2019

Author(s): Alexandre G. R. Day, Marin Bukov, Phillip Weinberg, Pankaj Mehta, and Dries Sels

We study the problem of preparing a quantum many-body system from an initial to a target state by optimizing the fidelity over the family of bang-bang protocols. We present compelling numerical evidence for a universal spin-glasslike transition controlled by the protocol time duration. The glassy cr...

[Phys. Rev. Lett. 122, 020601] Published Tue Jan 15, 2019

Author(s): Arnab Pal, Iddo Eliazar, and Shlomi Reuveni

First passage under restart with branching is proposed as a generalization of first passage under restart. Strong motivation to study this generalization comes from the observation that restart with branching can expedite the completion of processes that cannot be expedited with simple restart; yet ...

[Phys. Rev. Lett. 122, 020602] Published Tue Jan 15, 2019

Author(s): Davide Girolami

A key computational resource to prepare a quantum system in a target state, an important subroutine of quantum information protocols, is identified and quantified.

[Phys. Rev. Lett. 122, 010505] Published Fri Jan 11, 2019

Author(s): Bernhard Irsigler, Jun-Hui Zheng, and Walter Hofstetter

Two-dimensional topological insulators possess conducting edge states at their boundary while being insulating in the bulk. We investigate the edge state emergent at a smooth topological phase boundary of interacting fermions within a full real-space analysis of the time-reversal invariant Hofstadte...

[Phys. Rev. Lett. 122, 010406] Published Thu Jan 10, 2019

Author(s): J. Casanova, E. Torrontegui, M. B. Plenio, J. J. García-Ripoll, and E. Solano

We develop energy efficient, continuous microwave schemes to couple electron and nuclear spins, using phase or amplitude modulation to bridge their frequency difference. These controls have promising applications in biological systems, where microwave power should be limited, as well as in situation...

[Phys. Rev. Lett. 122, 010407] Published Thu Jan 10, 2019

Author(s): Qi Yao, Jun Zhang, Xiao-Feng Yi, Li You, and Wenxian Zhang

Dynamical decoupling (DD) is an active and effective method for suppressing decoherence of a quantum system from its environment. In contrast to the nominal biaxial DD, this work presents a uniaxial decoupling protocol that requires a significantly reduced number of pulses and a much lower bias fiel...

[Phys. Rev. Lett. 122, 010408] Published Thu Jan 10, 2019

Author(s): T. M. Hazard, A. Gyenis, A. Di Paolo, A. T. Asfaw, S. A. Lyon, A. Blais, and A. A. Houck

We characterize a fluxonium qubit consisting of a Josephson junction inductively shunted with a NbTiN nanowire superinductance. We explain the measured energy spectrum by means of a multimode theory accounting for the distributed nature of the superinductance and the effect of the circuit nonlineari...

[Phys. Rev. Lett. 122, 010504] Published Thu Jan 10, 2019

Author(s): Jonathan Drori, Yuval Rosenberg, David Bermudez, Yaron Silberberg, and Ulf Leonhardt

An optical analogue of stimulated Hawking radiation is observed in nonlinear fiber optics used as a laboratory analogue of black holes.

[Phys. Rev. Lett. 122, 010404] Published Wed Jan 09, 2019

Author(s): Emily J. Davis, Gregory Bentsen, Lukas Homeier, Tracy Li, and Monika H. Schleier-Smith

Spin dynamics induced by nonlocal interactions are imaged for the first time in a system of cold atoms trapped in an optical cavity.

[Phys. Rev. Lett. 122, 010405] Published Wed Jan 09, 2019

Author(s): Yonghae Lee, Ryuji Takagi, Hayata Yamasaki, Gerardo Adesso, and Soojoon Lee

We consider a quantum communication task between two users Alice and Bob, in which Alice and Bob exchange their respective quantum information by means of local operations and classical communication assisted by shared entanglement. Here, we assume that Alice and Bob may have quantum side informatio...

[Phys. Rev. Lett. 122, 010502] Published Wed Jan 09, 2019

Author(s): Y.-Y. Huang, Y.-K. Wu, F. Wang, P.-Y. Hou, W.-B. Wang, W.-G. Zhang, W.-Q. Lian, Y.-Q. Liu, H.-Y. Wang, H.-Y. Zhang, L. He, X.-Y. Chang, Y. Xu, and L.-M. Duan

We experimentally realize a universal set of single-bit and two-bit geometric quantum gates by adiabatically controlling solid-state spins in a diamond defect. Compared with the nonadiabatic approach, the adiabatic scheme for geometric quantum computation offers a unique advantage of inherent robust...

[Phys. Rev. Lett. 122, 010503] Published Wed Jan 09, 2019

Author(s): Owen Howell, Phillip Weinberg, Dries Sels, Anatoli Polkovnikov, and Marin Bukov

We reveal a continuous dynamical heating transition between a prethermal and an infinite-temperature stage in a clean, chaotic periodically driven classical spin chain. The transition time is a steep exponential function of the drive frequency, showing that the exponentially long-lived prethermal pl...

[Phys. Rev. Lett. 122, 010602] Published Wed Jan 09, 2019

Author(s): C. J. Fujiwara, Kevin Singh, Zachary A. Geiger, Ruwan Senaratne, Shankari V. Rajagopal, Mikhail Lipatov, and David M. Weld

We report Floquet band engineering of long-range transport and direct imaging of Floquet-Bloch bands in an amplitude-modulated optical lattice. In one variety of Floquet-Bloch bands we observe tunable rapid long-range high-fidelity transport of a Bose condensate across thousands of lattice sites. Qu...

[Phys. Rev. Lett. 122, 010402] Published Tue Jan 08, 2019

Author(s): Thao P. Le and Alexandra Olaya-Castro

How the objective everyday world emerges from the underlying quantum behavior of its microscopic constituents is an open question at the heart of the foundations of quantum mechanics. Quantum Darwinism and spectrum broadcast structure are two different frameworks providing key insight into this ques...

[Phys. Rev. Lett. 122, 010403] Published Tue Jan 08, 2019

Author(s): Xinsheng Tan, Y. X. Zhao, Qiang Liu, Guangming Xue, Hai-Feng Yu, Z. D. Wang, and Yang Yu

We simulated highly tunable Weyl-semimetal bands using superconducting quantum circuits. Driving the superconducting quantum circuits with microwave fields, we mapped the momentum space of a lattice to the parameter space, realizing the Hamiltonian of a Weyl semimetal. By measuring the energy spectr...

[Phys. Rev. Lett. 122, 010501] Published Tue Jan 08, 2019

Author(s): Pedro Ribeiro and Tomaž Prosen

We consider a collective quantum spin s in contact with Markovian spin-polarized baths. Using a conserved superoperator charge, a differential representation of the Liouvillian is constructed to find its exact spectrum and eigenmodes. We study the spectral properties of the model in the large-s limi...

[Phys. Rev. Lett. 122, 010401] Published Fri Jan 04, 2019

Author(s): Erez Aghion, David A. Kessler, and Eli Barkai

We study a particle immersed in a heat bath, in the presence of an external force which decays at least as rapidly as 1/x, e.g., a particle interacting with a surface through a Lennard-Jones or a logarithmic potential. As time increases, our system approaches a non-normalizable Boltzmann state. We s...

[Phys. Rev. Lett. 122, 010601] Published Thu Jan 03, 2019