Author(s): Marko Ljubotina, Lenart Zadnik, and Tomaž Prosen
We demonstrate ballistic spin transport of an integrable unitary quantum circuit, which can be understood either as a paradigm of an integrable periodically driven (Floquet) spin chain, or as a Trotterized anisotropic ($XXZ$) Heisenberg spin-$1/2$ model. We construct an analytic family of quasilocal...
[Phys. Rev. Lett. 122, 150605] Published Fri Apr 19, 2019

Author(s): X. Turkeshi, T. Mendes-Santos, G. Giudici, and M. Dalmonte
We introduce a method for the search of parent Hamiltonians of input wave functions based on the structure of their reduced density matrix. The two key elements of our recipe are an ansatz on the relation between the reduced density matrix and parent Hamiltonian that is exact at the field theory lev...
[Phys. Rev. Lett. 122, 150606] Published Fri Apr 19, 2019

Author(s): Ludovico Lami, Bartosz Regula, and Gerardo Adesso
We compute analytically the maximal rates of distillation of quantum coherence under strictly incoherent operations (SIO) and physically incoherent operations (PIO), showing that they coincide for all states, and providing a complete description of the phenomenon of bound coherence. In particular, w...
[Phys. Rev. Lett. 122, 150402] Published Fri Apr 19, 2019

Author(s): Muzzamal I. Shaukat, Eduardo V. Castro, and Hugo Terças
We show that entanglement between two solitary qubits in quasi-one-dimensional Bose-Einstein condensates can be spontaneously generated due to quantum fluctuations. Recently we have shown that dark solitons are an appealing platform for qubits thanks to their appreciable long lifetime. We investigat...
[Phys. Rev. A 99, 042326] Published Thu Apr 18, 2019

Author(s): Re-Bing Wu, Haijin Ding, Daoyi Dong, and Xiaoting Wang
Robust and high-precision quantum control is extremely important but challenging for the functionalization of scalable quantum computation. In this paper, we show that this hard problem can be translated to a supervised machine learning task by thinking of the time-ordered quantum evolution as a lay...
[Phys. Rev. A 99, 042327] Published Thu Apr 18, 2019

Author(s): Olivier Maillet, Paolo A. Erdman, Vasco Cavina, Bibek Bhandari, Elsa T. Mannila, Joonas T. Peltonen, Andrea Mari, Fabio Taddei, Christopher Jarzynski, Vittorio Giovannetti, and Jukka P. Pekola
In very small systems like a single electron transistor, sometimes thermal fluctuations allow single shot extraction of work from the system beyond the bounds of the second law of thermodynamics.
[Phys. Rev. Lett. 122, 150604] Published Thu Apr 18, 2019

We design a series of quantum circuits that generate absolute maximally
entangled (AME) states to benchmark a quantum computer. A relation between
graph states and AME states can be exploited to optimize the structure of the
circuits and minimize their depth. Furthermore, we find that most of the
provided circuits obey majorization relations for every partition of the
system, and at every step of the quantum computation. The rational for our
approach is to benchmark quantum computers with maximal useful entanglement,

We look into the possibility of entanglement generation in a
parity(P)-time(T)-symmetric framework and demonstrate the non-violation of
non-signalling principle for the case of bipartite systems when at least one is
guided by PT-symmetric quantum mechanics. Our analysis is based on the use of
the CPT-inner product to construct the reduced density operators both before
and after the action of time evolution operator.

We present a new open-source Python package, krotov, implementing the quantum
optimal control method of that name. It allows to determine time-dependent
external fields for a wide range of quantum control problems, including
state-to-state transfer, quantum gate implementation and optimization for an
arbitrary perfect entangler. The user-friendly interface allows for combination
with other Python packages, and thus high-level customization. The package is

Quantum memories for light are important components for future long distance
quantum networks. We present on-chip quantum storage of telecommunications band
light at the single photon level in an ensemble of erbium-167 ions in an
yttrium orthosilicate photonic crystal nanobeam resonator. Storage times of up
to 10 $\mu$s are demonstrated using an all-optical atomic frequency comb
protocol in a dilution refrigerator under a magnetic field of 380 mT. We show
this quantum storage platform to have high bandwidth, high fidelity, and