Traditional public key cryptography will become obsolete when quantum computers are able to break it. The authors propose two quantum algorithms to solve the shortest-vector problem, which could play an important role in designing new cryptosystems for the postquantum era.
David Joseph, Adam Callison, Cong Ling, and Florian Mintert
Phys. Rev. A 103, 032433 (2021)
In this combined experimental and theoretical study, the authors report on the measurement of the absolute cross section for direct single-photon double ionization of Ar, which is orders of magnitude smaller than the corresponding cross section for a neutral target. The experimental data are in very good agreement with the results of a theoretical approach which describes the dominant two-step-one process as the product of a single ionization and a subsequent half collision.
A. Müller et al.
Phys. Rev. A 103, L031101 (2021)
The authors present a quantum algorithm for the pricing of options, a financial derivative, which works in the unary representation of the value of the underlying asset. Compared to a previous binary algorithm, the present one is designed to be simple in terms of logic operations and in terms of connectivity requirements, while still giving sufficiently accurate results with less than 100 qubits.
Sergi Ramos-Calderer et al.
Phys. Rev. A 103, 032414 (2021)
A physical agent must interact with its environment using actuators (to act on the environment) and sensors (to read the environment). In this article, the authors show that an optical agent which interacts with its environment using quantum mechanical actuators and sensors can experience a dramatic enhancement in its ability to learn its environment, and they study the thermodynamic properties of learning in such a physical agent.
M. J. Kewming, S. Shrapnel, and G. J. Milburn
Phys. Rev. A 103, 032411 (2021)
The author proves that the contemporary variational approach to quantum-enhanced algorithms enables a universal model of quantum computation. This brings the resources required for universal quantum computation closer to contemporary quantum processors.
Phys. Rev. A 103, L030401 (2021)
Nuclear structure effects lead to small corrections to electron energy-level shifts and isotope shifts in neutral atoms but have enhanced effects on heavy hydrogenlike ions. The authors analyze how nuclear structure effects scale with nuclear charge, mass number, and other parameters in various atoms and ions, with an emphasis on heavy hydrogenlike ions.
V. V. Flambaum, I. B. Samsonov, H. B. Tran Tan, and A. V. Viatkina
Phys. Rev. A 103, 032811 (2021)
The author derives an analytical expression for the electronic stopping cross section of atomic gas targets at nonrelativistic velocities for hydrogen ions. The expression is based on an ab initio approach to account for the electronic excitations and charge exchange processes at low collision energies and the correct Bethe approach at high collision energies.
Phys. Rev. A 103, 032812 (2021)
The authors experimentally demonstrate the production of quantum degenerate Bose-Bose mixtures of cesium and ytterbium with attractive and repulsive interactions through sympathetic cooling. This development adds another system to the ultracold-atom toolbox, enabling future studies of quantum droplets and binary fluid dynamics.
Kali E. Wilson, Alexander Guttridge, Jack Segal, and Simon L. Cornish
Phys. Rev. A 103, 033306 (2021)
The authors report on a method for scanning the collisional energies of a single ion with a cloud of ultracold atoms. This method is then applied to directly measure the collisional cross section between the two species, with high-energy resolution.
Ruti Ben-shlomi et al.
Phys. Rev. A 103, 032805 (2021)