Themed collection Quantum Computing and Quantum Information Storage

This themed collection includes a selection of articles on quantum computing and quantum information storage.

Ion trap quantum computing utilizes electronic states of atomic ions such as Ca⁺ to encode information on to a qubit.

The present calculations reveal the effects of intersystem crossings and spin–orbit couplings on laser cooling of the group VA hydrides, with an empirical law of “crossing point shifting down” down a group in the periodic table generalized.

Cat state entropies for n = 2, 5, 10, and 15 qubits, as functions of qubit accuracies a and b.

Traditional quantum chemistry is based on separability by particle. Here, we explore a radically different approach, based on separability by Cartesian component.

Using adaptive wavefunctions and spin restrictions to compute excited state energies of LiH in a VQE emulation greatly reduces ansatz depth, showing promise as a routine for molecular excited state calculations on near-term quantum computers.

We discuss a possibility of using mixed-valence dimers comprising paramagnetic metal ions as molecular cells for quantum cellular automata. Charge distributions in these systems encode binary information with additional option of spin switching.

Two blocking energy barriers observed experimentally are confirmed by ab initio calculations. The blocking energy barrier of the Tb complexes that is approximately twice as large as that of the Dy analogues is explained.

The theory of open quantum systems (OQSs) is applied to partition the squared spin operator into fragment (local spin) and interfragment (spin-coupling) contributions in a molecular system.

Linear combination S of spin-projection correlation functions in the Clauser–Horne–Shimony–Holt inequality, from runs on an IBM quantum computer, after error mitigation. Values of S > 2 rule out local hidden-variable theories.

The magnetic properties of mononuclear Yb^III complexes have been explored by using multiconfigurational CASPT2/RASSI calculations.

Rotations of MgF molecules can be entangled via strong dipole–dipole interactions when trapped in optical tweezers with a magic polarization angle.

Quantum information processors are proposed, based on optical cycling centers trapped attached to a surface.

The interplay of external fields and internal structure of two interacting ultracold trapped molecules produces rich magnetization diagrams and nonequilibrium dynamics.

We explore coherent multi-photon processes in ⁸⁷Rb¹³³Cs molecules using 3-level lambda and ladder configurations of rotational and hyperfine states, and discuss their relevance to future applications in quantum computation and quantum simulation.

As expected from experiment, the [Mn₃O(O₂CMe)dpd_3/2]₂ dimer exists in an S = 12 ferromagnetic state. However the monomeric building blocks regardless of termination, are found in antiferromagnetic state with unusual local moments (S = 1).

Interactions that dominate carbon-vacancy interchange were modeled on a quantum annealer. The method exploits the ground state and the excited states to extract the possible arrangements of vacancies in graphene and their relative formation energies.

Benchmark relativistic coupled-cluster calculations for yttrium monoxide (YO) with accurate treatment of relativistic and electron correlation effects are reported.

The Quantum Annealer Eigensolver (QAE) is applied to the calculation of quantum scattering resonances and their lifetimes on a D-Wave quantum annealer.

Mechanisms including two types of Raman laser coupling (Ω₁ & Ω₂) and rf field coupling (Ω_rf) are applied to drive transitions between different hyperfine spin states. We investigated the entanglement between the spin and momentum degrees of freedom.

We introduce a quantum algorithm for simulating molecular vibrational excitations during vibronic transitions. The algorithm is used to simulate vibrational excitations of pyrrole and butane during photochemical and mechanochemical excitations.

Using a recently developed quantum embedding theory, we present first principles calculations of strongly correlated states of spin defects in diamond.

We outline a path towards universal quantum computation using the dipole–phonon interaction of polar molecular ions in an ion trap.

Three laser fields drive the population of AlH+ to a single hyperfine state.

Molecular quantum computing simulations are currently limited by the use of minimal Gaussian bases, a problem we overcome using a canonical transcorrelated Hamiltonian to accelerate basis convergence, with unitary coupled cluster as an example.

Theoretical study of the implementation of qubits and clock transitions in the spin, rotational, and vibrational degrees of freedom of molecular nitrogen ions including the effect of magnetic fields.

We present minimal depth circuits implementing the variational quantum eigensolver algorithm and successfully use it to compute the band structure of silicon on a quantum machine for the first time.

A strong Fermi contact (FC)-driven and electrically tunable hyperfine interaction is predicted for the neutral Tb(II)(Cp^iPr5)₂ single-molecule magnet.

The setup for polarization-based dispersive imaging of molecules that relies on the intrinsic anistropy of their excited states to generate optical birefringence.

Optical cycling, a continuous photon scattering off atoms or molecules, is the key tool in quantum information science.

We propose an approach based on the Lie algebra – Lie group connection that reduces the order dependence in unitary transformations used in quantum computing.