Themed collection Quantum Computing and Quantum Information Storage

27 items
Editorial

Quantum computing and quantum information storage

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

Graphical abstract: Quantum computing and quantum information storage
Paper

Molecular excited state calculations with adaptive wavefunctions on a quantum eigensolver emulation: reducing circuit depth and separating spin states

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.

Graphical abstract: Molecular excited state calculations with adaptive wavefunctions on a quantum eigensolver emulation: reducing circuit depth and separating spin states
Paper

Toward multifunctional molecular cells for quantum cellular automata: exploitation of interconnected charge and spin degrees of freedom

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.

Graphical abstract: Toward multifunctional molecular cells for quantum cellular automata: exploitation of interconnected charge and spin degrees of freedom
Paper

Understanding the magnetization blocking mechanism in N23−-radical-bridged dilanthanide single-molecule magnets

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.

Graphical abstract: Understanding the magnetization blocking mechanism in N23−-radical-bridged dilanthanide single-molecule magnets
From the themed collection: 2021 PCCP HOT Articles
Paper

Local spin and open quantum systems: clarifying misconceptions, unifying approaches

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.

Graphical abstract: Local spin and open quantum systems: clarifying misconceptions, unifying approaches
Paper

Bell inequalities for entangled qubits: quantitative tests of quantum character and nonlocality on quantum computers

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.

Graphical abstract: Bell inequalities for entangled qubits: quantitative tests of quantum character and nonlocality on quantum computers
Paper

Magnetic anisotropy in YbIII complex candidates for molecular qubits: a theoretical analysis

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

Graphical abstract: Magnetic anisotropy in YbIII complex candidates for molecular qubits: a theoretical analysis
From the themed collection: 2021 PCCP HOT Articles
Paper

Entanglement via rotational blockade of MgF molecules in a magic potential

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

Graphical abstract: Entanglement via rotational blockade of MgF molecules in a magic potential
Paper

Surface chemical trapping of optical cycling centers

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

Graphical abstract: Surface chemical trapping of optical cycling centers
From the themed collection: 2021 PCCP HOT Articles
Paper

Magnetic properties and quench dynamics of two interacting ultracold molecules in a trap

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

Graphical abstract: Magnetic properties and quench dynamics of two interacting ultracold molecules in a trap
Paper

Coherent manipulation of the internal state of ultracold 87Rb133Cs molecules with multiple microwave fields

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.

Graphical abstract: Coherent manipulation of the internal state of ultracold 87Rb133Cs molecules with multiple microwave fields
Paper

Electromagnetic control of spin ordered Mn3 qubits: a density functional study

As expected from experiment, the [Mn3O(O2CMe)dpd3/2]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).

Graphical abstract: Electromagnetic control of spin ordered Mn3 qubits: a density functional study
Paper

Vacancies in graphene: an application of adiabatic quantum optimization

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.

Graphical abstract: Vacancies in graphene: an application of adiabatic quantum optimization
Paper

Towards accurate prediction for laser-coolable molecules: relativistic coupled-cluster calculations for yttrium monoxide and prospects for improving its laser cooling efficiencies

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

Graphical abstract: Towards accurate prediction for laser-coolable molecules: relativistic coupled-cluster calculations for yttrium monoxide and prospects for improving its laser cooling efficiencies
Paper

Solving complex eigenvalue problems on a quantum annealer with applications to quantum scattering resonances

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

Graphical abstract: Solving complex eigenvalue problems on a quantum annealer with applications to quantum scattering resonances
Paper

Spin-momentum entanglement in a Bose–Einstein condensate

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

Graphical abstract: Spin-momentum entanglement in a Bose–Einstein condensate
Paper

Quantum algorithm for simulating molecular vibrational excitations

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.

Graphical abstract: Quantum algorithm for simulating molecular vibrational excitations
Paper

First-principles studies of strongly correlated states in defect spin qubits in diamond

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

Graphical abstract: First-principles studies of strongly correlated states in defect spin qubits in diamond
Paper

Dipole–phonon quantum logic with alkaline-earth monoxide and monosulfide cations

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

Graphical abstract: Dipole–phonon quantum logic with alkaline-earth monoxide and monosulfide cations
Paper

Protocol for optically pumping AlH+ to a pure quantum state

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

Graphical abstract: Protocol for optically pumping AlH+ to a pure quantum state
Paper

Quantum simulation of electronic structure with a transcorrelated Hamiltonian: improved accuracy with a smaller footprint on the quantum computer

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.

Graphical abstract: Quantum simulation of electronic structure with a transcorrelated Hamiltonian: improved accuracy with a smaller footprint on the quantum computer
Open Access Paper

From megahertz to terahertz qubits encoded in molecular ions: theoretical analysis of dipole-forbidden spectroscopic transitions in N2+

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.

Graphical abstract: From megahertz to terahertz qubits encoded in molecular ions: theoretical analysis of dipole-forbidden spectroscopic transitions in N2+
Paper

Quantum computation of silicon electronic band structure

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.

Graphical abstract: Quantum computation of silicon electronic band structure
Paper

Electrically tuned hyperfine spectrum in neutral Tb(II)(CpiPr5)2 single-molecule magnet

A strong Fermi contact (FC)-driven and electrically tunable hyperfine interaction is predicted for the neutral Tb(II)(CpiPr5)2 single-molecule magnet.

Graphical abstract: Electrically tuned hyperfine spectrum in neutral Tb(ii)(CpiPr5)2 single-molecule magnet
Paper

Nondestructive dispersive imaging of rotationally excited ultracold molecules

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

Graphical abstract: Nondestructive dispersive imaging of rotationally excited ultracold molecules
Paper

In search of molecular ions for optical cycling: a difficult road

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

Graphical abstract: In search of molecular ions for optical cycling: a difficult road
Paper

On the order problem in construction of unitary operators for the variational quantum eigensolver

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

Graphical abstract: On the order problem in construction of unitary operators for the variational quantum eigensolver
27 items

About this collection

Quantum computing and information storage promise to revolutionize our information technology. Some basic theory of quantum computing has been established over the past two decades and researchers are on the cusp of quantum supremacy for truly useful systems. Yet, for quantum computing to become a reality we need to find a practical physical platform for realizing qubits with enough fidelity and depth to solve important problems. At present it is not clear what platform will succeed at this.
This topical collection will highlight physical chemistry/chemical physics aspects of quantum computing and quantum information storage and will welcome contributions from experimental and theoretical communities working on atomic, molecular, and optical aspects of emerging quantum information technology.
Guest Edited by: John Doyle (Harvard University, USA), Anna Krylov, (University of Southern California, USA) and Kang-Kuen Ni (Harvard University, USA)

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