# Chemistry on Quantum Computers with Virtual Quantum Subspace Expansion.

@article{Urbnek2020ChemistryOQ, title={Chemistry on Quantum Computers with Virtual Quantum Subspace Expansion.}, author={Miroslav Urb{\'a}nek and Daan Camps and Roel Van Beeumen and Wibe A. de Jong}, journal={Journal of chemical theory and computation}, year={2020} }

Simulating chemical systems on quantum computers has been limited to a few electrons in a minimal basis. We demonstrate experimentally that the virtual quantum subspace expansion (Takeshita, T.; Phys. Rev. X 2020, 10, 011004, 10.1103/PhysRevX.10.011004) can achieve full basis accuracy for hydrogen and lithium dimers, comparable to simulations requiring 20 or more qubits. We developed an approach to minimize the impact of experimental noise on the stability of the generalized eigenvalue problem…

## 11 Citations

Equation-of-motion variational quantum eigensolver method for computing molecular excitation energies, ionization potentials, and electron affinities

- Chemistry
- 2022

Ayush Asthana, Ashutosh Kumar, Vibin Abraham, Harper Grimsley, Yu Zhang, Lukasz Cincio, Sergei Tretiak, 4 Pavel A. Dub, Sophia E. Economou, Edwin Barnes, and Nicholas J. Mayhall ∗ Department of…

Wave Function Adapted Hamiltonians for Quantum Computing.

- PhysicsJournal of chemical theory and computation
- 2022

A modified VQE scheme in which the form of the molecular Hamiltonian is adapted to the circuit ansatz through an optimization procedure and is able to recover a significant amount of electron correlation even with only empirical ansatzes with shallow circuit depth.

Fermi.jl: A Modern Design for Quantum Chemistry.

- Computer ScienceJournal of chemical theory and computation
- 2022

The quantum chemistry package Fermi.jl is introduced, which contains the first implementations of post-Hartree-Fock methods written in Julia, which is a modular package designed to maximize code reusability by relying on general functions with specialized methods for particular cases.

Flexibility of the factorized form of the unitary coupled cluster Ansatz.

- Computer ScienceThe Journal of chemical physics
- 2022

This work shows that the factorized form of the unitary coupled cluster Ansatz is quite flexible, allowing one to range from a conventional configuration interaction, to conventional unitARY coupled cluster, to efficient approximations that lie in between these two.

Real-Time Evolution for Ultracompact Hamiltonian Eigenstates on Quantum Hardware

- BiologyPRX Quantum
- 2022

This research attacked the mode confusion problem by developing a modeling framework that allowed us to estimate the level of uncertainty in the model’s response to various levels of uncertainty.

Analytical Ground- and Excited-State Gradients for Molecular Electronic Structure Theory from Hybrid Quantum/Classical Methods

- Physics
- 2021

We develop analytical gradients of groundand excited-state energies with respect to system parameters including the nuclear coordinates for the hybrid quantum/classical multistate contracted…

Classically-Boosted Variational Quantum Eigensolver

- Physics
- 2021

The ability of near-termquantumcomputers to represent classically-intractable quantum states has brought much interest in using such devices for estimating the ground and excited state energies of…

Local, expressive, quantum-number-preserving VQE ansätze for fermionic systems

- PhysicsNew Journal of Physics
- 2021

We propose VQE circuit fabrics with advantageous properties for the simulation of strongly correlated ground and excited states of molecules and materials under the Jordan–Wigner mapping that can be…

Benchmarking Quantum Chemistry Computations with Variational, Imaginary Time Evolution, and Krylov Space Solver Algorithms

- Computer ScienceAdvanced Quantum Technologies
- 2021

Electronic structure calculations have advanced rapidly, to routine chemical accuracy for simple molecules, from their inception on quantum computers a few short years ago, and they point to further rapid progress to larger molecules as the power of NISQ devices grows.

Fermionic Partial Tomography via Classical Shadows.

- Computer SciencePhysical review letters
- 2021

This work proves that estimating all k-RDM elements to additive precision ϵ requires on the order of (n/k)k^{3/2}log(n)/ϵ^{2} repeated state preparations, which is optimal up to the logarithmic factor.

## References

SHOWING 1-10 OF 60 REFERENCES

Phys

- Rev. X 10, 011004
- 2020

Hartree-Fock on a superconducting qubit quantum computer

- PhysicsScience
- 2020

Several quantum simulations of chemistry with up to one dozen qubits are performed, including modeling the isomerization mechanism of diazene, and error-mitigation strategies based on N-representability that dramatically improve the effective fidelity of the experiments are demonstrated.

Classical Optimizers for Noisy Intermediate-Scale Quantum Devices

- Computer Science, Physics2020 IEEE International Conference on Quantum Computing and Engineering (QCE)
- 2020

We present a collection of optimizers tuned for usage on Noisy Intermediate-Scale Quantum (NISQ) devices. Optimizers have a range of applications in quantum computing, including the Variational…

Quantum orbital-optimized unitary coupled cluster methods in the strongly correlated regime: Can quantum algorithms outperform their classical equivalents?

- Physics, Computer ScienceThe Journal of chemical physics
- 2020

Several variants of the standard q-UCCSD Ansatz in which only a subset of excitations is included are evaluated and it is shown that these approaches can capture the dissociation/distortion profiles of challenging systems, such as H4, H2O, and N2 molecules, as well as the one-dimensional periodic Fermi-Hubbard chain.

Quantum equation of motion for computing molecular excitation energies on a noisy quantum processor

- Physics, Computer Science
- 2019

This work introduces an efficient excited states quantum algorithm, that employs a quantum version of the well-established classical equation of motion approach, which allows the calculation of the excitation energies of a given system using an approximated description of its ground state wave function.

Unfolding quantum computer readout noise

- Physicsnpj Quantum Information
- 2020

In the current era of noisy intermediate-scale quantum computers, noisy qubits can result in biased results for early quantum algorithm applications. This is a significant challenge for interpreting…