The Fermionic Quantum Emulator

Rubin, Nicholas C.; Gunst, Klaas; White, Alec F.; Freitag, Leon; Throssell, Kyle; Chan, Garnet Kin‐Lic; Babbush, Ryan; Shiozaki, Toru

doi:10.22331/q-2021-10-27-568

Cited by 19 publications

(29 citation statements)

References 37 publications

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“…In the two-electron integral case, we demonstrate unitary compression optimized through a global least-squares and the greedy approach both fail to recover high-quality factorizations for a simple system. All calculations are accomplished with PySCF, OpenFermion, the Fermionic Quantum Emulator, and a custom implementation of the tensor decomposition schemes.…”

Section: Resultsmentioning

confidence: 99%

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Compressing Many-Body Fermion Operators under Unitary Constraints

Rubin

Babbush

2022

J. Chem. Theory Comput.

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The most efficient known quantum circuits for preparing unitary coupled cluster states and applying Trotter steps of the arbitrary basis electronic structure Hamiltonian involve interleaved sequences of Fermionic Gaussian circuits and Ising interaction-type circuits. These circuits arise from factorizing the two-body operators generating those unitaries as a sum of squared one-body operators that are simulated using product formulas. We introduce a numerical algorithm for performing this factorization that has an iteration complexity no worse than single particle basis transformations of the two-body operators and often results in many times fewer squared one-body operators in the sum of squares, compared to the analytical decompositions. As an application of this numerical procedure, we demonstrate that our protocol can be used to approximate generic unitary coupled cluster operators and prepare the necessary high-quality initial states for techniques (like ADAPT-VQE) that iteratively construct approximations to the ground state.

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Section: Resultsmentioning

confidence: 99%

“…Gradients were obtained through the dynamic programming approach described in ref . All numerics were performed with the Fermionic quantum emulator …”

Section: Resultsmentioning

confidence: 99%

Compressing Many-Body Fermion Operators under Unitary Constraints

Rubin

Babbush

2022

J. Chem. Theory Comput.

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“…The Fermionic Quantum Emulator (FQE) described above is an open source library under the Apache 2.0 license [40]. Currently, the library is completely implemented in Python to facilitate extension and code reuse.…”

Section: Closing Thoughts and Future Directionsmentioning

confidence: 99%

The Fermionic Quantum Emulator

Rubin,

Gunst,

White

et al. 2021

Preprint

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The fermionic quantum emulator (FQE) is a collection of protocols for emulating quantum dynamics of fermions efficiently taking advantage of common symmetries present in chemical, materials, and condensed-matter systems. The library is fully integrated with the OpenFermion software package and serves as the simulation backend. The FQE reduces memory footprint by exploiting number and spin symmetry along with custom evolution routines for sparse and dense Hamiltonians, allowing us to study significantly larger quantum circuits at modest computational cost when compared against qubit state vector simulators. This release paper outlines the technical details of the simulation methods and key technical advantages.

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“…28,29 Meanwhile, the largest scale numerical molecular VQE simulation is C 2 H 4 (28 qubits). 27 The simulation of even large molecular systems might be realized in the future with the recently developed fermionic quantum emulator, 30 which utilizes the particle number and spin symmetry along with custom evolution routines for Hamiltonians to reduce the memory requirement.…”

Section: Introductionmentioning

confidence: 99%