US 12,249,404 B2
Efficient and noise resilient measurements for quantum chemistry
Ryan Babbush, Venice, CA (US); William Huggins, Oakland, CA (US); and Jarrod Ryan McClean, Marina del Rey, CA (US)
Assigned to Google LLC, Mountain View, CA (US)
Appl. No. 17/630,482
Filed by Google LLC, Mountain View, CA (US)
PCT Filed Jul. 28, 2020, PCT No. PCT/US2020/043884
§ 371(c)(1), (2) Date Jan. 26, 2022,
PCT Pub. No. WO2021/021813, PCT Pub. Date Feb. 4, 2021.
Claims priority of provisional application 62/879,750, filed on Jul. 29, 2019.
Prior Publication US 2022/0254453 A1, Aug. 11, 2022
Int. Cl. G16C 10/00 (2019.01); G06N 5/01 (2023.01); G06N 10/00 (2022.01); G06N 10/60 (2022.01)
CPC G16C 10/00 (2019.02) [G06N 5/01 (2023.01); G06N 10/00 (2019.01); G06N 10/60 (2022.01)] 13 Claims
OG exemplary drawing
 
1. A method performed by a classical processor and quantum computing hardware in data communication with the classical processor, the method comprising:
measuring an energy of a chemical system, comprising:
obtaining, as input to the classical processor, a Hamiltonian describing the chemical system, wherein the Hamiltonian is expressed in an orthonormal basis;
implementing, by the classical processor and the quantum computing hardware, a basis rotation grouping measurement strategy of a qubit system included in the quantum computing hardware, the basis rotation grouping measurement strategy comprising:
decomposing, by classical computation, the Hamiltonian describing the chemical system into a sum of terms, wherein each term comprises i) a respective operator that effects a respective single particle basis rotation, and ii) one or more particle density operators;
for each group comprising terms with a same operator that effects a respective single particle basis rotation, measuring expectation values of the terms included in the group, comprising, for each repetition in a plurality of repetitions, wherein a number of repetitions in the plurality of repetitions is dependent on a predetermined accuracy:
encoding, by quantum computation on the quantum computing hardware, a state of the chemical system in a state of the qubit system;
performing, by quantum computation on the quantum computing hardware, the respective single particle basis rotation of the group on the state of the qubit system encoding the state of the chemical system, comprising applying a quantum circuit to the qubit system; and
measuring, by quantum computation on the quantum computing hardware and in a computational basis, the qubit system, comprising measuring Jordan-Wigner transformations of the one or more particle density operators in the group to obtain a respective measurement result for the group; and
determining, by classical computation, the energy of the chemical system using the obtained measurement results.