IP Library › Granted Patent US 12,411,687
Granted Patent B1
US 12,411,687 · App. 18/753,079 · Granted Sep 9, 2025

Accelerating hybrid quantum/classical algorithms

Inventor: Nicholas C. Rubin (Berkeley, CA)
Assignee: Rigetti & Co, LLC
G06F9/3001G06F17/16G06N10/00G06N10/70G06N10/80
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Quick Facts
Patent No.
US 12,411,687
App. No.
18/753,079
Granted
Sep 9, 2025
Kind
B1
Abstract

In a general aspect, hybrid quantum/classical algorithms are executed in a computing system. A first set of values representing a measurement of a reduced density matrix (RDM) is obtained. The first set of values is based on sampling quantum states generated by a quantum processor. A classical processor generates a second, different set of values to represent the measurement of the RDM. The second set of values is constructed based on the first set of values by a process that imposes one or more n-representability conditions on the second set of values to represent the measurement of the RDM.

Claims (43)

1. A computing method performed by a hybrid classical-quantum computing system comprising one or more classical processors and one or more quantum processors, the method comprising:

causing the one or more quantum processors to execute a quantum logic circuit comprising a plurality of quantum logic gates applied to qubits;

by operation of the one or more classical processors, obtaining expected values of operators based on output quantum states generated by executing the quantum logic circuit;

by operation of the one or more classical processors, generating a first reduced density matrix (RDM) based on the expected values; and

by operation of the one or more classical processors, executing a semidefinite program with one or more n-representability conditions to construct a second RDM based on the first RDM.

2. The computing method of claim 1 , comprising:

providing the second RDM in an iteration of a hybrid quantum-classical algorithm executed by the hybrid classical-quantum computing system.

3. The computing method of claim 1 , wherein executing the quantum logic circuit comprises:

initializing the qubits in initial states;

transforming the initial states to the output quantum states; and

extracting the output quantum states.

4. The computing method of claim 1 , wherein obtaining the expected values of operators comprises:

performing a partial tomography of the output quantum states.

5. The computing method of claim 1 , wherein obtaining the expected values of operators comprises:

calculating the expected values of k-local fermionic operators.

6. The computing method of claim 1 , wherein the one or more n-representability conditions comprise one or more fermionic n-representability conditions.

7. The computing method of claim 1 , wherein the first RDM comprises a two-particle RDM.

8. The computing method of claim 1 , wherein the semidefinite program is a fixed-trace semidefinite program (SDP) projection.

9. The computing method of claim 1 , wherein constructing the second RDM removes errors associated with the first RDM.

10. The computing method of claim 1 , wherein executing the semidefinite program with the one or more n-representative conditions minimizes a Schatten norm.

11. A system comprising:

one or more classical processors; and

one or more quantum processors;

wherein the one or more classical processors are configured to:

cause the one or more quantum processors to execute a quantum logic circuit comprising a plurality of quantum logic gates applied to qubits;

obtain expected values of operators based on output quantum states generated by executing the quantum logic circuit;

generate a first reduced density matrix (RDM) based on the expected values; and

execute a semidefinite program with one or more n-representability conditions to construct a second RDM based on the first RDM.

12. The system of claim 11 , wherein the one or more classical processors are configured to:

provide the second RDM in an iteration of a hybrid quantum-classical algorithm executed by the hybrid classical-quantum computing system.

13. The system of claim 11 , wherein executing the quantum logic circuit comprises:

initializing the qubits in initial states;

transforming the initial states to the output quantum states; and

extracting the output quantum states.

14. The system of claim 11 , wherein obtaining the expected values of operators comprises:

performing a partial tomography of the output quantum states.

15. The system of claim 11 , wherein obtaining the expected values of operators comprises:

calculating the expected values of k-local fermionic operators.

16. The system of claim 11 , wherein the one or more n-representability conditions comprise one or more fermionic n-representability conditions.

17. The system of claim 11 , wherein the first RDM comprises a two-particle RDM.

18. The system of claim 11 , wherein the semidefinite program is a fixed-trace semidefinite program (SDP) projection.

19. The system of claim 11 , wherein constructing the second RDM removes errors associated with the first RDM.

20. The system of claim 11 , wherein executing the semidefinite program with the one or more n-representative conditions minimizes a Schatten norm.

Assignments (2)
CHANGE OF NAME Recorded Jul 12, 2024
From: RIGETTI & CO, INC.
To: RIGETTI & CO, LLC
Reel/Frame 068314/0864 →
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Jul 10, 2024
From: RUBIN, NICHOLAS C.
To: RIGETTI & CO., INC.
Reel/Frame 067955/0481 →
Continuity (4)
Continuation 18180513 · Mar 8, 2023
Continuation 15917731 · Mar 11, 2018
Provisional Application 62553667 · Sep 1, 2017
Provisional Application 62500361 · May 2, 2017
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