US 11,809,957 B2
Three qubit entangling gate through two-local hamiltonian control
Yuezhen Niu, El Segundo, CA (US); Vadim Smelyanskiy, Mountain View, CA (US); and Sergio Boixo Castrillo, Rancho Palos Verdes, CA (US)
Assigned to Google LLC, Mountain View, CA (US)
Appl. No. 16/981,606
Filed by Google LLC, Mountain View, CA (US)
PCT Filed Jan. 31, 2019, PCT No. PCT/US2019/016047
§ 371(c)(1), (2) Date Sep. 16, 2020,
PCT Pub. No. WO2020/106313, PCT Pub. Date May 28, 2020.
Claims priority of provisional application 62/769,398, filed on Nov. 19, 2018.
Prior Publication US 2021/0390442 A1, Dec. 16, 2021
Int. Cl. G06N 10/00 (2022.01); H10N 60/12 (2023.01)
CPC G06N 10/00 (2019.01) [H10N 60/12 (2023.02)] 30 Claims
OG exemplary drawing
 
1. A method for implementing a three-qubit quantum gate on a quantum system comprising a first qubit, second qubit and third qubit, wherein the second qubit is coupled to the first qubit and to the third qubit, the three qubit quantum gate implementing a full or partial swap operation between the first qubit and the third qubit, the swap operation being conditioned on the second qubit being in an excited state, and assigning a minus sign to the swapped basis states, the method comprising:
evolving a state of the quantum system under a Hamiltonian describing the quantum system for a predetermined time, wherein during the evolving:
the ground and first excited state of the second qubit are separated by a first energy gap;
the first and second excited state of the second qubit are separated by a second energy gap that is equal to the first energy gap minus a qubit anharmoniticity;
the ground and first excited state of the first qubit and ground and first excited state of the third qubit are separated by a third energy gap that is equal to the first energy gap minus the qubit anharmonicity; and
the first and second excited state of the first qubit and first and second excited state of the third qubit are separated by a fourth energy gap that is equal to the first energy gap minus twice the qubit anharmonicity.