DYNAMICALLY DECOUPLED DRIVEN CONTROLLED-Z GATE
Systems and methods are provided for performing a dynamic decoupled controlled-Z gate operation. A superconducting circuit of an exemplary system can include a first qubit and a second qubit transversely coupled to the first qubit, lire system can apply an external magnetic flux to the second qubit to bring a frequency of the second qubit into resonance with a frequency of the first qubit. The system can apply a continuous alternating drive with continuous phase to the second qubit, a duration and a magnitude of the continuous alternating drive configured to synchronize agate time of the dynamic decoupled controlled-Z gate operation to an integer number of Rabi oscillation periods. The system can read out a state of the quantum computing system, after providing the continuous alternating drive.
1 . A quantum computing system for performing a dynamically decoupled controlled-Z gate operation, comprising:
a superconducting circuit comprising:
a first qubit;
a second qubit transversely coupled to the first qubit; and
at least one computing device configured to:
provide, to a first drive source, first instructions causing the first drive source to apply an external magnetic flux to the second qubit to bring a frequency of the second qubit into resonance with a frequency of the first qubit; and
provide, to a second drive source, second instructions causing the second drive source to apply a continuous alternating drive with continuous phase to the second qubit.
2 . The quantum computing system of claim 1 , wherein:
a duration and a magnitude of the continuous alternating drive is configured to synchronize a gate time of the dynamically decoupled controlled-Z gate operation to an integer number of Rabi oscillation periods
3 . The quantum computing system of claim 1 , wherein:
a magnitude of the continuous alternating drive is selected based on a magnitude of an interaction term between the first qubit and the second qubit in a Hamiltonian of the superconducting circuit, the Hamiltonian specified for a frame rotating with the first and second qubits.
4 . The quantum computing system of claim 3 , wherein:
the magnitude of the continuous alternating drive is between one and three times the magnitude of the interaction term.
5 . The quantum computing system of claim 1 , wherein:
a duration of the continuous alternating drive is inversely based on a magnitude of the continuous alternating drive.
6 . The quantum computing system of claim 1 , wherein:
a duration of the continuous alternating drive is selected to be within 10% of a quotient of pi divided by a magnitude of the continuous alternating drive.
7 . The quantum computing system of claim 1 , wherein:
a magnitude of the continuous alternating drive is selected to correspond to a peak in a relationship between the magnitude and a fidelity of the dynamically decoupled controlled-Z gate operation.
8 . The quantum computing system of claim 7 , wherein:
the peak comprises a first peak in the relationship.
9 . The quantum computing system of claim 1 , wherein:
the first qubit and the second qubit are both fluxonium qubits.
10 . The quantum computing system of claim 1 , wherein:
the at least one computing device is further configured to provide, after providing the second instructions to the second drive source, third instructions to read out a state of the quantum computing system.
11 . A method for performing a dynamically decoupled controlled-Z gate operation, comprising:
providing, by a first drive source to a second qubit of a superconducting circuit of a quantum computing system, an external magnetic flux to tune a frequency of the second qubit to a frequency of a first qubit, the first qubit being transversely coupled to the second qubit;
providing, by a second drive source to the second qubit, a continuous alternating drive, a magnitude of the continuous alternating drive corresponding to a peak in a relationship between the magnitude and a fidelity of the dynamically decoupled controlled-Z gate operation; and
reading out, after providing the second drive source, a state of the quantum computing system.
12 . The method of claim 11 , wherein:
the magnitude of the continuous alternating drive is selected based on a magnitude of an interaction term between the first qubit and the second qubit in a Hamiltonian of the superconducting circuit, the Hamiltonian specified for a frame rotating with the first and second qubits.
13 . The method of claim 12 , wherein:
the magnitude of the continuous alternating drive is between one and three times the magnitude of the interaction term.
14 . The method of claim 11 , wherein:
a duration of the continuous alternating drive is based inversely on the magnitude of the continuous alternating drive.
15 . The method of claim 11 , wherein:
a duration of the continuous alternating drive is selected to be within 10% of a quotient of pi divided by the magnitude of the continuous alternating drive.
16 . The method of claim 11 , wherein:
the peak comprises a first peak in the relationship.
17 . The method of claim 11 , wherein:
a duration and the magnitude of the continuous alternating drive are selected to synchronize a gate time for the dynamically decoupled controlled-Z gate operation to an integer number of Rabi oscillation periods.
18 . The method of claim 11 , wherein:
the first qubit and the second qubit are both fluxonium qubits.
19 . A non-transitory computer-readable medium comprising instructions that, when processed by a quantum computing system, cause the quantum computing system to perform first operations for implementing a dynamically decoupled controlled-Z gate operation, the first operations comprising:
providing, by a first drive source to a second qubit of a superconducting circuit, an external magnetic flux to tune a frequency of the second qubit to a frequency of a first qubit, the first qubit being transversely coupled to the second qubit;
providing, by a second drive source to the second qubit, a continuous alternating drive, a duration of the continuous alternating drive:
based inversely on a magnitude of the continuous alternating drive; and
within 10% of a quotient of pi divided by the magnitude of the continuous alternating drive; and
reading out, after providing the second drive source, a state of the quantum computing system.
20 . The non-transitory computer-readable medium of claim 19 , wherein:
the magnitude of the continuous alternating drive is selected to correspond to a first peak in a relationship between the magnitude and a fidelity of the dynamically decoupled controlled-Z gate operation.
21 . The non-transitory computer-readable medium of claim 19 , wherein:
the duration and the magnitude of the continuous alternating drive is selected to synchronize a gate time of the dynamically decoupled controlled-Z gate operation to an integer number of Rabi oscillation periods.
22 . The non-transitory computer-readable medium of claim 19 , wherein:
the first qubit and the second qubit are both fluxonium qubits.