Ancilla qubit devices in a superconducting quantum processor
View Patent ↗In a general aspect, a quantum computing system includes ancilla qubit devices. In some aspects, a quantum computing system includes a quantum processor cell that includes a superconducting quantum circuit system. The superconducting quantum circuit system includes a tunable-frequency primary qubit device; a flux-bias device coupled to the tunable-frequency primary qubit device; and a fixed-frequency ancilla qubit device. The fixed-frequency ancilla qubit device is connected only to the tunable-frequency primary qubit device in the superconducting quantum circuit system. The quantum computing system also includes a control system communicably coupled to the quantum processor cell. The control system is configured to apply a parametrically-activated two-qubit quantum logic gate to the tunable-frequency primary qubit device and the fixed-frequency ancilla qubit device by sending, to the flux-bias device, a radio-frequency control signal that modulates the tunable-frequency primary qubit device.
1. A quantum computing system comprising:
a quantum processor cell comprising a superconducting quantum circuit system, the superconducting quantum circuit system comprising:
a tunable-frequency primary qubit device;
a flux-bias device coupled to the tunable-frequency primary qubit device; and
a fixed-frequency ancilla qubit device connected only to the tunable-frequency primary qubit device; and
a control system communicably coupled to the quantum processor cell and configured to apply a parametrically-activated two-qubit quantum logic gate to the tunable-frequency primary qubit device and the fixed-frequency ancilla qubit device, wherein the control system is configured to apply the parametrically-activated two-qubit quantum logic gate by sending, to the flux-bias device, a radio-frequency control signal that modulates the tunable-frequency primary qubit device.
2. The quantum computing system of claim 1 , wherein the superconducting quantum circuit system comprises a capacitive connection that connects the tunable-frequency primary qubit device and the fixed-frequency ancilla qubit device.
3. The quantum computing system of claim 1 , wherein the superconducting quantum circuit system comprises a readout resonator device connected to the tunable-frequency primary qubit device.
4. The quantum computing system of claim 3 , wherein the control system is configured to detect a quantum state of the tunable-frequency primary qubit device by sending a control signal to the tunable-frequency primary qubit device through the readout resonator device.
5. The quantum computing system of claim 3 , wherein the superconducting quantum circuit system comprises at least one other qubit device connected to the tunable-frequency primary qubit device.
6. The quantum computing system of claim 5 , wherein the at least one other qubit device includes at least one other ancilla qubit device.
7. The quantum computing system of claim 6 , wherein the at least one other qubit device includes at least one other primary qubit device.
8. The quantum computing system of claim 1 , wherein the parametrically-activated two-qubit quantum logic gate comprises an iSWAP gate.
9. The quantum computing system of claim 1 , wherein the parametrically-activated two-qubit quantum logic gate comprises a controlled-Z gate.
10. The quantum computing system of claim 1 , wherein the control system is configured to operate the fixed-frequency ancilla qubit device as a memory qubit device without a dedicated readout device connected to the fixed-frequency ancilla qubit device.
11. The quantum computing system of claim 1 , wherein the control system is configured to operate the fixed-frequency ancilla qubit device in the application of an error correcting code.
12. The quantum computing system of claim 1 , wherein the quantum processor cell comprises a number of primary qubit devices, and the control system is configured to use the fixed-frequency ancilla qubit device to extend a quantum computational capacity of the quantum processor cell beyond the number of primary qubit devices in the quantum processor cell.
13. The quantum computing system of claim 1 , wherein the control system is configured to:
obtain a binary readout value by measuring a first qubit device in the quantum processor cell; and
store the binary readout value in the fixed-frequency ancilla qubit device.
14. A quantum computing method comprising:
storing information in a quantum processor cell comprising a superconducting quantum circuit system, the superconducting quantum circuit system comprising:
a tunable-frequency primary qubit device;
a flux-bias device coupled to the tunable-frequency primary qubit device; and
a fixed-frequency ancilla qubit device connected only to the tunable-frequency primary qubit device; and
by operation of a control system communicably coupled to the quantum processor cell, applying a parametrically-activated two-qubit quantum logic gate to the tunable-frequency primary qubit device and the fixed-frequency ancilla qubit device, wherein applying the parametrically-activated two-qubit quantum logic gate comprises sending, to the flux-bias device, a radio-frequency control signal that modulates the tunable-frequency primary qubit device.
15. The quantum computing method of claim 14 , wherein the superconducting quantum circuit system comprises a readout resonator device connected to the tunable-frequency primary qubit device, and the method comprises detecting a quantum state of the tunable-frequency primary qubit device by sending a control signal to the tunable-frequency primary qubit device through the readout resonator device.
16. The quantum computing method of claim 14 , wherein applying the parametrically-activated two-qubit quantum logic gate comprises applying an iSWAP gate.
17. The quantum computing method of claim 14 , wherein applying the parametrically-activated two-qubit quantum logic gate comprises applying a controlled-Z gate.
18. The quantum computing method of claim 14 , comprising operating the ancilla qubit device as a memory qubit device without a dedicated readout device connected to the ancilla qubit device.
19. The quantum computing method of claim 14 , comprising operating the fixed-frequency ancilla qubit device in an error correcting code.
20. The quantum computing method of claim 14 , wherein the quantum processor cell comprises a number of primary qubit devices, and the method comprises using the fixed-frequency ancilla qubit device to extend a quantum computational capacity of the quantum processor cell beyond the number of primary qubit devices in the quantum processor cell.
21. The quantum computing method of claim 14 , comprising:
obtaining a binary readout value by measuring a first qubit device in the quantum processor cell; and
storing the binary readout value in the fixed-frequency ancilla qubit device.
22. The quantum computing method of claim 21 , further comprising retrieving the binary readout value from the fixed-frequency ancilla qubit device.
23. A quantum computing system comprising:
a quantum processor cell comprising a superconducting quantum circuit system, the superconducting quantum circuit system comprising:
tunable-frequency primary qubit devices;
flux-bias devices coupled to the respective tunable-frequency primary qubit devices;
fixed-frequency ancilla qubit devices, each fixed-frequency ancilla qubit device connected only to a respective one of the tunable-frequency primary qubit devices; and
connections between neighboring pairs of primary and ancilla qubit devices, each neighboring pair comprising one of the tunable-frequency primary qubit devices and one of the fixed-frequency ancilla qubit devices; and
a control system communicably coupled to the quantum processor cell and configured to apply parametrically-activated two-qubit quantum logic gates to the neighboring pairs, wherein the control system is configured to apply the parametrically-activated two-qubit quantum logic gates by sending, to the flux-bias device coupled to the tunable-frequency primary qubit device in a respective neighboring pair, a radio-frequency control signal that modulates the tunable-frequency primary qubit device in the respective neighboring pair.
24. The quantum computing system of claim 23 , comprising additional connections between neighboring pairs of primary qubit devices, each neighboring pair of primary qubit devices comprising at least one of the tunable-frequency primary qubit devices.
25. The quantum computing system of claim 23 , wherein the superconducting quantum circuit system comprises readout resonator devices connected to the respective tunable-frequency primary qubit devices.
26. The quantum computing system of claim 23 , wherein each of the tunable-frequency primary qubit devices is connected to exactly one of the fixed-frequency ancilla qubit devices.
27. The quantum computing system of claim 23 , wherein each of the tunable-frequency primary qubit devices is connected to more than one of the fixed-frequency ancilla qubit devices.
28. The quantum computing system of claim 23 , wherein the control system is configured to operate the fixed-frequency ancilla qubit devices as memory qubit devices without dedicated readout devices connected to the ancilla qubit devices.
29. The quantum computing system of claim 23 , wherein the control system is configured to operate the fixed-frequency ancilla qubit devices in an error correcting code.
30. The quantum computing system of claim 23 , wherein the quantum processor cell comprises a number of primary qubit devices, and the control system is configured to use the fixed-frequency ancilla qubit devices to extend a quantum computational capacity of the quantum processor cell beyond the number of primary qubit devices in the quantum processor cell.