# US 10,374,612 B1 · Ancilla qubit devices in a superconducting quantum processor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,374,612 B1 - Document ID: US10374612B1 - Status: Granted - Kind: B1 - Application number: 16/151,902 - Filed: 2018-10-04 - Granted: 2019-08-06 - Earliest claimed: 2017-10-06 - Assignees: Rigetti & Co, LLC - Applicants: Rigetti & Co, Inc. - Inventors: Rodney Franklyn Sinclair; Matthew J. Reagor - Web page: https://patentgrep.com/patent/US10374612B1 ## CPC - H03K 19/195: using superconductive devices - G06N 10/20: Models of quantum computing, e.g. quantum circuits or universal quantum computers - G06N 10/40: Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control - G06N 10/70: Quantum error correction, detection or prevention, e.g. surface codes or magic state distillation - H10D 62/814: {Quantum box structures} - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) - G06N: COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract 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. ## Claims ### Claim 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. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 1) 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. ### Claim 4 (depends on 3) 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. ### Claim 5 (depends on 3) 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. ### Claim 6 (depends on 5) The quantum computing system of claim 5, wherein the at least one other qubit device includes at least one other ancilla qubit device. ### Claim 7 (depends on 6) The quantum computing system of claim 6, wherein the at least one other qubit device includes at least one other primary qubit device. ### Claim 8 (depends on 1) The quantum computing system of claim 1, wherein the parametrically-activated two-qubit quantum logic gate comprises an iSWAP gate. ### Claim 9 (depends on 1) The quantum computing system of claim 1, wherein the parametrically-activated two-qubit quantum logic gate comprises a controlled-Z gate. ### Claim 10 (depends on 1) 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. ### Claim 11 (depends on 1) 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. ### Claim 12 (depends on 1) 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. ### Claim 13 (depends on 1) 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. ### Claim 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. ### Claim 15 (depends on 14) 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. ### Claim 16 (depends on 14) The quantum computing method of claim 14, wherein applying the parametrically-activated two-qubit quantum logic gate comprises applying an iSWAP gate. ### Claim 17 (depends on 14) The quantum computing method of claim 14, wherein applying the parametrically-activated two-qubit quantum logic gate comprises applying a controlled-Z gate. ### Claim 18 (depends on 14) 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. ### Claim 19 (depends on 14) The quantum computing method of claim 14, comprising operating the fixed-frequency ancilla qubit device in an error correcting code. ### Claim 20 (depends on 14) 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. ### Claim 21 (depends on 14) 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. ### Claim 22 (depends on 21) The quantum computing method of claim 21, further comprising retrieving the binary readout value from the fixed-frequency ancilla qubit device. ### Claim 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. ### Claim 24 (depends on 23) 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. ### Claim 25 (depends on 23) 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. ### Claim 26 (depends on 23) 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. ### Claim 27 (depends on 23) 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. ### Claim 28 (depends on 23) 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. ### Claim 29 (depends on 23) 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. ### Claim 30 (depends on 23) 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.