# US 12,120,965 B2 · Mode-selective couplers for frequency collision reduction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,120,965 B2 - Document ID: US12120965B2 - Status: Granted - Kind: B2 - Application number: 18/160,465 - Filed: 2023-01-27 - Published: 2023-06-01 - Granted: 2024-10-15 - Earliest claimed: 2020-06-08 - Assignees: International Business Machines Corporation - Applicants: International Business Machines Corporation - Inventors: Aaron Finck; John Blair - Web page: https://patentgrep.com/patent/US12120965B2 ## CPC - H10N 60/805: {for Josephson-effect devices} - H10N 69/00: Integrated devices, or assemblies of multiple devices, comprising at least one superconducting element covered by group H10N60/00 - G06N 10/40: Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control - H10N 60/12: Josephson-effect devices - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - G06N: COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS ## Abstract Systems and techniques that facilitate mode-selective couplers for frequency collision reduction are provided. In various embodiments, a device can comprise a control qubit. In various aspects, the device can comprise a first target qubit coupled to the control qubit by a first mode-selective coupler. In various instances, the first mode-selective coupler can facilitate A-mode coupling between the control qubit and the first target qubit. In various embodiments, the device can comprise a second target qubit coupled to the control qubit by a second mode-selective coupler. In various aspects, the second mode selective coupler can facilitate B-mode coupling between the control qubit and the second target qubit. In various embodiments, the first mode-selective coupler can comprise a capacitor that capacitively couples a middle capacitor pad of the control qubit to a middle capacitor pad of the first target qubit. In various embodiments, the second mode-selective coupler can comprise a first capacitor that capacitively couples an end capacitor pad of the control qubit to an end capacitor pad of the first target qubit and can comprise a second capacitor that capacitively couples the end capacitor pad of the control qubit to a middle capacitor pad of the second target qubit. ## Claims ### Claim 1 A device, comprising: a control qubit coupled to a first mode-selective coupler, a second mode-selective coupler, a third mode-selective coupler, and a fourth mode-selective coupler; a first target qubit coupled to the first mode-selective coupler, wherein the first mode-selective coupler allows A-mode coupling between the control qubit and the first target qubit, and prevents B-mode coupling between the control qubit and the first target qubit; a second target qubit coupled to the second mode-selective coupler, wherein the second mode-selective coupler allows the B-mode coupling between the control qubit and the second target qubit, and prevents the A-mode coupling between the control qubit and the second target qubit; a third target qubit coupled to the third mode-selective coupler, wherein the third mode-selective coupler allows A-mode coupling between the control qubit and the third target qubit, and prevents B-mode coupling between the control qubit and the third target qubit; and a fourth target qubit coupled to the fourth mode-selective coupler, wherein the fourth mode-selective coupler allows the B-mode coupling between the control qubit and the second target qubit, and prevents the A-mode coupling between the control qubit and the fourth target qubit. ### Claim 2 (depends on 1) The device of claim 1, wherein the first target qubit is degenerate with respect to the second target qubit. ### Claim 3 (depends on 1) The device of claim 1, wherein the third target qubit is degenerate with respect to the fourth target qubit. ### Claim 4 (depends on 1) The device of claim 1, wherein the first target qubit and the second target qubit are non-degenerate with respect to the third target qubit and the fourth target qubit. ### Claim 5 (depends on 1) The device of claim 1, wherein at least one of the control qubit, the first target qubit, the second target qubit, the third target qubit, or the fourth target qubit is a two-junction transmon qubit. ### Claim 6 (depends on 1) The device of claim 1, wherein the control qubit is entangled with at least one of the first target qubit or the third target qubit in response to the control qubit being driven by a microwave tone corresponding to an A-mode excitation frequency. ### Claim 7 (depends on 6) The device of claim 6, wherein the control qubit is entangled with at least one of the second target qubit or the fourth target qubit in response to the control qubit being driven by a microwave tone corresponding to an B-mode excitation frequency. ### Claim 8 A method, comprising: coupling a control qubit to a first target qubit by a first mode-selective coupler that allows A-mode coupling between the control qubit and the first target qubit, and prevents B-mode coupling between the control qubit and the first target qubit; coupling the control qubit to a second target qubit by a second mode-selective coupler that allows the B-mode coupling between the control qubit and the second target qubit, and prevents the A-mode coupling between the control qubit and the second target qubit; coupling the control qubit to a third target qubit by a third mode-selective coupler that allows the A-mode coupling between the control qubit and the third target qubit, and prevents the B-mode coupling between the control qubit and the third target qubit; and coupling the control qubit to and a fourth target qubit by a fourth mode-selective coupler that allows the B-mode coupling between the control qubit and the fourth target qubit, and prevents the A-mode coupling between the control qubit and the fourth target qubit. ### Claim 9 (depends on 8) The method of claim 8, wherein the first target qubit is degenerate with respect to the second target qubit. ### Claim 10 (depends on 8) The method of claim 8, wherein the third target qubit is degenerate with respect to the fourth target qubit. ### Claim 11 (depends on 8) The method of claim 8, wherein the first target qubit and the second target qubit are non-degenerate with respect to the third target qubit and the fourth target qubit. ### Claim 12 (depends on 8) The method of claim 8, wherein at least one of the control qubit, the first target qubit, the second target qubit, the third target qubit, or the fourth target qubit is a two-junction transmon qubit. ### Claim 13 (depends on 8) The method of claim 8, wherein the control qubit is entangled with at least one of the first target qubit or the third target qubit in response to the control qubit being driven by a microwave tone corresponding to an A-mode excitation frequency. ### Claim 14 (depends on 13) The method of claim 13, wherein the control qubit is entangled with at least one of the second target qubit or the fourth target qubit in response to the control qubit being driven by a microwave tone corresponding to an B-mode excitation frequency. ### Claim 15 A computer program product for facilitating selectively coupling a control qubit to target qubits, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to: couple the control qubit to a first target qubit by a first mode-selective coupler that allows A-mode coupling between the control qubit and the first target qubit, and prevents B-mode coupling between the control qubit and the first target qubit; couple the control qubit to a second target qubit by a second mode-selective coupler that allows the B-mode coupling between the control qubit and the second target qubit, and prevents the A-mode coupling between the control qubit and the second target qubit; couple the control qubit to a third target qubit by a third mode-selective coupler that allows the A-mode coupling between the control qubit and the third target qubit, and prevents the B-mode coupling between the control qubit and the third target qubit; and couple the control qubit to a fourth target qubit by a fourth mode-selective coupler that allows the B-mode coupling between the control qubit and the fourth target qubit, and prevents the A-mode coupling between the control qubit and the fourth target qubit. ### Claim 16 (depends on 15) The computer program product of claim 15, wherein the first target qubit is degenerate with respect to the second target qubit. ### Claim 17 (depends on 15) The computer program product of claim 15, wherein the third target qubit is degenerate with respect to the fourth target qubit. ### Claim 18 (depends on 15) The computer program product of claim 15, wherein the first target qubit and the second target qubit are non-degenerate with respect to the third target qubit and the fourth target qubit. ### Claim 19 (depends on 15) The computer program product of claim 15, wherein at least one of the control qubit, the first target qubit, the second target qubit, the third target qubit, or the fourth target qubit is a two-junction transmon qubit. ### Claim 20 (depends on 15) The computer program product of claim 15, wherein the control qubit is entangled with at least one of the first target qubit or the third target qubit in response to the control qubit being driven by a microwave tone corresponding to an A-mode excitation frequency, and wherein the control qubit is entangled with at least one of the second target qubit or the fourth target qubit in response to the control qubit being driven by a microwave tone corresponding to an B-mode excitation frequency.