# US 12,184,339 B2 · Microwave photon control device, microwave photon transmitter, microwave photon receiver, microwave photon repeater, and quantum computer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,184,339 B2 - Document ID: US12184339B2 - Status: Granted - Kind: B2 - Application number: 17/790,819 - Filed: 2020-12-28 - Published: 2022-11-24 - Granted: 2024-12-31 - Earliest claimed: 2020-01-08 - Assignees: Japan Science and Technology Agency - Applicants: Japan Science and Technology Agency - Inventors: Shingo Kono; Yasunobu Nakamura - Web page: https://patentgrep.com/patent/US12184339B2 ## CPC - H04B 10/70: Photonic quantum communication - G06N 10/40: Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control - G21K 1/20: for confining charged particles or handling confined charged particles, e.g. ion traps - H04B: TRANSMISSION - G06N: COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS - G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES ## Abstract A microwave photon control device includes a first qubit and a second qubit that are connected in parallel to a waveguide through which microwave photons propagate, and a direct coupling between the first qubit and the second qubit. An interval between the first qubit and the second qubit is (¼+n/2) times as long as a wavelength of microwave photons (where n is an integer equal to or larger than 0). A quantum entangled state is formed between the first qubit and the second qubit. The direct coupling cancels out a coupling via the waveguide between the first qubit and the second qubit. By a relaxation rate of the first qubit and the second qubit, and a phase of the quantum entangled state being controlled, the microwave photon control device operates while switching between a first operation mode, a second operation mode, and a third operation mode. ## Claims ### Claim 1 A microwave photon control device comprising: a first qubit and a second qubit that are connected in parallel to a waveguide through which microwave photons propagate, and a direct coupling between the first qubit and the second qubit, wherein an interval between the first qubit and the second qubit is ¼+n/2 times as long as a wavelength of microwave photons where n is an integer equal to or larger than 0, wherein a quantum entangled state is formed between the first qubit and the second qubit, wherein the direct coupling cancels out a coupling via the waveguide between the first qubit and the second qubit, and wherein, by a phase of the quantum entangled state between the first qubit and the second qubit, and/or couplings between the first qubit and the second qubit, and the waveguide being controlled, the microwave photon control device operates while switching between a first operation mode for emitting microwave photons in one direction of the waveguide, a second operation mode for absorbing microwave photons that have propagated from one direction of the waveguide, and a third operation mode for letting through microwave photons that have propagated from one direction of the waveguide, to propagate. ### Claim 2 (depends on 1) The microwave photon control device according to claim 1, further comprising: a first resonator and a second resonator, wherein the first qubit and the second qubit are connected to the waveguide via the first resonator and the second resonator, respectively, wherein the direct coupling is formed between the first resonator and the second resonator, wherein the direct coupling is temporally constant, and wherein control of couplings between the first qubit and the second qubit, and the waveguide is control of a coupling between the first qubit and the first resonator, and a coupling between the second qubit and the second resonator. ### Claim 3 (depends on 1) The microwave photon control device according to claim 1, further comprising: a coupling controller and a quantum entangled state generator, wherein the coupling controller controls a coupling between the first qubit and the waveguide, and a coupling between the second qubit and the waveguide, and wherein the quantum entangled state generator generates a quantum entangled state between the first qubit and the second qubit. ### Claim 4 (depends on 1) The microwave photon control device according to claim 1, wherein control of a relaxation rate of the first qubit and the second qubit, and a phase of the quantum entangled state is performed using received microwaves. ### Claim 5 (depends on 1) The microwave photon control device according to claim 1, wherein the first qubit and the second qubit are superconducting qubits. ### Claim 6 (depends on 1) A quantum computer comprising: a plurality of microwave photon control devices according to claim 1 that are arranged at ends of a quantum circuit module on which a plurality of superconducting qubits is implemented, wherein the microwave photon control devices transmit and receive quantum states between the quantum circuit modules. ### Claim 7 A microwave photon transmitter comprising: a first qubit and a second qubit that are connected in parallel to a waveguide through which microwave photons propagate, and a direct coupling between the first qubit and the second qubit, wherein an interval between the first qubit and the second qubit is ¼+n/2 times as long as a wavelength of microwave photons where n is an integer equal to or larger than 0, wherein a quantum entangled state is formed between the first qubit and the second qubit, wherein the direct coupling cancels out a coupling via the waveguide between the first qubit and the second qubit, and wherein, by a phase of the quantum entangled state between the first qubit and the second qubit, and/or couplings between the first qubit and the second qubit, and the waveguide being controlled, the microwave photon transmitter emits microwave photons in one direction of the waveguide. ### Claim 8 (depends on 7) The microwave photon transmitter according to claim 7, further comprising: a first resonator and a second resonator, wherein the first qubit and the second qubit are connected to the waveguide via the first resonator and the second resonator, respectively, wherein the direct coupling is formed between the first resonator and the second resonator, wherein the direct coupling is temporally constant, and wherein control of couplings between the first qubit and the second qubit, and the waveguide is control of a coupling between the first qubit and the first resonator, and a coupling between the second qubit and the second resonator. ### Claim 9 A microwave photon receiver comprising: a first qubit and a second qubit that are connected in parallel to a waveguide through which microwave photons propagate, and a direct coupling between the first qubit and the second qubit, wherein an interval between the first qubit and the second qubit is ¼+n/2 times as long as a wavelength of microwave photons (where n is an integer equal to or larger than 0, wherein the direct coupling cancels out a coupling via the waveguide between the first qubit and the second qubit, and wherein, by bringing both the first qubit and the second qubit into a ground state as an initial state, the microwave photon receiver absorbs microwave photons that have propagated from one direction of the waveguide. ### Claim 10 (depends on 9) The microwave photon receiver according to claim 9, further comprising: a first resonator and a second resonator, wherein the first qubit and the second qubit are connected to the waveguide via the first resonator and the second resonator, respectively, wherein the direct coupling is formed between the first resonator and the second resonator, and wherein the direct coupling is temporally constant. ### Claim 11 A microwave photon repeater comprising: a first qubit and a second qubit that are connected in parallel to a waveguide through which microwave photons propagate, and a direct coupling between the first qubit and the second qubit, wherein an interval between the first qubit and the second qubit is ¼+n/2 times as long as a wavelength of microwave photons (where n is an integer equal to or larger than 0, wherein the direct coupling cancels out a coupling via the waveguide between the first qubit and the second qubit, and wherein, by turning off relaxation from the first qubit and the second qubit to the waveguide, the microwave photon repeater lets through microwave photons that have propagated from one direction of the waveguide, to propagate. ### Claim 12 (depends on 11) The microwave photon repeater according to claim 11, further comprising: a first resonator and a second resonator, wherein the first qubit and the second qubit are connected to the waveguide via the first resonator and the second resonator, respectively, wherein the direct coupling is formed between the first resonator and the second resonator, and wherein the direct coupling is temporally constant.