Microwave photon control device, microwave photon transmitter, microwave photon receiver, microwave photon repeater, and quantum computer

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.

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.

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.