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.

A quantum device includes a non-reciprocal transmission structure, wherein the transmission structure is designed such that for first waves traversing the transmission structure in a forward direction the phases of the first waves are at least partially conserved, and for second waves traversing the transmission structure in a backward direction, the phases of the second waves are at least partially replaced by random ones, such that the phase conservation is more pronounced in the forward direction than in the backward direction.

A quantum device includes a non-reciprocal transmission structure, wherein the transmission structure is designed such that for first waves traversing the transmission structure in a forward direction the phases of the first waves are at least partially conserved, and for second waves traversing the transmission structure in a backward direction, the phases of the second waves are at least partially replaced by random ones, such that the phase conservation is more pronounced in the forward direction than in the backward direction.

A method for generating digital quantum chaotic orthonormal wavepacket signals includes the following steps: construct a N-dimensional Hermitian matrix Ĥ; calculate N eigen-wavefunctions φ.sub.j of a quantum Hamiltonian system with the Hamiltonian Ĥ by some numerical calculation methods, wherein the Hamiltonian is the Hermitian matrix Ĥ; extract some or all of the eigen-functions φ.sub.j with obvious chaos features as quantum chaotic eigen-wavefunctions according to a chaos criterion; generate some semi-classical digital quantum chaotic wavepacket signals φ.sub.j(n) with the same mathematical form as the quantum chaotic eigen-wavefunctions and length N from the selected quantum chaotic eigen-wavefunctions according to the mathematical correspondence between the classical signal and the wavefunction in quantum mechanics. By combining the quantum state chaotic transition theory and the classical time-frequency analysis, some semi-classical quantum chaotic wavepacket digital signals are generated according to the mathematical correspondence between the classical time-frequency signal and the wavefunction in quantum mechanics.

A method for generating digital quantum chaotic orthonormal wavepacket signals includes the following steps: construct a N-dimensional Hermitian matrix Ĥ; calculate N eigen-wavefunctions φ.sub.j of a quantum Hamiltonian system with the Hamiltonian Ĥ by some numerical calculation methods, wherein the Hamiltonian is the Hermitian matrix Ĥ; extract some or all of the eigen-functions φ.sub.j with obvious chaos features as quantum chaotic eigen-wavefunctions according to a chaos criterion; generate some semi-classical digital quantum chaotic wavepacket signals φ.sub.j(n) with the same mathematical form as the quantum chaotic eigen-wavefunctions and length N from the selected quantum chaotic eigen-wavefunctions according to the mathematical correspondence between the classical signal and the wavefunction in quantum mechanics. By combining the quantum state chaotic transition theory and the classical time-frequency analysis, some semi-classical quantum chaotic wavepacket digital signals are generated according to the mathematical correspondence between the classical time-frequency signal and the wavefunction in quantum mechanics.

There is herein provided a method of performing Quantum Key Distribution, the method comprising, transmitting, in a first basis state, a first photon from a quantum transmitter to a quantum receiver; transmitting, in a second basis state, a second photon from the quantum transmitter to the quantum receiver, the second basis state being non-orthogonal to the first basis state and the transmitter and receiver being optically connected by both a first optical channel and a second optical channel, wherein the step of transmitting the first photon from the quantum transmitter to the quantum receiver in the first basis state comprises: transmitting the first photon from the quantum transmitter to the quantum receiver along either the first optical channel or the second optical channel, wherein the step of transmitting the second photon from the quantum transmitter to the quantum receiver in the second basis state comprises: transmitting a first portion of the probability distribution of the second photon from the transmitter to the receiver along the first optical channel; and transmitting a second portion of the probability distribution of the second photon from the transmitter to the receiver along the second optical channel.

There is herein provided a method of performing Quantum Key Distribution, the method comprising, transmitting, in a first basis state, a first photon from a quantum transmitter to a quantum receiver; transmitting, in a second basis state, a second photon from the quantum transmitter to the quantum receiver, the second basis state being non-orthogonal to the first basis state and the transmitter and receiver being optically connected by both a first optical channel and a second optical channel, wherein the step of transmitting the first photon from the quantum transmitter to the quantum receiver in the first basis state comprises: transmitting the first photon from the quantum transmitter to the quantum receiver along either the first optical channel or the second optical channel, wherein the step of transmitting the second photon from the quantum transmitter to the quantum receiver in the second basis state comprises: transmitting a first portion of the probability distribution of the second photon from the transmitter to the receiver along the first optical channel; and transmitting a second portion of the probability distribution of the second photon from the transmitter to the receiver along the second optical channel.

An operational environment is disclosed herein that includes a cryogenic environment and a signal source. The cryogenic environment includes a signal target, an optical link, signal converter devices, and an electrical link. Outside of the cryogenic environment, the signal source generates an electric signal. An electric-to-optical converter converts the electrical signal into an optical signal. The optical link delivers the optical signal into the cryogenic environment. Inside the cryogenic environment, an optical-to-electrical converter converts the optical signal back into an electrical signal. The optical-to-electrical converter transfers the electric signal to the signal target.

An operational environment is disclosed herein that includes a cryogenic environment and a signal source. The cryogenic environment includes a signal target, an optical link, signal converter devices, and an electrical link. Outside of the cryogenic environment, the signal source generates an electric signal. An electric-to-optical converter converts the electrical signal into an optical signal. The optical link delivers the optical signal into the cryogenic environment. Inside the cryogenic environment, an optical-to-electrical converter converts the optical signal back into an electrical signal. The optical-to-electrical converter transfers the electric signal to the signal target.

The present invention provides devices, systems, and methods for producing bi-photons without the need for complex alignment or source design by the user. The invention provides a tunable source of high-brightness, high-visibility, bi-photons that can be configured for a number of applications.