Microwave Photon Control Device Using Qubit Entanglement
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Solution Overview
Problem
Existing circulators, such as ferrite and superconducting circulators, face challenges in controlling the propagation direction of microwave photons in quantum networks due to magnetic field requirements, high propagation loss, large physical size, low extensibility, and limited frequency band, making them unsuitable for complex topologies and routing.
Innovation Solution
A microwave photon control device comprising two qubits connected in parallel to a waveguide with a direct coupling, where the interval between the qubits is (¼+n/2) times the wavelength, forming a quantum entangled state to cancel out waveguide coupling and control the propagation direction, allowing switching between emission, absorption, and transmission modes without the need for circulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a ferrite circulator is used to control microwave photon propagation direction, then direction control is achieved, but propagation loss increases and performance decreases
Solution Approach 1:
The patent replaces the ferrite circulator (which uses magnetic fields and mechanical-like rotation of polarization) with a quantum circuit consisting of two qubits and a beam splitter. This substitution eliminates the need for magnetic fields and reduces propagation loss by using superconducting quantum circuits that are compatible with the quantum network environment.
Solution Approach 2:
The patent changes the operational parameters by using quantum states (superposition states of single photon and vacuum) and controlling the phase difference between two qubits. By adjusting the phase parameter φ and the coupling strength g, the system achieves direction control without the energy losses inherent in ferrite materials.
2Ease of operation
If a ferrite circulator is used, then direction control is achieved, but physical size becomes large reducing extensibility
Solution Approach 1:
The patent divides the circulator function into two separate qubits that can be independently controlled and positioned. This segmentation allows each qubit to be small in size while collectively achieving the circulator function, thereby reducing the overall physical footprint and improving extensibility in quantum network designs.
Solution Approach 2:
The patent transitions from the spatial rotation mechanism of ferrite circulators to a quantum state space manipulation approach. By operating in the dimension of quantum phase space rather than physical space rotation, the system achieves direction control without requiring large physical dimensions.
3Ease of operation
If a ferrite circulator is used, then direction control is achieved, but the propagation direction is fixed and cannot be controlled to change temporally
Solution Approach 1:
The patent introduces dynamic control by making the qubit states and coupling parameters time-dependent. The phase difference φ(t) and coupling strength g(t) can be modulated in real-time, allowing the propagation direction to be dynamically adjusted. This enables the system to function as a router that can change propagation directions temporally, unlike fixed ferrite circulators.
Solution Approach 2:
The patent implements feedback control mechanisms where the quantum states of the two qubits are monitored and adjusted based on the desired propagation direction. By using measurement and feedback loops, the system can adaptively change the propagation direction in response to network conditions, achieving temporal control and routing functionality.
4Adaptability or versatility
If a superconducting circulator is used, then compatibility with superconducting qubits is improved, but the number of microwave sources and cables increases making adjustment difficult
Solution Approach 1:
The patent merges the functions of multiple microwave sources and cables into a single quantum circuit architecture. By using two qubits coupled to a common bus and controlled by a unified control system, the patent reduces the number of independent microwave sources and cables required, thereby simplifying adjustment while maintaining compatibility with superconducting qubits.
Solution Approach 2:
The patent creates a universal quantum circuit module that can perform multiple functions (direction control, routing, state manipulation) using a single integrated design. This multi-functional approach eliminates the need for separate dedicated components for each function, reducing overall device complexity while maintaining full compatibility with superconducting qubit systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables control of microwave photon propagation direction in quantum networks without circulators, improving extensibility and flexibility, and allowing for efficient routing and quantum state transmission between quantum circuit modules.
Implementation Method 1
A quantum entangled state is formed between the first qubit and the second qubit
Implementation Method 2
The direct coupling cancels out a coupling via the waveguide between the first qubit and the second qubit
Implementation Method 3
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
Data Source
AI summary
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.