Microwave Photonic Quantum Processor Scaling
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Solution Overview
Problem
Current quantum computing solutions face challenges in scaling due to fragile quantum states of Josephson junction-based superconducting qubits and limited interaction between optical photons, which hinders the implementation of universal quantum computation.
Innovation Solution
A quantum computing circuit using microwave photons as flying qubits, leveraging well-developed fabrication techniques and high-fidelity state manipulation, with gates implemented by components of fixed physical location, allowing for strong coupling and long coherence times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Josephson junction-based superconducting qubits are used, then high-fidelity state preparation and controllability are achieved, but coherence time is short and scaling is difficult
Solution Approach 1:
The patent introduces microwave photons as intermediary carriers to transfer quantum information between superconducting qubits. The photons travel through transmission lines and interact with qubits via coupling resonators, enabling long-distance communication without direct qubit-qubit interaction. This mediator approach allows high-fidelity state transfer while maintaining qubit coherence during propagation.
Solution Approach 2:
The patent replaces direct mechanical coupling between superconducting qubits with an optical-microwave hybrid system. Instead of relying on fragile direct qubit interactions that limit coherence, the system uses microwave photons (optical domain) to mediate interactions, substituting the mechanical coupling mechanism with a photonic one that enables longer coherence times and easier scaling.
2Duration of action of stationary object
If optical photons are used for quantum computation, then long coherence time is achieved, but interaction between photons is weak and universal computation is difficult
Solution Approach 1:
The patent uses microwave photons as intermediaries to enable interactions between optical photons. The microwave photons couple to both optical photons and superconducting qubits, creating a bridge that allows optical photons to interact indirectly through the microwave domain. This mediator approach restores interaction capability while preserving the long coherence time of optical photons.
Solution Approach 2:
The patent creates a universal quantum communication platform that works with multiple photon types (optical and microwave) and supports various encoding schemes (time-bin, frequency, spatial mode). The system can perform different quantum operations (single-qubit gates, two-qubit gates, measurement) using the same architectural framework, achieving versatility across multiple quantum computation tasks.
3Ease of manufacture
If stationary superconducting qubits are used, then well-developed fabrication techniques are available, but hardware scaling is difficult due to crosstalk
Solution Approach 1:
The patent divides the quantum computing system into modular components: superconducting qubits, microwave photons, optical photons, and various gates implemented as separate functional blocks. Each component can be fabricated and tested independently using established superconducting circuit techniques, then assembled into larger systems. This segmentation enables gradual scaling while managing crosstalk through spatial separation and modular design.
Solution Approach 2:
The patent transitions from two-dimensional planar qubit arrangements to three-dimensional stacked architectures with qubits, resonators, and transmission lines arranged in multiple layers. This vertical stacking reduces in-plane crosstalk between adjacent qubits while maintaining fabrication compatibility, enabling higher qubit counts without proportionally increasing device complexity in the planar view.
4Adaptability or versatility
If pulse channels are added to each qubit for gate operations, then gate functionality is achieved, but space requirements increase
Solution Approach 1:
The patent implements universal quantum gates using a small set of reusable components: microwave-to-optical converters, coupling resonators, and transmission line elements. These same components can perform different gate operations (CNOT, CZ, Hadamard, phase shifts) by adjusting control parameters such as pulse duration, frequency, or coupling strength. This multi-functionality eliminates the need for separate dedicated circuits for each gate type, significantly reducing chip area.
Solution Approach 2:
The patent uses dynamically controllable coupling strengths and interaction times to achieve different gate operations. By adjusting the duration and intensity of microwave pulses applied to coupling resonators, the same physical structure can implement various quantum gates. This dynamic control allows a single hardware component to serve multiple computational functions, reducing the overall hardware footprint compared to static dedicated gate implementations.
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
This approach enables efficient and scalable quantum computation with long coherence times and fast processing, overcoming the limitations of existing solutions by combining the advantages of microwave and optical quantum computing domains.
Implementation Method 1
The operations are performed on the propagating state using optical elements... photons travel at a high speed and go through fixed gates
Implementation Method 2
photons interact weakly with the environment, so their state is stable during the propagation... long coherence time of a few seconds
Implementation Method 3
well-developed fabrication techniques; high-fidelity of preparation and controllability of state; possibility to engineer large coupling strength between microwave photons
Data Source
AI summary
A quantum processor is provided according to one embodiment of the present invention. The quantum processor uses propagating microwave photons as flying qubits, encoded in a dual-rail configuration. The dual-rail configuration is characterised by the fact that one photon encodes a qubit, and one photon at most is present in a transmission line. The quantum processor comprises single-qubit gates and two-qubit gates for performing state operations on the qubits. The single-qubit gates comprise directional couplers and phase shifters, while the two-qubit gates comprise electronic circuits including LC oscillators and Josephson junctions. The quantum processor further comprises a single microwave photon generation circuit and a microwave photon detector circuit.