Superconducting Qubit Coupler With Reserve Ports for Fault Tolerance
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Solution Overview
Problem
In quantum annealers using Josephson Parametric Oscillators (JPOs), qubits may fail to parametrically oscillate due to manufacturing defects or noise, leading to missing qubits and disrupting four-body interactions, affecting the overall connectivity and functionality of the quantum circuit.
Innovation Solution
A superconducting quantum circuit apparatus with a reserve coupling port is introduced, allowing signals to be supplied to this port instead of missing qubits, maintaining four-body interactions by enabling qubits to function via the coupler, even when some qubits are stopped.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a quantum annealer uses JPOs as qubits with four-body couplers for all-to-all connections, then the quantum circuit achieves high connectivity and functionality, but manufacturing defects or noise can cause qubits to fail parametric oscillation, disrupting the system
Solution Approach 1:
The patent introduces reserve coupling ports as a preemptive measure to handle potential qubit failures. These reserve ports are prepared in advance and can be activated when manufacturing defects or noise cause qubits to fail parametric oscillation, thus cushioning against reliability issues before they disrupt the entire system.
Solution Approach 2:
The patent creates functional copies of qubit coupling capabilities through reserve coupling ports. When a physical qubit fails, the reserve port provides a substitute coupling interface that maintains the logical connectivity, effectively copying the coupling function to compensate for the failed component.
2Reliability
If reserve coupling ports are added to the quantum circuit, then fault tolerance and resilience are improved, but the device complexity and number of coupling ports increase
Solution Approach 1:
The reserve coupling ports are designed with multi-functionality: they serve as idle ports during normal operation and can be activated as substitutes for failed qubit ports. This universal design allows the same hardware structure to fulfill both routine and emergency functions, reducing the need for entirely separate redundant systems.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting which coupling ports are active based on system state. When all qubits function normally, the reserve ports remain inactive; when failures occur, the system reconfigures to activate reserve ports, changing the operational parameters of the coupling network to maintain functionality.
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 enhances fault tolerance and maintains all-to-all connections in the quantum annealing machine, ensuring continuous operation and improved resilience against qubit failures.
Implementation Method 1
Parametric oscillation occurs at a frequency half of the pump signal in the JPO, when a microwave (pump signal) with almost twice a resonance frequency of the JPO, is applied to the SQUID of the JPO
Implementation Method 2
a Josephson junction or a non-linear resonator including the Josephson junction can be used as a four-body coupler
Implementation Method 3
JPO is a superconducting non-linear resonator that includes a superconducting quantum Interference device (SQUID)
Data Source
AI summary
A superconducting quantum circuit apparatus includes: a coupler; a plurality of coupling ports; a plurality of qubits coupled to the coupler via the plurality of coupling ports, respectively; and a reserve port provided as a spare coupling port to be coupled to the coupler, separately from the plurality of coupling ports.