Superconducting QPU Bus Architecture for Programmable Connectivity
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Solution Overview
Problem
Existing quantum computing systems face challenges in scaling due to noise in quantum gates, limited qubit connectivity, and high error rates in entangling distant qubits, which restricts the complexity and coherence of quantum circuits.
Innovation Solution
A superconducting quantum processor unit (QPU) architecture with an arbitrarily programmable interaction connectivity graph, utilizing a common high-quality superconducting meander coplanar waveguide resonator (bus) to modulate qubit couplings dynamically, enabling parametric photon exchange and pair-creation interactions between arbitrary qubit pairs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cascading multiple nearest neighbor two-qubit gates is used to entangle distant qubits, then qubit connectivity is improved, but the compound operation error rate increases exponentially with distance
Solution Approach 1:
The patent introduces a superconducting resonator as an intermediary component that couples multiple qubits simultaneously. The resonator acts as a mediator that enables direct entanglement between distant qubits without requiring cascaded gate operations, thereby reducing the compound error rate while maintaining system connectivity.
Solution Approach 2:
The patent transitions from a one-dimensional nearest-neighbor connectivity model to a many-body coupled system where all qubits are connected through the common resonator. This dimensional change in the connectivity graph allows arbitrary qubit pairs to interact directly, eliminating the need for sequential gate cascades.
2Adaptability or versatility
If an all-to-all reconfigurable qubit connectivity graph is implemented, then resource efficiency and flexibility are improved, but the complexity of scaling qubit-count and connectivity while maintaining high gate fidelity increases
Solution Approach 1:
The superconducting resonator serves multiple functions simultaneously: it couples all qubits together, enables arbitrary qubit interactions, provides a common communication channel, and allows dynamic reconfiguration of the connectivity graph. This multi-functionality reduces the need for additional specialized components that would increase system complexity.
Solution Approach 2:
The patent merges the connectivity function with the quantum state mediation function into a single resonator component. By combining these functions, the system achieves all-to-all connectivity without requiring separate control mechanisms for each qubit pair, thereby reducing overall device complexity.
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 architecture allows for efficient and reconfigurable qubit connectivity, reducing the overhead of synthesizing interactions between distant qubits, and maintaining high qubit gate fidelity and coherence, thereby accelerating the exploration of NISQ-era quantum applications.
Implementation Method 1
Two ends (boundaries) of the bus are connected to the ground plane via two Superconducting-Quantum-Interference-Devices (SQUIDs) respectively. Microwave waveguides are designed near the SQUIDs that are used for controlling the magnetic flux through these devices during operation. The magnetic flux applied through the SQUIDs will change their respective impedances and modify the microwave boundary conditions of the bus.
Implementation Method 2
Since the qubits are dispersively coupled to the common bus, the qubits are mutually coupled through virtual photonic coupling processes. Parametric photon exchange and pair-creation interactions can be created, on-demand, between arbitrary qubit pairs concurrently.
Implementation Method 3
no fewer than eight superconducting transmon qubits that are coupled to a common high-quality superconducting meander coplanar waveguide resonator (Bus)
Data Source
AI summary
A superconducting quantum processor unit for quantum computing is provided. The processor unit is formed from the union of a qubit chip and a wiring chip with superconducting bonding bumps and spacers. The bumps may be densely distributed around active elements between the two chips and effectively form a Faraday-Cage around the qubits, control signal waveguides etc. The qubit chip has strategically spaced qubits and an inductively coupled probe line and the wiring chip has a bus coupling resonator with a number of voltage nodes and anti-nodes, a resonator pump and at least one SQUID. Magnetic flux applied through the SQUIDs changes their impedances and modifies the microwave boundary conditions of the bus. This allows in-situ shifting of electric field distributions of the resonance modes of the bus along the length of the bus. This tunes the coupling rates of the bus to all qubits simultaneously.