Galvanic Qubit Couplers with Compound Josephson Junctions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current quantum processor technologies face challenges in efficiently coupling superconducting qubits over long distances due to reduced energy scales and perturbations in the qubit energy spectrum, leading to suboptimal performance in quantum annealing and computation.
Innovation Solution
The implementation of a galvanic coupling mechanism using compound Josephson junctions and symmetric long-range couplers, which include a Josephson junction inductance and mutual inductances to enhance coupling strength and maintain a homogeneous energy scale across qubits, along with capacitive couplings to achieve a non-stoquastic Hamiltonian for improved tunneling and computation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional coupling mechanisms are used to couple superconducting qubits over long distances, then the coupling range is extended, but the energy scale of the coupler is reduced and perturbations in the qubit energy spectrum increase
Solution Approach 1:
The patent introduces a symmetric coupler as an intermediary element that mediates the interaction between qubits over long distances. The coupler includes a first inductance coupled to a first qubit, a second inductance coupled to a second qubit, and a mutual inductance coupling the first and second inductances, creating a controlled intermediate coupling path that maintains energy scale stability while extending coupling range
Solution Approach 2:
The patent employs parameter changes by utilizing Josephson junctions with specific inductances and adjusting coupling parameters to optimize the energy scale. The symmetric coupler design allows for tuning of inductance values and mutual inductance to maintain homogeneous energy scales across the quantum processor, resolving the contradiction between long-distance coupling and energy stability
2Ease of operation
If couplers are present in the quantum processor, then qubit coupling is enabled, but perturbations in the qubit energy spectrum occur
Solution Approach 1:
The patent applies local quality by designing the symmetric coupler with specific local properties - the first and second inductances are configured with matched characteristics, and the mutual inductance is optimized to create homogeneous coupling conditions. This localized symmetry in the coupler design ensures that perturbations to the qubit energy spectrum are minimized while maintaining effective coupling
Solution Approach 2:
The symmetric coupler design creates equipotential conditions by ensuring that the coupling path from the first qubit to the second qubit is symmetric in terms of inductance and mutual inductance. This symmetry equalizes the energy conditions experienced by both qubits, reducing spectral perturbations and maintaining energy scale homogeneity across the system
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 the energy scale of couplers, reduces the impact of coupler presence on qubit energy spectra, and facilitates efficient multi-qubit tunneling and computation, particularly in quantum annealing, by maintaining a consistent energy scale and enabling non-stoquastic Hamiltonian operations.
Implementation Method 1
a superconducting coupler including a compound Josephson junction galvanically communicatively coupled to each of the first and the second loop of material; a first Josephson inductance comprising a first Josephson junction interrupting the first loop of material
Implementation Method 2
each of the first and the second loop of material superconductive in a range of temperatures below a respective critical temperature
Data Source
AI summary
Josephson junctions (JJ) may replace primary inductance of transformers to realize galvanic coupling between qubits, advantageously reducing size. A long-range symmetric coupler may include a compound JJ (CJJ) positioned at least approximately at a half-way point along the coupler to advantageously provide a higher energy of a first excited state than that of an asymmetric long-range coupler. Quantum processors may include qubits and couplers with a non-stoquastic Hamiltonian to enhance multi-qubit tunneling during annealing. Qubits may include additional shunt capacitances, e.g., to increase overall quality of a total capacitance and improve quantum coherence. A sign and/or magnitude of an effective tunneling amplitude Δeff of a qubit characterized by a double-well potential energy may advantageously be tuned. Sign-tunable electrostatic coupling of qubits may be implemented, e.g., via resonators, and LC-circuits. YY couplings may be incorporated into a quantum anneaier (e.g., quantum processor).