Orthogonal Qubit Control for Extended Chain Connectivity
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Solution Overview
Problem
In quantum processors, increasing the length of qubit chains is desirable to enhance effective connectivity, but this is limited by the exponential reduction in effective tunneling amplitude, which brings qubits out of the quantum regime and into classical behavior, and adjusting tunneling amplitudes affects persistent currents, making orthogonal control of qubit parameters challenging.
Innovation Solution
The method involves forming logical qubits by communicatively coupling qubits such that the tunneling amplitude of inner qubits is increased while outer qubits have lower amplitudes, maintaining effective tunneling amplitude and avoiding exponential decay, and using orthogonal control qubits to adjust parameters without affecting persistent currents, allowing longer chains without degrading performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the length of qubit chains is increased to enhance connectivity, then the effective connectivity is improved, but the effective tunneling amplitude exponentially reduces, bringing qubits out of the quantum regime
Solution Approach 1:
The patent applies local quality by differentiating between inner qubits and outer qubits in the chain, assigning different tunneling amplitude characteristics to different positions. Inner qubits have higher tunneling amplitudes while outer qubits have lower amplitudes, allowing the chain to maintain quantum regime operation throughout its length while achieving extended connectivity.
Solution Approach 2:
The patent changes the tunneling amplitude parameter along the qubit chain, specifically increasing it for inner qubits compared to outer qubits. This parameter variation compensates for the exponential decay that would normally occur in uniform chains, maintaining the quantum regime and stable operation across longer chain lengths.
2Reliability
If the tunneling amplitude is adjusted to maintain quantum regime operation, then the quantum behavior is preserved, but the persistent current is affected, making orthogonal control challenging
Solution Approach 1:
The patent segments the control of qubit parameters by introducing orthogonal control qubits that are coupled to specific target qubits. This segmentation allows independent adjustment of tunneling amplitudes for individual qubits or groups of qubits without affecting persistent currents, thereby achieving orthogonal control and resolving the coupling between these two parameters.
Solution Approach 2:
The patent uses orthogonal control qubits as intermediaries to indirectly adjust the tunneling amplitudes of target qubits. Instead of directly controlling the target qubit's tunneling amplitude (which would affect persistent current), the control is mediated through the orthogonal control qubit, enabling independent parameter adjustment.
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 the formation of longer qubit chains with stable effective tunneling amplitudes, maintaining quantum regime operation and improving connectivity without affecting persistent currents, thus enhancing the capability of quantum processors.
Implementation Method 1
the exponential reduction in effective tunneling amplitude, which brings qubits out of the quantum regime and into classical behavior
Data Source
AI summary
Achieving orthogonal control of non-orthogonal qubit parameters of a logical qubit allows for increasing the length of a qubit chain thereby increasing the effective connectivity of the qubit chain. A hybrid qubit is formed by communicatively coupling a dedicated second qubit to a first qubit. By tuning a programmable parameter of the second qubit of a hybrid qubit, an effective programmable parameter of the hybrid qubit is adjusted without affecting another effective programmable parameter of the hybrid qubit thereby achieving orthogonal control of otherwise non-orthogonal qubit parameters. The length of the logical qubit may thus be increased by communicatively coupling a plurality of such hybrid qubits together.