Persistent Current Loop Frequency Shifting for Quantum Qubits
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Solution Overview
Problem
As the number of qubits in quantum computing systems grows, the complexity and cost of fine-tuning direct current (DC) fluxes increase due to the need for numerous cables and equipment, which can introduce low-frequency noise and limit coherence times, making it challenging to control DC sources for large numbers of qubits or couplers.
Innovation Solution
The implementation of a quantum computing element frequency shifting arrangement using persistent current loops with Josephson junctions, shunt resistive elements, and inductive elements, which are coupled to signal lines to induce persistent currents and shift the frequency of quantum computing elements with a reduced number of signal lines and signal sources, eliminating the need for continuous external current for fine-tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DC wires and equipment are used to fine-tune per qubit DC fluxes, then frequency tuning capability is achieved, but system complexity and cost increase
Solution Approach 1:
The patent applies periodic action by using pulsed current signals instead of continuous DC fluxes. The control unit delivers periodic pulse signals to the signal lines, which induce persistent currents in the persistent current loops. This periodic pulsing mechanism enables frequency tuning of quantum computing elements without requiring continuous external current, thereby reducing system complexity while maintaining adaptability.
Solution Approach 2:
The patent introduces persistent current loops as intermediary elements between the control unit and quantum computing elements. These loops contain Josephson junctions and inductive elements that convert external pulse signals into persistent currents, which then couple to the quantum computing elements to achieve frequency tuning. This intermediary mechanism eliminates the need for direct DC wire connections to each qubit, reducing overall system complexity.
2Adaptability or versatility
If DC wires are used for fine-tuning, then frequency control is achieved, but low frequency noise is introduced that limits coherence times
Solution Approach 1:
By using periodic pulse signals instead of continuous DC fluxes, the system avoids the low frequency noise inherently associated with continuous wire-based current delivery. The pulsed nature of the excitation minimizes noise exposure to the quantum computing elements while still achieving the necessary frequency control through induced persistent currents.
Solution Approach 2:
The persistent current loops act as noise-isolating intermediaries. The external pulse signals are delivered through signal lines to the persistent current loops, which then generate the persistent currents that couple to the quantum computing elements. This intermediary structure isolates the quantum elements from the external wiring, reducing the transmission of low frequency noise while maintaining frequency control capability.
3Ease of operation
If mechanical or semiconductor switches are used at various temperature stages, then current control is achieved, but system complexity and disadvantages accumulate
Solution Approach 1:
The patent extracts and eliminates the need for mechanical or semiconductor switches from the system architecture. By using persistent current loops with Josephson junctions that can be controlled through inductive coupling from signal lines, the system removes the requirement for physical switches at various temperature stages, thereby reducing system complexity while maintaining current control capability.
Solution Approach 2:
The patent replaces mechanical switches with a field-based control mechanism. Instead of using mechanical or semiconductor switches to control current flow, the system uses inductively coupled signal lines to induce persistent currents in the persistent current loops. This substitution of mechanical control with electromagnetic induction eliminates the complexity and reliability issues associated with physical switches across temperature stages.
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 solution reduces the complexity and cost of quantum computing systems by allowing frequency tuning of qubits and couplers with fewer signal lines and sources, minimizing noise and maintaining coherence times, while eliminating the need for continuous external current.
Implementation Method 1
each persistent current loop comprising at least one Josephson junction, at least one shunt resistive element, and at least one inductive element
Implementation Method 2
each persistent current loop is configured to induce a persistent current in the persistent current loop in response to a pulse in a corresponding signal line
Data Source
AI summary
According to an embodiment, an arrangement for quantum computing element frequency shifting comprises: a plurality of persistent current loops, each persistent current loop being couplable to a corresponding quantum computing element; a first plurality of signal lines, wherein each persistent current loop is coupled to a corresponding signal line in the first plurality of signal lines; and a second plurality of signal lines, wherein each persistent current loop is coupled to a corresponding signal line in the second plurality of signal lines; wherein each persistent current loop is configured to induce a persistent current in the persistent current loop in response to a pulse in a corresponding signal line in the first plurality of signal lines and/or in a corresponding signal line in the second plurality of signal lines, wherein the persistent current is configured to cause a shift in a frequency of the corresponding quantum computing element.