SFQ Qubit Flux Controller for Fewer Cryostat Connections
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The scaling of quantum computing systems using superconducting qubits is hindered by the need for multiple coaxial cables and connectors to supply control signals, leading to space and reliability constraints, as well as increased heat load in the cryostat.
Innovation Solution
A controller for superconducting qubits is developed, utilizing an inductive loop for inductive coupling with a small mutual inductance, and a pulse shaping circuit that applies current pulses with predefined shapes, leveraging single flux quantum (SFQ) circuits to control the magnetic flux and manage the qubit operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple coaxial cables and connectors are used to supply control signals to superconducting qubits, then control signal delivery is achieved, but space constraints and reliability issues worsen
Solution Approach 1:
Multiple control signals for different qubits are merged into a single shared coaxial cable through the use of an inductive bus and capacitive coupling. Instead of requiring separate cables for each qubit, the system combines signal transmission pathways, reducing the total number of connections while maintaining individual qubit control capability
Solution Approach 2:
An inductive bus structure serves as an intermediary between the control electronics and qubits. The bus provides magnetic coupling to multiple qubits simultaneously, acting as a mediator that distributes control signals without requiring direct physical connections to each qubit, thereby reducing connection complexity
2Reliability
If multiple coaxial cables and connectors are used to supply control signals, then control signal delivery is achieved, but heat load in the cryostat increases
Solution Approach 1:
Multiple control signals are combined into a single coaxial cable transmission pathway, reducing the total surface area and thermal conduction pathways into the cryostat. This merging of signal paths directly reduces the heat load while maintaining control signal delivery to all qubits through the shared bus
3Device complexity
If inductive coupling with small mutual inductance is used, then connection complexity is reduced, but control precision may be compromised
Solution Approach 1:
The inductive bus provides localized magnetic coupling to each qubit at specific positions along the bus. By optimizing the geometry and positioning of the bus relative to each qubit, strong local coupling is achieved at each interaction point while maintaining a simple overall bus structure, thus preserving control precision without requiring complex connections
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 enables precise control of qubit operations with high fidelity, reduces the number of connections required, and minimizes heat load in the cryostat, thus facilitating the scaling of quantum computing systems.
Implementation Method 1
an inductance forming inductive loop and configured to be inductively coupled to a qubit
Implementation Method 2
a pulse shaping circuit configured to apply a current pulse with a predefined shape across the inductance, the pulse shaping circuit comprising: a superconducting circuit configured to output single flux quanta 'SFQ' pulses
Data Source
AI summary
A superconducting controller for a superconducting qubit to execute high fidelity quantum gates using magnetic flux drive. The controller comprises: an inductance forming an inductive loop and configured to be inductively coupled to a qubit with a small mutual inductance; a pulse shaping circuit configured to apply a current pulse with a predefined shape across the inductance. The pulse shaping circuit comprises: a superconducting circuit configured to output single flux quanta (SFQ) pulses and a digital counter circuit configured to produce the shape of the current (magnetic flux) pulse by controlling the number of SFQ pulses applied to the inductive loop by incrementing or decrementing the current across the inductance by one SFQ pulse at a time.