SFQ Qubit Resonance Control With Low-Static-Power RSFQ Logic
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Solution Overview
Problem
Existing superconductor circuits, particularly those using Rapid Single Flux Quantum (RSFQ) logic, face challenges in reducing static power consumption and devising efficient means for controlling the logical state of quantum bits (qubits), which limits their operational efficiency and scalability.
Innovation Solution
The implementation of an apparatus and method to control the resonance frequency of qubits by using an external electromagnetic field, wherein a first circuit produces a flux quantum that is received by a second circuit with a qubit, and a controller activates the electromagnetic field to change the qubit's resonance frequency, allowing for precise control of the qubit's energy state through set and reset signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If DC bias is supplied to Josephson Junction in conventional RSFQ circuits, then the junction can perform switching operations, but static power consumption increases significantly
Solution Approach 1:
The patent applies periodic action by using clocked pulse sequences instead of continuous DC bias. The Josephson Junction is excited by periodic SFQ pulses synchronized with a clock signal, enabling switching operations only during active clock periods while eliminating static power consumption between pulses. This transforms the continuous power consumption model into a pulsed operation model.
Solution Approach 2:
The patent substitutes the electrical DC bias mechanism with a magnetic flux quantum-based control mechanism. Instead of using continuous electrical current to maintain junction state, the invention uses quantized magnetic flux packets (SFQ pulses) that temporarily excite the junction and then dissipate without requiring continuous power supply, replacing the DC electrical field mechanism with a pulsed magnetic flux mechanism.
2Measurement precision
If multiple qubits are controlled independently in conventional approaches, then each qubit can be precisely controlled, but device complexity and control overhead increase
Solution Approach 1:
The patent implements universality by designing a single controllable coupling mechanism that can simultaneously control multiple qubit interactions. The coupling element responds to control signals that can selectively enable or disable coupling between different qubit pairs, allowing one control system to manage multiple qubit operations including single-qubit rotations and two-qubit gates through unified control protocols.
Solution Approach 2:
The patent applies dynamics by making the coupling between qubits dynamically controllable rather than fixed. The coupling strength can be adjusted in real-time through external control signals, allowing the system to switch between coupled and uncoupled states as needed for different quantum operations. This dynamic control enables flexible qubit interaction patterns without requiring separate dedicated control circuits for each qubit pair.
3Ease of operation
If conventional control methods are used for qubits, then basic operations can be performed, but crosstalk between adjacent circuits increases power consumption and reduces accuracy
Solution Approach 1:
The patent introduces an intermediary coupling element between qubits that mediates their interaction. This coupling element acts as a buffer that can be selectively activated or deactivated, allowing controlled energy transfer between qubits while preventing direct electromagnetic coupling that would cause crosstalk. The intermediary enables desired quantum operations while isolating qubits from unwanted interactions with adjacent circuits.
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 reduces static power consumption and enhances the control over qubit states, enabling more efficient and scalable quantum operations by minimizing crosstalk and power consumption while allowing for hierarchical control of multiple qubits.
Implementation Method 1
a first circuit for producing an electro-magnetic field; a second circuits positioned proximal to the first circuit to receive the electro-magnetic field
Implementation Method 2
Devices based upon the characteristics of a Josephson Junction are valuable in high speed circuits. Josephson junctions can be designed to switch in times of a few picoseconds.
Implementation Method 3
The SQUID stores a flux quantum and the magnetic field of the SQUID is quantized to a value proportional to the Planck's constant.
Data Source
AI summary
In one embodiment, the disclosure relates to a method and apparatus for controlling the energy state of a qubit by bringing the qubit into and out of resonance by coupling the qubit to a flux quantum logic gate. The qubit can be in resonance with a pump signal, with another qubit or with some quantum logic gate. In another embodiment, the disclosure relates to a method for controlling a qubit with RSFQ logic or through the interface between RSFQ and the qubit.