Baseband Qubit Control with Multiplexing for Scalable Cryogenic Chips
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Solution Overview
Problem
Current quantum computing hardware faces challenges such as high error rates, limited scalability, and high costs due to the need for complex control systems and high thermal loads, particularly in the 'brute-force scaling era' where each qubit requires multiple control and readout wires.
Innovation Solution
The implementation of collocated electronics using cryogenic CMOS or single-flux quantum (SFQ) logic allows for efficient single-qubit and two-qubit control through baseband pulsing, which reduces the need for costly microwave sources and enables scalable quantum computing by multiplexing control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resonant microwave pulses are used to control qubits, then qubit state rotation can be achieved, but amplitude noise and control complexity increase
Solution Approach 1:
The patent replaces resonant microwave pulse control with a static qubit frequency offset (detuning) combined with variable amplitude pulses. Instead of using resonant driving at frequency f01, the system detunes the qubit frequency by applying a static flux bias, then uses amplitude-modulated pulses to achieve the desired state rotation. This substitution eliminates the need for precise resonant frequency control and reduces susceptibility to amplitude noise.
2Ease of operation
If conventional control wiring is used for each qubit, then individual qubit control is achieved, but scalability is limited by wire count
Solution Approach 1:
The patent implements a universal control approach where a single control line with a variable amplitude source can control multiple qubits. By detuning different qubits to different frequencies and using amplitude-modulated pulses, the same control line can selectively address and control any qubit in the array. This multi-functional control scheme eliminates the need for dedicated control wires for each qubit, enabling scalable quantum processors.
3Ease of operation
If room temperature control electronics are used, then control signals can be generated, but thermal load on the quantum processor increases
Solution Approach 1:
The patent extracts the high-power microwave generation function from the cryogenic environment and places it at room temperature. The system uses a room temperature variable amplitude source to generate control pulses, which are then transmitted through coaxial cables to the qubit chip. This separation allows the control electronics to operate at room temperature while minimizing thermal load on the quantum processor, as only low-power signal transmission lines need to penetrate the cryogenic environment.
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 leads to improved precision, reduced instrumentation noise, and lower power dissipation, enabling the use of low-frequency 'protected qubits' and allowing for the integration of control electronics with qubit chips, thus enhancing scalability and reducing costs.
Implementation Method 1
control a state of each of the plurality of qubits by controlling the multiplexing circuit to couple particular ones of the plurality of qubits to a pulsed baseband waveform
Implementation Method 2
controlling the multiplexing circuit to couple particular ones of the plurality of qubits to a pulsed baseband waveform
Data Source
AI summary
According to one aspect of the disclosure, a system for performing quantum computations includes: a first environment for being maintained at an ambient temperature, having a classical computing processor; and a second environment for being maintained at a cryogenic temperature, having a plurality of qubits and a multiplexing circuit coupled to the plurality of qubits, each of the plurality of qubits having a gap transition frequency; wherein the classical computing processor is configured to change the states of each of the plurality of qubits by controlling the multiplexing circuit to couple particular ones of the plurality of qubits to a pulsed baseband waveform.