Qubit Readout Multiplexing Across a Shared HEMT Amplifier
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current superconducting quantum computing systems face challenges in designing a readout system for a large number of qubits due to thermal dissipation issues from amplifiers, which limits the number of qubits that can be effectively read out and maintained at low temperatures within the constraints of a cryostat's cooling capability.
Innovation Solution
A multiplexed readout system is developed, utilizing a directional multiplexer to passively frequency-multiplex multiple readout channels across the full bandwidth range of a HEMT amplifier, allowing non-overlapping frequency bands for each channel, and employing pre-amplifiers that act as frequency converters to optimize the use of available bandwidth and reduce thermal dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple amplifiers are used to read out multiple qubits, then the readout capability increases, but the thermal dissipation increases and exceeds the cryostat's cooling capability
Solution Approach 1:
Multiple readout channels are merged into a single shared transmission line that connects to a single HEMT amplifier. The directional multiplexer combines signals from multiple channels (each serving multiple qubits) onto one amplifier input, eliminating the need for multiple amplifiers and their associated thermal loads while maintaining the ability to read out many qubits in parallel through frequency multiplexing
Solution Approach 2:
A single HEMT amplifier is designed to handle multiple frequency bands simultaneously, making it a universal readout device for multiple qubit channels. The amplifier processes signals from all channels through frequency-division multiplexing, allowing one amplifier to perform the function that would otherwise require multiple amplifiers, thereby reducing thermal dissipation while maintaining high readout capability
2Productivity
If the bandwidth of the amplifier is increased to read out more qubits, then the readout capacity increases, but the thermal dissipation from the amplifier increases
Solution Approach 1:
The frequency spectrum is segmented into multiple non-overlapping frequency bands, with each band assigned to a specific readout channel. This segmentation allows a single amplifier to handle multiple channels simultaneously by processing different frequency ranges, effectively increasing readout capacity without requiring multiple amplifiers and their associated thermal loads
Solution Approach 2:
The system utilizes frequency as a distinguishing parameter to separate multiple readout channels. By assigning each channel a unique frequency band and using directional multiplexers to route signals based on frequency, the system enables a single amplifier to read out many qubits across different frequency bands, increasing capacity while maintaining low thermal dissipation
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 a larger number of qubits to be read out per HEMT amplifier by efficiently utilizing the bandwidth and reducing thermal dissipation, thereby overcoming the limitations of existing systems in terms of cooling power and qubit count.
Implementation Method 1
the second amplifier is a Josephson junction parametric amplifier
Implementation Method 2
a circulator disposed between an output of the second transmission line and the Josephson junction parametric amplifier, arranged to receive and direct the readout signals to the second transmission line towards the plurality of resonators and to direct the readout signals reflected from the plurality of resonators to the Josephson junction parametric amplifier
Implementation Method 3
the directional multiplexer is arranged such that the readout signals travels uni-directionally towards the first amplifier in the first transmission line
Implementation Method 4
the fourth port of the first directional coupler is connected to the fourth port of the second directional coupler via the first quarter wave connector, and wherein the third port of the first directional coupler is connected to the third port of the second directional coupler via the second quarter wave connector
Data Source
AI summary
A circuit is presented which includes a first amplifier having an input, a transmission line having first and second ends. The first end of the transmission line is coupled to an input of the first amplifier and a plurality of channels. Each channel includes a plurality of resonators arranged to read out a plurality of qubits, respectively and a readout line arranged to receive read out signals from the plurality of resonators. The readout line of each channel is coupled to the transmission line and each channel is configured to output a respective signal in a respective frequency band which is different from frequency bands of other channels in the plurality of channels.