[Paper Review] A Scalable Microarchitecture for Efficient Instruction-Driven Signal Synthesis and Coherent Qubit Control

Nader Khammassi, Randy Morris+8 more|arXiv (Cornell University)|May 13, 2022

Quantum Computing Algorithms and Architecture4 citations

TL;DR

This paper presents a scalable, instruction-driven microarchitecture for quantum qubit control that uses a custom instruction set architecture (ISA) to dynamically generate nanosecond-accurate control signals via a direct digital synthesis (DDS) pipeline. The system enables higher channel density, improved programmability, and lower cost compared to traditional arbitrary waveform generators (AWGs), demonstrating efficient and coherent control of superconducting qubits in experimental validation.

ABSTRACT

Execution of quantum algorithms requires a quantum computer architecture with a dedicated quantum instruction set that is capable of supporting translation of workloads into actual quantum operations acting on the qubits. State-of-the-art qubit control setups typically utilize general purpose test instruments such as arbitrary waveform generators (AWGs) to generate a limited set of waveforms or pulses. These waveforms are precomputed and stored prior to execution, and then used to produce control pulses during execution. Besides their prohibitive cost and limited scalability, such instruments suffer from poor programmability due to the absence of an instruction set architecture (ISA). Limited memory for pulse storage ultimately determines the total number of supported quantum operations. In this work, we present a scalable qubit control system that enables efficient qubit control using a flexible ISA to drive a direct digital synthesis (DDS) pipeline producing nanosecond-accurate qubit control signals dynamically. The designed qubit controller provides a higher density of control channels, a scalable design, better programmability, and lower cost compared to state-of-the-art systems. In this work, we discuss the new qubit controller's capabilities, its architecture and instruction set, and present experimental results for coherent qubit control.

Motivation & Objective

• To address the limitations of state-of-the-art qubit control systems that rely on general-purpose AWGs with poor programmability and limited scalability.
• To design a scalable, cost-effective qubit controller with a dedicated instruction set architecture (ISA) for dynamic signal generation.
• To enable high-density, nanosecond-accurate control of multiple qubits using a flexible, programmable signal synthesis pipeline.
• To overcome memory constraints of precomputed waveforms by enabling on-the-fly pulse generation through an ISA-driven DDS pipeline.
• To demonstrate coherent qubit control with experimental validation of the proposed microarchitecture.

Proposed method

• Design of a custom instruction set architecture (ISA) that maps quantum algorithm instructions to low-level control signals.
• Implementation of a direct digital synthesis (DDS) pipeline to generate nanosecond-precise waveforms in real time based on ISA instructions.
• Use of a scalable microarchitectural design to support a high density of independent qubit control channels.
• Integration of the ISA with a hardware-software stack that enables dynamic, on-demand signal synthesis without pre-stored waveforms.
• Employment of a programmable control engine that decodes instructions and drives the DDS for precise pulse shaping.
• Adoption of a modular, reconfigurable design to support future expansion and integration with large-scale quantum processors.

Experimental results

Research questions

• RQ1 How can a scalable and cost-effective microarchitecture be designed to replace traditional AWG-based qubit control systems?
• RQ2 To what extent can a custom instruction set architecture (ISA) improve programmability and reduce reliance on precomputed waveforms?
• RQ3 Can a DDS-based pipeline achieve nanosecond-accurate signal generation for coherent qubit control when driven by an ISA?
• RQ4 What is the maximum number of control channels that can be supported with this architecture while maintaining low latency and high precision?
• RQ5 How does the performance of this system compare to state-of-the-art AWG-based setups in terms of scalability, cost, and control fidelity?

Key findings

• The proposed microarchitecture supports a significantly higher density of qubit control channels compared to conventional AWG-based systems.
• The system achieves nanosecond-accurate signal generation through an ISA-driven DDS pipeline, enabling precise control of superconducting qubits.
• Experimental results confirm coherent qubit control with high-fidelity Rabi and Ramsey oscillations, validating the system's precision and stability.
• The architecture eliminates the need for pre-storing waveforms, enabling dynamic, on-the-fly pulse generation and improving programmability.
• The design reduces system cost and improves scalability over traditional AWG solutions, making it suitable for large-scale quantum processors.
• The ISA-based approach allows for efficient compilation of quantum workloads into low-level control signals with minimal latency.