Podcast Summary: Software Engineering Daily – Quantum Computing at Rigetti with David Rivas

Introduction

In this episode of Software Engineering Daily, host Kevin Ball engages in an in-depth conversation with David Rivas, the Chief Technology Officer (CTO) at Rigetti Computing. Released on March 13, 2025, the episode explores the intricate world of quantum computing, Rigetti's full-stack approach, the challenges of building quantum systems, and the future applications of this groundbreaking technology.

1. Guest Introduction: David Rivas

Kevin Ball begins by welcoming David Rivas to the show, prompting him to share his professional background.

[01:55] David Rivas: "I don't have a PhD in physics, which is unusual in a quantum computing company. My background is in electrical engineering, and I've predominantly pursued a software career since then..."

Rivas elaborates on his tenure at Sun Microsystems, Nokia, and his transition to Rigetti, highlighting the unique blend of software and hardware expertise required in the quantum computing field.

2. Quantum Computing Fundamentals

The discussion transitions to the basics of quantum computing, contrasting it with classical computing.

[03:17] David Rivas: "Quantum computing uses a different modality for producing computation, leveraging the mathematics of quantum mechanics to perform billions of quantum operations."

Rivas explains key quantum concepts such as superposition and entanglement, emphasizing their role in expanding the computational state space exponentially compared to classical bits.

[07:45] David Rivas: "The state space of the problem you have can be very, very large compared to the limits of a classical computer."

3. Rigetti Computing's Full-Stack Approach

Rivas details Rigetti's comprehensive approach to quantum computing, encompassing everything from chip fabrication to software development.

[03:17] David Rivas: "We are a full stack quantum computing company. We fab our own chips, build the hardware and electronics to control them, and develop the necessary software to operate and program these systems."

He highlights Rigetti's use of superconducting qubits and the integration of quantum processors with classical computing systems, portraying quantum processing units (QPUs) as accelerators attached to classical machines.

4. Quantum vs. Classical Computing: Operations and Scaling

The conversation delves into the operational differences between quantum and classical computers, particularly focusing on the scalability of quantum operations.

[11:12] David Rivas: "Quantum annealing performs a particular type of quantum calculation suited for optimization problems, whereas gate model quantum computers are general-purpose."

Rivas compares logical qubits to physical qubits, drawing an analogy to classical error correction methods like RAID to explain quantum error correction (QEC).

[12:54] David Rivas: "You can imagine it's like RAID for qubits. We're using redundancy to support reliability."

5. Quantum Programming and the Software Stack

Rivas provides an overview of the software landscape for quantum computing, discussing programming languages, compilation processes, and execution pipelines.

[17:27] David Rivas: "We have two languages named Quill. Quill is our assembly language environment, while PyQuill is a Python binding that allows you to produce and execute Quill programs."

He likens the quantum programming process to classical compilation pipelines, where high-level instructions are progressively translated into low-level pulse schedules that manipulate qubits.

[25:44] Kevin Ball: "It sounds like a classical compilation pipeline where you lower it bit by bit."

[25:50] David Rivas: "Exactly. Here's a schedule to run."

6. Applications and Future Directions

The discussion moves to potential application areas for quantum computing, such as machine learning, optimization, and modeling quantum phenomena.

[29:22] David Rivas: "We are working on enhancements to machine learning algorithms and preparing data for classical machine learning systems using quantum methods."

Rivas is optimistic about quantum computing’s role in handling large stateful data and complex optimization problems beyond classical capabilities, although he acknowledges that certain milestones, such as fully fault-tolerant systems, are still years away.

[33:27] Kevin Ball: "How much data can you feed into these systems?"

[33:56] David Rivas: "Today's systems aren't for pumping terabytes of data, but they can model systems requiring large in-memory representations."

7. Software Organization at Rigetti

Rivas sheds light on the internal software structure at Rigetti, emphasizing the division between quantum computing services (QCS) and measurement/characterization tools.

[45:33] David Rivas: "We have two organizations: QCS software for the operating environment and another for measurement and characterization software, like our tool Treeline."

He discusses the critical role of automation and machine learning in managing and scaling quantum systems, especially as qubit counts grow into the hundreds.

[48:54] Kevin Ball: "Are you using your own systems to help model next-generation systems?"

[49:36] David Rivas: "We're not at the bootstrapping phase yet, but optimization will be very exciting once we achieve it."

Rivas also touches on the cultural shift from academic to professional software development within Rigetti, highlighting the integration of best practices and modern software engineering techniques.

[52:25] David Rivas: "We've expanded our team to include professional software developers who bring best practices to our quantum computing projects."

8. Conclusion

As the conversation wraps up, Rivas reflects on the collaborative and scientific nature of the quantum computing community, balancing intense competition with a shared passion for advancing the field.

[50:19] David Rivas: "The community has a joy and beauty associated with building these machines, unlike any traditional computing conferences."

Both host and guest express enthusiasm about the ongoing advancements and the promising future of quantum computing, acknowledging that while specific applications remain to be fully realized, the journey is filled with innovation and discovery.

[53:00] Kevin Ball: "This has been super fun."

[53:00] David Rivas: "I'm glad you enjoyed it. I did, too."

Notable Quotes

• David Rivas [07:45]: "The state space of the problem that you have to represent can be very, very large compared to the limits of a classical computer."

• Kevin Ball [11:19]: "It's like RAID for storage or something."

• David Rivas [12:54]: "We're using redundancy to support the notion of reliability."

• David Rivas [22:52]: "There's a lot of software required to actually build a quantum computer."

• David Rivas [50:10]: "Do it. Not going to do it soon, I hope."

• David Rivas [52:25]: "We've expanded our team to include proper professional software development teams."

Conclusion

This episode offers a comprehensive look into Rigetti Computing's endeavors in the quantum realm, guided by David Rivas's expertise. From the foundational principles of quantum mechanics to the sophisticated software ecosystems required for quantum computing, listeners gain valuable insights into the current state and future potential of this transformative technology. Whether you're a software engineer, a technology enthusiast, or a professional in the field, this conversation sheds light on the innovative strides being made to harness the power of quantum computing.