Superposition in quantum cavities with Yvonne Gao

In this episode of The New Quantum Era, your host, Sebastian Hassinger sits down with Dr. Yvonne Gao, a leading experimental physicist specializing in superconducting devices and quantum cavities. Recorded at the American Physical Society's Global Summit, the conversation explores the intersection of curiosity-driven research and technological advancement in quantum physics.

Key Topics Discussed

1. Research Focus: Quantum Cavities and Superposition

• Dr. Gao shares her team's work on using cavities (harmonic oscillators) coupled with a single qubit to probe fundamental quantum effects.
• The experiments focus on quantum superposition and entanglement using minimal hardware—just one qubit and one cavity—eschewing the race for more qubits in favor of deeper scientific insights.
• Discussion of "cat states" as iconic demonstrations of quantum superposition, and how their properties can be engineered for robustness and sensitivity without specialized hardware.

2. Experimental Innovation

• The team investigates loss mechanisms in cavity-based quantum states and explores ways to make these states more resilient through state engineering rather than hardware changes.
• Dr. Gao describes using standard, "vanilla" qubits and cavities, making their techniques accessible to other labs.

3. Fundamental Questions and Quantum Playground

• Dr. Gao emphasizes the value of the circuit QED platform as a "playground" for exploring quantum phenomena, particularly entanglement and its quantification in real hardware.
• The challenge of visualizing and intuitively understanding quantum phenomena is highlighted, with experiments designed to make abstract concepts more tangible.

4. Device Fabrication and Advancements

• Dr. Gao's lab at NUS has developed in-house fabrication capabilities, gradually building up expertise and infrastructure.
• The field is witnessing rapid improvements in device performance, driven by advances in materials science and process integration.

5. Multipartite Entanglement and Future Directions

• Plans for multi-cavity devices: Moving from single and two-cavity systems to three, enabling the study of tripartite entanglement and richer quantum dynamics.
• The potential for these systems to serve as both research tools and pedagogical aids, demonstrating quantum strangeness in a hands-on way.

6. Synergy Between Science and Technology

• The conversation explores the unique moment in quantum research where fundamental science and technological objectives are closely aligned.
• Knowledge flows both ways: curiosity-driven experiments inform processor design, while industrial advances in fabrication and control benefit academic labs.

7. The "Perfect Quantum Lab" Thought Experiment

• Dr. Gao shares her wish list for a hypothetical, fault-tolerant quantum computer: to directly observe textbook quantum phenomena and simulate complex quantum behaviors in a tangible way.

Memorable Quotes

"We're very proud that we only use one qubit and one cavity... We tried to build in creative features and techniques from control and measurement perspectives to tease out interesting dynamics and features on the harmonic oscillator.""A lot of what we do is trying to find the most intuitive picture to capture what these abstract physical phenomena actually look like in the lab.""There's this nice synergy between the drive to make practical quantum processors and the more academic, curiosity-driven research focusing on the fundamental."

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