Cavity-Integrated Electro-Optics: Measuring, Converting and Manipulating Microwaves with Light

Introduction

Electro-optic technologies have emerged as one of the leading platforms in both classical and quantum communication landscapes. The advent of circuit quantum electrodynamics (cQED) based on low-loss Josephson junction circuits has led to spectacular scientific breakthroughs in quantum science and technology. In recent years, these breakthroughs have been translated into commercial quantum computing efforts worldwide, targeting a market with an estimated value of 1 billion Euro.

Challenges in Quantum Technologies

Despite these achievements, there are fundamental limitations to quantum technologies based solely on microwaves. Operating in a millikelvin environment, the space required for wiring and electronics, as well as the associated heat loads, are barriers for scaling up the quantum processors to the size needed to address societal challenges.

Proposed Solution

Electro-optic interconnects capable of coherently distributing and transferring quantum information from superconducting processors to a room temperature environment would address this challenge. Such devices would enable quantum processors to be scaled up in a modular fashion, which will be key to realizing complex and capable quantum machines that remain controllable and error-correctable.

Additional Applications

Moreover, these microwave-optical interfaces would also form the basis for efficient laser-driven microwave technologies relevant to sensing applications, such as:

1. Microwave astronomy
2. Robust and low-noise microwave amplification

Project Goals

In CIELO, we aim to lay the foundation for laser-based manipulation of microwave fields using cavity electro-optics. This approach will enable:

• Amplification
• Quantum-limited optical detection
• Interconversion
• Qubit readout
• Laser cooling
• Masing

This is in stark contrast to the commonly used electrical techniques. We will leverage a combination of unique expertise in integrated photonics, advanced materials, and superconducting qubits to realize cavity electro-optic devices operating in the quantum regime.