Periodic Reporting for period 4 - ECLIPSE (Exotic superconducting CIrcuits to Probe and protect quantum States of light and mattEr)
Reporting period: 2024-09-01 to 2025-02-28
Quantum systems can occupy peculiar states, such as superposition or entangled states. These states are intrinsically fragile and eventually get wiped out by inevitable interactions with the environment. Protecting quantum states against decoherence is a formidable and fundamental problem in physics, which is pivotal for the future of quantum computing. The theory of quantum error correction provides a solution, but its current envisioned implementations require daunting resources: a single bit of information is protected by encoding it across tens of thousands of physical qubits.
Project ECLIPSE aims to protect quantum information in an entirely new type of qubit coined the cat-qubit with two key specificities. First, it will be encoded in a single superconducting circuit resonator whose infinite dimensional Hilbert space can replace large registers of physical qubits. Second, this qubit will be rf-powered, continuously exchanging photons with a reservoir. This approach challenges the intuition that a qubit must be isolated from its environment. Instead, the reservoir acts as a feedback loop which continuously and autonomously corrects against errors. This correction takes place at the level of the quantum hardware and reduces the need for error syndrome measurements which are resource intensive.
Project ECLIPSE aims to protect quantum information in an entirely new type of qubit coined the cat-qubit with two key specificities. First, it will be encoded in a single superconducting circuit resonator whose infinite dimensional Hilbert space can replace large registers of physical qubits. Second, this qubit will be rf-powered, continuously exchanging photons with a reservoir. This approach challenges the intuition that a qubit must be isolated from its environment. Instead, the reservoir acts as a feedback loop which continuously and autonomously corrects against errors. This correction takes place at the level of the quantum hardware and reduces the need for error syndrome measurements which are resource intensive.
The achievement of project ECLIPSE culminated in the realization of a cat-qubit with bit-flip times exceeding 10 seconds. This was a four order of magnitude improvement over previous cat-qubit implementations. We prepared and imaged quantum superposition states, and measured phase-flip times above 490 nanoseconds. Most importantly, we controlled the phase of these quantum superpositions without breaking bit-flip protection. This experiment demonstrated the compatibility of quantum control and inherent bit-flip protection at an unprecedented level, showing the viability of these dynamical qubits for future quantum technologies.
The work was published in Nature: Quantum control of a cat-qubit with bit-flip times exceeding ten seconds, by Réglade et al. Nature 629, 778-783 (2024).
The work was published in Nature: Quantum control of a cat-qubit with bit-flip times exceeding ten seconds, by Réglade et al. Nature 629, 778-783 (2024).
The success of project ECLIPSE has inspired other groups and especially private companies to develop a quantum computer based on cat-qubits. The two front runners are French company Alice&Bob (that have recently raised 100 million euros), and US company Amazon (that have recently reached the milestone of building a chain of 5 cat-qubits for quantum error correction [Putterman et al. Nature 638, 927–934 (2025)]).
Over the past 5 years, cat-qubits have evolved from a niche research topic to a serious candidate as the building block for future quantum technologies. This was made possible by a steady progress in understanding the complex details of non-linear driven-dissipative Josephson circuits, led both by project ECLIPSE and an expanding community of scientists and engineers.
Over the past 5 years, cat-qubits have evolved from a niche research topic to a serious candidate as the building block for future quantum technologies. This was made possible by a steady progress in understanding the complex details of non-linear driven-dissipative Josephson circuits, led both by project ECLIPSE and an expanding community of scientists and engineers.