Periodic Reporting for period 1 - QuPhon (Generation of Quantum multi-Phonon states in a mechanical oscillator)
Okres sprawozdawczy: 2021-04-01 do 2023-03-31
Superconducting-qubit systems play a crucial role in modern quantum science and technology, serving as a highly promising platform for large-scale quantum processors. The QuPhon project proposed an innovative approach by using a megahertz-frequency mechanical oscillator as a long-lived quantum memory to support superconducting quantum computing. Despite advanced quantum control of mechanical oscillators based on cavity optomechanics in the microwave domain, integrating circuit optomechanical devices into large-scale superconducting-qubit systems has proven challenging due to the extremely small optomechanical coupling and the poor scalability of such optomechanical systems. The QuPhon project uses a quantum link based on itinerant microwave photons to combine a low-frequency mechanical oscillator with a superconducting qubit. Unlike all-in-one hybrid quantum systems, this approach maximizes the advantages of circuit optomechanics and superconducting qubits by establishing a quantum link between separate modules, avoiding unwanted side effects.
In addition to the main goal of the QuPhon project, several important milestones in superconducting cavity optomechanics and superconducting qubits have been achieved. The project demonstrated multi-mode superconducting circuit optomechanical lattices in non-trivial topological phases, expanding the possibilities for studying many-body physics based on such an optomechanical platform. It also demonstrated the ability to track the thermalization of a quantum-squeezed mechanical state. This demonstrates that our mechanical oscillator possesses an ultra-coherence, providing an experimental platform for studying macroscopic quantum phenomena and quantum gravity. Moreover, these demonstrations based on circuit optomechanics confirmed that our revolutionary mechanical oscillators are useful for scalable and long-lived quantum memories for quantum computing and communication in modern science and technology.
The project also established superconducting qubits for the first time at EPFL (École Polytechnique Fédérale de Lausanne), enhancing the institute's research capabilities. It has realized ultra-coherent superconducting qubits with lifetimes exceeding 0.4 milliseconds, which are among the best lifetimes in the field. With the exceptionally long qubit lifetimes, the project has discovered a new qubit loss mechanism for causing correlated errors induced by mechanical shocks, suggesting future mitigation strategies for scalable superconducting quantum computing.
In addition to the main goal of the QuPhon project, several important milestones in superconducting cavity optomechanics and superconducting qubits have been achieved. The project demonstrated multi-mode superconducting circuit optomechanical lattices in non-trivial topological phases, expanding the possibilities for studying many-body physics based on such an optomechanical platform. It also demonstrated the ability to track the thermalization of a quantum-squeezed mechanical state. This demonstrates that our mechanical oscillator possesses an ultra-coherence, providing an experimental platform for studying macroscopic quantum phenomena and quantum gravity. Moreover, these demonstrations based on circuit optomechanics confirmed that our revolutionary mechanical oscillators are useful for scalable and long-lived quantum memories for quantum computing and communication in modern science and technology.
The project also established superconducting qubits for the first time at EPFL (École Polytechnique Fédérale de Lausanne), enhancing the institute's research capabilities. It has realized ultra-coherent superconducting qubits with lifetimes exceeding 0.4 milliseconds, which are among the best lifetimes in the field. With the exceptionally long qubit lifetimes, the project has discovered a new qubit loss mechanism for causing correlated errors induced by mechanical shocks, suggesting future mitigation strategies for scalable superconducting quantum computing.
Objectives of QuPhon are the following:
1. Implementation of quantum interface between mechanical oscillator and itinerant microwave photons.
2. Implementation of quantum interface between microwave cavity and itinerant microwave photons.
Overall, the project has accomplished the following milestones:
1. Demonstration of multi-mode superconducting circuit optomechanical lattices in nontrivial topological phase.
2. Demonstration of tracking thermalization of a quantum squeezed mechanical state in an ultra-coherent superconducting circuit optomechanical system.
3. Establishment of superconducting qubits for the first time at EPFL.
4. Demonstration of ultra-coherent superconducting qubits with lifetimes exceeding 0.4 milliseconds, on par with the best qubit lifetimes reported.
5. Discovery of a new source of correlated bit-flip errors among highly coherent superconducting qubits, induced by mechanical shocks.
Deliverables of QuPhon include:
1. Publication of topological lattices realized in circuit optomechanics (Nature).
2. Publication of a squeezed ultra-coherent mechanical oscillator (Nature Physics in press).
3. Publication of mechanically induced errors on ultra-coherent superconducting qubits (arXiv).
The research results from this project have been published in high impact journals, mainly Nature and Nature Physics (in press) and are currently under review at PRX. In addition, the researcher has participated in several academic conferences and has given invited oral presentations on these research results.
1. Implementation of quantum interface between mechanical oscillator and itinerant microwave photons.
2. Implementation of quantum interface between microwave cavity and itinerant microwave photons.
Overall, the project has accomplished the following milestones:
1. Demonstration of multi-mode superconducting circuit optomechanical lattices in nontrivial topological phase.
2. Demonstration of tracking thermalization of a quantum squeezed mechanical state in an ultra-coherent superconducting circuit optomechanical system.
3. Establishment of superconducting qubits for the first time at EPFL.
4. Demonstration of ultra-coherent superconducting qubits with lifetimes exceeding 0.4 milliseconds, on par with the best qubit lifetimes reported.
5. Discovery of a new source of correlated bit-flip errors among highly coherent superconducting qubits, induced by mechanical shocks.
Deliverables of QuPhon include:
1. Publication of topological lattices realized in circuit optomechanics (Nature).
2. Publication of a squeezed ultra-coherent mechanical oscillator (Nature Physics in press).
3. Publication of mechanically induced errors on ultra-coherent superconducting qubits (arXiv).
The research results from this project have been published in high impact journals, mainly Nature and Nature Physics (in press) and are currently under review at PRX. In addition, the researcher has participated in several academic conferences and has given invited oral presentations on these research results.
The QuPhon project has led to significant breakthroughs in both circuit optomechanics and superconducting qubits, which are long-lasting goals, including the demonstration of scalable and ultra-coherent circuit optomechanics and the enhancement of superconducting qubit lifetimes. Hence, the QuPhon project has served as a platform for uncovering new technical hurdles towards fault-tolerant quantum computing and has driven both the researcher and the host laboratory to achieve ground-breaking research results and innovative solutions. The remarkable extension of qubit lifetime achieved by the project has revealed a previously unknown mechanism of qubit loss, triggered by mechanical shocks, leading to correlated errors. This discovery paves the way for future approaches to mitigate such errors and advance the feasibility of scalable superconducting quantum computing.
The impact of this project includes:
1. Revolutionizing superconducting circuit optomechanics: The project has made advances in ultra-coherent and scalable superconducting circuit optomechanics. This breakthrough has the potential to revolutionize quantum science and technology by provindg a promising platform for scalable and reliable mechanical oscillator-based quantum memories for quantum computing and communication.
2. Ultra-coherent superconducting transmon qubits: The project successfully realized ultra-coherent superconducting transmon qubits based on niobium electrodes conventionally used in the field, achieving lifetimes exceeding 0.4 milliseconds, on par with the best. This achievement challenges the prevailing belief that new materials are needed to improve qubit coherence, opening up new possibilities for achieving remarkable coherence in superconducting qubits. The transparency of the project, demonstrated by the sharing of fabrication details through an open-access repository, fosters collaboration and encourages academic groups to invest more effort in improving qubit lifetime.
3. Uncovering a novel correlated error mechanism: The project uncovered a novel mechanism that induces correlated qubit errors arising from vibrational noise generated by the pulse tube cooler of a dilution refrigerator. This discovery poses a significant challenge to quantum error correction techniques, which are crucial for reliable and scalable quantum computing. It raises questions about the feasibility of fault-tolerant superconducting quantum computing without active measures to mitigate this phenomenon. The findings have implications for cryostat manufacturing, cryogenic wiring, sample packaging, and shielding, attracting interest from industrial companies involved in superconducting quantum computing technologies. Future strategies may include acoustically shielded superconducting devices, shock-resistant sample packaging, and vibration-free dilution refrigerators.
The QuPhon project has made a significant contribution to the EU’s H2020 program in research excellence, demonstrating Europe's continued ability to generate world-class scientific advances and positioning Europe as a pioneer in the advancement of solid-state physics technologies.
The impact of this project includes:
1. Revolutionizing superconducting circuit optomechanics: The project has made advances in ultra-coherent and scalable superconducting circuit optomechanics. This breakthrough has the potential to revolutionize quantum science and technology by provindg a promising platform for scalable and reliable mechanical oscillator-based quantum memories for quantum computing and communication.
2. Ultra-coherent superconducting transmon qubits: The project successfully realized ultra-coherent superconducting transmon qubits based on niobium electrodes conventionally used in the field, achieving lifetimes exceeding 0.4 milliseconds, on par with the best. This achievement challenges the prevailing belief that new materials are needed to improve qubit coherence, opening up new possibilities for achieving remarkable coherence in superconducting qubits. The transparency of the project, demonstrated by the sharing of fabrication details through an open-access repository, fosters collaboration and encourages academic groups to invest more effort in improving qubit lifetime.
3. Uncovering a novel correlated error mechanism: The project uncovered a novel mechanism that induces correlated qubit errors arising from vibrational noise generated by the pulse tube cooler of a dilution refrigerator. This discovery poses a significant challenge to quantum error correction techniques, which are crucial for reliable and scalable quantum computing. It raises questions about the feasibility of fault-tolerant superconducting quantum computing without active measures to mitigate this phenomenon. The findings have implications for cryostat manufacturing, cryogenic wiring, sample packaging, and shielding, attracting interest from industrial companies involved in superconducting quantum computing technologies. Future strategies may include acoustically shielded superconducting devices, shock-resistant sample packaging, and vibration-free dilution refrigerators.
The QuPhon project has made a significant contribution to the EU’s H2020 program in research excellence, demonstrating Europe's continued ability to generate world-class scientific advances and positioning Europe as a pioneer in the advancement of solid-state physics technologies.