--- _id: '13175' abstract: - lang: eng text: "About a 100 years ago, we discovered that our universe is inherently noisy, that is, measuring any physical quantity with a precision beyond a certain point is not possible because of an omnipresent inherent noise. We call this - the quantum noise. Certain physical processes allow this quantum noise to get correlated in conjugate physical variables. These quantum correlations can be used to go beyond the potential of our inherently noisy universe and obtain a quantum advantage over the classical applications. \r\n\r\nQuantum noise being inherent also means that, at the fundamental level, the physical quantities are not well defined and therefore, objects can stay in multiple states at the same time. For example, the position of a particle not being well defined means that the particle is in multiple positions at the same time. About 4 decades ago, we started exploring the possibility of using objects which can be in multiple states at the same time to increase the dimensionality in computation. Thus, the field of quantum computing was born. We discovered that using quantum entanglement, a property closely related to quantum correlations, can be used to speed up computation of certain problems, such as factorisation of large numbers, faster than any known classical algorithm. Thus began the pursuit to make quantum computers a reality. \r\n\r\nTill date, we have explored quantum control over many physical systems including photons, spins, atoms, ions and even simple circuits made up of superconducting material. However, there persists one ubiquitous theme. The more readily a system interacts with an external field or matter, the more easily we can control it. But this also means that such a system can easily interact with a noisy environment and quickly lose its coherence. Consequently, such systems like electron spins need to be protected from the environment to ensure the longevity of their coherence. Other systems like nuclear spins are naturally protected as they do not interact easily with the environment. But, due to the same reason, it is harder to interact with such systems. \r\n\r\nAfter decades of experimentation with various systems, we are convinced that no one type of quantum system would be the best for all the quantum applications. We would need hybrid systems which are all interconnected - much like the current internet where all sorts of devices can all talk to each other - but now for quantum devices. A quantum internet. \r\n\r\nOptical photons are the best contenders to carry information for the quantum internet. They can carry quantum information cheaply and without much loss - the same reasons which has made them the backbone of our current internet. Following this direction, many systems, like trapped ions, have already demonstrated successful quantum links over a large distances using optical photons. However, some of the most promising contenders for quantum computing which are based on microwave frequencies have been left behind. This is because high energy optical photons can adversely affect fragile low-energy microwave systems. \r\n\r\nIn this thesis, we present substantial progress on this missing quantum link between microwave and optics using electrooptical nonlinearities in lithium niobate. The nonlinearities are enhanced by using resonant cavities for all the involved modes leading to observation of strong direct coupling between optical and microwave frequencies. With this strong coupling we are not only able to achieve almost 100\\% internal conversion efficiency with low added noise, thus presenting a quantum-enabled transducer, but also we are able to observe novel effects such as cooling of a microwave mode using optics. The strong coupling regime also leads to direct observation of dynamical backaction effect between microwave and optical frequencies which are studied in detail here. Finally, we also report first observation of microwave-optics entanglement in form of two-mode squeezed vacuum squeezed 0.7dB below vacuum level. \r\nWith this new bridge between microwave and optics, the microwave-based quantum technologies can finally be a part of a quantum network which is based on optical photons - putting us one step closer to a future with quantum internet. " acknowledged_ssus: - _id: M-Shop - _id: SSU - _id: NanoFab alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Rishabh full_name: Sahu, Rishabh id: 47D26E34-F248-11E8-B48F-1D18A9856A87 last_name: Sahu orcid: 0000-0001-6264-2162 citation: ama: Sahu R. Cavity quantum electrooptics. 2023. doi:10.15479/at:ista:13175 apa: Sahu, R. (2023). Cavity quantum electrooptics. Institute of Science and Technology Austria. https://doi.org/10.15479/at:ista:13175 chicago: Sahu, Rishabh. “Cavity Quantum Electrooptics.” Institute of Science and Technology Austria, 2023. https://doi.org/10.15479/at:ista:13175. ieee: R. Sahu, “Cavity quantum electrooptics,” Institute of Science and Technology Austria, 2023. ista: Sahu R. 2023. Cavity quantum electrooptics. Institute of Science and Technology Austria. mla: Sahu, Rishabh. Cavity Quantum Electrooptics. Institute of Science and Technology Austria, 2023, doi:10.15479/at:ista:13175. short: R. Sahu, Cavity Quantum Electrooptics, Institute of Science and Technology Austria, 2023. date_created: 2023-06-30T08:07:43Z date_published: 2023-05-05T00:00:00Z date_updated: 2024-10-29T09:11:06Z day: '05' ddc: - '537' - '535' - '539' degree_awarded: PhD department: - _id: GradSch - _id: JoFi doi: 10.15479/at:ista:13175 ec_funded: 1 file: - access_level: open_access checksum: 7d03f1a5a5258ee43dfc3323dea4e08f content_type: application/pdf creator: cchlebak date_created: 2023-06-30T08:17:25Z date_updated: 2023-06-30T08:17:25Z file_id: '13176' file_name: thesis_pdfa.pdf file_size: 18688376 relation: main_file success: 1 - access_level: closed checksum: c3b45317ae58e0527533f98c202d81b7 content_type: application/x-zip-compressed creator: cchlebak date_created: 2023-07-06T11:35:15Z date_updated: 2023-07-06T11:35:15Z file_id: '13196' file_name: thesis.zip file_size: 37847025 relation: source_file file_date_updated: 2023-07-06T11:35:15Z has_accepted_license: '1' keyword: - quantum optics - electrooptics - quantum networks - quantum communication - transduction language: - iso: eng license: https://creativecommons.org/licenses/by-nc-sa/4.0/ month: '05' oa: 1 oa_version: Published Version page: '202' project: - _id: 26336814-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '758053' name: A Fiber Optic Transceiver for Superconducting Qubits - _id: 9B868D20-BA93-11EA-9121-9846C619BF3A call_identifier: H2020 grant_number: '899354' name: Quantum Local Area Networks with Superconducting Qubits - _id: bdb108fd-d553-11ed-ba76-83dc74a9864f name: QUANTUM INFORMATION SYSTEMS BEYOND CLASSICAL CAPABILITIES / P5- Integration of Superconducting Quantum Circuits publication_identifier: isbn: - 978-3-99078-030-5 issn: - 2663 - 337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '12900' relation: old_edition status: public - id: '9114' relation: part_of_dissertation status: public - id: '10924' relation: part_of_dissertation status: public status: public supervisor: - first_name: Johannes M full_name: Fink, Johannes M id: 4B591CBA-F248-11E8-B48F-1D18A9856A87 last_name: Fink orcid: 0000-0001-8112-028X title: Cavity quantum electrooptics tmp: image: /images/cc_by_nc_sa.png legal_code_url: https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode name: Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) short: CC BY-NC-SA (4.0) type: dissertation user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 year: '2023' ... --- _id: '12900' abstract: - lang: eng text: "About a 100 years ago, we discovered that our universe is inherently noisy, that is, measuring any physical quantity with a precision beyond a certain point is not possible because of an omnipresent inherent noise. We call this - the quantum noise. Certain physical processes allow this quantum noise to get correlated in conjugate physical variables. These quantum correlations can be used to go beyond the potential of our inherently noisy universe and obtain a quantum advantage over the classical applications. \r\n\r\nQuantum noise being inherent also means that, at the fundamental level, the physical quantities are not well defined and therefore, objects can stay in multiple states at the same time. For example, the position of a particle not being well defined means that the particle is in multiple positions at the same time. About 4 decades ago, we started exploring the possibility of using objects which can be in multiple states at the same time to increase the dimensionality in computation. Thus, the field of quantum computing was born. We discovered that using quantum entanglement, a property closely related to quantum correlations, can be used to speed up computation of certain problems, such as factorisation of large numbers, faster than any known classical algorithm. Thus began the pursuit to make quantum computers a reality. \r\n\r\nTill date, we have explored quantum control over many physical systems including photons, spins, atoms, ions and even simple circuits made up of superconducting material. However, there persists one ubiquitous theme. The more readily a system interacts with an external field or matter, the more easily we can control it. But this also means that such a system can easily interact with a noisy environment and quickly lose its coherence. Consequently, such systems like electron spins need to be protected from the environment to ensure the longevity of their coherence. Other systems like nuclear spins are naturally protected as they do not interact easily with the environment. But, due to the same reason, it is harder to interact with such systems. \r\n\r\nAfter decades of experimentation with various systems, we are convinced that no one type of quantum system would be the best for all the quantum applications. We would need hybrid systems which are all interconnected - much like the current internet where all sorts of devices can all talk to each other - but now for quantum devices. A quantum internet. \r\n\r\nOptical photons are the best contenders to carry information for the quantum internet. They can carry quantum information cheaply and without much loss - the same reasons which has made them the backbone of our current internet. Following this direction, many systems, like trapped ions, have already demonstrated successful quantum links over a large distances using optical photons. However, some of the most promising contenders for quantum computing which are based on microwave frequencies have been left behind. This is because high energy optical photons can adversely affect fragile low-energy microwave systems. \r\n\r\nIn this thesis, we present substantial progress on this missing quantum link between microwave and optics using electrooptical nonlinearities in lithium niobate. The nonlinearities are enhanced by using resonant cavities for all the involved modes leading to observation of strong direct coupling between optical and microwave frequencies. With this strong coupling we are not only able to achieve almost 100\\% internal conversion efficiency with low added noise, thus presenting a quantum-enabled transducer, but also we are able to observe novel effects such as cooling of a microwave mode using optics. The strong coupling regime also leads to direct observation of dynamical backaction effect between microwave and optical frequencies which are studied in detail here. Finally, we also report first observation of microwave-optics entanglement in form of two-mode squeezed vacuum squeezed 0.7dB below vacuum level. \r\nWith this new bridge between microwave and optics, the microwave-based quantum technologies can finally be a part of a quantum network which is based on optical photons - putting us one step closer to a future with quantum internet. " acknowledged_ssus: - _id: M-Shop - _id: SSU - _id: NanoFab alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Rishabh full_name: Sahu, Rishabh id: 47D26E34-F248-11E8-B48F-1D18A9856A87 last_name: Sahu orcid: 0000-0001-6264-2162 citation: ama: Sahu R. Cavity quantum electrooptics. 2023. doi:10.15479/at:ista:12900 apa: Sahu, R. (2023). Cavity quantum electrooptics. Institute of Science and Technology Austria. https://doi.org/10.15479/at:ista:12900 chicago: Sahu, Rishabh. “Cavity Quantum Electrooptics.” Institute of Science and Technology Austria, 2023. https://doi.org/10.15479/at:ista:12900. ieee: R. Sahu, “Cavity quantum electrooptics,” Institute of Science and Technology Austria, 2023. ista: Sahu R. 2023. Cavity quantum electrooptics. Institute of Science and Technology Austria. mla: Sahu, Rishabh. Cavity Quantum Electrooptics. Institute of Science and Technology Austria, 2023, doi:10.15479/at:ista:12900. short: R. Sahu, Cavity Quantum Electrooptics, Institute of Science and Technology Austria, 2023. date_created: 2023-05-05T11:08:50Z date_published: 2023-05-05T00:00:00Z date_updated: 2024-10-29T09:11:05Z day: '05' ddc: - '537' - '535' - '539' degree_awarded: PhD department: - _id: GradSch - _id: JoFi doi: 10.15479/at:ista:12900 ec_funded: 1 file: - access_level: closed checksum: 8cbdab9c37ee55e591092a6f66b272c4 content_type: application/x-zip-compressed creator: rsahu date_created: 2023-05-09T08:45:14Z date_updated: 2023-06-06T22:30:03Z embargo_to: open_access file_id: '12928' file_name: thesis.zip file_size: 36767177 relation: source_file - access_level: closed checksum: 439659ead46618147309be39d9dd5a8c content_type: application/pdf creator: rsahu date_created: 2023-05-09T08:51:17Z date_updated: 2023-07-06T11:37:40Z file_id: '12929' file_name: thesis_pdfa_final.pdf file_size: 17501990 relation: main_file file_date_updated: 2023-07-06T11:37:40Z has_accepted_license: '1' keyword: - quantum optics - electrooptics - quantum networks - quantum communication - transduction language: - iso: eng month: '05' oa_version: Published Version page: '190' project: - _id: 26336814-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '758053' name: A Fiber Optic Transceiver for Superconducting Qubits - _id: 9B868D20-BA93-11EA-9121-9846C619BF3A call_identifier: H2020 grant_number: '899354' name: Quantum Local Area Networks with Superconducting Qubits - _id: bdb108fd-d553-11ed-ba76-83dc74a9864f name: QUANTUM INFORMATION SYSTEMS BEYOND CLASSICAL CAPABILITIES / P5- Integration of Superconducting Quantum Circuits publication_identifier: isbn: - 978-3-99078-030-5 issn: - 2663 - 337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '9114' relation: part_of_dissertation status: public - id: '10924' relation: part_of_dissertation status: public - id: '13175' relation: new_edition status: public status: public supervisor: - first_name: Johannes M full_name: Fink, Johannes M id: 4B591CBA-F248-11E8-B48F-1D18A9856A87 last_name: Fink orcid: 0000-0001-8112-028X title: Cavity quantum electrooptics tmp: image: /images/cc_by_nc_sa.png legal_code_url: https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode name: Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) short: CC BY-NC-SA (4.0) type: dissertation user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 year: '2023' ...