{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/156556"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/156556","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"The Quarton Coupler for Near-Ultrastrong Nonlinear Light-Matter Coupling in Superconducting Circuits","abstract":"The interaction between an atom and an electromagnetic mode of a resonator is of both fundamental interest and is ubiquitous in quantum technologies. Most prior work studies a linear light-matter coupling of the form [formula], where 𝑔 measured relative to photonic (𝜔ₐ) and atomic (𝜔 subscript 𝑏) mode frequencies can reach the ultrastrong regime [formula]. In contrast, a nonlinear light-matter coupling of the form [formula] has the advantage of commuting with the atomic [formula] and photonic â superscript † 𝑎 Hamiltonian, allowing for fundamental operations such as quantum-non-demolition (QND) measurement. However, due to the perturbative nature of nonlinear coupling, the state-of-the-art 𝜒/max(𝜔𝑎, 𝜔𝑏) is limited to < 10⁻². In this thesis, we develop the theory of quarton couplers and experimentally demonstrate, for the first time, a near-ultrastrong 𝜒/max(𝜔ₐ, 𝜔 subscript 𝑏) = (4.852 ± 0.006) × 10⁻² nonlinear coupling of a superconducting artificial atom and a nearly-linear resonator. We also show signatures of light-light nonlinear coupling [formula], and 𝜒/2𝜋 = 580.3 ± 0.4 MHz matter-matter nonlinear coupling [formula] which represents the largest reported 𝑍𝑍 interaction between two coherent qubits. Finally, we present a new qubit readout scheme that uses the quarton coupler to enable simulated performance of 5 ns readout time with greater than 99% readout and QND fidelity. Our work reveals a new path for order-of-magnitude improvements of fundamental superconducting qubit operations by engineering nonlinear light-matter couplings in parameter regimes unreachable by existing designs.","abstract_html":"The interaction between an atom and an electromagnetic mode of a resonator is of both fundamental interest and is ubiquitous in quantum technologies. Most prior work studies a linear light-matter coupling of the form [formula], where 𝑔 measured relative to photonic (𝜔ₐ) and atomic (𝜔 subscript 𝑏) mode frequencies can reach the ultrastrong regime [formula]. In contrast, a nonlinear light-matter coupling of the form [formula] has the advantage of commuting with the atomic [formula] and photonic â superscript † 𝑎 Hamiltonian, allowing for fundamental operations such as quantum-non-demolition (QND) measurement. However, due to the perturbative nature of nonlinear coupling, the state-of-the-art 𝜒/max(𝜔𝑎, 𝜔𝑏) is limited to &lt; 10⁻². In this thesis, we develop the theory of quarton couplers and experimentally demonstrate, for the first time, a near-ultrastrong 𝜒/max(𝜔ₐ, 𝜔 subscript 𝑏) = (4.852 ± 0.006) × 10⁻² nonlinear coupling of a superconducting artificial atom and a nearly-linear resonator. We also show signatures of light-light nonlinear coupling [formula], and 𝜒/2𝜋 = 580.3 ± 0.4 MHz matter-matter nonlinear coupling [formula] which represents the largest reported 𝑍𝑍 interaction between two coherent qubits. Finally, we present a new qubit readout scheme that uses the quarton coupler to enable simulated performance of 5 ns readout time with greater than 99% readout and QND fidelity. Our work reveals a new path for order-of-magnitude improvements of fundamental superconducting qubit operations by engineering nonlinear light-matter couplings in parameter regimes unreachable by existing designs.","abstract_has_math":false,"creators":["Ye, Yufeng"],"institution":"Massachusetts Institute of Technology","degree_name":"Doctoral","degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science","school":null,"contributors":[],"advisors":["O’Brien, Kevin P."],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024-05","date_published":"2024-05","updated_at":"2026-07-22T22:21:30Z","subjects":[],"languages":[],"rights":["In Copyright - Educational Use Permitted","Copyright retained by author(s)"],"rights_urls":["https://rightsstatements.org/page/InC-EDU/1.0/"],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1721.1/156556","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["O’Brien, Kevin P."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. 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Most prior work studies a linear light-matter coupling of the form [formula], where 𝑔 measured relative to photonic (𝜔ₐ) and atomic (𝜔 subscript 𝑏) mode frequencies can reach the ultrastrong regime [formula]. In contrast, a nonlinear light-matter coupling of the form [formula] has the advantage of commuting with the atomic [formula] and photonic â superscript † 𝑎 Hamiltonian, allowing for fundamental operations such as quantum-non-demolition (QND) measurement. However, due to the perturbative nature of nonlinear coupling, the state-of-the-art 𝜒/max(𝜔𝑎, 𝜔𝑏) is limited to < 10⁻². In this thesis, we develop the theory of quarton couplers and experimentally demonstrate, for the first time, a near-ultrastrong 𝜒/max(𝜔ₐ, 𝜔 subscript 𝑏) = (4.852 ± 0.006) × 10⁻² nonlinear coupling of a superconducting artificial atom and a nearly-linear resonator. We also show signatures of light-light nonlinear coupling [formula], and 𝜒/2𝜋 = 580.3 ± 0.4 MHz matter-matter nonlinear coupling [formula] which represents the largest reported 𝑍𝑍 interaction between two coherent qubits. Finally, we present a new qubit readout scheme that uses the quarton coupler to enable simulated performance of 5 ns readout time with greater than 99% readout and QND fidelity. Our work reveals a new path for order-of-magnitude improvements of fundamental superconducting qubit operations by engineering nonlinear light-matter couplings in parameter regimes unreachable by existing designs."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["The Quarton Coupler for Near-Ultrastrong Nonlinear Light-Matter Coupling in Superconducting Circuits"]}]}],"canonical_facts":{"dc:contributor.advisor":["O’Brien, Kevin P."],"dc:contributor.department":["Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science"],"dc:creator":["Ye, Yufeng"],"dc:date.accessioned":["2024-09-03T21:07:14Z"],"dc:date.available":["2024-09-03T21:07:14Z"],"dc:date.issued":["2024-05"],"dc:description.abstract":["The interaction between an atom and an electromagnetic mode of a resonator is of both fundamental interest and is ubiquitous in quantum technologies. Most prior work studies a linear light-matter coupling of the form [formula], where 𝑔 measured relative to photonic (𝜔ₐ) and atomic (𝜔 subscript 𝑏) mode frequencies can reach the ultrastrong regime [formula]. In contrast, a nonlinear light-matter coupling of the form [formula] has the advantage of commuting with the atomic [formula] and photonic â superscript † 𝑎 Hamiltonian, allowing for fundamental operations such as quantum-non-demolition (QND) measurement. However, due to the perturbative nature of nonlinear coupling, the state-of-the-art 𝜒/max(𝜔𝑎, 𝜔𝑏) is limited to < 10⁻². In this thesis, we develop the theory of quarton couplers and experimentally demonstrate, for the first time, a near-ultrastrong 𝜒/max(𝜔ₐ, 𝜔 subscript 𝑏) = (4.852 ± 0.006) × 10⁻² nonlinear coupling of a superconducting artificial atom and a nearly-linear resonator. We also show signatures of light-light nonlinear coupling [formula], and 𝜒/2𝜋 = 580.3 ± 0.4 MHz matter-matter nonlinear coupling [formula] which represents the largest reported 𝑍𝑍 interaction between two coherent qubits. Finally, we present a new qubit readout scheme that uses the quarton coupler to enable simulated performance of 5 ns readout time with greater than 99% readout and QND fidelity. Our work reveals a new path for order-of-magnitude improvements of fundamental superconducting qubit operations by engineering nonlinear light-matter couplings in parameter regimes unreachable by existing designs."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["https://hdl.handle.net/1721.1/156556"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["In Copyright - Educational Use Permitted","Copyright retained by author(s)"],"dc:rights.uri":["https://rightsstatements.org/page/InC-EDU/1.0/"],"dc:title":["The Quarton Coupler for Near-Ultrastrong Nonlinear Light-Matter Coupling in Superconducting Circuits"],"dc:type":["Thesis"],"thesis:degree_name":["Doctoral","Doctor of Philosophy"]},"updated_at":"2026-07-22T22:21:30Z"}