Quantum-limited amplification in the microwave frequency range is of both practical and fundamental importance. The weak signals corresponding to single microwave photons require substantial amplification to resolve. When probing quantum excitations of the electromagnetic field, the substantial noise produced by standard amplifiers dominates the signal, therefore, several averages must be accumulated to achieve even a modest signal-to-noise ratio. Even worse, the back-action on the system due to amplifier noise can hasten the decay of the quantum state. In recent years, low-noise microwave-frequency amplification has been advancing rapidly and one field that would benefit greatly from this is circuit quantum electrodynamics (cQED). The development of circuit quantum electrodynamics---which implements techniques of quantum optics at microwave frequencies---has led to revolutionary progress in the field of quantum information science. cQED employs quantum bits (qubits) and superconducting microwave resonators in place of the atoms and cavities used in quantum optics permitting preparation and control of low energy photon states in macroscopic superconducting circuits at millikelvin temperatures. We have developed a microstrip superconducting quantum interference device (SQUID) amplifier (MSA) to provide the first stage of amplification for these systems. Employing sub-micron Josephson tunnel junctions for enhanced gain, these MSAs operate at microwave frequencies and are optimized to perform with near quantum-limited noise characteristics.
Our MSA is utilized as the first stage of amplification to probe the dynamics of a SQUID oscillator. The SQUID oscillator is a flux-tunable microwave resonator formed by a capacitively shunted dc SQUID. Josephson plasma oscillations are induced by pulsed microwave excitations at the resonant frequency of the oscillator. Once pulsed, decaying plasma oscillations are observed in the time domain. By measuring with pulse amplitudes approaching the critical current of the SQUID, it is possible to probe the free evolution of a highly nonlinear oscillator.
","abstract_html":"<p>Quantum-limited amplification in the microwave frequency range is of both practical and fundamental importance. The weak signals corresponding to single microwave photons require substantial amplification to resolve. When probing quantum excitations of the electromagnetic field, the substantial noise produced by standard amplifiers dominates the signal, therefore, several averages must be accumulated to achieve even a modest signal-to-noise ratio. Even worse, the back-action on the system due to amplifier noise can hasten the decay of the quantum state. In recent years, low-noise microwave-frequency amplification has been advancing rapidly and one field that would benefit greatly from this is circuit quantum electrodynamics (cQED). The development of circuit quantum electrodynamics---which implements techniques of quantum optics at microwave frequencies---has led to revolutionary progress in the field of quantum information science. cQED employs quantum bits (qubits) and superconducting microwave resonators in place of the atoms and cavities used in quantum optics permitting preparation and control of low energy photon states in macroscopic superconducting circuits at millikelvin temperatures. We have developed a microstrip superconducting quantum interference device (SQUID) amplifier (MSA) to provide the first stage of amplification for these systems. Employing sub-micron Josephson tunnel junctions for enhanced gain, these MSAs operate at microwave frequencies and are optimized to perform with near quantum-limited noise characteristics.</p> <p>Our MSA is utilized as the first stage of amplification to probe the dynamics of a SQUID oscillator. The SQUID oscillator is a flux-tunable microwave resonator formed by a capacitively shunted dc SQUID. Josephson plasma oscillations are induced by pulsed microwave excitations at the resonant frequency of the oscillator. Once pulsed, decaying plasma oscillations are observed in the time domain. By measuring with pulse amplitudes approaching the critical current of the SQUID, it is possible to probe the free evolution of a highly nonlinear oscillator.</p>","abstract_has_math":false,"creators":["DeFeo, Michael Paul"],"institution":null,"degree_name":"Doctor of Philosophy (PhD)","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Britton L.T. Plourde"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2012,"date_issued":"2012-08-01T07:00:00Z","date_published":"2012-08-01T07:00:00Z","updated_at":"2026-07-24T04:54:17Z","subjects":["low-noise amplification","Quantum information","Quantum-limited amplifier","Superconducting device","Superconductivity","Physics"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://surface.syr.edu/phy_etd/127","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Britton L.T. Plourde"]},{"key":"dc:creator","label":"Author","values":["DeFeo, Michael Paul"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["low-noise amplification","Quantum information","Quantum-limited amplifier","Superconducting device","Superconductivity","Physics"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://surface.syr.edu/phy_etd/127"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Quantum-limited amplification in the microwave frequency range is of both practical and fundamental importance. The weak signals corresponding to single microwave photons require substantial amplification to resolve. When probing quantum excitations of the electromagnetic field, the substantial noise produced by standard amplifiers dominates the signal, therefore, several averages must be accumulated to achieve even a modest signal-to-noise ratio. Even worse, the back-action on the system due to amplifier noise can hasten the decay of the quantum state. In recent years, low-noise microwave-frequency amplification has been advancing rapidly and one field that would benefit greatly from this is circuit quantum electrodynamics (cQED). The development of circuit quantum electrodynamics---which implements techniques of quantum optics at microwave frequencies---has led to revolutionary progress in the field of quantum information science. cQED employs quantum bits (qubits) and superconducting microwave resonators in place of the atoms and cavities used in quantum optics permitting preparation and control of low energy photon states in macroscopic superconducting circuits at millikelvin temperatures. We have developed a microstrip superconducting quantum interference device (SQUID) amplifier (MSA) to provide the first stage of amplification for these systems. Employing sub-micron Josephson tunnel junctions for enhanced gain, these MSAs operate at microwave frequencies and are optimized to perform with near quantum-limited noise characteristics.
Our MSA is utilized as the first stage of amplification to probe the dynamics of a SQUID oscillator. The SQUID oscillator is a flux-tunable microwave resonator formed by a capacitively shunted dc SQUID. Josephson plasma oscillations are induced by pulsed microwave excitations at the resonant frequency of the oscillator. Once pulsed, decaying plasma oscillations are observed in the time domain. By measuring with pulse amplitudes approaching the critical current of the SQUID, it is possible to probe the free evolution of a highly nonlinear oscillator.
"]},{"key":"dc:title","label":"Title","values":["Microstrip Superconducting Quantum Interference Devices for Quantum Information Science"]}]}],"canonical_facts":{"dc:contributor":["Britton L.T. Plourde"],"dc:creator":["DeFeo, Michael Paul"],"dc:description.abstract":["Quantum-limited amplification in the microwave frequency range is of both practical and fundamental importance. The weak signals corresponding to single microwave photons require substantial amplification to resolve. When probing quantum excitations of the electromagnetic field, the substantial noise produced by standard amplifiers dominates the signal, therefore, several averages must be accumulated to achieve even a modest signal-to-noise ratio. Even worse, the back-action on the system due to amplifier noise can hasten the decay of the quantum state. In recent years, low-noise microwave-frequency amplification has been advancing rapidly and one field that would benefit greatly from this is circuit quantum electrodynamics (cQED). The development of circuit quantum electrodynamics---which implements techniques of quantum optics at microwave frequencies---has led to revolutionary progress in the field of quantum information science. cQED employs quantum bits (qubits) and superconducting microwave resonators in place of the atoms and cavities used in quantum optics permitting preparation and control of low energy photon states in macroscopic superconducting circuits at millikelvin temperatures. We have developed a microstrip superconducting quantum interference device (SQUID) amplifier (MSA) to provide the first stage of amplification for these systems. Employing sub-micron Josephson tunnel junctions for enhanced gain, these MSAs operate at microwave frequencies and are optimized to perform with near quantum-limited noise characteristics.
Our MSA is utilized as the first stage of amplification to probe the dynamics of a SQUID oscillator. The SQUID oscillator is a flux-tunable microwave resonator formed by a capacitively shunted dc SQUID. Josephson plasma oscillations are induced by pulsed microwave excitations at the resonant frequency of the oscillator. Once pulsed, decaying plasma oscillations are observed in the time domain. By measuring with pulse amplitudes approaching the critical current of the SQUID, it is possible to probe the free evolution of a highly nonlinear oscillator.
"],"dc:identifier":["https://surface.syr.edu/phy_etd/127"],"dc:subject":["low-noise amplification","Quantum information","Quantum-limited amplifier","Superconducting device","Superconductivity","Physics"],"dc:title":["Microstrip Superconducting Quantum Interference Devices for Quantum Information Science"],"thesis:degree_discipline":["Physics"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-24T04:54:17Z"}