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dc.contributor.authorZhao, Songyuan
dc.contributor.authorWithington, Stafford
dc.date.accessioned2021-06-28T13:27:22Z
dc.date.available2021-06-28T13:27:22Z
dc.date.issued2021-06-28
dc.date.submitted2021-04-13
dc.identifier.issn0022-3727
dc.identifier.otherdac0b74
dc.identifier.otherac0b74
dc.identifier.otherjphysd-127733.r1
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/324486
dc.description.abstractAbstract: We have performed a quantum mechanical analysis of travelling-wave parametric amplifiers (TWPAs) in order to investigate five experimental phenomena related to their operations, namely the effect of impedance mismatch, the presence of upper idler modes, the presence of quantum and thermal noise, the generation of squeezed states, and the preservation of pre-squeezed states during amplification. Our analysis uses momentum operators to describe the spatial evolution of quantised modes along a TWPA. We calculate the restriction placed on pump amplitude as well as amplifier gain as a result of impedance mismatch between a TWPA and its external system. We apply our analysis to upper idler modes and demonstrate that they will result in suppressed gain. We show that an ideal TWPA is indeed quantum-limited—i.e. it introduces a half-quantum of zero-point fluctuation which is the minimum possible noise contribution for a phase-preserving linear amplifier. We analyse the thermal noise associated with a TWPA by considering the effect of distributed sources along an amplifier transmission line. Our analysis predicts a doubling of thermal noise in the high gain limit as a result of wave-mixing between signal and idler modes. We study the operation of a TWPA in the presence of a DC bias current, and have shown that highly squeezed states can in principle be generated. However, amplifying a pre-squeezed state using a non-degenerate TWPA generally reduces the squeezing advantage.
dc.languageen
dc.publisherIOP Publishing
dc.subjectPaper
dc.subjectCondensed matter
dc.subjectparametric amplifier
dc.subjectquantum noise
dc.subjectthermal noise
dc.subjectsuperconducting amplifier
dc.titleQuantum analysis of second-order effects in superconducting travelling-wave parametric amplifiers
dc.typeArticle
dc.date.updated2021-06-28T13:27:22Z
prism.issueIdentifier36
prism.publicationNameJournal of Physics D: Applied Physics
prism.volume54
dc.identifier.doi10.17863/CAM.71938
dcterms.dateAccepted2021-06-15
rioxxterms.versionofrecord10.1088/1361-6463/ac0b74
rioxxterms.versionVoR
rioxxterms.licenseref.urihttp://creativecommons.org/licenses/by/4.0
dc.contributor.orcidZhao, Songyuan [0000-0002-5712-6937]
dc.identifier.eissn1361-6463
pubs.funder-project-idChina Scholarship Council (CSC Cambridge Scholarship)


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