Towards calorimetric detection of individual itinerant microwave photons

Joonas Govenius

Published Jan 1, 2016• 1 citation

Abstract

This dissertation focuses on the development of a new type of thermal microwave photodetector based on superconductor–normal-metal–superconductor (SNS) junctions. We motivate the development of the detector mainly by microwave quantum optics applications in the context of superconducting qubits coupled to microwave transmission lines and resonators, i.e., in the context of circuit quantum electrodynamics (cQED). In cQED, single-photon microwave pulses naturally arise as a results of a qubit exchanging its excitation with a transmission line. While immense progress has been achieved in cQED in general, and in linear microwave amplification in particular, the challenge of developing an efficient and practical detector for single itinerant photons remains open, mostly due to the exceedingly small energy of individual microwave photons. This prevents microwave implementations of a certain class of quantum optical protocols, including the parity measurement protocol proposed in this dissertation. The core of this dissertation is dedicated to introducing our detector design, discussing the thermal properties of the detector in detail, and demonstrating the operation of the detector in a time-gated threshold detection mode. In particular, we demonstrate threshold detection of coherent 8.4 GHz microwave pulses containing roughly 200 photons, or 1.1 zJ of energy. Compared to other thermal detectors, this is an order of magnitude improvement in the energy of the detected pulses. In addition, we characterize the linear response of the SNS junctions as separate components. That is, we embed the junctions in a microwave circuit that is specifically designed to allow determining the electrical admittance of the SNS junctions from the response of the circuit as a whole.; Tama vaitoskirja keskittyy uudentyyppisen mikroaaltofotoni-ilmaisimen kehitykseen. Ilmaisin perustuu suprajohde–normaalimetalli–suprajohde-liitoksiin (SNS). Ilmaisin on suunnattu lahinna mikroaaltotaajuuksilla tapahtuviin kvanttioptiikan sovellutuksiin, joissa suprajohtavat kvanttibitit (eli kubitit) kytketaan mikroaaltosiirtolinjoihin. Tallaisissa niin sanotuissa piirikvanttisahkodynamiikan kokeissa yhden fotonin mikroaaltopulsseja syntyy luonnollisesti virittyneen kubitin luovuttaessa energiansa mikroaaltosiirtolinjaan. Yhden fotonin liikkuvia mikroaaltopulsseja ei kuitenkaan kyeta havaitsemaan tehokkaasti nykyaan kaytossa olevalla tekniikalla, lahinna yksittaisten mikroaaltofotonien haviavan pienen energian vuoksi. Tama siitakin huolimatta, etta lineaariset vahvistimet, joita useimmiten kaytetaan mikroaaltomittauksissa, ovat kehittyneet viime vuosina vahvasti. Ilman yksifotoni-ilmaisia eraita kvanttioptiikan menetelmia ei voida kuitenkaan hyodyntaa, mukaan lukien pariteettimittausmenetelma, jota ehdotetaan tassa vaitoskirjassa. Vaitoskirjan keskeisimmassa osassa esitetaan ilmaisimen toimintaperiaate ja tarkeimmat termodynaamiset ominaisuudet seka tutkitaan kuinka heikkoja mikroaaltopulsseja ilmaisin kykenee havaitsemaan. Jos pulssin…

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This dissertation focuses on the development of a new type of thermal microwave photodetector based on superconductor–normal-metal–superconductor (SNS) junctions.

We motivate the development of the detector mainly by microwave quantum optics applications in the context of superconducting qubits coupled to microwave transmission lines and resonators, i.e., in the context of circuit quantum electrodynamics (cQED). In cQED, single-photon microwave pulses naturally arise as a results of a qubit exchanging its excitation with a transmission line. While immense progress has been achieved in cQED in general, and in linear microwave amplification in particular, the challenge of developing an efficient and practical detector for single itinerant photons remains open, mostly due to the exceedingly small energy of individual microwave photons. This prevents microwave implementations of a certain class of quantum optical protocols, including the parity measurement protocol proposed in this dissertation.

The core of this dissertation is dedicated to introducing our detector design, discussing the thermal properties of the detector in detail, and demonstrating the operation of the detector in a time-gated threshold detection mode. In particular, we demonstrate threshold detection of coherent 8.4 GHz microwave pulses containing roughly 200 photons, or 1.1 zJ of energy. Compared to other thermal detectors, this is an order of magnitude improvement in the energy of the detected pulses.

In addition, we characterize the linear response of the SNS junctions as separate components. That is, we embed the junctions in a microwave circuit that is specifically designed to allow determining the electrical admittance of the SNS junctions from the response of the circuit as a whole.; Tama vaitoskirja keskittyy uudentyyppisen mikroaaltofotoni-ilmaisimen kehitykseen. Ilmaisin perustuu suprajohde–normaalimetalli–suprajohde-liitoksiin (SNS).

Ilmaisin on suunnattu lahinna mikroaaltotaajuuksilla tapahtuviin kvanttioptiikan sovellutuksiin, joissa suprajohtavat kvanttibitit (eli kubitit) kytketaan mikroaaltosiirtolinjoihin. Tallaisissa niin sanotuissa piirikvanttisahkodynamiikan kokeissa yhden fotonin mikroaaltopulsseja syntyy luonnollisesti virittyneen kubitin luovuttaessa energiansa mikroaaltosiirtolinjaan. Yhden fotonin liikkuvia mikroaaltopulsseja ei kuitenkaan kyeta havaitsemaan tehokkaasti nykyaan kaytossa olevalla tekniikalla, lahinna yksittaisten mikroaaltofotonien haviavan pienen energian vuoksi. Tama siitakin huolimatta, etta lineaariset vahvistimet, joita useimmiten kaytetaan mikroaaltomittauksissa, ovat kehittyneet viime vuosina vahvasti. Ilman yksifotoni-ilmaisia eraita kvanttioptiikan menetelmia ei voida kuitenkaan hyodyntaa, mukaan lukien pariteettimittausmenetelma, jota ehdotetaan tassa vaitoskirjassa.

Vaitoskirjan keskeisimmassa osassa esitetaan ilmaisimen toimintaperiaate ja tarkeimmat termodynaamiset ominaisuudet seka tutkitaan kuinka heikkoja mikroaaltopulsseja ilmaisin kykenee havaitsemaan. Jos pulssin…