Bolometric techniques for circuit quantum electrodynamics

Roope Kokkoniemi

Bolometric techniques for circuit quantum electrodynamics

Julkaisun otsikon käännös: Bolometric techniques for circuit quantum electrodynamics

Roope Kokkoniemi

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Suprajohtava kvanttibitti, eli qubitti, on lupaava alusta suuren mittakaavan kvanttitietokoneen toteuttamiselle. Qubittien ohjaamiseen ja lukemiseen tarvittavan elektroniikan ja instrumenttien lukumäärä kasvaa käsi kädessä yhdelle piisirulle ladottujen toimivien qubittien lukumäärän kanssa. Tämän vuoksi kvanttitietokoneiden rakentamisessa tulee eteen väistämättä tilanne, jossa kaikki ohjauslinjat eivät mahdu kryostaattiin. Tästä syystä suuri määrä kansainvälisen tutkimuksen resursseja on keskitetty perinteisten huoneen lämmössä toimivien komponenttien siirtämiseksi mataliin lämpötiloihin. Keskeinen rakennuspala näiden komponenttien toteuttamisessa suprajohtavissa virtapiireissä on niin sanottu Josephsonin liitos. Tässä väitöskirjassa tutkitaan tarkemmin erästä Josephsonin liitoksen tyyppiä, suprajohde-normaalimetalli-suprajohde liitosta. Mittaamme tällaisen liitoksen admittanssin taajuuksilla, joita tyypillisesti käytetään suprajohtavissa piireissä. Työssä myös osoitetaan teoreettisesti ja kokeellisesti, että Josephsonin liitoksilla voidaan rakentaa magneettikentällä säädettävä vaihesiirrin, joka on yksi apukomponenteista suuren mittakaavan kvanttitietokoneessa. Tämän väitöskirjan pääaihe on bolometria. Se on yli vuosisata sitten keksitty tekniikka säteilyn ilmaisemiseen epäsuorasti mittaamalla lämpötilan muutosta. Korkeasta iästä huolimatta tekniikka on edelleen laajassa käytössä aina kuluttajaelektroniikasta hiukkasfysiikkaan ja astronomiaan. Huippuluokan bolometrien kohinaa vastaava teho (NEP) on 300 zW√Hz ja niillä voidaan havaita yksittäisiä 1.6 THz:n fotoneita, mikä vastaa 1.1 zJ:n energiaa. Suprajohtavat kvanttitietokoneet käyttävät mikroaaltotaajuuden fotoneita toiminnassaan. Tätä rajapyykkiä bolometrit eivät ole vielä saavuttaneet sillä näiden mikroaaltofotonien energia on kertaluokkia pienempi kuin infrapunafotonien. Tässä väitöskirjassa viedään bolometrien suorituskyky syvälle mikroaaltoalueelle. Kulta-palladium nanolankaan perustuvalla bolometrilla kohinaa vastaavan tehon ennätystä pienennetään lukemaan 50 zW/√Hz. Lisäämällä mittapiiriin Josephsonin parametrinen vahvistin, kohinaa vastaava teho pienenee edelleen lukemaan 20 zW/√Hz. Yhdessä matalan termisen aikavakion kanssa tuloksista voidaan laskea energiaresoluutioksi 0.32 zJ. Lisäksi väitöskirjassa tutkitaan grafeeniin perustuvaa bolometria. Grafeeni on lupaava vaihtoehto metallille sen kaksiulotteisen rakenteen vuoksi. Kohinaa vastaavan tehon mitataan olevan samaa luokkaa kulta-palladium bolometrin kanssa, mutta terminen aikavakio on kaksi kertaluokkaa lyhyempi. Tämä indikoi energiaresoluution olevan 20 yJ, mikä vastaa yhden 30 GHz:n fotonin energiaa.

Julkaisun otsikon käännös	Bolometric techniques for circuit quantum electrodynamics
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Möttönen, Mikko, Vastuuprofessori Girard, Jean-Philippe, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-64-0170-6
Sähköinen ISBN	978-952-64-0171-3
Tila	Julkaistu - 2020
OKM-julkaisutyyppi	G5 Tohtorinväitöskirja (artikkeli)

Tutkimusalat

bolometria
kvanttilaskenta

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http://urn.fi/URN:ISBN:978-952-64-0171-3

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@phdthesis{83679b5e1d914fbcbc32cb24bc0b641e,

title = "Bolometric techniques for circuit quantum electrodynamics",

abstract = "Superconducting quantum bits, or qubits, provide a promising platform for realizing large-scale quantum computers. As the number of qubits on a chip keeps increasing, so does the amount of required electronics and instruments needed for qubit control and readout. Eventually, it will be impossible to fit all the control lines into a cryostat. Therefore, there is an on-going effort to move the conventional room-temperature components into the lower-temperature stages. So-called Josephson junction is one of the fundamental building blocks used to realize these components in superconducting circuits. In this thesis, we study a particular type of a Josephson junction, a superconductor—normal-metal—superconductor junction. We experimentally measure its admittance at typical frequencies used in superconducting circuits. Furthermore, we show theoretically and experimentally that Josephson junctions can be used to realize one of the components aiding in scaling up quantum computers, a magnetic-flux-tunable phase shifter. The main topic of this thesis is bolometry. It is one of the oldest forms of thermal radiation detection invented over a century ago. Yet, it remains as a tool-of-choice in many applications ranging from consumer electronics to particle physics and astronomy. State-of-the-art bolometers have noise equivalent power (NEP) of 300 zW√Hz and can detect single 1.6-THz photons, which corresponds to the energy of 1.1 zJ. However, superconducting quantum computers utilize light at microwave frequencies in their operation. Thermal detectors have yet to reach this frontier due to orders of magnitude lower energy of the microwave photons than far-infrared photons. In this thesis, we bring the performance of bolometers deep into the microwave regime. First, we study a gold-palladium-nanowire-based bolometer. We are able to decrease the NEP record down to 50 zW√Hz. By introducing a Josephson parametric amplifier to the measurement circuitry, we can further improve the NEP to 20 zW√Hz. Together with the low thermal time constant below 100 µs, this result indicates an energy resolution of 0.32 zJ. Second, we investigate graphene as a substitute for gold-palladium. Graphene is a promising candidate for bolometry due to its two-dimensional nature. We find NEP on par with the gold-palladium bolometer. Importantly, the thermal time constant with graphene is about two orders of magnitude shorter, which implies an energy resolution of 20 yJ, corresponding to the energy of a single 30-GHz photon.",

keywords = "bolometry, cQED, quantum computing, bolometria, kvanttilaskenta, bolometry, cQED, quantum computing",

author = "Roope Kokkoniemi",

year = "2020",

language = "English",

isbn = "978-952-64-0170-6",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "203",

address = "Finland",

school = "Aalto University",

}

TY - THES

T1 - Bolometric techniques for circuit quantum electrodynamics

AU - Kokkoniemi, Roope

PY - 2020

Y1 - 2020

N2 - Superconducting quantum bits, or qubits, provide a promising platform for realizing large-scale quantum computers. As the number of qubits on a chip keeps increasing, so does the amount of required electronics and instruments needed for qubit control and readout. Eventually, it will be impossible to fit all the control lines into a cryostat. Therefore, there is an on-going effort to move the conventional room-temperature components into the lower-temperature stages. So-called Josephson junction is one of the fundamental building blocks used to realize these components in superconducting circuits. In this thesis, we study a particular type of a Josephson junction, a superconductor—normal-metal—superconductor junction. We experimentally measure its admittance at typical frequencies used in superconducting circuits. Furthermore, we show theoretically and experimentally that Josephson junctions can be used to realize one of the components aiding in scaling up quantum computers, a magnetic-flux-tunable phase shifter. The main topic of this thesis is bolometry. It is one of the oldest forms of thermal radiation detection invented over a century ago. Yet, it remains as a tool-of-choice in many applications ranging from consumer electronics to particle physics and astronomy. State-of-the-art bolometers have noise equivalent power (NEP) of 300 zW√Hz and can detect single 1.6-THz photons, which corresponds to the energy of 1.1 zJ. However, superconducting quantum computers utilize light at microwave frequencies in their operation. Thermal detectors have yet to reach this frontier due to orders of magnitude lower energy of the microwave photons than far-infrared photons. In this thesis, we bring the performance of bolometers deep into the microwave regime. First, we study a gold-palladium-nanowire-based bolometer. We are able to decrease the NEP record down to 50 zW√Hz. By introducing a Josephson parametric amplifier to the measurement circuitry, we can further improve the NEP to 20 zW√Hz. Together with the low thermal time constant below 100 µs, this result indicates an energy resolution of 0.32 zJ. Second, we investigate graphene as a substitute for gold-palladium. Graphene is a promising candidate for bolometry due to its two-dimensional nature. We find NEP on par with the gold-palladium bolometer. Importantly, the thermal time constant with graphene is about two orders of magnitude shorter, which implies an energy resolution of 20 yJ, corresponding to the energy of a single 30-GHz photon.

AB - Superconducting quantum bits, or qubits, provide a promising platform for realizing large-scale quantum computers. As the number of qubits on a chip keeps increasing, so does the amount of required electronics and instruments needed for qubit control and readout. Eventually, it will be impossible to fit all the control lines into a cryostat. Therefore, there is an on-going effort to move the conventional room-temperature components into the lower-temperature stages. So-called Josephson junction is one of the fundamental building blocks used to realize these components in superconducting circuits. In this thesis, we study a particular type of a Josephson junction, a superconductor—normal-metal—superconductor junction. We experimentally measure its admittance at typical frequencies used in superconducting circuits. Furthermore, we show theoretically and experimentally that Josephson junctions can be used to realize one of the components aiding in scaling up quantum computers, a magnetic-flux-tunable phase shifter. The main topic of this thesis is bolometry. It is one of the oldest forms of thermal radiation detection invented over a century ago. Yet, it remains as a tool-of-choice in many applications ranging from consumer electronics to particle physics and astronomy. State-of-the-art bolometers have noise equivalent power (NEP) of 300 zW√Hz and can detect single 1.6-THz photons, which corresponds to the energy of 1.1 zJ. However, superconducting quantum computers utilize light at microwave frequencies in their operation. Thermal detectors have yet to reach this frontier due to orders of magnitude lower energy of the microwave photons than far-infrared photons. In this thesis, we bring the performance of bolometers deep into the microwave regime. First, we study a gold-palladium-nanowire-based bolometer. We are able to decrease the NEP record down to 50 zW√Hz. By introducing a Josephson parametric amplifier to the measurement circuitry, we can further improve the NEP to 20 zW√Hz. Together with the low thermal time constant below 100 µs, this result indicates an energy resolution of 0.32 zJ. Second, we investigate graphene as a substitute for gold-palladium. Graphene is a promising candidate for bolometry due to its two-dimensional nature. We find NEP on par with the gold-palladium bolometer. Importantly, the thermal time constant with graphene is about two orders of magnitude shorter, which implies an energy resolution of 20 yJ, corresponding to the energy of a single 30-GHz photon.

KW - bolometry

KW - cQED

KW - quantum computing

KW - bolometria

KW - kvanttilaskenta

KW - bolometry

KW - cQED

KW - quantum computing

M3 - Doctoral Thesis

SN - 978-952-64-0170-6

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Bolometric techniques for circuit quantum electrodynamics

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