Light-Matter Interaction and Quantum Computing in Rare-Earth-Ion-Doped Crystals Kinos, Adam

134 Pages·2017·18.35 MB·English

by  Adam Kinos

Light-Matter Interaction and Quantum Computing in Rare-Earth-Ion-Doped Crystals
Kinos, Adam
2018
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Citation for published version (APA):
Kinos, A. (2018). Light-Matter Interaction and Quantum Computing in Rare-Earth-Ion-Doped Crystals. [Doctoral
Thesis (compilation), Atomic Physics]. Atomic Physics, Department of Physics, Lund University.
Total number of authors:
1
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LUND UNIVERSITY
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Download date: 06. Feb. 2023
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Lund Reports on Atomic Physics, LRAP-543 (2018) 78 18
9

Light-matter interaction and
quantum computing in
rare-earth-ion-doped crystals
Adam Kinos
Doctoral Thesis
2018
Akademisk avhandling som f¨or avla¨ggande av teknologie doktorsexamen vid tekniska fakulteten vid Lunds Universitet
kommerattoffentligenf¨orsvarasden2mars2018,kl. 09.15iRydbergssal,p˚aFysiskaInstitutionen,Professorsgatan1,
Lund.
Fakultetsopponent: Dr. CharlesW.Thiel
MontanaStateUniversity,USA
Academicthesiswhich,byduepermissionoftheFacultyofEngineeringatLundUniversity,willbepubliclydefendedon
2ndofMarch2018,at09.15a.m. inRydberg’shall,attheDepartmentofPhysics,Professorsgatan1,Lund,forthedegree
ofDoctorofPhilosophyinEngineering.
Faculty opponent: Dr. CharlesW.Thiel
MontanaStateUniversity,USA
Organization Document name
LUND UNIVERSITY DOCTORAL DISSERTATION
Date of issue
Division of Atomic Physics January, 2018
Department of Physics
P.O. Box 118 Sponsoring organization
SE-221 00 Lund, Sweden

Author
Adam Kinos
Title and subtitle
Light-Matter Interaction and Quantum Computing in Rare-Earth-Ion-Doped Crystals
Abstract
In this thesis, crystals of yttrium orthosilicate (Y2SiO5) that are randomly doped with another rare-earth element, such as
praseodymium (Pr), europium (Eu), or cerium (Ce), are investigated with lasers locked to ultra-stable cavities using the
Pound-Drever-Hall locking technique.

Many of these rare-earth elements have long-lived 4f-4f transitions, hundreds of microseconds to a few milliseconds, with
even longer ground hyperfine lifetimes of up to several days. The coherence properties are, to the best of the author's
knowledge, the longest achieved for any material, currently with a record of six hours for the nuclear spin states of
Eu3+:Y2SiO5 measured at cryogenic temperatures. Furthermore, due to natural trapping and differences in the local
environments, each dopant ion experiences a slightly different crystal field, and thus an inhomogeneity in the 4f-4f
transition exists between all ions in a crystal. Since the homogeneous linewidth is in the order of kHz or below, whereas
the inhomogeneous profile can be several GHz wide, these materials have dense storing capabilities.

This thesis explores how light interacts with such rare-earth-ion-doped crystals; how the absorption and light polarization
varies during propagation; how spectral features in the inhomogeneous absorption profile can be tailored to create
narrowband spectral filters; how the speed of light is slowed down significantly in such narrow transmission windows;
and how that can be used to either frequency shift incoming light, control its group velocity, or temporally compress
pulses.

It also uses rare-earth-ions to research quantum computing, the field of using quantum mechanical effects such as
superpositions and entanglements to outperform classical computers on certain specific problems. This is done by
examining how two-color pulses can be used to rapidly induce coherence from an initially mixed state; how qubit-qubit
interactions can be performed experimentally using ensemble qubits, which opens the door to two-qubit experiments such
as the CNOT-gate and entanglements; how a scalable quantum computer might be constructed using a single ion qubit
approach with a dedicated readout ion and buffer ion(s) to improve readout fidelity; and how cerium is investigated as a
candidate for such a dedicated readout ion.
Key words:
Rare-earth-ion-doped crystals, Light-matter interaction, Quantum computing, Slow light
Classification system and/or index terms (if any):
Supplementary bibliographical information: Language
English
ISSN and key title: ISBN
ISSN 0281-2762, Lund Reports on Atomic Physics, LRAP-543 978-91-7753-543-0
Recipient’s notes Number of pages Price
219
Security classification

I, the undersigned, being the copyright owner of the abstract of the above-mentioned dissertation, hereby grant
to all reference sources permission to publish and disseminate the abstract of the above-mentioned dissertation.

Signature Date January 22nd 2018
Light-matter interaction and
quantum computing in
rare-earth-ion-doped crystals
Adam Kinos
Doctoral Thesis
2018
Light-matter interaction and quantum computing in rare-earth-
ion-doped crystals
'2018AdamKinos
Allrightsreserved
PrintedinSwedenbyMedia-Tryck,Lund,2018
DivisionofAtomicPhysics
DepartmentofPhysics
FacultyofEngineering,LTH
LundUniversity
P.O.Box118
SE–22100Lund
Sweden
http://www.atomic.physics.lu.se
ISSN: 0281-2762
LundReportsonAtomicPhysics,LRAP-543 (2018)
ISBN(print): 978-91-7753-543-0
ISBN(pdf): 978-91-7753-544-7
Abstract
In this thesis, crystals of yttrium orthosilicate (Y SiO ) that
2 5
are randomly doped with another rare-earth element, such as
praseodymium (Pr), europium (Eu), or cerium (Ce), are inves-
tigatedwithlaserslockedtoultra-stablecavitiesusingthePound-
Drever-Hall locking technique.
Many of these rare-earth elements have long-lived 4f-4f transi-
tions, hundreds of microseconds to a few milliseconds, with even
longer ground hyperfine lifetimes of up to several days. The co-
herence properties are, to the best of the author’s knowledge, the
longest achieved for any material, currently with a record of six
hoursforthenuclearspinstatesofEu3+:Y SiO measuredatcryo-
2 5
genictemperatures. Furthermore,duetonaturaltrappinganddif-
ferences in the local environments, each dopant ion experiences a
slightly different crystal field, and thus an inhomogeneity in the
4f-4f transition exists between all ions in a crystal. Since the ho-
mogeneous linewidth is in the order of kHz or below, whereas the
inhomogeneous profile can be several GHz wide, these materials
have dense storing capabilities.
This thesis explores how light interacts with such rare-earth-
ion-doped crystals; how the absorption and light polarization
varies during propagation; how spectral features in the inhomo-
geneous absorption profile can be tailored to create narrowband
spectral filters; how the speed of light is slowed down significantly
in such narrow transmission windows; and how that can be used
to either frequency shift incoming light, control its group velocity,
or temporally compress pulses.
Italsousesrare-earth-ionstoresearchquantumcomputing,the
field of using quantum mechanical effects such as superpositions
and entanglements to outperform classical computers on certain
specificproblems. Thisisdonebyexamininghowtwo-colorpulses
can be used to rapidly induce coherence from an initially mixed
state; how qubit-qubit interactions can be performed experimen-
tally using ensemble qubits, which opens the door to two-qubit
experiments such as the CNOT-gate and entanglements; how a
scalable quantum computer might be constructed using a single
iii
ion qubit approach with a dedicated readout ion and buffer ion(s)
to improve readout fidelity; and how cerium is investigated as a
candidate for such a dedicated readout ion.
iv
Popula¨rvetenskaplig
sammanfattning
Ljus-materia v¨axelverkan ¨ar n˚agot som finns ¨overallt: ljus gener-
eras i lampor; absorberas eller reflekteras av material; fokuseras
p˚a n¨athinnorna med hj¨alp av linserna i v˚ara ¨ogon; tapparna och
stavarna absorberar ljuset; och signaler skickas via synnerven vi-
dare till hj¨arnan s˚a att vi kan tolka v¨arlden runtom oss i f¨arger,
m¨orker, och ljus.
V¨aldigt kortfattat fungerar det enligt f¨oljande: det inkom-
mande ljusets sv¨angningar f˚ar atomernas elektroner att b¨orja
sv¨anga och skicka ut sitt eget ljus, som tillsammans med det
ursprungliga ljuset, likt tv˚a vattenv˚agor, kan sl¨acka ut eller
f¨orst¨arka varandra. Samtidigt kan atomerna absorbera energin
fr˚an ljusv˚agen och exciteras.
Denna avhandlingen handlar om hur ljus interagerar med ett
specifikt material, n¨amligen kristaller dopade med s¨allsynta jor-
dartsmetaller som, t.ex., praseodymium eller europium. S˚adana
atomer ¨ar intressanta att unders¨oka eftersom de har v¨aldigt
l˚anga livstider, vilket betyder att de kan vara exciterade en rel-
ativt (millisekunder) l˚ang tid innan de ˚ater faller tillbaka till
grundtillst˚andet, ibland genom att skicka ut nytt ljus.
Dedopadekristallernaunders¨oksianknytningtillkvantdatorer
som,ikontrastmedenvanligdatorvarsbitarendastkanvaranol-
lor och ettor, har kvantbitar som ¨aven kan vara i tillst˚and som ¨ar
b˚ade noll och ett samtidigt, s˚a kallade superpositioner. Man kan
s¨agaattenkvantdatorhartillg˚angtillflervalm¨ojligheterf¨orvarje
kvantbit. Dock, n¨ar man ska l¨asa ut vad en kvantbit ¨ar, f˚ar man
alltid antingen noll eller ett som svar, ¨aven om kvantbiten innan
man gjorde utl¨asningen var lite av b˚ada samtidigt. Detta betyder
att utl¨asningen av en vanlig bit och en kvantbit b˚ada inneh˚aller
endast en enhet av information (¨aven kallat en bit av informa-
tion). Vid f¨orsta anblicken kan man d¨arf¨or tro att en kvantdator
inte tillf¨or n˚agot som en klassisk dator inte redan har, men tack
varaenkvantdatorsf¨orm˚agaattanv¨andakvantmekaniskafenomen
s˚asom superpositioner och sammanfl¨atningar (engelska: entangle-
v