Abstracts from Invited Speakers
Keiji Ono (RIKEN)

A High-temperature Silicon Qubit and its Quantum Interference
Spin qubits are attractive building blocks for quantum computers. Si is a promising host material
for spin qubits since it could enable long coherence, high-density integration, and high compatibility
with classical computers. Spin qubits have been implemented in Si using gate-defined quantum dotsor shallow impurities. However, these qubits must be operated at temperatures <0.1 K, limiting the
expansion of qubit technology. We used deep impurities in Si to achieve room-temperature singleelectron tunnelling and spin qubit operation at 5–10 K [1]. We employed tunnel field-effect transistors(TFETs) instead of conventional metal–oxide–semiconductor field-effect transistors and achieved
strong confinement of the single quantum dots embraced in TFETs up to 0.3 eV. Furthermore, doublequantum-dot devices were operated as spin qubits, and read-out was realized using a spin blockade.
These results will enable broadening of the range of spin qubit applications such as sensing, security,and quantum computing.
We also study quantum interference eﬀects of a qubit whose energy levels are continuously
modulated [2]. The qubit energy levels are modulated via its gate-voltage-dependent g-factors, witheither rectangular, sinusoidal, or ramp radio-frequency waves. The energy-modulated qubit is probed
by the electron spin resonance. Our results demonstrate the potential of spin qubit interferometry thatis implemented in a Si device and is operated at a relatively high temperature.
[1] K. Ono, T. Mori, S. Moriyama, High-Temperature Operation of Spin Qubits based on Silicon
Tunnel Field-Effect Transistors, arXiv:1804.03364, Scientific reports, in print.
[2] K. Ono, S. N. Shevchenko, T. Mori, S. Moriyama, Franco Nori, Quantum interferometry with ahigh-temperature single-spin qubit, arXiv:1809.02326.
Sergei Studenikin (NRC)

Tunable Single-hole EDSR in a Lateral GaAs/AlGaAs Quantum Dot Device
Single holes are attractive for fundamental physics research and also for spin qubit applications
due to their unique properties as compared to electrons, for example, a reduced hyperfine interaction
to mitigate nuclear decoherence, a strong spin-orbit coupling for sub-nanosecond spin rotations usinggates, and the absence of valleys to completely eliminate the harmful qubit valley degeneracy
problem encountered in electron silicon qubits.
In my talk I will review our recent Electric Dipole Spin Resonance (EDSR) experiments on asingle hole confined in a lateral GaAs/AlGaAs double quantum dot (DQD) device described in Ref.
[1].

1

A single hole is confined in one of the dots with the Fermi level of the adjacent lead positioned
in between the Zeeman split spin states so the current through the DQD is energetically blocked. A
small microwave voltage is applied to a plunger gate to mediate hole EDSR to flip hole spin from thelower to the upper spin state above the Fermi level to allow the hole to exit to the lead. Spin resonanceis detected as a small current increase when the EDSR resonant condition is fulfilled. The g-factor
tunability is achieved by setting the DQD device in the very strong inter-dot coupling regime. The
Zeeman-split levels of the second axillary dot are used to tune the g-factor of the first dot by gate
detuning in the millivolt range. The axillary dot is never occupied and is employed as a vehicle totune the effective g-factor in the first dot via strong spin-dependent inter-dot tunnel coupling.
[1]

A. Bogan et al., Phys. Rev. Lett. 120, 207701 (2018).

Mona Berciu (University of British Columbia)

Using Polaronic Effects to Engineer the Dispersion and Effective Interactions of
Quasiparticles
The polaron which forms when a particle interacts with bosons from its environment isgenerically believed to be heavier than the original particle, and the boson-mediated effective
interactions between polarons are generically expected to be attractive. In my talk, I will highlight a
few examples where these expectations turn out to be wrong: polarons that are lighter than the bareparticles can form in the strong coupling limit, and boson-mediated interactions can also be repulsive,or attractive but with very unusual form. This proves that the quasiparticles' dispersion and effective
interactions can be suitably tailored by a careful engineering of their environment.
Ryuichi Ohta (NTT)

Mechanical Control of Localized Excitons: Strain-induced Coupling between
Dark and Bright States and Mechanical Control of Exciton Lifetimes
Ryuichi Ohta1, Hajime Okamoto1, Takehiko Tawara1,2, Hideki Gotoh1, Hiroshi Yamaguchi1
1

NTT Basic Research Laboratories, NTT Corporation,
NTT Nanophotonics Center, NTT Corporation,
3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198, Japan.
2

Mechanical strain has been employed to control the optical and electrical properties of solid-state
two-level systems instead of electric and magnetic fields. For instance, the exciton energies ofquantum dots [1] and the electron spins of nitrogen vacancy centers [2] have been controlled by thevibrational strains. In this talk, we demonstrate two alternative mechanical controls of exciton
dynamics. One is strain-induced coupling between dark and bright states, which enables one to2

optically address the long-lived dark excitons [3]. The other is mechanical modulation of exciton
lifetime [4]. We further investigate the back-action effect from excitons to the mechanical motion via
this dissipative process. These results open the way to manipulate the various solid-state two-levelsystems with microelectromechanical systems and acoustic devices.
[1] M. Montinaro et al., Nano Lett. 14, 4454 (2014).
[2] A. Barfuss et al., Nat. Phys. 11, 820 (2015).
[3] R. Ohta et al., Phys. Rev. Lett. 120, 267401 (2018).
[4] R. Ohta et al., Phys. Rev. B 99, 115315 (2019).
Paul Barclay (University of Calgary)

Diamond Opto-mechanical Devices for Coupling Photons, Phononsand Spins
Cavity opto-mechanical devices couple light to mechanical resonator motion via radiationpressure. By fabricating cavity opto-mechanical devices with low mechanical and optical dissipation,
combined with wavelength scale optical field confinement and resulting strong opto-mechanicalcoupling, it is possible to coherently transfer energy between photons and phonons in these systems.
Diamond devices offer the additional benefit incorporating colour centre spins useful for quantum
information processing. This talk will present our progress in using diamond opto-mechanical devices
for optical information processing (memory and switching) and for spin-opto-mechanics.
Takao Aoki (Waseda University)

Coupled-Cavities Quantum Electrodynamics
In a cavity quantum electrodynamics (QED) system, where atoms coherently interact withphotons in a cavity, the eigenstates of the system are the superposition states of atoms and cavity
photons, the so-called dressed states of atoms. When two cavities are connected by an optical fiberwith negligible loss, the coherent coupling between the cavities gives rise to photonic normal modes.
Here we demonstrate the setting of coupled-cavities QED, where two nanofiber cavity-QED systems[1] are coherently connected by a meter-long low-loss channel in an all-fiber fashion. Specifically,
we observe dressed states of distant atoms with delocalized photons of the ‘fiber-dark’ normal mode[2], as well as remote excitation and nonlocal saturation of atoms in the ‘cavity-dark’ normal mode
[3].
[1] S. Kato and T. Aoki, Phys. Rev. Lett. 115, 093603 (2015).
[2] S. Kato, N. Német, K. Senga, S. Mizukami, X. Huang, S. Parkins, and T. Aoki, Nature
Communications 10, 1038 (2019).
[3] D. White, S. Kato, N. Német, S. Parkins, and T. Aoki, submitted.
3Francois Sfigakis (University of Waterloo)

To be confirmed
Akira Oiwa (Osaka University)

Photon-spin Quantum Interface Using Gate-defined Quantum Dots
Communications using qubits entangled each other provide quantum internet for quantum key
distribution, secure access to remote quantum computers and other novel concepts of quantum
technologies. We are investigating the quantum repeaters based on photon-electron spin quantum
interface (Poincaré interface) consisting of gate-define quantum dots (QDs). The electron spins in thegate-defined GaAs QDs have a great potential for the quantum repeaters; coupling to polarization ofphotons at optical communication wavelength and long coherence time. The ingredient technologies
are quantum state conversion from single photons to single electron spins and the entanglement
conversion from photon pairs to electron spin pairs. In this talk, we present the recent experimental
progresses on the quantum state conversion in a gate-defined QD and the coincidence measurement
between single photo-electron detection in a QD and single photon detection using an entangled
photon source. Moreover the recent progresses on the enhancement of the coupling between photons
and electron spins in QDs and future prospects are discussed.
Satoshi Iwamoto (University of Tokyo)

Confinement of Light in Semiconductor Using Topological Concept
We will discuss topological localized states of light realized in semiconductor photonic crystal(PhC) platforms. We designed two topologically distinct PhC nano-beams and experimentallydemonstrated lasing oscillation using a topological localized mode at the interface between them. A
nano-cavity using a topological corner state in a 2D PhC slab will be also discussed.
Kin Fai Mak (Cornell University, USA)

Path Towards Exciton Condensation at High T emperatures
Excitons, composite Bosons made of Coulomb bound electron-hole pairs, are important objects
underlying the operations of many optoelectronics devices in our daily life. As a result of the muchsmaller exciton mass compared to that of atoms, they also hold great promise in the realization of
Bose-Einstein condensation at high temperatures. However, the small exciton binding energy inconventional semiconductors has so far limited the condensation temperature to below 1K. In the past
few years, a new class of two-dimensional (2D) semiconductors with much larger exciton binding
energy has emerged. In this talk, I will first discuss the measurement of the exciton binding energy
4

in these materials by optical spectroscopy methods. I will then tell you the path we have taken intrying to realize exciton condensation in these materials. Signatures of exciton condensation above
100 K have been observed in a recent set of experiments. Prospects of condensate-based
optoelectronics and exciton-mediated high-temperature superconductivity will also be discussed.
Ryota Negishi (Osaka University )Anomalous Electrical Transport Properties of Multilayer Graphene with Turbostratic Stacking Fabricated by CVD on Graphene Templates
Ryota Negishi1 and Yoshihiro Kobayashi1
1Osaka University

The multilayer graphene with a turbo-stratic stacking has weak interlayer coupling, resulting inpreserving linear dispersion relation similar to monolayer graphene. This unique feature is completely
different from the usual AB stacking graphene, and enables us to expect to emerge exotic quantum
properties beyond graphene in addition to the excellent performance of monolayer graphene.
Although theoretical researches have predicted anomalous electrical properties due to the pseudolinear dispersion, the precise control of the layer numbers and the stacking structures have remained
as critical issues for fabricating the turbo-stratic graphene. In this study, we successfully fabricatedthe turbo-stratic graphene using chemical vapor deposition (CVD) at high temperature. The highly
crystalline graphene multilayer was grown on a monolayer graphene template. The turbo-stratic
stacking was confirmed by a variety of structural analysis such as Raman spectroscopy, scanningtransmission electron microscopy and reflection high energy positron diffraction. In the analysis ofelectrical transport, the turbo-stratic graphene exhibits higher conductivity and carrier mobility thanthe monolayer template graphene. These improved carrier transport properties are originated fromthe pseudo-linear dispersion and the screening effect for the charge impurities on the substrate. The
quasi-monolayer characteristics clarified here lead us to investigate the quantum transports in theturbo-stratic graphene such as half-integer quantum Hall effect.
Mark Freeman (University of Alberta)

Hybrid Nanomagnetic-nanomechanical Systems
Nano-cavity opto-mechanics dramatically extends the capabilities of sensors based on nanomechanical displacement detection. Our group and collaborators have been developing hybrid nanomagnetic-nano-mechanical systems as mechanical torque-based probes of magnetism. Particularfeatures of the approach include Einstein - de Haas torque as a general purpose tool at radio
frequencies, and mechanical detection of spin resonance. The present measurements are far fromquantum-limited, suggesting the promise of further development of hybrid spin-mechanical systems.
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Junko Ishi -Hayase (Keio University)

Quantum Protocols for AC Magnetic Field Sensing using Nitrogen-vacancy
Centers in Diamond
Electric spin of negatively-charged nitrogen-vacancy (NV) centers in diamond are utilized forhighly-sensitive nanoscale quantum sensor at room temperature [1]. In this study, we propose anddemonstrate two quantum protocols for highly-sensitive AC magnetic field sensing using NV center
ensemble in diamond.
One of the proposed protocol is effective to improve the sensitivity for vector magnetic fieldsensing by multi-frequency control of electric spins of NV centers. The key idea is that four types of
NV centers with different axes are simultaneously controlled by multi-frequency microwave pulses[2, 3]. Another protocol enables us to detect high-frequency (MHz range) AC magnetic field with
continuous application of microwave and laser. This method fully utilizes spin-1 properties ofelectron spins of NV centers [4].
This work was done in collaboration with Dr. Matsuzaki, Dr. Watanabe (AIST), Dr. Saito, Dr.
Kakuyanagi (NTT BRL), Prof. Mizuochi (Kyoto Univ.), Prof. Itoh and Hayase Laboratory members(Keio Univ.). This work was supported by JSPS KAKENHI (Grant No. 15K17732) and MEXT
KAKENHI (Grants No. 18H01502, 15H05868, 15H05870, 15H03996, 26220602, and 26249108),and Spin-NRJ.
Kazuhiko Hirakawa (University of Tokyo)

Terahertz Dynamics of Electron-vibron Coupling in Single Molecules with
Tunable Electrostatic Potential
K. Hirakawa1 and S. Q. Du1
1

Institute of Industrial Science and INQIE, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo
153-8505, Japan
Clarifying electronic and vibronic properties of individual molecules provides key insights tofuture tailor-made medicine, chemistry, nanoelectronics, and quantum information technologies.
Terahertz (THz) spectroscopy has been developed as a powerful tool for clarifying vibrational
dynamics of various kinds of molecules. Because of the long-wavelength nature of the THz
radiation (typically, ~100 microns), however, spectral information was obtained only for ensemble
average of a huge number of molecules. It has been a formidable challenge to overcome thediffraction limit and focus THz radiation on a single molecule. Furthermore, the number of mobile
charges that can absorb THz radiation in a single molecule is very few, which makes THz absorption
by a single molecule extremely small.
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Here, we report on the THz spectroscopy of single molecules by using the single molecule
transistor (SMT) geometry [1]. Using the source and drain electrodes separated by a sub-nm gap as
a THz antenna [2], we focused the THz radiation onto a single fullerene molecule trapped in the
nanogap electrodes and measured THz-induced photocurrent in the SMT. A great advantage of thepresent SMT geometry is that the electrostatic potential and the number of electrons on the moleculecan be precisely controlled. We have observed low energy vibrational modes due to the center-ofmass nanomechanical motion of the fullerene molecule. Furthermore, we found that the observed
peaks are finely split into two, reflecting the difference in the van der Waals potential profile
experienced by the molecule on the metal surface when the number of electrons on the molecule
fluctuates by one during the single electron tunneling process. Such an ultrahigh-sensitivity to theelectronic/vibronic structures of a single molecule upon adding/removing a single electron has beenachieved by using the THz spectroscopy in the SMT geometry. This SMT scheme provides a novel
opportunity for investigating ultrafast THz dynamics of sub-nm scale systems.
[1] S. Q. Du, K. Yoshida, Y. Zhang, I. Hamada, and K. Hirakawa, Nature Photonics 12, 608 (2018).
[2] K. Yoshida, K. Shibata, and K. Hirakawa, Phys. Rev. Lett., 115, 138302 (2015).
Amr Helmy (University of Toronto)

Integrated Photonic Paradigms which Enable Emerging Quantum Technologies
In this talk I plan to overview the capabilities of an intergraded photonics platform in the context
of enhancing quantum photonics functionality and integration density on chip. A platform based on
active and passive compound semiconductors, where battery operated source of photon pairs and thecircuitry that prepared quantum states generated from these sources to benefit applications in quantum
sensing will be reviewed.
Yuichiro Matsuzaki (AIST Tsukuba)

Quantum Remote Sensing with Asymmetric Information Gain
Quantum technology technologies enable high precision sensing. In the future, people might use
the quantum sensor located at a distant place via internet. A client-server model describes such a
circumstance. The client needs to measure target fields from a sample, but he/she does not have asensitive field sensor. The client delegates the sensing task to a remote server with a high-precision
sensor. The server honestly obeys every instruction from the client. The server measures the sample,
sends the information to the client, and returns the sample to the client. However, if the server’s sensor
is stolen by eavesdroppers after the protocol, the information stored in the sensor can be leaked,
because classical information is inerasable. To overcome the problem, we will introduce a novel
quantum sensing scheme with a security in build. Interestingly, there is an asymmetric information

7

gain where the amount of achievable information at the client side can be much larger than that of
the server side. This guarantees the security even if the sensor of the server is stolen.
[1] M. Doherty, et al., Phys. Reports, 528, 1 (2013).
[2] S. Kitazawa, et al., Phys. Rev. A 96, 042115 (2017).
[3] K. Yahata, et al., Appl. Phys. Lett. 114, 022404 (2019).
[4] S. Saijo, et al., Appl. Phys. Lett. 113, 082405 (2018).
Jack Sankey (McGill University)
Spin Transfer Controlled Magnetic Dynamics Probed with a Single Bulk NV Spin
The point-like nature and exquisite magnetic field sensitivity of bulk nitrogen vacancy (NV)centers can be used to gain new insights into the inner workings of spintronic and magnetic nanocircuits. We fabricate a spin transfer (ST) controlled magnetic nanowire upon a single crystal
diamond substrate containing NVs embedded tens of nanometers below the surface. By probing the
nanowire's stray field with a nearby NV spin, we observe unambiguous evidence of ST tuned,parametrically pumped, large-angle magnetic oscillations, and demonstrate how these oscillations
can directly drive NV spin transitions. We also use the NV as a local noise thermometer, observing
strong ST damping of the stray field noise, consistent with magnetic cooling from room temperatureto ∼150 K (a lower temperature than previously reported, likely due to the high power handling of
the diamond substrate).
Shintaro Nomura (Tsukuba University)

Wide-field Imaging of Microwave with Nitrogen-vacancy Center Ensembles in
DiamondMicrowave imaging has been performed either by using a scanning dipole antenna or a dipole
array for imaging in the mm-scale resolution. There have been difficulties, however, in higher
resolution imaging due to sensitivity and the mutual coupling that is present when an array is used.
Wide field imaging of microwave using ensembles of nitrogen-vacancy (NV) center ensembles indiamond offers high resolution-imaging in the micro- and nano-scale, avoiding the mutual coupling.
In this talk, we will present our results of quantitative imaging of microwave field distribution by
driving the Rabi oscillations of the NV electronic spin. We measured microwave field distribution in
the vicinity of micrometer-sized non-fed antenna structures. The obtained microwave images revealthat the microwave field amplitude (intensity) is enhanced by a factor of 21.5 (462) near a
micrometer-sized antenna structure. Our method may contribute to local control of quantum spins,
evaluation of microwave devices, and microwave bio-imaging.

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Mikio Eto (Keio University)

Physics in Double Quantum Dot in Parallel
I will talk about two topics: (i) The Kondo effect is theoretically examined in one of the quantum
dots when the other has a broad linewidth. This is a tractable model for the quantum dot interferometer,
an Aharonov-Bohm ring with an embedded single quantum dot. We find an asymmetric Fano-Kondo
resonance or conventional Kondo plateau, depending on the number of conduction channels in theleads. (ii) The photocurrent is examined through identical quantum dots in parallel, under theirradiation of the terahertz (THz) light. The THz light induces the excitation of an electron from anenergy level below the Fermi level to that above the Fermi level, which results in the electric current
in the presence of asymmetry of tunnel couplings for the associated energy levels. We propose asensitive THz detector by the Dicke effect, a reverse process of "superradiance".
Moritz Cygorek (University of Ottawa)

Million-atom Simulations of InAs/InP Nanowire Quantum Dots and Quantum
Dot Arrays
The growth of quantum dots in nanowires allows a precise control of their sizes and shapes.
Moreover, multiple dots can be grown within the same nanowire, which enables studies of quantum
dot molecules or arrays and might ultimately lead to solid state implementations of synthetic Haldane
chains with symmetry protected topological ground states. We present recent advances in modelling
InAs/InP nanowire quantum dots in the wurtzite phase using the tight-binding and configurationinteraction tool QNANO involving calculations of about a million atoms and we show how thegeometry, the As concentration and the randomness of alloying influence the excitonic andmultiexcitonic spectra.
Michihisa Yamamoto (RIKEN Center for Emergent Matter Science)

Measurement of the Kondo Cloud Length
Kondo effect arises due to the interaction between a localized magnetic moment and surrounding
conducting electrons. In the Kondo ground state, the localized magnetic moment is screened byformation of a Kondo cloud, known as a spatially extended many-body singlet state between thelocalized magnetic moment and many conducting electrons. Since the Kondo cloud has a finite size𝜉𝐾 , universal scaling of the Kondo effect by the dimension of the system has been theoreticallyinvestigated. However, detection of the Kondo screening length as well as the corresponding
universal scaling has been elusive. We perform experiments on detection of the Kondo screening
length using a quantum dot containing a localized electron spin coupled to a one-dimensional FabryPerot interferometer. The Kondo temperature is modified by the density of states in the interferometer9when the interferometer length L is smaller than 𝜉𝐾 . We find both theoretically and experimentallythat the modified Kondo temperature normalized by the Kondo temperature without theinterferometer shows a universal scaling and depends only on L/𝜉𝐾 .
Eva Dupont-Ferrier (University of Sherbrooke)

Hybrid devices: Interfacing Spins in Silicon with Superconducting Resonators
Hybrid systems between superconducting circuits and spins acting as a quantum memory havebeen explored [1]. In this context spins of Bismuth appears as a very good candidate as they exhibit
exceptionally long coherence times (up to 2.7 s) and a narrow spin linewidth of 270 kHz when placedin 28 Si [2] and when placed under magnetic field of 26 mT, at the so-called clock transition. Tuning
the frequency of superconducting resonator to bring in and out of resonance with the spin is an
important requirement. We report on magnetic field and SQUID tuning of the superconducting
resonators made out of Nb, able to withstand magnetic field required to reach the Bi clock transition[3]. Tunability up to 100 MHz while maintaining quality factors of 10000 has been observed, opening
the way for coherent transfer between the Bi spins and superconducting circuits.
[1] Kubo et al Phys. Rev. Lett. 107, 220501 (2011); Zhu et al. Nature 478, 221 (2011); Schuster et al.
Phys. Rev. Lett. 105, 140501 (2010); Bienfait et al. Nature 531, 74 (2016); Tosi, et al. Nature Comm.
8, 450 (2017).
[2] Wolfowicz et al. Nature Nanotechnology 8, 561 (2013).
[3] Kennedy et al. Phys. Rev. Applied 11, 014006 (2019).
Marek Korkusinski (NRC)

Interaction of Nuclear and Electron Spins in a Hybrid Quantum System
M. Korkusinski1 and Hawrylak2
12

National Research Council, Ottawa, K1A 0R6, Canada,
Physics Department, University of Ottawa, Ottawa, K1N 6N5, Canada.

There is currently interest in hybrid quantum systems combining electrons and nuclear and/or
localized impurity spins due to their long coherence times [1-4]. These localized spins could be
utilized as a resource in quantum information provided that they can be manipulated with spins ofelectrons. The major problems with the hyperfine coupling to nuclear spins are a) the microscopic
understanding of the coupling of valence electrons to nuclear spin, and b) matching the energy to flip
the electron spin with the corresponding energy to flip the nuclear spin. Here we start with a theoryof the interaction of a nuclear spin with the domain wall formed by the spins of electrons in a twodimensional electron gas confined in an InSb quantum well and in a weak lateral parabolic
10

confinement [5]. The formation of spin domains in this quantum Hall ferro-magnet [4] is madepossible by the degeneracy of subsequent Landau levels with opposite spins, brought about by thelarge g factor of InSb. We map out the energy structure of the droplet from the spin singlet =2 phaseto the fully spin-polarized phase involving two Landau levels. We show that any state with anintermediate spin polarization contains a well-defined domain wall, separating the spin-polarized
droplet in the center and spin-unpolarized outer region of the charge density. The electron spinnuclear spin interaction is modeled by the hyperfine interaction and therefore depends strongly on
the relative position of the impurity and the domain wall. We demonstrate that energy needed to flip
one electron spin, i.e., to move the domain wall by one orbital, and the Zeeman splitting of the nuclear
spin states are of the same order, enabling manipulation of the nuclear spin by electrical means.
[1] Y. Hirayama, G. Yusa, K. Hashimoto, N. Kumada, T. Ota, and K. Muraki, Semicond. Sci. Technol.
24, 023001 (2009).
[2] A. H. Trojnar, M. Korkusinski, M. Potemski, and P. Hawrylak, Phys. Rev. B 85, 165415 (2012);[3] H. W. Liu, K. F. Yang, T. D. Mishima, M. B. Santos, and Y. Hirayama, Phys. Rev. B 82, 241304(2010).
[4] E. H. Rezayi, T. Jungwirth, A. H. MacDonald, and F. D. M.Haldane, Phys. Rev. B 67, 201305(2003).
[5] M. Korkusinski, P. Hawrylak, H. W. Liu, and Y. Hirayama, Scientific Reports 7, 43553 (2017).

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Abstracts from Poster Presenters
Yunhui Wu (Tokyo University)

Experimental Investigation of Size Effect on Surface Phonon
Polaritons on SiN Submicron Membranes
Thermal conduction becomes less efficient as structures scale down into
submicron sizes since phonon -boundary scattering becomes predominant and impede
phonons more efficientl y than Umklapp scattering. Recent studies indicated that thesurface phonon polar itons (SPhPs), which are the evanescent electromagnetic waves
generated by the hybridization of the optical phonons and the photons andpropagating at the surface of a polar dielectric material surface, potentiall y serve as
novel heat carriers to enhance t he thermal performance in micro - and nanoscale
devices. We study the condition of SPhPs existing in a dielectric submicron filmwith a broad frequency range. The calculation of SPhPs thermal conductivit y basedon Boltzmann transport equation (BTE) demonstr ates that the heat flux carried by
SPhPs exceeds the one carried by phonons. We also conduct a time -domain-thermalreflectance (TDTR) measurement of SiN submicron films and demonstrate that thestronger the in-plane thermal conductivity enhancement exists at high temperaturesby decreasing the film thickness, potentiall y due to the contribution of the SPhPs.
The results presented here have future applications in the field of heat transfer,thermal management, near -field radiation and polaritonics.
Motoi Takahashi (NRC, Tohoku University)

EDSR of a Single Heavy Hole in a Lateral GaAs/AlGaAs Double
Quantum Dot Device
Motoi Takahashi1,2, Sergei Studenikin1, Guy Austing1, Alex Bogan1, Louis Gaudreau1, Marek
Korkusinski1, Piotr Zawadzki1, Yoshiro Hirayama2, and Andy Sachrajda1
1
2

Emerging Technologies, National Research Council of Canada, Ottawa, Canada
Department of Physics, Tohoku University, Sendai, Japan.

Single holes are attractive as spin qubits due to their advantageous properties
which include a redu ced hyperfine interaction, a strong spin -orbit coupling for sub nanosecond spin rotations, and the absence of valley complications. Here we report
single hole electric dipole spin resonanc e (EDSR) measurements over the 1 0-50 GHz
range taking advantage of t he strong spin -orbit coupling. The experiment isperformed in a GaAs double quantum dot device described in [1] tuned in such way
12that strong hybridization of the single dot orbitals occurs leading to the formationof quantum molecular states and onl y one of the dots contains a single heavy holewith the Fermi level of the adjacent lead positioned in between the Zeeman split
spin states. We first show the high bias transport characteristics and the magnetic
field dependence of states in the single -hole regime. A new signal due to EDSR isobserved on application of micro -waves when the current is energy blockaded. The
frequency of the EDSR signal is found to shift linearl y with magnetic field and weshow that the effective g -factor can be electricall y tuned i n the range of 30% by asmall change of gate voltage. Because of the strong spin -orbit interaction, we areable to realize a tunable hybrid spin -charge system. As a function of dot detuning,
the EDSR signal can be continuousl y changed from being mostly spi n-like to chargelike.
[1] A. Bogan et al., Phys. Rev. Lett. 120, 207701 (2018).
Kanta Asakawa (Yokohama National University)

Nanoscale Phase Change on Ge 2 Sb 2 Te 5 Induced by Laser-driven STM
Kanta Asakawa 1 , Shotaro Yaguchi 1 , Katsumasa Yoshioka 1 , Ikufumi Katayama 1 ,Yusuke Arashida 1 , 2 , Shoji Yoshida 2 , Hidemi Shigekawa 2 , Masashi Kuwahara 3 ,and Jun Takeda 1
1

Yokohama National University,
University of Tsukuba,
3
National Institute of Advanced Industrial Science and Technology (AIST)2

Ge 2 Sb 2 Te 5 , which is a layered chalcogenide, is attracting interest for its
topological band structure [1] and its light -induced phase change which can beutilized for future application for chalcogenide superlattice memory devices. In
conventional optical storage dev ices, the capacit y was determined by the markdiameter (~150 nm) which is governed by the wavelength of the laser. In the present
study, we demonstrate that the near -field light generated by focusing laser pulses
onto the STM tip can be utilized for produc ing few-nanometer-sized amorphousmarks on Ge 2 Sb 2 Te 5 surfaces.
[1] Paul y et al., Appl. Phys. Lett. 103, 243109 (2013).
[2] Yu et al., Scientific Reports 5, 12612 (2015).

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Kazuya Saso (Keio University)

Fabrication and Evaluation of Stacked Quantum Dots Embedded in
Fabry-Pérot Resonator for Improving Photon Echo Generation
Efficiency
Kazuya Saso 1 , Ryutaro Ide 1 , Kouichi Akahane 2 , and Junko Ishi -Hayase 1
1School of Fundamental Science and Technology, Keio University, 3 -14-1 Hiyoshi,
Kohoku-ku, Yokohama, Kanagawa 223 -8522, Japan
2
National Institute of Information and Communications Technology (NICT), 4 -2-1
Nukuikitamachi, Koganei, Tokyo 102 -8544, Japan
Photon echo (PE) technique combining quantum dot (QD) ensemble is a powerfultool for implementing quantum interface with a large (10 THz) bandwidth. Recentl y,
our group succeeded in a coherent transfer of broadband (1 THz) optical pulses atthe single photon level by using PE technique in highl y -stacked InAs QDs. However,PE generation efficiency was e xtremel y low, because the efficiency is limited by
low absorption of QD sample. In this presentation, we report on the improving PE
generation efficiency from an ensemble of QDs embedded in Fabry –Pérot resonator.
By performing numerical calculations, we de signed an optimum sample structure to
maximize absorption coefficient with keeping large (1 THz) bandwidth. We
fabricated a sample including 50 layers of InAs QDs sandwiched between
InP/ InGaAlAs and TiO 2 /SiO 2 DBRs. It is found that the absorption coefficie nt of
the fabricated sample is increased more than 5 times as bare QDs (150 layers). As aresult, PE efficiency can be increased by an order of magnitude compared with that
in QDs (150 layers) without resonator. This work was supported by MEXT
KAKENHI (Grants No. 15H05868,), and Spin -NRJ. The samples were fabricated at
Advanced ICT Device Laboratory, NICT.
Hiroyasu Yamahara (University of Tokyo)

Flexoelectricity and Magnetism in Strain-gradient Rare-earth Iron
Garnet Thin Films
Hiroyasu Yamahara 1 , Sarker Md Shamim 1 and Hitoshi Tabata 1
1

University of Tokyo, Tokyo, Japan

Rare-earth iron garnets (R IGs) are ferrimagnetic insulators whose chemical
formula is R 3 Fe 5 O 1 2 (R: rare-earth elements). They have been industriall y available
14

for optical devices such as optical isolators since they show large magneto -opticaleffect. On the other hand, they are unlikely to show remnant dielectric polarizationin bulk, because their crystal structures are centrosymmetric cubic. If remnant
magnetization and dielectric polari zation co-exist in R IGs, multiferroic behaviors
and magneto-electric correlation (ME -effect) are expected, which is promisingmaterial for future application on spintronics devices. In this research, Sm 3 Fe 5 O 1 2(SmIG) films are grown on Gd 3 Ga 5 O 1 2 (GGG) substrates by a pulsed laser deposition.
The lattice mismatch between SmIG and GGG is −1.2%, so that the critical thickness
where misfit dislocation occurs is estimated to be 60 nm. Sm IG films grown on GGG
show tetragonal, strain -gradient, and cubic struct ures from the interface to thesurface due to the epitaxial strain and the lattice relaxation. In the strain -gradientregion, the inhomogeneous strain can generate flexoelectric polarization,

Pflexo   (u x) , where  and (u x) are flexoelectric tensor and strain -gradient,
respectivel y. The inhomogeneous atomic displacement and the presence of dielectric
polarization in the strain -gradient region are confirmed by a scanning transmission
electron microscopy (STEM) and a scanning nonlinear dielectric microscopy(SNDM), respectively. We conclude that remnant magnetization and dielectric
polarization co -exist in strain -gradient SmIG film, and the strain -engineering is oneof the possible approaches to creat e novel multi -functional materials.
Chaopeng Wei (Osaka University)

Improvement of Carrier Transport Properties in Multilayer Graphenewith Turbostratic Stacking Structure
Chaopeng Wei,1 Ryota Negishi,1 Yui Ogawa,1 Yoshitaka Taniyasu1 and Yoshihiro Kobayashi1
1Osaka University, Osaka, Japan

Graphene is attracting people’s attention with its extremely high carrier mobility, which resultsin the promising potential for device applications. However, the electrical transport properties of themonolayer graphene are degraded by such surrounding environments as charge impurity and surface
roughness on a substrate due to the thickness of a single carbon atom sheet. In order to overcome theissue, the turbostratic multilayer graphene (TMG) was synthesized by graphene layer growth on themonolayer graphene template. Conductivity of the TMG shows higher values than that of themonolayer graphene, meaning that the carrier scattering due to the charge impurities on the substrateis efficiently suppressed by the screening effect of the multi-stacking. Furthermore, the temperaturedependence of the sheet resistance in the TMG is closer to that of the sheet resistance in monolayer
graphene. This indicates that the TMG with a relatively weak interlayer coupling forms the linear
dispersion similar to monolayer graphene. The screening effect and pseudo-linear dispersion in the15

TMG result in higher carrier mobility as a comparison with monolayer graphene. This result meansthat the synthesized TMG has the potential to become an effective material to produce the device
application with high electrical performance.
Toru Tomimatsu (Tohoku University)

Scanning Gate Experiment of Filling factor-dependent Incompressible
Phase in Quantum Hall System
The quantum Hall system (QHS) is characterized by the universal quantizationof resistance under a strong magnetic field, where the localization of electronic
states plays an important role. Scanning gate microscopy (SGM) is one of thepowerful tools for probing microscopic structures in QHS due to its high spatial
resolution. This technique allows us to approach the local electron scattering event
by mapping the global resistance as a function of local potential perturbation. Here,
we show the SGM imaging of incompressible (IC) phases in QHS by modifying therate of el ectron tunneling through the IC phases under non -equilibrium conditions.
We assess the filling factor dependence of SGM patterns to discuss its relation to
the formation of IC phases in non -dissipative QHS regime.
Koji Ishibashi (RIKEN)

Physics and Devices with Nanoscale Hybrid Systems: Research Overview ofAdvanced Device Laboratory in RIKEN
Koji Ishibashi1,2, Russell S. Deacon1,2, Keiji Ono1,2, Akira Hida1, Tomohiro Yamaguchi1, andMasashi Nantoh1
1

Advance Device Laboratory, and 2Center for Emergent Matter Science (CEMS), RIKEN, 2-1,
Hirosawa, Wako, Saitama 351-0198, JapanWe are interested in quantum devices to control and manipulate electrons, spins, photons,
excitons and cooper pairs in hybrid quantum structures. Current projects are,
1) Nanofabrication of quantum structures based on the carbon nanotubes and atom manipulations(Hida, Yamaguchi and Nantoh)
2) High temperature spin qubits with Si nanoscale transistors (Ono)3) Superconductor/topological insulator hybrid structures to study Andreev and Majorana states(Deacon)A brief outline will be presented in our poster.

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Alex Bogan (NRC)

Theory of Gate-Tunable Single-Hole EDSR in a Lateral GaAs/AlGaAs
Double Quantum Dot
Aviv Padawer-Blatt1, Marek Korkusinski1, Jordan Ducatel1, Motoi Takahashi1,2, Sergei
Studenikin1, Guy Austing1, Alex Bogan1, Louis Gaudreau1, Piotr Zawadzki1, Yoshiro
Hirayama2, and Andy Sachrajda1
1
2

Emerging Technologies, National Research Council of Canada, Ottawa, Canada
Department of Physics, Tohoku University, Sendai, Japan

We theoretically study the tunability of the single-hole effective g-factor corresponding to thespin energy gap in a GaAs/AlGaAs double quantum dot. A significant tuning over a small range ofgate voltages is predicted. Also, tuning of the effective g-factor can be engineered by changing themagnetic field and the inter-dot coupling. The effective g-factor directly quantifying the Zeeman
splitting energy is extracted from data by fitting the position of the electric dipole spin resonance(EDSR) signal as a function of dot detuning and microwave frequency at constant magnetic field.
Furthermore, we are able to demonstrate that the effective g-factors for the two dots differ slightly invalue by ~5%. The ability to simultaneously extract the spin-conserving, tN, and spin-flipping, tF,
tunneling matrix elements from the characteristics of the EDSR signal enables us to map the behavior
of tN and tF over a wide range of magnetic field for different inter-dot couplings. Our theory accurately
reproduces key features of the experimental data.
Jason Phoenix (NRC)

Full Polarisation Control of Fibre -delivered Light in a Dilution
Refrigerator
While quantum repeaters have often been imagined in an all-optical scheme involving Bell statemeasurements at a beam splitter, we propose a novel type of quantum repeater which combines thelong-distance advantages of photonic qubits with the long memory and manipulation capabilities ofspin qubits in semiconductor quantum dots. This ‘photon-to-spin’ quantum repeater would enable theheralded transfer of quantum information from a photonic qubit to a spin qubit, which could then be
stored, manipulated and read out. Photonic qubits in this scheme could be encoded in the polarization
state of photons, which would be transmitted to their destination via optical fibre. Standard fibres,
however, have birefringent cores which alter the polarization state of the light they transmit and may
even cause random variations in the polarization over time. As part of our attempt to create a photonto-spin system, we have therefore developed a method of fully controlling the polarization of lightsent through a fibre and have demonstrated our ability to deliver arbitrary polarization states to ourdilution refrigerator, which operates at milli-kelvin temperatures. Monitoring the polarization over17

time has revealed that our system is highly stable and can deliver high-fidelity polarization states tothe fridge over a period of several days.
David Northeast (NRC)

Integrating Quantum Dot Nanowires with Integrated Photonic
Circuits
Future quantum technologies such as quantum computing and encryption will benefit fromefficient and on-demand sources of quantum states. Semiconductor quantum dots have proven to be
excellent sources of both single photon and entangled pair quantum states. Controlled incorporationof previously characterised quantum dots into integrated photonic circuits can provide bright lightsources for experiments in optical quantum computing and metrology. We report on our progress
towards integrating InAsP quantum dots in InP nanowires with SiN ridge waveguide structures.
Photoluminescence and second order correlation measurements are made before and after integration
to compare the effects of transferring using a nano-manipulator probe system.
Patrick Laferriere (NRC)

Multiplexed Single Photon Source from Quantum Dots Embedded in
Nanowires
Optical-based information technologies require efficient sources of single photons and entangled
photon pairs at high emission rates. Quantum dots embedded in nanowire waveguides havedemonstrated high purity single photon and high fidelity entangled photon pair generation. Ultimate
repetition rates, however, are limited by transition lifetimes of ~1ns. The selective-area vapor-liquidsolid epitaxial growth process allows for the integration of multiple quantum dots in the same
nanowire waveguide coupled to the same optical mode. In this study we demonstrate such a multidot system. In particular, we show bright single photon emission from five quantum dots embedded
in a single nanowire.
Jacques Lefebvre (NRC)High Purity Semiconducting Single -walled Carbon Nanotubes: A Key
Material for Emerging Electronics
Carbon nanotubes of semiconductor type (sc-SWCNT) sit amongst the most promisingnanomaterials for a new generation electronic devices. Numerous laboratory demonstrations reveal
the potential of sc-SWCNTs for logic circuits, radio-frequency devices, radiation hard memories, andsensors of all types on conventional substrates or flexible and stretchable surfaces. Progress towards
commercial applications is combined with challenges related with materials development and its
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characterization, fabrication methods together with device modeling. I will describe recent
improvements in sc-SWCNT material’s quality which are the foundation of application prototypes inboth large area printable electronics and high density integrated circuits.
Paul Finnie (NRC)

Intensity and the Environment: Simultaneous Photoluminescence
Emission and Phonon Scattering from Individual ( n, m) Air Suspended
Single Walled Carbon Nanotubes
Paul Finnie1, Yuichiro Tanaka2, and Yoshikazu Homma2
1

Security and Disruptive Technologies Research Centre, National Research Council Canada, 1200
Montreal Road, Ottawa, ON, Canada, K1A 0R6
2
Department of Physics, Tokyo University of Science, Shinjuku, Tokyo 162-8601
Single walled carbon nanotubes (SWCNTs) are ideal one dimensional materials. The electronic andexcitonic states of SWCNTs are strongly changed by molecular adsorbates from the surrounding
atmosphere. Water-adsorbed SWCNTs have different excitation and vibrational spectra than desorbed
SWCNTs. The intensity of Raman scattering (RS) and photoluminescence (PL) emission fromsemiconducting SWCNTs is changed by changes in molecular adsorbates on and in SWCNTs. Here
we perform optical spectroscopic measurements on pillar suspended chemical vapor deposition(CVD) grown SWCNTs in a controlled atmosphere environment. We identify individual (9,8) and(12,1) SWCNTs and compare their adsorbed and outgased PL and RS spectra, measured
simultaneously. We show that the RS and PL intensities are affected differently by molecularadsorption. We explore how this difference can be rationalized using simple models of the quantum
mechanical matrix elements for RS and PL processes.
Khabat Heshami (NRC)

Coherent Storage Based on Dynamical Autler -Townes Splitting
Photonic quantum information technologies rely on quantum memory for long-lived storage andcoherent manipulation of short pulses of non-classical light. The optical quantum memories exploredover the past two decades are based on various coherent light–matter interaction schemes, but despite
impressive progress, practical memories featuring efficient, broadband and long-lived operation
remain elusive, due to the technical demands and inherent limitations of the established schemes.
Here, we introduce a technique for high-speed quantum memory and manipulation that overcomes
these obstacles. This scheme relies on dynamically controlled absorption of light via the ‘Autler–
Townes effect’, which mediates reversible transfer between photonic coherence and the collective
ground-state coherence of the storage medium. We experimentally demonstrate proof-of-concept
19storage and signal processing capabilities of our protocol in a laser-cooled gas of rubidium atoms,
including storage of nanoseconds-long single-photon-level laser pulses for up to a microsecond. Thisapproach opens up new avenues in quantum optics, with immediate applications on atomic and solidstate platforms.
Philip Bustard (NRC)

THz-bandwidth All-optical Switching of Heralded Single Photons
Connor Kupchak, Jennifer Erskine, Duncan G. England, and Benjamin J. Sussman
NRC, Canada
The ability to switch single photons rapidly, without introducing quantum noise, is important for
applications in quantum technologies and optical gating. We present an ultrafast Kerr-gate techniquein optical fibre, which allows picosecond-duration single photons to be switched with efficiencies of
up to 97%.
Yasser Saleem (University of Ottawa)

Oscillations of the Bandgap with Size in Armchair and Zigzag
Graphene Quantum Dots
We determine here the evolution of the bandgap energy with size in graphene quantum dots
(GQDs). We find oscillatory behavior of the bandgap and explain its origin in terms of armchair andzigzag edges. The electronic energy spectra of GQDs are computed using both the tight binding modeland ab initio density functional methods. The results of the tight binding model are analyzed by
dividing zigzag graphene quantum dots into concentric rings. For each ring, the energy spectra, thewave functions and the bandgap are obtained analytically. The effect of inter-ring tunneling on theenergy gap is determined. The growth of zigzag terminated GQD into armchair GQD is shown to be
associated with the addition of a one-dimensional Lieb lattice of carbon atoms with a shell of energy
levels in the middle of the energy gap of the inner zigzag terminated GQD. This introduces a different
structure of the energy levels at the bottom of the conduction and top of the valence band in zigzag
and armchair GQD which manifests itself in the oscillation of the energy gap with increasing size.
The evolution of the bandgap with the number of carbon atoms is compared with the notion ofconfined Dirac Fermions and tested against ab initio calculations of Kohn–Sham and TD-DFT energy
gaps.

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Wei Cui (University of Ottawa)

Grating-assisted Non-collinear THz Detection
Electro-optic sampling (EOS) is an optical detection technique widely implemented to dosensitive time-resolved terahertz (THz) measurements to monitor ultrafast dynamics in materials.
This technique depends on numerous experimental parameters, including the properties of a nonlinear
crystal, called the EOS crystal, used to detect THz waves via their nonlinear interaction with a nearinfrared femtosecond pulse. The thickness of such an EOS crystal is linearly correlated with the THz
detection efficiency, but it is also inversely proportional to the spectral detection range.
Experimentalists usually use a 100 µm thick crystal, which is a compromise between good detection
efficiency and sufficient spectral range. Here we demonstrated that a contact grating fabricated on thefront surface of an EOS crystal can be used to change phase matching conditions and overcome thethickness limitation to achieve a broadband detection range. In our experiment, a contact grating is
plasma-etched on the front surface of a 1 mm thick GaP crystal used as an EOS crystal. We compare
this new geometry with a standard configuration and demonstrate a larger detection bandwidth, by afactor of two, in addition to an enhancement of the detection efficiency. Our work paves the way
towards new THz detection devices enabling broadband and high-sensitivity THz detection for many
applications such as molecular sensing, security scan, and pharmaceuticals quality control.
Samantha Scarfe (University of Ottawa)

Exploring Graphene in the THz Regime
Samantha Scarfe, Alexei Halpin, Justin Boddison-Chouinard, Jean-Michel Ménard, Adina
Luican-Mayer
University of Ottawa, Canada
Two dimensional materials refer to a class of crystals that are atomically thin. Since the isolationof the first 2D material, graphene, the study of such low-dimensional systems has attracted
widespread attention with the goals of advancing fundamental knowledge and of facilitating thedevelopment of next-generation optoelectronic technologies. Crucial to realizing translations toindustrial applications is understanding light-matter interactions in 2D materials. In this work, wereport on experimental progress in investigating optical properties and interactions in the 2D material
graphene. In particular, we use terahertz time-domain spectroscopy to study free-carrier dynamics ingraphene. We discuss light-matter interactions in graphene samples that are supported by substrates
with distinct optical properties.

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Ryan Plumadore, Justin Chouinard (University of Ottawa)

2D Materials Quantum Structures and their Electronic Properties
Ryan Plumadore, Justin Chouinard, Adina Luican-Mayer
University of Ottawa, Canada
We seek to uncover novel quantum phenomena at the nanoscale by constructing custom-madehetero-structure material systems by stacking atomically thin layers of van der Waals bonded
materials. To explore such structures, we use Scanning Tunneling Microscopy (STM) andSpectroscopy (STS) as experimental techniques that can spatially resolve both the local electronicand structural properties of materials down to atomic scale. We characterize the morphology, crystal
structure and local density of states for various 2D materials including their defects and proximity
effects at their boundaries. In addition, we are further reducing the dimensions of the 2D materials tocreate electrostatically defined quantum structures with the goal of understanding and manipulating
their electronic states.

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