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Understanding and controlling the properties of 2D materials to our advantage can be contemplated with the development of experimental tools to probe and manipulate electrons and their interactions at the atomic scale. In this talk, I will present scanning tunnelling microscopy and spectroscopy experiments aimed at: elucidating the nature of atomic-scale defects in 2D materials [1], visualizing moiré patterns between crystals with different symmetries [2] and imaging surface and edge states in a magnetic topological system. Moreover, I will discuss how we leverage our expertise in probing and engineering electronic states at surfaces of 2D materials to further the development of graphene-based gas sensors [3] and gated quantum dot circuits based on 2D semiconductors [4]. 

REFERENCES

[1] Plumadore et al., PRB, (2020) 
[2] Plumadore et al., Journal of Applied Physics, (2020)
[3] Rautela et al., ACS Applied Materials &amp; Interfaces (2020) 
[4] Boddison-Chouinard, Appl. Phys. Lett., (2019)

CAP Virtual Congress 2021

Quantum materials at the atomic scale

scanning probes

quantum materials

2d materials

**WELCOME TO THE 2021 CAP VIRTUAL CONGRESS UNDERLINE PLATFORM**

The CAP staff and our organizing and program committees are pleased to welcome you to our 2021 Congress filled with plenary talks, technical sessions/talks, student presentations and competition sessions, workshops, and several symposia offered by the CAP divisions and its partners.  

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Understanding and controlling the properties of 2D materials to our advantage can be contemplated with the development of experimental tools to probe and manipulate electrons and their interactions at the atomic scale. In this talk, I will present scanning tunnelling microscopy and spectroscopy experiments aimed at: elucidating the nature of atomic-scale defects in 2D materials [1], visualizing moiré patterns between crystals with different symmetries [2] and imaging surface and edge states in a magnetic topological system. Moreover, I will discuss how we leverage our expertise in probing and engineering electronic states at surfaces of 2D materials to further the development of graphene-based gas sensors [3] and gated quantum dot circuits based on 2D semiconductors [4]. 

REFERENCES

[1] Plumadore et al., PRB, (2020) 
[2] Plumadore et al., Journal of Applied Physics, (2020)
[3] Rautela et al., ACS Applied Materials & Interfaces (2020) 
[4] Boddison-Chouinard, Appl. Phys. Lett., (2019)

technical paper

In this talk I will discuss how one may view four-dimensional de Sitter space as a coherent Glauber-Sudarshan state in string theory. I will also discuss why a de Sitter space cannot exist as a vacuum state in string theory.

de Sitter space in string landscape

Bell nonlocality describes a manifestation of quantum mechanics that cannot be explained by any local hidden variable model. Its origin lies in the nature of quantum entanglement, although understanding the precise relationship between nonlocality and entanglement has been a notorious open problem. In this talk, I will describe a resolution to this problem by developing a dynamical framework in which quantum Bell nonlocality emerges as special form of entanglement, and both are unified as resources under local operations and classical communication (LOCC). The framework is built on the notion of quantum processes, which are abstract quantum channels mapping elements between fixed intervals in space and time. Entanglement is then identified as a quantum process that cannot be generated by LOCC while Bell nonlocality is the subset of these processes that have an instantaneous input- output delay time. LOCC pre-processing is a natural set of free operations in this theory, thereby enabling all entangled states to activate some form of Bell nonlocality.

Entanglement and Bell nonlocality are one and the same

I will present my group’s recent efforts to combine atomic ensembles with nanophotonic structures. I will describe our experiment in which photons emitted by a quantum dot embedded in a semiconductor nanowire are sent into an ensemble of laser-cooled caesium atoms confined inside a hollow-core photonic-crystal fibre to realize photon storage and single-photon wavelength conversion. Additionally, I will report on our progress in developing new types of mesoscopic optical cavities based on dichroic mirrors realized with chiral photonic crystal slabs and metasurfaces. This research was undertaken in part due to funding from the Canada First Research Excellence Fund.”

Nanophotonic platforms for quantum optics with atomic ensembles

To utilize the advantages of different quantum platforms, we need an interface (transducer) to transfer quantum information from one to another. Unfortunately, realistic transducers are imperfect due to, e.g. weak interaction strength or unwanted coupling. In this talk, I will present a surprising strategy to remedy the transduction imperfections: by applying a bad transducer twice [1]. I will first introduce a novel characterization of all coherent transducers by their analogous position and momentum noises. I will then show how destructive interference and measurement can be employed to eliminate the unwanted noise. I will also illustrate how the remaining noise can be corrected by using bosonic codes. Our proposal can relax the stringent technological requirement of implementing perfect transducer, and potentially enhance the speed of information transfer.

[1] Hoi-Kwan Lau and Aashish A. Clerk, npj Quantum Information 5, 31 (2019)

Realizing a perfect quantum transduction by applying a bad transducer twice

Here I discuss the possibilities to use nanomechanical resonators to converter information between microwave and optical domains. Additionally, I demonstrate an on-chip magnetic-free circulator based on reservoir-engineered electromechanical interactions. Directional circulation is achieved with controlled phase-sensitive interference of six distinct electromechanical signal conversion paths. Finally, I show that a parametrically driven mechanical oscillator can entangle electromagnetic fields. We observe stationary emission of path-entangled microwave radiation from a micro-machined silicon nanostring oscillator, squeezing the joint field operators of two thermal modes by 3.40 (37) ~ dB below the vacuum level.

Quantum electromechanics: photon conversion, nonreciprocity, and entanglement

H2 continues to provide fundamental insights into the mechanisms of intense light-matter interactions [1]. Recently, there has been significant interest in so-called light-induced conical intersections (LICI) that arise from the angle dependence of the single-photon coupling of electronic states. Analogously to regular conical intersections, electronic and nuclear motions are strongly coupled in the vicinity of LICIs. As a signature of such rovibronic dynamics, weak modulations in the angular distribution of protons emitted from H2+ have been reported [2]. More generally speaking, infrared (IR) laser pulses couple the 1sg and 2pu electronic states of H2+ typically through several pathways involving an odd number of photons [1], which can produce complex light-induced potential energy landscapes, and consequently even richer dynamics.
In this talk we will present theory and experiment to show that the full complexity of such light-induced potential energy surfaces can be uncovered using a two-step scheme [3]. In this scheme a few cycle optical pulse projects a coherent wavepacket onto the ionic state of H2 and a weak, non-ionizing, mid-infrared, and perpendicularly polarized pulse creates the light-induced potential energy landscapes upon which the H2+ wavepacket can propagate. We observe a strongly modulated angular distribution of protons which has escaped prior observation. These modulations result directly from ultrafast dynamics on the light-induced molecular potentials and can be modified by varying the amplitude, duration and phase of the mid-infrared dressing field.

[1] H. Ibrahim, C. Lefebvre, A.D. Bandrauk, A. Staudte and F. Légaré. J. Phys. B 51, 042002 (2018).
[2] A. Natan, M.R. Ware, V.S. Prabhudesai, U. Lev, B.D. Bruner, O. Heber, and P.H. Bucksbaum, Phys. Rev. Lett. 116, 143004 (2016).
[3] M. Kübel, M. Spanner, Z. Dube, A.Yu. Naumov, S. Chelkowski, A.D. Bandrauk, M.J.J. Vrakking, P.B. Corkum, D.M. Villeneuve, and A. Staudte. Nature Communications 10, 1042 (2019).

Signatures of light-induced potential energy surfaces in H2+ - beyond conical intersections

The non-adiabatic coupling of nuclear and electronic degrees of freedom underlies many fundamental processes in Nature, including solar energy conversion and photosynthesis. The formation of electronic coherences by nuclear motion is a new aspect of such dynamics and requires new measurement techniques and methods of analysis. We will discuss Ultrafast Time-Resolved Xray Absorption and Time-Resolved Photoelectron Spectroscopy, powerful methods suited to addressing this problem. In particular, we present a new approach to fully separating electronic coherences from electronic population dynamics, a long-standing problem, based on the use and analysis of Time-Resolved Photoelectron Angular Distributions.

Coherent Ultrafast Electronic Dynamics in Molecules

Superconducting radiofrequency (SRF) cavities have been used for more than 50 years to increase the energy of charged particles. In Canada there are two accelerator centres which use SRF technology, i.e TRIUMF and the Canadian Light Source (CLS). The CLS was the first light source to use an SRF cavity in a storage ring from the beginning of operations in 2004. TRIUMF began developing SRF technology in 2000 which led in 2006 to the commissioning of the ISAC-II heavy ion superconducting linac for the post-acceleration of radioactive beams. More recently, the ARIEL SRF electron accelerator was installed at TRIUMF as a second driver for radioactive isotope production. In this talk, I will first give an overview of Canada’s SRF infrastructure and the underlying concepts. Then, I will briefly present how performance has globally evolved since the early days. Nowadays, state of the art niobium cavities reach fundamental limitations in terms of accelerating gradient (energy gain per unit length) and power dissipation. Increasing performance requires specialized chemical and surface treatments which must be tailored to specific cavity types and exploring materials beyond bulk niobium. I will highlight recent research highlights from TRIUMF and UVic including results from testing new surface treatments on unique multimode coaxial resonators and material science investigations using beta detected nuclear magnetic resonance (beta-NMR) and muon spin rotation and relaxation (muSR).

Superconducting Radiofrequency Science and Technology in Canada

Inhaled hyperpolarized gas lung MRI was proven to be useful for the observation and treatment planning of several pulmonary diseases including chronic obstructive pulmonary disease, asthma, COVID-19 and lung cancer. The combined economic burden of COPD and asthma in Canada, Ontario being $5.7 billion (2011). While these statistics are alarming, they don’t fully reflect the impact on economic growth and the opportunity costs that stem from such a large number of chronically ill Canadian adults and children. Moreover, both asthma and COPD are progressive and punctuated by sudden, acute worsening of symptoms or “exacerbations” that require immediate medical care – a source of enormous stress on our healthcare system. Lung cancer caused the premature deaths of 21,100 Canadians in 2017 (with an additional 28,600 being diagnosed), accounting for 26% of all cancer related deaths in Canada. People who are diagnosed with lung cancer are most likely to survive if the tumour can be surgically removed. However, nearly 1 in 4 Canadians who have their lung tumour surgically removed have lung complications following surgery called “postoperative pulmonary complications.” Presently, there is very little effort to predict these complications. So, it is not surprising that there has been a growing interest in developing new lung imaging techniques such as hyperpolarized 129Xe MRI to better understand various disruptive pulmonary, cardiac & neurodegenerative chronic diseases. In Canada, four research sites (London, Hamilton, Toronto, and Thunder Bay) have started a 129Xe MRI program, and two other sites (Vancouver, Montreal,) are in the preparation stage. Collectively, these Canadian sites urgently need novel 129Xe MR imaging methods as well as an advanced hardware package including a static-cell xenon polarizer, RF coil asymmetric unshielded rigid transmitter and multi-channel phased array receiver. Thinking about 129Xe’s place in MRI research globally, it is known that presently, 129Xe lung MRI is translating towards a clinical tool, and it has recently been approved and used as a clinical tool in the UK and USA. This opens door for better diagnoses, treatment planning and treatment assessment of patients with chronic lung, COVID-19, cardio and neuro diseases.

Noble gas MRI: A Decade of Progress Towards Clinical Translation

In response to the needs for ventilators for critically ill Covid-19 patients a collaboration of international particle physicists, engineers, software specialists, industry and medical specialists came together to create rapidly a simple, low-cost, open-source ventilator tailored specifically for such patients. The project was initiated by Professor Cristian Galbiati, spokesperson of the DarkSide-20k experiment designed to use about 55 tons of low-radioactivity liquid Argon to search for high-mass WIMPS as Dark Matter candidate particles at the Gran Sasso underground laboratory. This experiment is a successor to the DEAP experiment and pre-cursor to the proposed ARGO experiment at SNOLAB. It was realized that the expertise in gas handling and computer control that has been developed for these experiments could be used to develop the Mechanical Ventilator Milano (MVM). The Italian group was immediately joined by Canadian scientists and engineers from TRIUMF laboratory, CNL Chalk River, SNOLAB and the McDonald Institute and other international collaborators. A prototype was working in the lab within 10 days, papers were published openly for the design, industrialized versions were developed and the collaboration won a Canadian government contract that has now resulted in the delivery of over 6000 ventilators to the Canadian stockpile following Health Canada Interim Authorization. Donation to other countries in need is another possibility under discussion. A description will be provided of how this highly motivated team pivoted their work to make a contribution to the COVID-19 pandemic.

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Quantum materials at the atomic scale

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de Sitter space in string landscape

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