Events

Effective JC and anti-JC Interactions via Strong Driving 

The Jaynes-Cummings Model (JCM) approximates the Quantum Rabi Model (QRM) in some regimes and is exactly solvable by only keeping the rotating or `energy-conserving’ terms and dropping the counter-rotating or `non-energy conserving’ terms.

Since the proposal of the JCM, questions on the effect and presence of counter-rotating terms popped up.

Using strong driving, one can induce the effects of the counter-rotating terms on a comparable timescale to the rotating terms. In such a scenario, one can create a Schrödinger cat state in a resonant manner without the need for any type of Kerr nonlinearity.

In this talk, we review the QRM and its descendant, the JCM. Then, we discuss the realization of a Schrödinger cat state, its challenges in practice and how to solve them.

TQT’s Quantum For Health (Q4Health), is open to all at the University of Waterloo, seeking opportunities where quantum can advance health.

On September 19, TQT will host a Q4Health Launch Event in the Mike and Ophelia Lazaridis Quantum-Nano Centre Rm 0101. This event will include descriptions of quantum for health case studies. Following the talks, there will be a meet and greet to assist in team building. Attendees will receive information updates and an opportunity to register and learn more about upcoming Lunch and Learn sessions.

Register by September 16 (for refreshment planning purposes). There will be limited onsite registration at the event.

Jonathan Lavoie, Experimental Physicist, Xanadu Quantum Technologies

A quantum computer attains computational advantage when outperforming the best classical computers running the best-known algorithms on well-defined tasks. No photonic machine offering programmability over all its quantum gates has demonstrated quantum computational advantage: previous machines were largely restricted to static gate sequences. I will discuss a quantum computational advantage using Borealis, the latest of Xanadu’s photonic processors offering dynamic programmability and available on the cloud. This work is a critical milestone on the path to a practical quantum computer, validating key technological features of photonics as a platform for this goal.

Quantum Chaos in Kicked Top

Quantum-classical correspondence is of fundamental interest as it allows for computing and analysing the quantum properties with respect to their classical counterparts. This helps us study the transition from the quantum to the classical. According to the correspondence principle, quantum mechanics should agree with classical mechanics in appropriate limits. In our first project, we show that currently available NISQ computers can be used for versatile quantum simulations of chaotic systems. We introduce a classical-quantum hybrid approach for exploring the dynamics of the chaotic quantum kicked top (QKT) on a  universal quantum computer. The programmability of this approach allows us to experimentally explore the complete range of QKT chaoticity parameter regimes inaccessible to previous studies. Furthermore, the number of gates in our simulation does not increase with the number of kicks, thus making it possible to study the QKT evolution for arbitrary number of kicks without fidelity loss. Using a publicly accessible NISQ computer (IBMQ), we observe periodicities in the evolution of the 2-qubit QKT, as well as signatures of chaos in the time-averaged 2-qubit entanglement. We also demonstrate a connection between entanglement and delocalization in the 2-qubit QKT, confirming theoretical predictions. However, the connection between classical and quantum mechanics is not straightforward, especially in chaotic systems. The question of why a chaotic system, in certain situations, breaks the correspondence principle remains one of the open questions. Nevertheless, the breaking of Quantum classical correspondence for a large system i.e., the large value of j (but finite), is surprising. It suggests that the system never behaves classically in certain situations, irrespective of the system size. It is also worth exploring this strange behavior from an experimental point of view, as it will decide the parameters of the experimental setup designed for studying Quantum Chaos.

There's growing awareness of the lack of diversity in science and the presence of barriers to inclusion. What factors lead to disparities in representation? Why should we be motivated to effect change? What can we do to change things? Will our actions really make a difference? 

This presentation will focus on ideas to challenge the status quo – actions to advance equity, diversity, and inclusion (EDI). We will discuss recent research to illustrate and raise awareness of the many EDI challenges in science, then explore various practical ways to take action to advance EDI. These practical actions stem from our recently released "Science is For Everyone" Teaching toolkit, which provides an abundance of ideas to diversify science education and further support recruitment, retention, and advancement of all students. We will touch on the importance of diversifying content and talk about how Indigenous content is being brought into post-secondary science courses. Finally, we will give an overview of other exciting science EDI initiatives across research and academic life.

IQC Colloquium featuring Professor Jaewan Kim, Professor/Vice-President of Korea Institute for Advanced Study (KIAS), President of Quantum Information Society of Korea (QisK)

A coherent state can be interpreted as a superposition of pseudo-number states with equal weight. Using cross-Kerr nonlinearity two coherent states can be made into a maximal entanglement of pseudo-number states and pseudo-phase states. Some applications of the entanglements of pseudo-number/phase states, such as quDit teleportations, will be discussed.

Young-June Kim: Alpha-RuCl3: a progress report

Abstract: A bond-dependent anisotropic magnetic interaction called the Kitaev interaction can be found in honeycomb lattice materials with strong spin-orbit coupling, which has made a profound impact on quantum magnetism research. In particular, alpha-RuCl3 has been heralded as a realization of the Kitaev quantum spin liquid state, an elusive new state of matter that harbours Majorana fermions. In this talk, I will give a brief overview of the current status of research on alpha-RuCl3 and discuss recent experimental developments and a few surprising findings using ultra-high-quality samples grown in our laboratory. Our samples have minimal stacking faults even at low temperatures, allowing us to determine the low-temperature crystal structure unambiguously. We also found that the magnetic properties are surprisingly sensitive to the inter-layer configuration, giving rise to various magnetic transition temperatures. We also compare low-energy spin-orbit excitations in various Kitaev materials using resonant inelastic x-ray scattering (RIXS). We found that non-local physics is important for describing the spin-orbit excitations in these materials, in contrast to the conventional belief that local Jeff=1/2 physics is sufficient in these compounds.

Avenues focusing reference frame independent protocols to enhance free space satellite quantum communications channels

Free-space quantum channels for real world quantum information applications are rapidly emerging, with Canada developing the quantum encryption and science satellite (QEYSSat). For polarization-based systems, one challenge is aligning the reference frame of the polarization states. For example, the physical orientation of the satellites is crucial in maintaining the proper geometric reference frame alignment. However, reference frame independent (RFI) protocols overcome this issue because they don’t require all the polarization states to be fixed. Furthermore, using time bin encoding completely removes the need for a geometric reference, but presents its own challenges when used over a free space channel. In this talk, we will discuss the development done at the University of Waterloo towards the use of reference frame independent protocols for free-space quantum channels. Furthermore, we will discuss the benefits of using time bin encoding over free-space channels, and present our implementations of such systems and what they mean for future QEYSSat missions and applications on other platforms.

All-optic fine structure splitting eraser

Reliable entangled photon sources are important for testing fundamentals in quantum mechanics, achieving secure quantum key distribution, among other things. Quantum dots are a hot topic for precisely this need of the scientific community. Quantum dots act as artificial atoms by confining electrons and holes in wells. They emit polarization entangled photons in an exciton-biexciton cascade. The expected entangled state from the cascade is               
The confining potential of these wells can be asymmetric which causes fine structure splitting in the intermediate energy level of the cascade.
 
The presented work offers a way to achieve perfectly entangled photon pairs with quantum dots in vertical nanowires, on demand and with a high count rate. Fine structure splitting is seen in all quantum dot systems whether they are quantum dots in nanowires, micropillars, or, self-assembled quantum dots. This proposal is universal because it can be used to compensate for energy dependent entanglement degradation in all entangled photon sources.
The fine structure splitting in the dot leads to a difference in energy of the photons in different polarizations. This renders the quantum dot system less effective for quantum key distribution applications. Therefore, countering fine structure splitting is highly desirable.

This talk will discuss the approach taken in Quantum Photonic Devices lab to counter the fine structure splitting.

Yong-Baek Kim: Quantum Spin Liquids and Criticality in Multipolar Materials

Abstract: Multipolar quantum materials possess local moments carrying higher-rank quadrupolar or octupolar moments. These higher-rank multipolar moments arise due to strong spin-orbit coupling and local symmetry of the crystal-electric-field environment. In magnetic insulators, the interaction between multipolar local moments on frustrated lattices may promote novel quantum spin liquids. In heavy fermion systems, the interaction between multipolar local moments and conduction electrons may lead to unusual non-Fermi liquids and quantum criticality. In this talk, we first discuss a novel quantum spin ice state, a three-dimensional quantum spin liquid with emergent gauge field, that may have been realized in Ce₂Zr₂O₇ and Ce₂Sn₂O₇, where Ce³⁺ ions carry dipolar-octupolar moments. We present a theoretical analysis of possible quantum spin ice states in this system and compare the theoretical results of dynamical spin structure factors with recent neutron scattering experiments. Next, we present a theoretical model to describe the unusual Kondo effect and quantum criticality in Ce₃Pd₂₀Si₆, where Ce³⁺ moments carry a plethora of dipolar, quadrupolar, and octupolar moments. We show that two consecutive Kondo-destruction-type phase transitions can occur with the corresponding Fermi surface reconstructions. We compare these results with existing experiments and suggest future ultrasound experiments for the detection of emergent quantum critical behaviors.