News
Designing for a sustainable future using quantum technologies
On April 18, Transformative Quantum Technologies (TQT) awarded six research teams and their design ideas for the Quantum for Environment (Q4Environment) Design Challenge, whose green-tech solutions address global environmental issues. Ideas included using quantum computing to improve medical devices, and sensors that can detect microplastics and toxic nanomaterials in our oceans.
IQC Welcomes Dr. Bradley Hauer
Breakthroughs in understanding how gravity affects quantum mechanics could be on the horizon at the Institute for Quantum Computing (IQC) with the addition of Dr. Bradley Hauer as IQC's newest faculty member and Assistant Professor in the Department of Electrical and Computer Engineering. Hauer’s research focuses on studying cavity optomechanical systems and superconducting circuits and their applications in metrology, quantum information and non-classical state preparation.
Entangling undergraduate students with quantum success
Each year, the Institute for Quantum Computing (IQC) invites top undergraduate students from around the world to the University of Waterloo for the opportunity to immerse themselves in quantum information science and technology. This program, the Undergraduate School on Experimental Quantum Information Processing (USEQIP), provides participants with lectures on quantum information theory and experimental approaches to quantum devices, as well as over 30 hours of hands-on laboratory and experimental exploration.
Events
ETSI/IQC Quantum Safe Cryptography Conference 2024
ETSI and the Institute for Quantum Computing are pleased to announce the 10th ETSI/IQC Quantum Safe Cryptography Conference, taking place in Singapore on May 14-16, 2024. The event will be hosted by the Centre for Quantum Technologies, National University of Singapore.
This event was designed for members of the business, government, and research communities with a stake in cryptographic standardization to facilitate the knowledge exchange and collaboration required to transition cyber infrastructures and business practices to make them safe in an era with quantum computers. It aims to showcase both the most recent developments from industry and government and cutting-edge potential solutions coming out of the most recent research.
Paul Oh PhD Thesis Defense
Entangled photon source for a long-distance quantum key distribution
Remote
Satellite-based Quantum Key Distribution (QKD) leverages quantum principles to offer unparalleled security and scalability for global quantum networks, making it a promising solution for next-generation secure communication systems. However, many technical challenges need to be overcome. This thesis focuses on theoretical modeling and experimental validation for long-distance QKD, as well as the development and testing of the quantum source necessary for its implementation, to take strides towards realization. While various approaches exist for demonstrating long-distance QKD, here we focus on discussing the approach of sending entangled photon pairs from an optical quantum ground station (OQGS), one through free-space on one end (uplink), and the other one through ground on the other end. This is also because our research team at the Quantum Photonics Laboratory (QPL), collaborating with the Canadian Space Agency (CSA), is planning to demonstrate Canada's first ground-to-space QKD in the near future. The mission is called Quantum Encryption and Science Satellite (QEYSSat) mission, which is planned to deploy a Low-Earth Orbit (LEO) satellite for the purpose for demonstrating QKD.
In the thesis, we first discuss the considerations relevant to establishing a long-distance quantum link. Since a substantial amount of research has already been conducted on optical fiber communication through ground-based methods, our focus is specifically directed towards ground-to-space (i.e., free space) quantum links. One of the most concerning aspects in free- space quantum communication is signal attenuation caused by environmental factors. We particularly examine pointing errors that arise from satellite tracking systems. To investigate this further, we designed a tracking system employing a specific tracking algorithm and conducted tracking tests to validate its accuracy, using the International Space Station (ISS) as a test subject. Our findings illustrate the potentially significant impact of inaccurate ground station-to- satellite alignment on link attenuation, according to our theoretical model. Given that photons serve as the signals for the QKD, we also investigate the background light noise resulting from light pollution, which is another concerning aspect, as it could worsen the link attenuation. Conducting light pollution measurements around our Optical Quantum Ground Station (OQGS), we estimate the minimum photon pair rate required for successful QKD, taking into account both the obtained values from these measurements and the expected level of link loss.
Having determined the minimum photon pair rate and other requirements for the long-distance QKD, we proceed to fully elaborate on the development process of the Entangled Photon Source (EPS), which is one of the crucial devices for demonstrating entanglement-based QKD. We use a nonlinear crystal for generating photon pairs, and experimentally obtain the photon pair rate produced from it. Here, the thesis also includes a detailed explanation of the customization process for the crystal oven. Next, we implement a beam displacer scheme along with the Sagnac loop scheme to create a robust interferometer, responsible for creating quantum entanglement. In addition, we demonstrate a novel approach to effectively compensate for the major weaknesses of the interferometer, namely spatial and temporal walk-offs. Finally, we conduct the entanglement test and demonstrate its suitability for long-distance QKD. As a side project, we
investigate the performance degradation of nonlinear crystals in response to proton radiation, exploring the potential of deploying the EPS in space for downlink QKD in the future. This thesis provides a comprehensive analysis and testing of elements required for long-distance QKD, contributing to the advancement of future global quantum networks.
Supervisor: Thomas Jennewein
Semiconductor spin qubits for quantum networking
IQC Colloquium - Akira Oiwa, Osaka University
Quantum-Nano Centre, 200 University Ave West, Room QNC 1501 Waterloo, ON CA N2L 3G1
Semiconductor spin qubits are well recognized as a promising platform for scalable fault-tolerant quantum computers (FTQCs) because of relatively long spin coherence time in solid state devices and high-electrical tuneability of the quantum states [1]. In addition, semiconductors have a great potential for applications in quantum communications because of their abilities in optical devices. Therefore, especially in quantum repeater applications, the semiconductor spin qubits provide a route to efficiently connect qubit modules or quantum computers via optical fibers and construct global quantum networks, contributing to realize secure quantum communications and distributed quantum computing [2]. In this talk, we present the physical process enabling the quantum state conversion from single photon polarization states to single electron spin states in gate-defined quantum dots (QDs) and its experimental demonstration [3]. As recent significant achievements, we discuss that the enhancement of the conversion efficiency from a single photon to a single spin in a quantum dot using photonic nanostructures [4]. Finally, we present a perspective of high conversion efficiency quantum repeater operating directly at a telecom wavelength based on semiconductor spin qubits.
[1] G. Burkard et al., Rev. Mod. Phys. 95, 025003 (2023). [2] A. Oiwa et al., J. Phys. Soc. Jpn. 86, 011008 (2017); L. Gaudreau et al., Semicond. Sci. Technol. 32, 093001 (2017). [3] T. Fujita et al., Nature commun. 10, 2991 (2019); K. Kuroyama et al., Phys. Rev. B 10, 2991 (2019). [4] R. Fukai et al., Appl. Phys. Express 14, 125001 (2021); S. Ji et al., Jpn. J. Appl. Phys. 62, SC1018 (2023).