Current graduate students

Mohammad Ayyash, IQC, Researcher

QNC building, 200 University Ave. Room 1201, Waterloo 

An overview of quantum harmonic oscillators is given. The phase space picture of quantum mechanics is discussed with a special focus on Wigner functions. An overview of Gaussian states and channels is discussed. Non-classical states and their phase-space signatures are explored. Some examples of non-classical states used for encoding logical quantum information and their properties are explored. If the time permits, current research directions and popular implementation platforms will be discussed.

CS/Math Seminar - Pulkit Sinha, IQC

QNC building, 200 University Ave. Online only, Waterloo 

A basic question in the PAC model of learning is whether proper learning is harder than improper learning. In the classical case, there are examples of concept classes with VC dimension d that have sample complexity Ω(d/ϵ log (1/ϵ)) for proper learning with error ϵ, while the complexity for improper learning is O(d/ϵ). One such example arises from the Coupon Collector problem.
Motivated by the efficiency of proper versus improper learning with quantum samples, Arunachalam, Belovs, Childs, Kothari, Rosmanis, and de Wolf (TQC 2020) studied an analogue, the Quantum Coupon Collector problem. Curiously, they discovered that for learning size k subsets of [n] the problem has sample complexity Θ(k log (min{k,n−k+1})), in contrast with the complexity of Θ(k log k) for Coupon Collector. This effectively negates the possibility of a separation between the two modes of learning via the quantum problem, and Arunachalam et al. posed the possibility of such a separation as an open question.  
In this work, we first present an algorithm for the Quantum Coupon Collector problem with sample complexity that matches the sharper lower bound of (1−o(1)) k ln( min{k,n−k+1} ) shown recently by Bab Hadiashar, Nayak, and Sinha (IEEE TIT 2024), for the entire range of the parameter k. Next, we devise a variant of the problem, the Quantum Padded Coupon Collector. We prove that its sample complexity matches that of the classical Coupon Collector problem for both modes of learning, thereby exhibiting the same asymptotic separation between proper and improper quantum learning as mentioned above.

Entanglement distillation and DIQKD

QNC building, 200 University Ave. Room 1201, Waterloo 

Quantum entanglement can be quantified in many ways, some of which bear clear operational meanings. The Distillable Entanglement and DIQKD rate are two such measures, speculated to be equivalent as stated by the Revised Peres Conjecture (Friedman and Leditzky, 21). Our research lays foundations to the conjecture’s proof, most notably using the notion of ‘private states’, a family of quantum states that arise naturally in the context of QKD.  Asking questions such as “what kind of private state can be resulted from a certain DIQKD protocol?”, we were able to provide simple sufficient conditions for the Revised Peres Conjecture to hold.

Professor Christine Muschik, Institute for Quantum Computing

RAC building, 475 Wes Graham Way, Waterloo Room 3003

This week's summer tutorial session will cover quantum error correction, starting from an overview of early successes in the field before introducing stablizer codes. 

Fermion-to-qubit mappings and their error mitigating properties

QNC building, 200 University Ave. Room 1201, Waterloo 

 As we move towards the era of quantum computers with 1000+ qubits, the most promising application able to harness the potential of such devices is quantum simulation. Simulating fermionic systems is both a well-formulated problem with clear real-world applications and a computationally challenging task. In order to simulate a system of fermions on a quantum computer, one has to map the fermionic Hamiltonian to a qubit Hamiltonian. The most popular such mapping is the Jordan-Wigner encoding, which suffers from inefficiencies caused by the non-locality of the encoded operators. As a result, alternative local mappings have been proposed that solve the problem of long encoded operators at the expense of constant factor of qubits. Some of these alternative mappings end up possessing non-trivial stabilizer structure akin to popular quantum error correction (QEC) codes. 

In this talk, I will introduce the problem of mapping fermionic operators to qubit operators and how the selection of an encoding could affect resource requirements in near-term simulations. I will also talk about error mitigation approaches utilizing the stabilizer structure of certain encodings as well as using stabilizer simulation to assess the effectiveness of such approaches.

Elena Bakos Lang and Kevin Henry, NCC Group

QNC building, 200 University Ave. Room 1201, Waterloo 

The security of cryptographic primitives and protocols is inextricably tied to that of the implementations deployed in the real world. Ensuring that these implementations are as secure as possible is thus a problem at the heart of cryptographic security.

This workshop will introduce common classes of cryptographic vulnerabilities, including improper randomness generation, side-channel attacks, flaws in primitives or protocols, and others, and discuss secure coding practices that can help mitigate them, based on our experiences auditing cryptographic code. This discussion will be complemented by a set of practical exercises to provide experience in spotting insecure constructions. Additionally, as implementation quality is often tied to the quality of the source material, we will present a case study on a recent widely implemented threshold signing protocol where ambiguous or unclear presentation in the academic source material has led to multiple critical implementation vulnerabilities.

This workshop is presented by NCC Group Cryptography Services practice in Waterloo, Ontario.

To attend this program please email us at cryptoworks21@uwaterloo.ca by July 17, 2024.

Douglas Stebila, University of Waterloo

QNC building, 200 University Ave. Room 1201, Waterloo 

This workshop will provide an introduction to the Tamarin prover, which is a security protocol verification tool that analyzes cryptographic protocols in a symbolic model and can automatically identify attacks or conclude that certain classes of attacks do not exist. The workshop will include a hands-on exercise using the Tamarin prover.

To attend this program please email us at cryptoworks21@uwaterloo.ca by July 16, 2024.

Daniel Nino, Xanadu

QNC building, 200 University Ave. Room 1201, Waterloo 

Xanadu is a Canadian quantum computing company with the mission to build quantum computers that are useful and available to people everywhere. Xanadu is one of the world’s leading quantum hardware and software companies and also leads the development of PennyLane, an open-source software library for quantum computing and application development.

Through this workshop, attendees will be given a broad overview of some applications of quantum computing to quantum chemistry. Through a series of hands-on exercises, attendees will learn about some PennyLane functionalities for workflows in quantum chemistry. By the end of the session, they will have hands-on experience in building quantum programs with PennyLane and how to use PennyLane datasets in applications to reduce time to research.

Please bring a laptop with you for this session. The workshop will run over Google Colab, no specific installation is required.

Improving information transmission using correlated auxiliary noise

QNC building, 200 University Ave. Room 1201, Waterloo 

Communicating information is a fundamentally important task that is often limited by noise. The physical origin of noise in a quantum channel is an interaction between the transmitted system and its surrounding environment. This interaction leads to correlations between the system and its environment that contain information about the original state, but are inaccessible to the receiver. However, a receiver may be able to recover some of this lost information if they are given access to an additional auxiliary system that interacts with the environment. In this talk, I will formalize a particular type of receiver side information and characterize the resulting improvement in classical and quantum channel capacities for an augmented bit flip channel. I will then discuss information-theoretic bounds on imperfect one-time pad cryptography schemes and passive environment-assisted quantum channel capacities.