Events

Security proof of QKD using Entropic Uncertainty relations

Quantum-Nano Centre, 200 University Ave West, Room QNC 1201 Waterloo, ON CA N2L 3G1

In this talk, I will describe the use of entropic uncertainty relations in QKD security proofs. I will show how this proof method requires a bound on the classical statistics of the underlying quantum state, and thus ultimately reduces to a sampling problem. I will then describe how the sampling problem is addressed in the literature under certain unphysical assumptions on the QKD hardware. Finally, I will describe how these assumptions can be removed, thereby rendering this proof technique applicable to practical scenarios.

IQC Seminar - Sarah Meng Li - University of Amsterdam, Centrum Wiskunde & Informatica (CWI)

Quantum-Nano Centre, 200 University Ave West, Room QNC 0101 Waterloo, ON CA N2L 3G1

: Quantum compiling translates a quantum algorithm into a sequence of elementary operations. There exists a correspondence between certain quantum circuits and matrices over some number rings. This number-theoretic perspective reveals important properties of gate sets and leads to improved quantum compiling protocols. Here, we demonstrate several algebraic methods in quantum circuit characterization and optimization, based on my master’s research at IQC.

First, we design two improved synthesis algorithms for Toffoli-Hadamard circuits, achieving an exponential reduction in circuit size. Second, we define a unique normal form for qutrit Clifford operators. This allows us to find a set of relations that suffice to rewrite any qutrit Clifford circuit to its normal form, adding to the family of number-theoretic characterization of quantum operators.

Optimal coupling for local entanglement extraction from a quantum field

Quantum-Nano Centre, 200 University Ave West, Room QNC 1201 Waterloo, ON CA N2L 3G1

Towards an on-demand, all-electrical single-photon source

Research Advancement Center, 485 Wes Graham Way, Room 2009 Waterloo, ON N2L 6R2

Single-photon sources (SPSs) are an elementary building block for quantum technologies. An ideal SPS is deterministic, on-demand and produces exactly one photon per pulse. Additionally, desirable features include a high repetition rate, an all-electrical driving mechanism and compatibility with semiconductor manufacturing techniques. Despite great advances in the field of single photon emitters, an SPS with all the features outlined above remains elusive. In this talk, we will present our proposed SPS, consisting of a single-electron pump integrated in proximity to a lateral PN-junction, which would allow our SPS to meet all the criteria listed above. We discuss progress towards our goal, and also discuss an unconventional electroluminescence mechanism observed during recent experiments.

Weight estimation for optical detection setups

QNC building, 200 University Ave. Room 1201, Waterloo 

Realistic models of optical detection setups are crucial for numerous quantum information tasks. For instance, squashing maps allow for more realistic descriptions of the detection setups by accounting for multiphoton detections. To apply squashing maps, one requires a population estimation of multiphoton subspaces of the input to the detection setup. So far, there has been no universal method for those subspace estimations for arbitrary detection setups.

We introduce a generic subspace estimation technique applicable to any passive linear optical setup, accounting for losses and dark counts. The resulting bounds are relevant for adversarial tasks such as QKD or entanglement verification. Additionally, this method enables a generic passive detection setup characterization, providing the necessary measurement POVM for e.g. QKD security proofs.

IQC Special Seminar, Jerome Wiesemann, Fraunhofer Heinrich Hertz Institute HHI

Quantum key distribution (QKD) is on the verge of becoming a robust security solution, backed by security proofs that closely model practical implementations.  As QKD matures, a crucial requirement for its widespread adoption is establishing standards for evaluating and certifying practical implementations, particularly against side-channel attacks resulting from device imperfections that can undermine security claims. Today, QKD is at a stage where the development of such standards is increasingly prioritized. This works aims to address some of the challenges associated with this task by focusing on the process of preparing an in-house QKD system for evaluation. We first present a consolidated and accessible baseline security proof for the one-decoy state BB84 protocol with finite-keys, expressed in a unified language. Building upon this security proof, we identify and tackle some of the most critical side-channel attacks by characterizing and implementing countermeasures both in the QKD system and within the security proof. In this process, we iteratively evaluate the risk of the individual attacks and re-assess the security of the system. Evaluating the security of QKD systems additionally involves performing attacks to potentially identify new loopholes. Thus, we also aim to perform the first real-time Trojan horse attack on a decoy state BB84 system, further highlighting the need for robust countermeasures. By providing a critical evaluation of our QKD system and incorporating robust countermeasures against side-channel attacks, our research contributes to advancing the practical implementation and evaluation of QKD as a trusted security solution.

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.

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.

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.

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.