Seminar

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.

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.

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.

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

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.

Designing a precision gravitational experiment and budgeting uncertainties

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

Neutrons have a long history at the forefront of precision metrology. Following in the footsteps of the first experiment that measured the effect of gravity on a quantum particle (the C.O.W. experiment), we aim to generate structured neutron momentum profiles and apply these states to measure the gravitational constant, big-G. The significant discrepancy between modern big-G experimental results underscores the need for new experiments whose systematic uncertainties can be decoupled from existing techniques. Previously, perfect-crystal neutron interferometers were used to measure local gravitational acceleration, little-g, unfortunately, the low neutron flux (a few neutrons per second) of these devices makes them impractical for precision measurements of big-G. The recently demonstrated Phase-Grating Moiré Interferometer (PGMI) offers an increase in neutron flux of several orders of magnitude while preserving the large interferometer area, and thus the sensitivity, of a perfect-crystal interferometer. This device possesses a set of systematic uncertainties that are independent from those in existing techniques that measure big-G. In this talk, I will discuss the feasibility of measuring big-G using a neutron PGMI apparatus with a test mass on the order of 1 tonne. Further, I will address how we can optimize this setup to maximize the phase shift from a 1-tonne mass and quantify the various sources of uncertainty in the proposed experiment.

CS/Math Seminar - Amir Arqand, IQC 

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

The entropy accumulation theorem, and its subsequent generalized version, is a powerful tool in the security analysis of many device-dependent and device-independent cryptography protocols. However, it has the drawback that the finite-size bounds it yields are not necessarily optimal, and furthermore, it relies on the construction of an affine min-tradeoff function, which can often be challenging to construct optimally in practice. In this talk, we address both of these challenges simultaneously by deriving a new entropy accumulation bound. Our bound yields significantly better finite-size performance, and can be computed as an intuitively interpretable convex optimization, without any specification of affine min-tradeoff functions. Furthermore, it can be applied directly at the level of R´enyi entropies if desired, yielding fully-R´enyi security proofs. Our proof techniques are based on elaborating on a connection between entropy accumulation and the frameworks of quantum probability estimation or f-weighted R´enyi entropies, and in the process we obtain some new results with respect to those frameworks as well.

IQC CS/Math Seminar - Amolak Ratan Kalra, University of Waterloo

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

In this talk I will discuss qutrit circuit synthesis over various families of universal gate sets. I will describe a method which relates the question of exact synthesis for both single qubits and single qutrits to the problem of solving a system of polynomial equations mod p.