Events

Fermionic encodings: BK Superfast, ternary trees, and even fermionic encodings

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

We give an introduction to fermionic encoding schemes applicable in the context of quantum simulation of fermionic systems in condensed matter physics, lattice gauge theories, and in quantum chemistry.
 
For this we will focus on the circuit depth overhead for a variety of constructions of fermionic encodings, more precisely in terms of their weight given by the choice of encoding within the Pauli group, and as such also in terms of their circuit depth due to multi-qubit rotation gates.
 
In particular we will introduce the Fenwick tree encoding due to Bravyi and Kitaev, as well as an optimal all-to-all encoding scheme in terms of ternary trees due to Jiang et al, and put those in perspective with the well-known fermionic encoding given by the Jordan-Wigner transformation. Such encoding schemes of fermionic systems with all-to-all connectivity become relevant especially in the context of molecular simulation in quantum chemistry.
 
We then further discuss the encoding of the algebra of even fermionic operators, which becomes particularly handy in the estimation of ground state energies for complex materials and their phase transitions in condensed matter physics.
 
In particular, we will introduce here the so-called Bravyi--Kitaev superfast encoding for the algebra of even fermionic operators, as well as the compact encoding due to Klassen and Derby as a particular variant thereof. These encoding schemes require the further use of stabilizer subspaces and so of fault-tolerant encoding schemes for their practical implementation for the purpose of quantum simulation. We then finish with a further improvement, the so-called supercompact encoding, due to Chen and Xu. In particular, we will focus here on its code parameters (more precisely its encoding rate and code distance) and put those in perspective with the previous compact encoding due to Klassen and Derby.
 
This talk is meant as an expository talk on available encoding schemes for fermionic systems, together with their best practices for the purpose of quantum simulations.

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

Clifford gates are ubiquitous in quantum computing. We consider the multiqudit analog for arbitrary d>1, which for example, includes the qudit Fourier transform. In this talk, we discuss the structure of the multiqudit projective Clifford group and give a high-level overview of a Clifford-based functional programming language whose underlying type system incorporates the resulting encoding scheme for projective Cliffords. This is joint work with Jennifer Paykin.

Entangled photon source for a long-distance quantum key distribution

Remote

Stable and Localized Emission from Ambipolar Dopant-Free Lateral p-n Junctions

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

Combining the architectures of a dopant-free lateral p-n junction and a single-electron pump in a GaAs/AlGaAs heterostructure material system could yield high-rate, electrically-driven quantum emitters with performances surpassing the competition in quantum sensing, communication and cryptography. Observed drawbacks of the dopant-free p-n junctions are a rapid decay in electroluminescence during operation, as well as delocalized emission that lowers the measured quantum efficiency. This talk details novel measurement protocols and gate architectures implemented by us to overcome these challenges.

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.

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.

Professor Brad Hauer, Institute for Quantum Computing

QNC building, 200 University Ave. Room 0101, Waterloo 

Join new IQC faculty member Professor Brad Hauer for a tutorial on quantum optomechanics and a preview of new research directions at IQC. This tutorial is designed for the USEQIP program to be accessible to advanced undergraduates, and all IQC members are welcome (no registration required).

Cavity optomechanics, which studies the interplay between confined electromagnetic fields and mechanical motion, has seen a flurry of activity over the past two decades. In particular, optomechanical devices have had great success in preparing, manipulating, and observing quantum states of motion in nanoscale mechanical resonators. With applications in quantum information and quantum sensing on the horizon, cavity optomechanical devices remain an exciting prospect for real-world quantum technologies, as well as probes of important physical quantities on both microscopic and cosmological scales.

In my tutorial, I will provide a brief overview of cavity optomechanics, describing both the theoretical fundamentals and physical implementations. Following this introduction, I will detail a number of recent experiments realizing quantum effects in mesoscale mechanical resonators, including ground state cooling and entanglement of their motion. I will also discuss how cavity optomechanics is being used to further our understanding of the universe through next-generation dark matter and gravity wave detectors. Finally, I will briefly discuss my own research studying newly developed mm-wave optomechanical circuits and how I plan to use these devices to continue advancing the field.

Aspects of Quantum Information in Quantum Field Theory: Particle detector models, entanglement, and complexity

Quantum-Nano Centre, 200 University Ave West, Room QNC 2101
Waterloo, ON CA N2L 3G1

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.