Faculty

IQC Seminar - Zahra Khanian, Technical University of Munich

200 University Ave W. Waterloo On Can QNC 1201

In the seminal 1948 paper "a mathematical theory of communication", Shannon introduced the concept of a classical source as a random variable and established its optimal compression rate, given by Shannon entropy. Nearly five decades later, Schumacher rigorously defined the notion of a quantum source and its compressibility. Schumacher's definition involved a quantum system and correlations with a purifying reference system. In our work, we build upon Schumacher's quantum source model, extending it to the most general form allowed by quantum mechanics. This extension involves considering the source and the reference in a mixed state, along with the presence of additional systems treated as side information. We address and solve various problems posed by these modifications, determining the optimal compression rates. While our work contributes significant progress in quantum source compression, we point out remaining open questions that require further exploration.

Research Advancement Centre, 475 Wes Graham Way, Room RAC 2009, Waterloo, ON, CA N2L 6R2

Graph-Theoretic Techniques for Optimizing NISQ Algorithms

Supervisor: Dr. Michele Mosca. Thesis available from mgo@uwaterloo.ca. Oral defence Friday, February 2, 9:00 a.m., online.

Development of III-V semiconductor surface quantum wells for hybrid superconducting device applications

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

Supervisor: Jonathan Baugh

IQC Colloquium - Sisi Zhou, The Perimeter Institute

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

 Quantum metrology studies estimation of unknown parameters in quantum systems. The Heisenberg limit of estimation precision 1/N, with N being the number of probes, is the ultimate sensing limit allowed by quantum mechanics that quadratically outperforms the classically-achievable standard quantum limit 1/√N. The Heisenberg limit is attainable using multi-probe entanglement in the ideal, noiseless case. However, in presence of noise, many quantum systems only allow a constant factor of improvement over the standard quantum limit. To elucidate the noise effect in quantum metrology, we prove a necessary and sufficient condition for achieving the Heisenberg limit using quantum controls. We show that when the condition is satisfied, there exist quantum error correction protocols to achieve the Heisenberg limit; when the condition is violated, no quantum controls can break the standard quantum limit (although quantum error correction can be used to maximize the constant-factor improvement). We will also discuss the modified sensing limits when only restricted types of quantum controls can be applied. 

Creating and probing laser-cooled atomic ensembles inside a hollow-core optical fibre

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

Supervisor: Michal Bajcsy

Optimization of the Optical Infrastructure and Trapping Potential for a Quantum Processor Based on Trapped Barium Ions

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

Supervisor: Kazi Rajibul Islam