QIT Thinking Seminar Schedule for Fall 2024:

A TERM 2024

• Wednesdays 11:00-11:50am, Room OH218, Olin Hall



• 28 August: No seminar
  

• 4 September: Bill Martin, WPI, "A sampler of basic themes"
  Abstract: This talk will give a linear algebra view of the basic ideas behind quantum algorithms. I'll talk about a qubit as a two-dimensional vector space, about quantum algorithms, quantum measurements, and one aspect of the relationship between discrete and continuous evolution of a finite-dimensional quantum state.

• 11 September: Anastasiia Minenkova, University of Hartford, "Perfect quantum state transfer and theorem of Joseph-Alfred Serret"
  Abstract: In this talk we will discuss several mathematical objects and discover the connections between them. Namely, we recast the Serret theorem about a characterization of palindromic continued fractions in the context of polynomial continued fractions. Then, using the relation between symmetric tridiagonal matrices and polynomial continued fractions we give a quick exposition of the mathematical aspect of the perfect quantum state transfer problem.

• 18 September: Harmony Zhan, WPI, "A gentle introduction to discrete quantum walks"
  Abstract: Discrete quantum walks are building blocks for quantum computers and quantum algorithms. For example, Grover's search algorithm can be seen as a discrete quantum walk on the complete graph with loops. In this talk, I will discuss basic models of discrete quantum walks, some desired phenomena including state transfer and mixing, and how linear algebra and graph theory can be used to study these properties.

• 25 September: Xiaohong Zhang, University of Montréal, "Continuous quantum walks"
  Abstract: Let M be the adjacency matrix or the Laplacian matrix of a graph X. The transition operator at time t for the continuous quantum walk on X relative to M is defined as U(t) = e^itM. Depending on whether there exists a time t such that some entries of U(t) have special values, several quantum state transfer phenomena can be defined. In this presentation, I will discuss some of these special transfers, how different weightings of the graph influence these transfer properties, and explore interesting algebraic and spectral graph theory problems that arise from quantum walks.

• 2 October: Informal discussion with Zachariah Addison, Physics, Wellesley College
  

• 9 October: Harmony Zhan, WPI, "A gentle introduction to discrete quantum walks", continued
  Abstract: Dr. Zhan will continue the discussion we began on September 18.

B TERM 2024

• Wednesdays 11:00-11:50am, Room OH218, Olin Hall



• 23 October: Aram Harrow, MIT, "Many-body entanglement in quantum computing"
  Abstract: The idea of quantum computers is that "More is different" when it comes to qubits. One qubit is not so interesting but many of them together can create exotic and computationally powerful forms of many-body entanglement.

  Given this, we might expect that many-body physics and quantum information would often be related. I will describe two recent examples.

  1. The Ising model is a simple model of a magnet. But it turns out to also describe the competition between quantum interactions creating entanglement and measurements destroying entanglement. This can tell us how about the power of near-term quantum computers.
  2. How can a closed system reach thermal equilibrium? There have been many answers to this question dating back to the 19th century. I will explain how entanglement is a plausible source of thermalization.

• 30 October: Frederic Green, Clark University, "Constant-Depth Quantum Circuits"
  Abstract: The natural model for quantum computation is the quantum circuit. To minimize decoherence, it is essential for such circuits to be as shallow as possible. In fact, even quantum circuits of constant depth are more powerful than originally expected: The quantum part of Shor's factoring algorithm (that is, excluding the required classical pre- and post-processing) can be efficiently well-approximated by quantum circuits of constant depth. Recent developments in quantum computer technology underscore the need to understand the capabilities of shallow circuits. However, the precise power of such circuits remains open. This talk will introduce the central ideas of this area of research for non-experts, and explain some of the ramifications and open problems regarding constant-depth quantum circuits.

• 6 November: Harmony Zhan, WPI, "Does Laplacian quantum fractional revival occur on trees?"
  Abstract: A spin network exhibits fractional revival if a state localized at site u evolves to a superposition of states localized at site u and site v. We explore this phenomenon on trees, which, as minimally connected graphs, are natural candidates for physical realization. We show that relative to the Laplacian Hamiltonian, no tree on more than three vertices admits this phenomenon, except in the trivial case of periodicity. On the other hand, we can classify all paths and double stars that admit a relaxed version of this phenomenon called pretty good Laplacian fractional revival. This is joint work with Chan, Johnson, Liu, Schmidt, and Yin.

• 13 November: Bill Martin, WPI, "Another introduction to quantum algorithms"
  Abstract: In this talk, I will assume no background in quantum information theory (QIT) but will use linear algebra to examine a few of the basic algorithms that show how a quantum computer could conceivably outperform any classical computer. For example, the Deutsch-Jozsa and Simon algorithms have simple descriptions and their use of quantum entanglement is evident. The talk contains no original material and is tutorial in nature.

• 20 November: Speaker TBD, "Title TBA"
  Abstract: This will be another day devoted to basic material.

• 27 November: No Seminar, Thanksgiving Break
  

• 4 December: Speaker TBD, "Title TBA"
  Abstract: TBD

• 11 December: Padmanabhan K. Aravind, WPI, "Title TBA"
  Abstract: TBD

Past Seminars

A,B TERM 2024

• WPI's quantum information theory and quantum algorithms seminars have been irregular over the past few years.