QSE Quantum Seminar, "A Little Incoherence Goes a Long Way: Enhancing Quantum and Classical Algorithms with Randomization" - John Martyn

Please join us for the QSE Center Quantum Seminar with John Martyn from Harvard University who will give the talk "A Little Incoherence Goes a Long Way: Enhancing Quantum and Classical Algorithms with Randomization" on Thursday November 13 from 12:30pm to 2:00pm
Location: BS 160

Pizzas will be available between the seminars at 12:00. All PhDs, postdocs, students, group leaders, and PIs are welcome to join us.

TITLE: "A Little Incoherence Goes a Long Way: Enhancing Quantum and Classical Algorithms with Randomization"

ABSTRACT:
In studying quantum systems, either with quantum algorithms or classical methods, we typically focus on coherent unitary dynamics. Decoherence arising from randomness or environmental noise is often viewed as detrimental, and sought to be suppressed. In this talk, I will demonstrate the opposite: incoherence, in small doses, is beneficial to both quantum and classical algorithms. 

I will illustrate this statement in two contexts. First, in quantum algorithms based on quantum signal processing, I will show how using a randomized channel, instead of the standard deterministic one, reduces costs (e.g., gate count) by 50%. Second, in the context of neural-network quantum states, I will prove how using a variational mixed state representation, instead of a pure state, provides more accurate estimates of ground state observables. In aggregate, these results reveal the surprising utility of incoherence in quantum information, and suggest wider applications in algorithm development. 

BIO:
John is a Quantum Initiative Fellow at Harvard University, and a Staff Scientist of Pacific Northwest National Laboratory. In his research, he explores the theoretical side of quantum information, with a focus on developing quantum and classical algorithms for simulating physics and solving hard computational problems. He recently received his PhD in physics from MIT, advised by Isaac Chuang, during which he spent time interning at IBM Quantum and Google X. In the beforetimes, he received a BS in physics from the University of Maryland, and worked as a student researcher at Caltech.