Category: Quantum Computing

2023 Fall – Advanced Quantum Computing

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Hello! Welcome to my site for quantum computing.

Please note that I am not the instructor for this semester’s advanced quantum computing course. The course is being taught by Prof. Wenchao Ge from the University of Rhode Island. UMass Dartmouth students should access the lectures via a link that will be provided soon.

You can find the syllabus here.

You can also click on the syllabus link in the site panel.

I will be providing some support on the UMass Dartmouth side, including an office hour which is TBA.

 

 

Are Quantum Computers Supreme Yet?

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We’ve had a few discussions during class about whether or not quantum computational systems have clearly demonstrated superiority to their classical counterparts. Google is widely acknowledged to have achieved “quantum advantage” in 2019 with its 53 qubit system called Sycamore. There is still some debate about it because IBM claimed to be able to perform the same computation over a period of a few days on its most powerful supercomputer. Nature has a nice piece on this:

https://www.nature.com/articles/d41586-019-03213-z

A little over a year ago a group in China built a photonics-based system that carried out a type of quantum computation (called boson sampling) in 200 seconds. Classical algorithms are much slower, clocking in at 2.5 billion years. Nevertheless, there are some caveats, the most important being is that the photonics system is especially suited to the task of boson sampling and is not a basis for general quantum computing. Furthermore, boson sampling itself is not known to have any useful applications other than allowing quantum computer systems to demonstrate “quantum advantage” over classical systems. Despite these somewhat deflationary notes, I think it’s an impressive feat!

More recently, a researchers were able to construct a programmable photonics chip. The idea behind such an approach is that photons can be used as quantum information carriers. My understanding (which is limited!) is that there have been problems with controlling and scaling up such systems, but that this recent work marks an important step forward in developing this approach. You can take a look at the “News and Views” article about this work in Nature:

https://www.nature.com/articles/d41586-021-00488-z

There’s also a nice description of this in Ars Technica:

https://arstechnica.com/science/2021/03/programmable-optical-quantum-computer-arrives-late-steals-the-show/

I’m not an expert in these matters, but it seems like the progress has been amazing.

 

Spring 2021 Quantum Computing – Fun Reads

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We were recently talking about Claude Shannon’s information theory, and I recalled reading a nice overview of Shannon and his work in quanta magazine:

https://www.quantamagazine.org/how-claude-shannons-information-theory-invented-the-future-20201222/

When it comes to controlling qubits, we still need classical processors. The trouble is that they heat up the environment and many qubit implementations require extremely low temperatures. This leads to limitations in the number of qubits you can actually work with. Some intriguing news out of Microsoft came out recently about chips that can function at ridiculously low temperatures. Personally, I don’t know enough (for now) about how much of this is realistic versus hyped, but it’s interesting nonetheless:

https://www.microsoft.com/en-us/research/blog/full-stack-ahead-pioneering-quantum-hardware-allows-for-controlling-up-to-thousands-of-qubits-at-cryogenic-temperatures/

Welcome to the Spring 2021 Quantum Information and Computing Class!

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Hello and welcome to my course on quantum information and computing (phy 410/510) for the 2021 spring semester. This site will serve as a central hub from which you can access my basic info (name, email, and whatnot), notes, videos, the lecture schedule, and assignments. If I’m feeling inspired, I may occasionally post links to interesting quantum-related things I’ve come across and given the time and energy, write some posts exploring issues related to our class discussions.

I’m really excited about this course, and why not? It’s an amazing subject in so many different ways. Here are a few:

  1. The technological side of quantum computing and communication is very real and huge advances are being made year-by-year if not month-by-month!
  2. Quantum information and computing most likely establish a completely new basis for computing in general, dramatically impacting our abilities to solve certain types of problems that are (likely) intractable using only classical computing. (Why do I write “likely”? Something worth thinking about!)
  3. The quantum computing/information approach to quantum theory has helped to illuminate some of the famously murky conceptual underpinnings of the theory. New modes of conceptualizing quantum theory lead to interesting new ways to teach the subject that are in many ways much more accessible than the traditional approach you would learn in a standard quantum physics course.

There are many more reasons that this area is fun and exciting and I’m looking forward to sharing them with you. I’m also quite interested in the ideas that the subject sparks among you as we explore it this semester.