Introduction to Quantum Information

First slide, viewed on my laptop.

First slide, viewed on my laptop.

I’m lazy. The only reason I ever do anything is that sometimes in a weak moment I agree to do something, and after that I don’t have the nerve to back out. And that’s how I happened to give the introductory lectures leading off the 12th Canadian Summer School on Quantum Information last June.

The video of the lectures recently became available on YouTube in two one-hour segments, which is my reason for posting about them now:

Here are the slides I used. The school is pitched at beginning graduate students who have a solid background in quantum mechanics but may not be very familiar with quantum information concepts.

Andrew Childs, who knows my character flaws well, invited me to lecture at the school nearly a year in advance. Undaunted by my silence, he kept resending the invitation at regular intervals to improve his chances of catching me on a weak day. Sure enough, feeling a twinge of guilt over blowing off David Poulin when he made the same request the year before, and with a haunting sense that I had refused to do something Andrew had asked me to do on an earlier occasion (though I can’t recall what), one day in September I said yes, feeling the inevitable stab of regret just seconds after pushing the Send button. I consoled myself with the thought that this could be a Valuable Service to the Community.

Actually, it was fun to think about what to include in my lectures. The job was easier because I knew that the other lecturers who would follow me, all of them excellent, would be able to dig more deeply into some of the topics I would introduce. I decided that my first responsibility should be to convey what makes the topic important and exciting, without getting too bogged down in technicalities which were likely to be addressed later in the school. That meant emphasizing the essence of what makes quantum information different from ordinary “classical” information, and expounding on the theme that classical systems cannot in general simulate quantum systems efficiently.

The conditions under which I delivered the lectures were not quite ideal. Preparing PowerPoint slides is incredibly time consuming, and I believe in the principle that such a task can fill however much time is allotted for it. Therefore, as a matter of policy, I try to delay starting on the slides until the last moment, which has sometimes gotten me into hot water. In this case it meant working on the slides during the flight from LA to Toronto, in the car from Toronto to Waterloo, and then for a few more hours in my hotel room until I went to bed about midnight, with my alarm set for 6 am so I could finish my preparations in the morning.

It seemed like a good plan. But around 2 am I was awakened by an incredibly loud pounding, which sounded like a heavy mallet hammering on the ceiling below me. As I discovered when I complained to the front desk, this was literally true — they were repairing the air-conditioning ducts in the restaurant underneath my room. I was told that the hotel could not do anything about the noise, because the restaurant is under different ownership. I went back to bed, but lost patience around 3:30 am and demanded a different room, on the other side of the hotel. I was settled in my (perfectly quiet) new room by 4 am, but I was too keyed up to sleep, and read a book on my iPad until it was 6 am and time to get up.

I worked in my room as late as I could, then grabbed a taxi, showing the driver a map with the location of the summer school marked on it. Soon after he dropped me off, I discovered I was on the wrong side of the University of Waterloo campus, about a 20 minute walk from where I was supposed to be. It was about 8:15, and the school was to begin at 8:30, so I started jogging, though not, as it turned out, in the right direction. After twice asking passersby for help, I got to the lecture hall just in time, my heart pounding and my shirt soaked with sweat. Not in the best of moods, I barked at Andrew that I needed coffee, which he dutifully fetched for me.

Though my head was pounding and my legs felt rubbery, adrenalin kicked in as I started lecturing. I felt like I was performing in a lower gear than usual, but I wasn’t sure whether the audience could tell.

And as often happens when I reluctantly agree to do something, when it was all over I was glad I had done it.

2017-01-13T10:05:57+00:00 December 17th, 2012|The expert's corner, Theoretical highlights|13 Comments


  1. shaunmaguire December 17, 2012 at 7:34 am - Reply

    Moments of weakness: this is the behavioral economic insight that underlies 1-click shopping! Translation: we all suffer from them. Amazon profits!

  2. Tony Silva December 17, 2012 at 10:20 am - Reply

    Reblogged this on Astronovae.

  3. David Preskill December 17, 2012 at 8:03 pm - Reply

    Your energy level seemed fine to me, Old Boy. I got through the first 20 min or so of the first video before discussion passed irrevocably over my head. I have to agree with you that these sorts of things are best left to the last minute. And it’s good to video the first take; it’s never as good if you try to do it again.

  4. David Poulin December 18, 2012 at 6:02 am - Reply

    Well, I think the lesson is clear: you should always accept my invitations and not Andrew’s. Nights were very peaceful in the national park where my summer school was held…

    • preskill December 18, 2012 at 11:29 am - Reply

      Yeah, only the pounding of falling trees downed by hard-working beavers.

  5. […] John’s posts invariably manage to be enjoyable as well as informative. Now he’s put up a couple of hour-long videos, lectures that he gave at the 12th Canadian Summer School on Quantum Information. Two hours is a […]

  6. Paul Ginsparg December 19, 2012 at 10:51 am - Reply

    Well I got as far as “there … are … so … many … exciting … things … to … work … on … (yawn) … ” before concluding that the speaker needed some coffee, and switched to peruse pdf of slides. But I’m guessing audience would have been impressed to know speaker ran a sub 4 min mile to get there (with backpack, 2 hrs sleep, and jetlagged), was it at least mentioned in intro?

    The pdfs are fun. But not having heard talk am wondering why in the 21 slides about the three coin example you never gave the entangled state? Was it verbal, or no one asked?
    (I couldn’t get away with that omission, but then again I usually require a limo directly to lecture hall.)

    • spiros December 19, 2012 at 11:09 am - Reply

      Paul, you missed out on all the good stuff by switching to pdf too soon. I was there when John gave the lectures and I will never forget the unveiling of the plan to build the first-ever 10K qubit quantum computer around minute 15. More importantly, John finally admitted to being much older than his good looks would betray (he had a young female filmmaker recently comment on his good looks).

      • Paul Ginsparg December 19, 2012 at 11:31 am - Reply

        > the unveiling of the plan to build the first-ever 10K qubit quantum computer

        right saw that in slides, from Martinis’ group, heard it in a talk by Mariantoni

        but i did just go back to listen to that 2 min stretch, and it was funny to hear no one knew whether to laugh re his youthful appearance

        > he had a young female filmmaker recently comment on his good looks

        you may be confusing him with John Edwards?

    • preskill December 19, 2012 at 11:18 am - Reply

      Identifying the shared entangled state, and the measurements made by the two parties, was a homework problem.

      I didn’t mention the sub 4 minute mile. I’m too modest.

      • Paul Ginsparg December 20, 2012 at 6:43 pm - Reply

        > Identifying the shared entangled state, and the measurements made by the two parties, was a homework problem.

        Well for the pedagogic record: by some odd coincidence appears someone did your homework tonight here: arXiv:1212.5214, based in part on your section 4.1.3 starting on p.7 here (in turn based on Mermin’s suggestion in his 1981 Am.J.Phys. article, which by another odd coincidence I learned as a student directly from Mermin at the time he was writing it…)

  7. R&D | Quantum Entanglement April 4, 2013 at 9:44 am - Reply

    […] he effectively summarized 50+ years of Quantum research and development into a one hour lecture. Quantum frontiers has some of the recorded lectures which readers may find […]

Leave A Comment