Commencement 2020: Entangled with Princeton

May 18, 2022

As delivered

As you know from prior experience, Princeton tradition allows the University president to say a few words to each graduating class at its Commencement exercises.  Giving that address is a special privilege, and one that I cherish.

That privilege today feels even more extraordinary than usual, since this ceremony is unprecedented in the University’s history.  No class since World War II has had to wait two years for an in-person graduation.  No previous class has shown your unique combination of persistence, achievement, and patience.  The undergraduate and graduate alumni who make up the Great Class of 2020 will always have a special place in Princeton’s history.

This graduation speech is also different from others that I have given for another reason, which is that I have already had an opportunity to address the Class of 2020 at your virtual ceremony two years ago.  I am honored, but also slightly daunted, by the opportunity to speak to you for a second time.  What wisdom can I hope to offer to a class that has already heard one round of graduation speeches?

After considering this challenge for some time, I decided to share with you a quirky Princeton story that may perhaps, with some imagination, provide insight into what you have experienced over the last two years, and what you will experience in the years ahead.

The story begins in 1935, when Albert Einstein and two post-doctoral researchers named Boris Podolsky and Nathan Rosen published one of the most famous papers in the history of physics.  All three were appointed at the Institute for Advanced Study, temporarily housed in what is now Jones Hall on the Princeton campus.

The paper was about quantum science, and it discussed a phenomenon that Einstein would later mock as “spooky action at a distance.”  Quantum mechanics, the authors pointed out, rests on an other-worldly idea called superposition, which says that physical systems can be in a combination of two inconsistent states at once.  A particle can be, for example, in a combination of an “up” state and a “down” state—it is both and neither, but if someone observes it, it immediately becomes either “up” or “down,” but not both.

In their paper, Einstein and his co-authors argued that these strange concepts led to the bizarre conclusion that observing a particle in one place—for example, right here on the Commencement stage—could instantly affect the state of another particle somewhere else—for example, at the opposite end of this stadium, or in Hawaii, or, for that matter, out by some distant star.

Podolsky annoyed Einstein by leaking the paper to the New York Times.  Lots of professors, I can assure you, would love to leak their papers to the New York Times.  In general, the Times does not care.  But a paper by Einstein was a different matter.

The Times ran the story on page 11 under the headline “Einstein Attacks Quantum Theory.”  Podolsky told the Times that Einstein and his co-authors had proven that, even if quantum mechanics made plenty of correct predictions, its consequences were too strange to provide a complete description of the physical world.

Everything in that bold and controversial 1935 paper has proven correct—except for its conclusion.  What Einstein derided as “spooky action at a distance,” and what scientists now call “quantum entanglement,” is a feature of the physical world—one with increasingly important practical applications.  When people talk about quantum computing, for example, they are talking about devices that use “spooky action at a distance.”

There is something marvelous in the fact that one of the most exciting and practically important fields of 21st century science depends on something that Albert Einstein, perhaps the greatest scientist of the 20th century, got emphatically wrong in one of his most famous papers.

That insight should give us all a dose of humility when we are tempted to declare, as Einstein did, that some novel idea is too bizarre to be true.  And, conversely, we can perhaps all draw inspiration from the fact that new and genuinely strange ideas, beyond the ken of the greatest thinkers the world has known, sometimes contain profound truths.

Quantum mechanical properties apply at the microscopic level; we do not see them in our ordinary lives.  But I sometimes think—and here is where I need to call upon your imaginations—that the strange metaphysics of the quantum world can provide an alternative perspective on the paradoxes and ambiguities that color our lives.

Take, for example, the idea of superposition, which says that a physical system can be a combination of two inconsistent states: “up” and “down” at the same time.  Could one say that about what you have experienced over the past two years?  In your senior spring, you were both at Princeton and not at Princeton.  You graduated, and yet you did not.  You were together, still Princeton’s Great Class of 2020, and yet you were apart.

And though it does not technically count as what Einstein would call “spooky action at a distance,” were you not throughout this period, are you not now, sublimely entangled with one another and with Princeton?  You dispersed throughout the country and the world, yet you were also connected by shared challenges, memories, and your identity as a class.  What happened here, and what happened to each of you, affected all of you.

Though I recognize that not every member of your class can be with us today, I hope that this day and this week nevertheless help to resolve the pandemic’s strange superposition of states so that we can now say emphatically:  yes, the Great Class of 2020 is not only connected but together!  Yes, the Great Class of 2020 has graduated in every sense of the word!  And yes, the Great Class of 2020 is here, observed and observable, roaring like Tigers on this campus once again!

I hope, too, that you remain entangled with Princeton and with each other.  All Princeton classes are, in my thoroughly biased opinion, great classes, but they are also distinct.  They acquire their own identities and personalities.  Some people speculate that the events of the last two years might weaken the bonds that tie you together.  I predict the opposite:  that your resilience and your creativity will make your connections to each other and your entanglement with Old Nassau ever stronger.

We shall see.  For now, just let me say, on behalf of the faculty and administration, we are so glad that you are here!  Welcome back!  And to everyone in the Great Class of 2020, undergraduate and graduate alumni, I say congratulations, and I hope to see you back on this campus many times in the years to come.  2020:  Congratulations!