Quantum Causes, Dots, and Other Fun Science: the 2018 APS March Meeting

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American Physical Society March Meeting

March 5, 2018

Los Angeles, California

Meeting host:

American Physical Society


Marie Rioux

SPS Chapter:

The room was enormous, filled with rows of chairs and dimly lit by lamps dotting dark gray walls. A lone podium stood in a spotlight of reflected light from a looming projector-screen, and Dr. Robert Spekkens from the Perimeter Institute for Theoretical Physics had just begun.

It was one of the opening talks for a morning session at the 2018 A.P.S. March Meeting in Los Angles, California, and everyday notions of cause and effect were already being turned on their heads.

Spekkens laid out his principles first, explaining that two variables that are causally disconnected have no common cause, and so are statistically independent.

“Learning the value of one is going to teaching you nothing about the other,” Spekkens said.

Similarly, if there’s a correlation between two variables, then there must be some common cause, unless the common cause is conditional, Spekkens elaborated: if a common cause between two variables is conditioned on, then the two variables don’t need to be correlated, and don’t have a common cause.

Then Spekkens contrasted two kinds of causal systems: a classical one and a quantum one. The classical corresponded to everyday experience, while the quantum system showed a correlation between probabilities of a wave and a certain outcome.

“Is it the case that it’s a common cause that accounts for the correlation, or is it the case maybe that the settings here influences the outcome on the distributed wave,” Spekkens said.

With only a smattering of undergraduate exposure to quantum mechanics, I was quickly lost beyond his classical system, but this was my second day at the APS Meeting—after spending the previous day in the company of professional researchers, professors and more, I was getting used to falling behind.

Even so, I was determined to know more.

Spekkens was heavily engrossed in a discussion when I approached him, and walking past me toward the door of the room. However, as S.P.S. President Brad Conrad would tell me later that same day, “It's not easy to introduce yourself to somebody you don't know. But you should just put your hand out there, introduce yourself, and you'd be amazed at the connections and where those can lead."

I hadn’t heard that advice yet, but my curiosity was strong, and I caught Spekkens’ attention with a soft “excuse me”. He agreed to share his slides, and volunteered several extra links to his extended presentations on the same topic, along with a wealth of clarifying information which has continued to provide me insights with every reading.

Investigating the foundations of quantum mechanics was fascinating, but there was much more to see, especially for an undergraduate student like myself.

Coming from a small college in Kansas surrounded by farms and fields, I found the bustle of several hundred scientists in the Los Angles Conference Center both slightly intimidating and incredibly engaging.

The presentations were collected into sessions that lasted several hours, but were focused on a single general topic. I found myself using the program I’d been handed at check-in to narrow down which sessions by topic and title, and then using the A.P.S. meeting app to read the individual presentation abstracts. It was a surprisingly easy juggling act after the first few times.

Since I’m involved in solar energy research, I sought out sessions focused on that topic, and found a few explicitly focused on quantum dots, which are nano-sized semiconductors that can absorb and reemit light.

It wasn’t surprising that even in sessions in my general area, my understanding was quickly outstripped. Far from intimidating though, it was inspiring—such as one presentation by Professor Ted Sargent from the University of Toronto on quantum dot sensor development.

One success from his team Sargent explained was later used in certified devices. “Essentially, what we had done is we’d improved the diffusion length through the minority of carriers in the quantum dot solid by a fairly significant margin, and that allowed us to make about a 600 nano-meter thick quantum dot active layer.” Sargent said.

Without a sufficient background in quantum dots, his finer points even so summarized were obscure to me, but the expertise necessary for developing complex and fragile nano-materials was striking, and it remained one of the most memorable presentations I attended.

Between sessions, I visited the graduate school and job fair, which were both placed in a giant room filled with tables. Each school and company with a table arranged a booth for curious meeting attendees to visit, and the colorful displays sported pens, cards, and an assortment of trinkets with logos and contact information printed on them.

It was there that I met S.P.S. President Brad Conrad. He was filled with infectious enthusiasm, telling me that the March Meeting happens to be one of his favorite meetings of the year.

“When you start coming year after year, you not only see your friends from undergrad but your friends from grad school, you see your colleagues, post-docs, and you get to see these people through a wide cross-section of the community. So, the nice thing about the March Meeting is that its like a family reunion. It’s like the physics family reunion,” Conrad said.

It piqued my curiosity—since he’d attended so many, I asked what he thought of the presentations this year.

His replay was unhesitating. He explained he’d been at the undergraduate sessions throughout the previous day and the following morning. “They were the best yet,” Conrad said.

It was an easy segue into a discussion about advice for undergraduates like myself in attending the meeting without the level of expertise so many other attendees had, and Conrad was full of advice.

“The most important thing you can do at the March APS Meeting, is meet people,” Conrad said, explaining that the meeting isn’t just for learning new things in the presentations, but also for making connections.

It was advice that I quickly experienced firsthand. Within moments of admitting that I study journalism as well as physics and that I’d applied for the S.P.S. Reporter Award on my S.P.S. Chapter Advisor’s recommendation, Conrad was introducing me to Project Manager Julie Majors from the American Institute of Physics journal, asking her to share some insight into the field of science communication with me.

It was a delight to discuss a field that overlapped with my current studies and interests—especially since Majors herself was passionate about her work. When she invited me to observe a press conference I eagerly accepted.

It was little different from staged press conferences in my tiny undergraduate classroom back home, with a variety tripods, cameras, lights and microphones scattered around a small, quiet room filled with chairs, a few tables, and a single podium.

 It was unassuming and simple, and was I wholly enamored with it. I watched silently as professors presented featured research projects, or discussed atomic particles in a panel session. With only two minutes left to spare, I finally parted to meet my friends for the final presentation of the day, where I proceeded to bombard them with details until the session began.

It was only the end of the second day, but from twisting my mind around cause and effect in a quantum world, through nano-materials exceeding my depth of experience, I was as exhausted as I was exhilarated—eager for whatever the next day might hold.

The 2018 A.P.S. March meeting was certainly full of surprises, and with the efforts of people like Spekkens, Sargent, Conrad, and Majors I expect it will be for many years to come.