May 20, 2026
Today has been one of those days when everything seems like it's going right, and then suddenly something small starts to go wrong, and then a magical solution avails itself, but at the last second the momentary chance of success is obliterated by something else going awry. And yet, I'm still holding out hope.
Today's multi-act play began at 6am, when I woke up to start a laundry load in anticipation of the rest of the day. I then presented at my research group's weekly journal club, before the entr'acte of lab lunch, accompanied by several enjoyable conversations with labmates. After lunch, I worked with some labmates to configure our experimental setup for the next round of experiments and did my routine lab maintenance tasks. I then headed home, packed, and departed for the airport for the final act: flying home to San Antonio (with a layover in St Louis) to spend some time with my grandparents and parents and sister during this extended Memorial Day weekend.
After a series of heat delays, rain delays, and crew diversions, it's currently 22:40 CDT and I just started writing this post on a plane from Boston to Nashville. As of several minutes ago, FlightAware suggests that I'll land at 23:05 CDT, a minute after the expected departure of the second leg to San Antonio at 23:04. I keep refreshing FlightAware, and the times keep shifting, and now it says the second flight will depart at 23:05 CDT, but nothing is final. Regardless, it may be moot: an hour ago, I received a text that I had been rebooked to fly from Nashville to Tampa tomorrow morning at 5:50 CDT and then Tampa to San Antonio at 9:40 CDT.
(Update: I reached Nashville at 23:06 CDT at gate C23, and FlightAware said the flight to San Antonio was "departing shortly" from gate C24, so I quickly exited the plane and went to the adjacent gate. It was still sitting at C24 and took until 23:13 CDT to push off from the gate, but the boarding agent said the doors had closed and told me to talk to customer service. Customer service was able to rebook me onto the direct flight to San Antonio in the morning, which had one remaining seat, instead of the route connecting through Tampa. So now I will finish this post and figure out my overnight accommodations.)
Today was my turn at my research group's weekly journal club. Each week, someone presents a paper or papers related to our research area (superconducting quantum circuits for quantum computing), and today I presented a paper titled "Systematic Construction of Time-Dependent Hamiltonians for Microwave-Driven Josephson Circuits."
We often apply external stimuli to our quantum circuits to induce certain desired processes and behaviors within our system. These external stimuli often take the form of currents and voltages, both at DC and at relevant system frequencies, and are typically applied through external coupling ports that allow us to interface between the outside world and the otherwise isolated world of the quantum system. Consequently, these external ports are also a channel for the information stored in the quantum system to leak into the outside world and lose its quantumness.
The paper I presented, with eighteen pages of main text and a medium-length supplement, discusses methods to study the behavior of a superconducting quantum circuit in the presence of external stimuli. It hopes to provide a recipe for how to efficiently characterize the behavior of these systems in the presence of these external stimuli, even when the system is complex and may not have an obvious circuit representation. The paper built on some existing methods that are popular in my field for analyzing systems under static conditions and also referenced some concepts that are of interest to members of my group. Many people asked insightful questions during my presentation, and during and after lunch, I had some fruitful conversations about this paper and some related work. I'm hoping some of the methods might provide an alternate supplemental approach for my own project, as well.
The devices we use in our experiments are electrical circuits. They are typically millimeter-sized and reside in housings that fit within one's palm, but they have currents and voltages and charges and fluxes just like the circuits we are familiar with in our everyday world. However, in specific regimes (when the circuit is cold enough to reach a superconducting state), the signals in these circuits behave in slightly different ways: they become small enough that we can consider discrete electromagnetic excitations of the system, and they exhibit quantum fluctuations about their average values. The research area of superconducting quantum circuits studies how to make better devices and how to integrate many of these devices together, with the eventual goal of building very large systems that are capable of executing algorithms and protocols that harness the quantum nature of these fluctuating signals.
These quantum fluctuations can often be overshadowed by thermal fluctuations, which increase as the temperature of the environment increases. Consequently, the workhorse of our experimental setup is the dilution refrigerator, a complex thermodynamic system that allows us to operate our devices at tens of millikelvin temperatures. In addition, we use a complex network of microwave-frequency filters and attenuators to limit the amount of thermal noise that can reach our system. Collectively, this allows us to suppress these thermal fluctuations so we can focus on the quantum nature of the electromagnetic fluctuations instead.
A typical workflow for experimental research is that we make new devices, bring the fridge to room temperature and pressure, open the fridge, install new devices, close the fridge, pump the fridge to vacuum and cool it to millikelvin temperatures, and then run experiments where we characterize the performance of these devices in this superconducting quantum state. Our goal is often to verify that our devices match our design targets and that they behave similarly to our simulations when we interact with them under experimental conditions (related to the themes of the paper I presented in the morning).
After lunch, I helped two of my labmates with the wiring on one of our group's dilution fridges. We identified which components had changed since the previous cooldown cycle and also replaced some other wires and made some new connections that were necessary for the new devices we were adding to our setup. After I left, my labmates finished up the wiring, closed the fridge, and began pumping it in the evening.
By the afternoon, it was nearing time for me to go home and prepare for my flight, so I made one last walk around our group's lab setups to check the liquid nitrogen supply. We use liquid nitrogen to remove impurities (other gases) from the gas mixture that we use for the thermodynamic cooling of the dilution refrigerator. One of my lab responsibilities is to manage the schedule for who fills the traps every other day and to make sure there's a constant stream of liquid nitrogen dewars available in the lab for these purposes. So every couple weeks I order a few dewars to our group's labs and then submit the delivery receipts through our purchasing portal once they arrive. Today, most of the labs had a sufficient LN2 supply, but since I'll be away for over a week I preemptively ordered a couple more to one of the labs. Then I headed home.
I had been meaning to go to the airport via Airport, as I wasn't sure if my two previous attempts in the previous direction counted by my own criteria. So today I budgeted extra time to walk to Central, take the RL to Park, take the GL to Gov't Center, take the Blue to Airport, and walk to the airport. Of course, nothing of this sort can ever go according to plan.
The forthcoming chaos was foreshadowed in the morning when I stepped out of my apartment in long sleeves and pants and immediately felt the heat. And then on my walk home from work, the temperature read 95 °F and I thought it fitting for getting me in the mood for Texas. I should have remembered my travels last summer on the Worcester commuter rail, when the extreme heat waves would routinely suppress train speeds at 30mph due to potential worries about track warping. I assume something similar resulted in the "signal error at JFK/UMass" that resulted in 15-30min system-wide delays on the RL today.
So after waiting at Central from 16:15 or so for around fifteen minutes and hearing "The next ... Ashmont ... train is stopped one station away," I set a deadline of 16:45 to call an Uber to avoid the risk of missing my flight. But then I saw that my flight had been delayed from 15:55 by around twenty minutes and figured it was worth the wait. So the RL train finally arrived, and I did my two transfers to the GL and BL, and then walked along the sidewalk to the airport (with lots of sneezing along the way, and it was hot when not shaded) and reached with time to spare. I quickly cleared through security made my way towards the gate ...
... only to see that the afternoon's sweltering heat had suddenly turned into a thunderstorm. We soon learned over the PA that the ramp was being temporarily closed while there was lightning in the area. And we then learned that although our inbound plane had arrived, our incoming crew had been diverted to TF Green Airport in Providence and would only be arriving by 20:00 EDT.
This was problematic because many of us had connections in St Louis around 20:45 CDT, and the Boston to St Louis leg would itself take three hours. So they called up all connecting passengers in one single-file line and began figuring out rebooking options. When it was my turn, I was told that I could stick with my current route and plan on taking an early-morning flight out of St Louis, but I would be on my own for lodging and the hotel would not be reimbursed since the ATC hold was weather-related.
So I instead went for the other option they offered, which was a 21:30 EDT flight to Nashville that would reach at 23:00 CDT and allow me to transfer to a 23:45 CDT flight. This flight would reach San Antonio by 25:30 CDT or so and at least get me home on the same day.
So I was surprised to get a text while on the Boston-to-Nashville flight saying that I had been rebooked to the next morning at 05:50 CDT from Nashville to Tampa(?!) to San Antonio. I asked the flight attendant and he suggested those seats might have been in higher demand and so this could just be a preemptive thing to hold me a spot tomorrow, whereas I could always switch back to the San Antonio flight if I made the connection in time. So based on his reassurance, I was still hopeful that I could reach in time and make it. And I was extra hopeful when I saw that I'd be landing in Nashville at C23 and the San Antonio flight would be departing from C24.
As the introduction section suggests, this did not happen: the connection was just barely infeasible, and a couple of us in the same boat stared in disbelief as we saw the plane still at the gate but with the doors close. I asked the gate agent in Nashville and he said it was likely due to the crew's hours limit. I learned that the hours requirements are related to when the flight takes off, not when it lands, so their priority would have been to push off and get moving as fast as possible if they were nearing the crew's hours limit. Nevertheless, it was frustrating to see the plane sitting there for another seven minutes after I arrived, especially with the expected positive ending that everything would work out.
In any case, I'm now finishing this post from an airport hotel in Nashville instead of reaching home around now. It seems unlikely that I'll be able to get a voucher from Southwest strictly for the initial delays (the customer service number said I'd have to ask at the gate, and the gate agent said they wouldn't give a hotel voucher for weather events); it remains to be seen whether their rebooking me onto a later leg with the promise of a guaranteed same-day connection in Nashville, only to inconvenience me when it didn't pan out, would be a reasonable reason for some sort of conciliatory travel credit.
Celebrating the positives of the day tends to be a good way to feel better. Here's a brief, non-exhaustive list: I listened to some new, different music on the way to and at the airport and had some new interesting ideas for a cappella covers; I had some fruitful conversations with labmates during and after lunch about implementing some of the concepts I discussed in my journal club talk; I enjoyed wiring up the fridge with my labmates; and I chatted with some nice people in the airport.