ewin

postdoc in theory, UC Berkeley EECS & Miller Institute
(off twitter, find me anywhere else)

[Laura Lewis @Laura_Lewis_1]

New paper with Ewin and John on learning local Lindbladians! https://t.co/SMGAChXftg

As a special case, we also get structure learning of Hamiltonians from high-temperature Gibbs states, which was wide open before our work 🙂

[ewin @ewintang]

@httpsXrth totally agree. still amazed that you can just sidestep the barrier and get everything you thought you couldn't have

[ewin @ewintang]

hello to my new followers. did you know that mixed state tomography reduces to pure state tomography

[ewin @ewintang]

for more, see https://t.co/5fZN8T3PYF, https://t.co/hJgkPMZ4qC, and the lovely exposition https://t.co/ENRKMj3b2x .

[ewin @ewintang]

and, though we've known for decades that you can't purify quantum states without violating quantum mechanics, we only just found out that purifying them *randomly* is possible? (and this is a super useful fact!)

[ewin @ewintang]

@preskill thank you John!!

[ewin @ewintang]

@Isaac__kim @AnuragAnshu4 @AlhambraAlvaro yes, this seems right. I don't know to what extent our measurements simplify for classical Hamiltonians, but nested commutators collapse and it looks like observables could become O(1)-local Paulis.

[ewin @ewintang]

dating a complexity theorist must be an adventure. one week she asks you to fold her laundry, the next week you find out you were actually filing her taxes

[ewin @ewintang]

intentionally losing a couple log factors in the analysis, to leave evidence of a struggle

[ewin @ewintang]

@QuantumMemeing she probably just didn't understand you, you should try repeating the information a few more times until it gets through to her

[ewin @ewintang]

if you're a better coder than me & looking for glory, it probably wouldn't be too hard to make this into a gif (using the parametrization in Eq 1.2) and put it on the Zolotarev polynomials Wikipedia page..

[ewin @ewintang]

have you ever seen a visualization in a paper and thought, wow, this is begging to be made animated or interactive? [Shadrin, Twelve proofs of the Markov inequality]

[ewin @ewintang]

@BigPrimesOrg it's a beaut!

[ewin @ewintang]

@JohnASmolin not sure, i'm starting to wonder why i even tweeted about it.

[ewin @ewintang]

babbage also created a lesser-known indifference engine. it was highly successful but quickly forgotten

[ewin @ewintang]

@QuantumManuel i don't think so? from the same chapter: "polynomial interpolants in Chebyshev points are problem-free when evaluated by the barycentric interpolation formula. They have the same behavior as discrete Fourier series for periodic functions, whose reliability nobody worries about."

[ewin @ewintang]

Enjoyed this collection of quotes from textbooks showing polynomial interpolation's decades-long bad reputation in numerical analysis.

"A great deal of confusion underlies remarks like these. Some of them are literally correct, but they are all misleading."―Trefethen, ATAP Ch.14

[ewin @ewintang]

what's funny about this is Trefethen's (plausible) theory that this pessimism is due, in part, to one famous paper showing that the *different* problem of root-finding given a polynomial's coefficients is ill-conditioned, discouraging investigation into polynomials in general

[ewin @ewintang]

@mittaltushant yeah, it sucks. i've had mild success with using things like anki to fix this but most of the time my research still doesn't fit in memory

[ewin @ewintang]

it's the best feeling when your research problem can finally fit in your head so you can think about it whenever.. instant buff to productivity