Po-Shen Loh

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Po-Shen Loh
Born (1982-06-18) June 18, 1982 (age 41)
Alma materCalifornia Institute of Technology (BS)
Cambridge University (MASt)
Princeton University (PhD)
Scientific career
InstitutionsCarnegie Mellon University
Doctoral advisorBenny Sudakov
Doctoral studentsMikhail Lavrov
Debsoumya Chakraborti[1]

Po-Shen Loh (born June 18, 1982) is an American professor of mathematics at Carnegie Mellon University, specializing in combinatorics, and formerly served as the national coach of the United States' International Math Olympiad team. He is the founder of educational websites Expii and Live, and lead developer of contact-tracing app NOVID.

Early life and education[edit]

Loh was born on June 18, 1982 in Madison, Wisconsin to Singaporean immigrants Wei-Yin and Theresa Loh.[3][4] As a middle school student, Loh twice represented Wisconsin in the national Mathcounts competition. He attended James Madison Memorial High School, and in 1999 won a silver medal representing the US in the International Mathematical Olympiad (IMO).[4][5]

Loh studied mathematics as an undergraduate student at the California Institute of Technology. In 2003, he won a Goldwater Scholarship.[3] In 2004, he graduated with honors, ranked first in his graduating class, and his undergraduate thesis received an honorable mention for the 2004 Morgan Prize.[6] Loh completed a one-year master's degree at Cambridge University on a Churchill Scholarship.[7]

Loh pursued graduate studies in mathematics at Princeton University with the support of a Hertz Fellowship,[6] and, under the supervision of Benny Sudakov, received a Ph.D. in 2010 with his dissertation Results in extremal and probabilistic combinatorics.[8]


Teaching and coaching[edit]

Loh's math coaching career started in 2002 when he first served as an assistant coach at the US national IMO training camp, Mathematical Olympiad Summer Program (MOSP). In 2010, Loh was appointed deputy leader Team USA for the IMO,[9] and in 2014 he was appointed leader[10][11] and was the national coach for 9 years, until 2023.[12] Under his coaching, the team won the competition in 2015, 2016, 2018, and 2019—their first victories since 1994.[13][14]

Loh has been a professor at Carnegie Mellon University since 2010, where he teaches courses on discrete mathematics and extremal combinatorics. Loh runs the training seminar for the Putnam competition for Carnegie Mellon undergraduates.[9]


Loh works at the intersections of combinatorics, graph theory, probability, and computer science,[3] and as of 2023 he has written 41 publications.[15]

In 2019, Loh developed an alternative method and exposition for the solution of quadratic equations, based on the symmetry of parabolas.[16]

Other projects [edit]

Loh is a prolific creator of expository math videos on YouTube under the channel name Daily Challenge with Po-Shen Loh. He has also made many appearances on other math-related channels, which have collectively been viewed millions of times.[17] Loh's videos have been frequently praised for their clean and high quality diagrams.[18]

Loh is the founder of Expii, a crowdsourced math lesson and problem solving website with tens of thousands of users.[13][19] Loh also founded Live, a math education site in which student teachers teach small courses surrounding middle and high school competition math concepts via livestreaming and video chat, as a way to improve interactivity of remote learning during the COVID-19 pandemic.[20]

In March 2020, Loh and other Hertz fellows were asked to assist in helping combat the COVID-19 pandemic. They developed NOVID, a contact tracing app with the unique feature of notifying users before exposure, whenever someone in their social network is affected, rather than after.[3] NOVID tracks infections anonymously using location information gathered from inter-communicating cell phones,[21] and was tested in pilot studies on college campuses.[22]


  1. ^ "Po-Shen Loh". Mathematics Genealogy Project. Retrieved 2023-12-04.
  2. ^ Sostek, Anya (May 13, 2019). "It took 36 years, but a girl has won the Pennsylvania middle school math championship". Pittsburgh Post-Gazette. Retrieved 2020-01-15.
  3. ^ a b c d Shamout, Omar (Spring 2022). "Math for the Masses: Inside the Mind of Po-Shen Loh". Caltech Magazine. Vol. 85, no. 1. pp. 35–37 (print version). Archived from the original on 2023-06-26. Retrieved 2023-06-26.
  4. ^ a b Erickson, Doug (July 18, 2015). "Former Memorial High School math whiz coaches Team USA to big international win". Wisconsin State Journal. Archived from the original on 2022-06-10. Retrieved 2023-06-19.
  5. ^ Po-Shen Loh's results at International Mathematical Olympiad
  6. ^ a b "Po-Shen Loh". Big Think. Retrieved 2023-06-08.
  7. ^ "Past Churchill Scholars". churchillscholarship.org. Archived from the original on 2021-04-15. Retrieved 2021-03-18.
  8. ^ Loh, Po-Shen (2010). Results in extremal and probabilistic combinatorics (PhD dissertation). Princeton University.
  9. ^ a b Pavlak, Amy (April 2012). "Passing the Torch: Po-Shen Loh Trains Students to be Math Olympians". Chinese American Forum. Vol. 27, no. 4. pp. 32–33.
  10. ^ Dunbar, Steven R. (2014). "Po-Shen Loh Appointed USA IMO Team Leader". MAA Focus. No. April/May 2014. p. 6. Retrieved 2023-07-18.
  11. ^ Sostek, Anya (August 14, 2017). "More than 300,000 students entered a math contest. The top score came from a 16-year-old in Pittsburgh Public Schools". Pittsburgh Post-Gazette. Retrieved 2017-12-28.
  12. ^ "MOP Academic Director AoV - 2023 Clean Copy" (PDF). Mathematical Association of America.
  13. ^ a b Strauss, Valerie (July 18, 2016). "U.S. students win prestigious International Math Olympiad — for second straight year". Washington Post. Archived from the original on 2016-07-20. Retrieved 2017-12-28.
  14. ^ Levy, Max G. (February 16, 2021). "The Coach Who Led the U.S. Math Team Back to the Top". Quanta.
  15. ^ "Loh, Po-Shen (751875)". MathSciNet. Retrieved 2023-06-05.
  16. ^ Chang, Kenneth; Corum, Jonathan (February 5, 2020). "This Professor's 'Amazing' Trick Makes Quadratic Equations Easier". The New York Times. Archived from the original on 2020-03-02. Retrieved 2023-06-26.
    Loh, Po-Shen (2019). "A Different Way to Solve Quadratic Equations". Daily Challenge with Po-Shen Loh (video). YouTube.
    Loh, Po-Shen (2019). "A simple proof of the quadratic formula". arXiv:1910.06709 [math.HO].
    Ben-Ari, Mordechai (2022). "7. Solving Quadratic Equations". Mathematical Surprises. Springer. pp. 73–87. doi:10.1007/978-3-031-13566-8_7. ISBN 978-3-031-13565-1.
    As mentioned by Chang & Corum, a similar method was previously independently developed in:

    Savage, John (1989). "Factoring Quadratics". The Mathematics Teacher. 82 (1): 35–36. doi:10.5951/MT.82.1.0035. JSTOR 27966090.

  17. ^ Sostek, Anya (May 7, 2018). "CMU professor brings math to the masses". Pittsburgh Post-Gazette. Mr. Loh has struck viral YouTube gold before. A 2016 YouTube math video, 'The Most Beautiful Equation in Math,' has more than 2.3 million views, with many of the more than 2,000 comments just appreciating how joyful Mr. Loh is in explaining it. [As of 2023, the video has 13 million views.]
  18. ^ Nevarez, Bryan (2021). "A Digital Touch to Teaching and Learning Mathematics". Journal of Mathematics Education at Teachers College. 12 (1): 57.
  19. ^ Karuppur, Abhiram (September 19, 2018). "Professor and Coach Po-Shen Loh *10 Challenges Rising Mathematicians". Princeton Alumni Weekly. Retrieved 2023-06-06.
  20. ^ Irvin-Mitchell, Atiya (January 25, 2023). "This CMU professor is making math classes less dull. Meet Live". Technical.ly. Retrieved 2023-06-02.
  21. ^ Engst, Adam (January 21, 2021). "NOVID Provides COVID-19 Early Warning System". TidBITS. Archived from the original on 2023-04-16. Retrieved 2023-04-10.
  22. ^ Loh, Po-Shen; Bershteyn, Anna; Yee, Shannon K. (2022). "Lessons learned in piloting a digital personalized COVID-19 'radar' on a university campus". Public Health Reports. 137 (2, supplement): 76S–82S. doi:10.1177/0033354922111253. PMC 9678787. PMID 35861290.

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