The 24-year-old Pole defeated the 13th seed 6-3, 6-1 in their fourth-round match at Flushing Meadows, improving her head-to-head record against Alexandrova to 5-2.
Świątek, the 2022 US Open champion, is bidding for her seventh Grand Slam singles title.
She reached the round of 16 in 2023 and the quarterfinals last year.
The Polish star opened this year’s campaign with a 6-1, 6-2 win over Colombia’s Emiliana Arango, before needing three sets to get past the Netherlands’ Suzan Lamens and Russia’s Anna Kalinskaya.
Świątek will next face either eighth-seeded American Amanda Anisimova or No. 18 seed Beatriz Haddad Maia of Brazil for a place in the semifinals.
The US Open, the year’s final Grand Slam tournament, runs through September 8.
(gs)
Source: IAR, PAP