X0609 4 2026-05-18 0001816431 Quantum-Si Inc QSI 0001076352 ROTHBERG JONATHAN M false C/O QUANTUM-SI INCORPORATED 29 BUSINESS PARK DRIVE BRANFORD CT 06405 true true false Class A Common Stock 1904866 I By NVR TR, LLC Class A Common Stock 1930960 I By JNR TR, LLC Class A Common Stock 1930960 I By GBR TR, LLC Class A Common Stock 1930960 I By EJR TR, LLC Class A Common Stock 2568443 D Class A Common Stock 1250000 I By JAR TR, LLC Class A Common Stock 1917067 I By 23rd Century Capital LLC Class A Common Stock 273422 I By Bonnie E Gould Rothberg MD Class B Common Stock 17943750 I By 4C Holdings I, LLC Class B Common Stock 1993750 I By 4C Holdings V, LLC Stock Option (right to buy) 0.8539 2026-05-18 4 A 0 251185 0 A 2036-05-18 Class A Common Stock 251185 251185 D Dr. Rothberg is the sole manager of 4C Holdings I, LLC, 4C Holdings V, LLC, NVR TR, LLC, JNR TR, LLC, GBR TR, LLC, EJR TR, LLC and JAR TR, LLC and Dr. Rothberg is the spouse of Bonnie E. Gould Rothberg MD and Dr. Rothberg's son is the manager of 23rd Century Capital LLC. Dr. Rothberg disclaims beneficial ownership of the shares held by his spouse and 23rd Century Capital LLC. The shares underlying this option vest on the date of the Issuer's next regular annual stockholders meeting, subject to continued service through the applicable vesting date. /s/ Christian LaPointe, Ph.D., Attorney-in-Fact. 2026-05-20