11 institutions reported holding $917,074 of QUANTUM SI INC (QSIAW) in SEC 13F filings for 2026-03-31. Largest institutional holders: IMC-Chicago, LLC ($351,474), SIMPLEX TRADING, LLC ($276,394), GROUP ONE TRADING LLC ($229,723), DEERFIELD MANAGEMENT COMPANY, L.P. ($36,200), SUSQUEHANNA INTERNATIONAL GROUP, LLP ($10,215). Source: SEC Form 13F.
| Rank | Institution | Value | Shares | Change |
|---|---|---|---|---|
| 1 | IMC-Chicago, LLC | $351,474 | 454,100 | Trimmed |
| 2 | SIMPLEX TRADING, LLC | $276,394 | 357,100 | Trimmed |
| 3 | GROUP ONE TRADING LLC | $229,723 | 296,800 | Trimmed |
| 4 | DEERFIELD MANAGEMENT COMPANY, L.P. | $36,200 | 333,333 | Hold |
| 5 | SUSQUEHANNA INTERNATIONAL GROUP, LLP | $10,215 | 85,121 | Trimmed |
| 6 | MILLENNIUM MANAGEMENT LLC | $9,454 | 87,054 | Hold |
| 7 | JANE STREET GROUP, LLC | $1,799 | 16,565 | Trimmed |
| 8 | WOLVERINE ASSET MANAGEMENT LLC | $1,577 | 14,522 | New |
| 9 | UBS Group AG | $227 | 2,080 | Trimmed |
| 10 | TORONTO DOMINION BANK | $11 | 100 | New |
| 11 | AlphaCore Capital LLC | $0 | 0 | Exited |
Source: SEC Form 13F filings · as of 2026-03-31