As of November 6, 2026, Quantum-Si Inc is a publicly traded company (Nasdaq: QSI). Jonathan M. Rothberg, a director and 10% owner, reports holding 100%, a majority of its shares. No bankruptcy or receivership appears in its SEC Form 8-K filings (Schedule 13D/A, August 28, 2026).
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Is Quantum-Si Inc a real, registered company?
- Quantum-Si Inc files with the SEC under CIK 1816431 (its SEC filings).
- Its shares are listed under the ticker QSI on Nasdaq (SEC company record).
- Incorporated in Delaware; business address in Branford, Connecticut, as its SEC filings state.
- Court and bankruptcy records: see Before you sign or pay below.
Before you sign or pay
- Court and bankruptcy: No federal court case or bankruptcy filing found under Quantum-Si Inc in our court records and SEC 8-K records (as of 2026-11-06).
- Ownership: 5%+ holders are reported on Schedule 13D or 13G; the latest names Rothberg Jonathan M (filed 2026-08-28).
Who are Quantum-Si Inc's owners and officers?
Quantum-Si Inc: incorporated in Delaware; business address in Branford, Connecticut; industry Measuring & Controlling Devices, NEC (Schedule 13D/A, 2026-08-28).
| Report | Holder | Share |
|---|---|---|
| Schedule 13D/A, 2026-08-28 | Rothberg Jonathan M | 100% |
| Schedule 13G/A, 2026-07-29 | Blackrock, Inc. | 2.3% |
| Schedule 13G/A, 2025-10-30 | The Vanguard Group | 4.77% |
| Schedule 13D/A, 2025-09-11 | Rothberg Jonathan M | 100% |
| Schedule 13G, 2025-07-29 | The Vanguard Group | 5.3% |
Questions about who owns Quantum-Si Inc
Who owns Quantum-Si Inc?
On this page, one holder's latest ownership filing reports 5% or more of Quantum-Si Inc: Rothberg Jonathan M (100%, Schedule 13D/A, filed 2026-08-28).
When did Rothberg Jonathan M buy into Quantum-Si Inc?
The filings give report dates, not purchase dates. The earliest filing from Rothberg Jonathan M on this page is the Schedule 13D/A, filed 2025-09-11, reporting 100%; its latest, Schedule 13D/A filed 2026-08-28, reports 100%. That earliest filing is itself an amendment, which updates an earlier report.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 5 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
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Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
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Which insiders own Quantum-Si Inc shares?
Directors, officers and holders of 10% or more report their shares on Forms 3, 4 and 5. Each line is the latest such report, largest holding first.
- , a director and 10% owner: 33,644,178 shares, 2,568,443 held directly and 31,075,735 indirectly (Form 4, 2026-05-20).
- , the chief executive and president: 3,639,950 shares (Form 4, 2026-09-23).
- , the chief financial officer: 1,716,684 shares (Form 4, 2026-09-23).
- , a director: 1,220,512 shares, 20,512 held directly and 1,200,000 indirectly (Form 4, 2026-05-20).
- , the general counsel and corp. secretary: 1,167,913 shares (Form 4, 2026-09-23).
Shares only: the company's cover page does not give one share count for a single class, so no percentage is worked out.
How much has Quantum-Si Inc raised?
No fundraising or offering filing from Quantum-Si Inc is on file with us.
Keep reading
More on Quantum-Si Inc and the records around it.
Quantum-Si Inc elsewhere on the record
- 5%+ stake filings Aug 2026
Companies that share a holder
- ROTHBERG JONATHAN M also filed stake reports on 1 other company: Butterfly Network, Inc. (Aug 2026)
- BlackRock, Inc. also filed stake reports on 1596 other companies: AvePoint, Inc. (Nov 2026), BIOMARIN PHARMACEUTICAL INC (Nov 2026), MSG RANGERS CORP (Nov 2026)
- The Vanguard Group also filed stake reports on 2384 other companies: BellRing Brands, Inc. (Sep 2026), CAL-MAINE FOODS INC (Sep 2026), FTAI Aviation Ltd. (Sep 2026)
Related pages
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