QUANTUM SI INC QSI
COM CL A · Common Stock · CUSIP 74765K105 · ISIN US74765K1051
- SectorTechnology
- IndustryMeasuring & Controlling Devices, NEC
- HeadquartersBranford, CT
- FilingsSEC EDGAR
* Summed across managers. Shares that two managers' reports both contain – a subsidiary's holdings that its parent's report includes too, or a sub-adviser's in its client's – are counted once ($3.5m this quarter). Holder counts are more reliable. Implied quarter-end price ≈ $0.89. Options: 7 managers hold calls ($1.6m notional), 6 hold puts ($672.0k).
Trends to Q2 2026
Institutional holders
Managers reporting a position, each quarter
Numbers
| Quarter | Holders |
|---|---|
| Q3 2022 | 102 |
| Q4 2022 | 106 |
| Q1 2023 | 101 |
| Q2 2023 | 92 |
| Q3 2023 | 97 |
| Q4 2023 | 92 |
| Q1 2024 | 96 |
| Q2 2024 | 101 |
| Q3 2024 | 108 |
| Q4 2024 | 122 |
| Q1 2025 | 138 |
| Q2 2025 | 136 |
| Q3 2025 | 125 |
| Q4 2025 | 135 |
| Q1 2026 | 157 |
| Q2 2026 | 141 |
Buyers vs sellers
Managers adding to or starting a position, vs cutting or selling out
Numbers
| Quarter | Bought or added | Cut or sold out |
|---|---|---|
| Q3 2024 | 41 | 45 |
| Q4 2024 | 71 | 42 |
| Q1 2025 | 80 | 55 |
| Q2 2025 | 70 | 52 |
| Q3 2025 | 56 | 62 |
| Q4 2025 | 65 | 58 |
| Q1 2026 | 79 | 58 |
| Q2 2026 | 63 | 98 |
Calls vs puts
Options held, notional value, last 4 quarters. P/C = puts ÷ calls
Numbers
| Quarter | Calls | Puts | P/C |
|---|---|---|---|
| Q3 2025 | $4.7m | $1.9m | 0.39 |
| Q4 2025 | $2.0m | $1.8m | 0.91 |
| Q1 2026 | $1.0m | $597.3k | 0.58 |
| Q2 2026 | $1.6m | $672.0k | 0.43 |
Biggest buyers
| MILLENNIUM MANAGEMENT LLC | New | +3.1m |
| JANE STREET GROUP, LLC | New | +2.1m |
| UBS Group AG | Added | +859.4k |
| VANGUARD CAPITAL MANAGEMENT LLC | Added | +556.3k |
| RENAISSANCE TECHNOLOGIES LLC | Added | +436.0k |
| BNP PARIBAS FINANCIAL MARKETS | Added | +360.2k |
| Aster Capital Management (DIFC) Ltd | New | +344.5k |
| ARK Investment Management LLC | Added | +288.8k |
| MORGAN STANLEY | Added | +193.5k |
| BARCLAYS PLC | Added | +166.6k |
Biggest sellers
| BlackRock, Inc. | Reduced | -8.2m |
| STATE STREET CORP | Reduced | -2.9m |
| GEODE CAPITAL MANAGEMENT, LLC | Reduced | -1.6m |
| VANGUARD PORTFOLIO MANAGEMENT LLC | Reduced | -1.0m |
| NORTHERN TRUST CORP | Reduced | -810.2k |
| Sumitomo Mitsui Trust Group, Inc. | Reduced | -506.4k |
| Amova Asset Management Americas, Inc. | Reduced | -506.4k |
| Nuveen, LLC | Reduced | -421.3k |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC | Reduced | -373.0k |
| Bank of New York Mellon Corp | Reduced | -364.3k |
Biggest calls
| GROUP ONE TRADING LLC | Added | $546.3k617.3k shares |
| SIMPLEX TRADING, LLC | Added | $303.1k342.5k shares |
| JANE STREET GROUP, LLC | Reduced | $218.9k247.3k shares |
| IMC-Chicago, LLC | Reduced | $178.9k202.2k shares |
| CITADEL ADVISORS LLC | Added | $160.2k181.0k shares |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP | Reduced | $153.3k172.2k shares |
| AlphaCore Capital LLC | New | $4.1k125 shares |
Biggest puts
| IMC-Chicago, LLC | Added | $231.7k261.8k shares |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP | Reduced | $221.2k248.5k shares |
| CITADEL ADVISORS LLC | Reduced | $95.2k107.6k shares |
| GROUP ONE TRADING LLC | Added | $58.9k66.5k shares |
| SIMPLEX TRADING, LLC | Reduced | $35.1k39.7k shares |
| JANE STREET GROUP, LLC | Added | $29.9k33.8k shares |
Options at notional value: the value of the shares the contracts control, as filers report them, not what the options cost. Not included in the holders, shares or buying above.
Major shareholders (over 5%)
Anyone who owns more than 5% of a class of the company's shares has to say so: on Schedule 13D if they may try to influence or control the company, on 13G if they're a passive investor, and update it as the stake changes. Each holder's latest filing, from 19 Dec 2024 on; percentages are of the share class, as the holder worked them out.
| Holder | Stake |
|---|---|
ROTHBERG JONATHAN M
13D · may seek influence
no change · filed 2026-08-28
Stated purposeIn connection with estate planning, entities owned by trusts created for the benefit of Dr. Jonathan Rothberg's children have entered into a trading plan pursuant to Rule 10b5-1 under the Securities Exchange Act of 1934, as amended (the "Plan"), a copy of which is attached hereto as Exhibit 6. Pursuant to the Plan, sales of up to 8,947,746 shares of Class A common stock may be effected during the plan sales period beginning following the cooling-off period contained in Rule 10b5-1(c) on January 15, 2027 and ending on January 15, 2028 in accordance with the terms and conditions of the Plan. The sale of shares of Class A common stock under the Plan is subject to minimum price parameters included in the Plan, and there is no assurance that any shares of Class A common stock will be sold under… Full filing |
100.0% |
Fell to 5% or below in the last year: BlackRock, Inc. (2.3%, 2026-07-29)
Insider purchases and sales since 1 Apr 2026
Shares bought or sold by the company's own officers, directors and 10% owners, in the open market or privately, as they reported to the SEC on Form 4 (due within two business days of the trade). Grants, option exercises, shares withheld for tax and gifts aren't included.
Officers and directors buying vs selling
Number of people, by quarter (10% owners not included)
Numbers
| Quarter | Buying | Bought | Selling | Sold | Sold under a plan |
|---|---|---|---|---|---|
| Q4 2024 | 0 | — | 2 | $11.7m | $11.7m |
| Q1 2025 | 0 | — | 4 | $57.7k | — |
| Q2 2025 | 0 | — | 4 | $106.6k | — |
| Q3 2025 | 0 | — | 5 | $160.0k | — |
| Q4 2025 | 0 | — | 5 | $164.9k | $80.1k |
| Q1 2026 | 2 | $564.4k | 4 | $55.8k | — |
| Q2 2026 | 0 | — | 4 | $314.7k | — |
| Q3 2026 | 0 | — | 3 | $39.5k | — |
| Date | Insider | Trade | Value |
|---|---|---|---|
| 2026-09-22 | Hawkins Jeffrey Alan President & CEO, director | Sold | $7.4k9.7k shares |
| 2026-09-22 | LaPointe Christian GC & Corp. Secretary | Sold | $3.6k4.7k shares |
| 2026-09-22 | Keyes Jeffry R. Chief Financial Officer | Sold | $1.9k2.5k shares |
| 2026-09-21 | Hawkins Jeffrey Alan President & CEO, director | Sold | $15.3k20.1k shares |
| 2026-09-21 | LaPointe Christian GC & Corp. Secretary | Sold | $7.4k9.8k shares |
| 2026-09-21 | Keyes Jeffry R. Chief Financial Officer | Sold | $3.9k5.2k shares |
| 2026-06-23 | Vieceli John S. Chief Product Officer | Sold | $13.6k15.1k shares |
| 2026-06-23 | Hawkins Jeffrey Alan President & CEO, director | Sold | $10.2k11.3k shares |
| 2026-06-23 | LaPointe Christian GC & Corp. Secretary | Sold | $7.0k7.8k shares |
| 2026-06-23 | Keyes Jeffry R. Chief Financial Officer | Sold | $3.7k4.1k shares |
| 2026-06-22 | Vieceli John S. Chief Product Officer | Sold | $14.5k15.1k shares |
| 2026-06-22 | Hawkins Jeffrey Alan President & CEO, director | Sold | $10.9k11.3k shares |
| 2026-06-22 | LaPointe Christian GC & Corp. Secretary | Sold | $7.5k7.8k shares |
| 2026-06-22 | Keyes Jeffry R. Chief Financial Officer | Sold | $4.0k4.1k shares |
| 2026-04-21 | Hawkins Jeffrey Alan President & CEO, director | Sold | $83.7k83.7k shares |
| 2026-04-21 | Keyes Jeffry R. Chief Financial Officer | Sold | $37.4k37.4k shares |
| 2026-04-20 | Hawkins Jeffrey Alan President & CEO, director | Sold | $84.5k83.7k shares |
| 2026-04-20 | Keyes Jeffry R. Chief Financial Officer | Sold | $37.8k37.4k shares |
Their holding: how much the trade added to or took from the insider's holding (direct, or the trust or fund named). The same trade is sometimes reported by more than one insider, such as a fund and the director who represents it; totals count it once. A value is left blank where the reported price is far from the market price (usually a typo).
Holders, Q2 2026
| Manager | Shares | Change |
|---|---|---|
| VANGUARD CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 7.6m $6.7m | Added +556.3k |
| ARK Investment Management LLC 0.04% of their portfolio | 7.2m $6.3m | Added +288.8k |
| BlackRock, Inc. 0.00% of their portfolio | 5.2m $4.6m | Reduced -8.2m |
| Sumitomo Mitsui Trust Group, Inc. 0.00% of their portfolio | 3.9m $3.4m | Reduced -506.4k |
| Amova Asset Management Americas, Inc. 0.04% of their portfolio | 3.9m $3.5m | Reduced -506.4k |
| MILLENNIUM MANAGEMENT LLC 0.00% of their portfolio | 3.1m $2.8m | New |
| UBS Group AG 0.00% of their portfolio | 2.6m $2.3m | Added +859.4k |
| AQR CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 2.3m $2.1m | Reduced -43.5k |
| GEODE CAPITAL MANAGEMENT, LLC 0.00% of their portfolio | 2.2m $2.0m | Reduced -1.6m |
| JANE STREET GROUP, LLC 0.00% of their portfolio | 2.1m $1.9m | New |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP 0.00% of their portfolio | 1.1m $988.3k | Reduced -347.8k |
| VANGUARD FIDUCIARY TRUST CO 0.00% of their portfolio | 1.1m $988.3k | Reduced -569 |
| STATE STREET CORP 0.00% of their portfolio | 890.7k $788.3k | Reduced -2.9m |
| Fosun International Ltd 0.15% of their portfolio | 743.9k $658.4k | Unchanged |
| RENAISSANCE TECHNOLOGIES LLC 0.00% of their portfolio | 553.9k $490.2k | Added +436.0k |
| VANGUARD PORTFOLIO MANAGEMENT LLC 0.00% of their portfolio | 497.1k $439.9k | Reduced -1.0m |
| GOLDMAN SACHS GROUP INC 0.00% of their portfolio | 476.3k $421.5k | Added +32.1k |
| NORTHERN TRUST CORP 0.00% of their portfolio | 450.5k $398.7k | Reduced -810.2k |
| Invesco Ltd. 0.00% of their portfolio | 443.9k $392.9k | Added +37.2k |
| BNP PARIBAS FINANCIAL MARKETS 0.00% of their portfolio | 398.6k $352.8k | Added +360.2k |
| IEQ CAPITAL, LLC 0.00% of their portfolio | 350.8k $310.5k | Reduced -6.9k |
| Aster Capital Management (DIFC) Ltd 0.06% of their portfolio | 344.5k $304.9k | New |
| MORGAN STANLEY 0.00% of their portfolio | 323.5k $286.3k | Added +193.5k |
| IQ EQ FUND MANAGEMENT (IRELAND) Ltd 0.02% of their portfolio | 321.1k $284.2k | Added +29.0k |
| Knollwood Investment Advisory, LLC 0.02% of their portfolio | 300.0k $265.5k | Unchanged |
| IMC-Chicago, LLC 0.00% of their portfolio | 285.8k $252.9k | Added +64.9k |
| BRIDGEWAY CAPITAL MANAGEMENT, LLC 0.00% of their portfolio | 206.1k $182.4k | Reduced -55.0k |
| BARCLAYS PLC 0.00% of their portfolio | 205.7k $182.0k | Added +166.6k |
| XTX Topco Ltd 0.00% of their portfolio | 177.7k $157.2k | Reduced -211.6k |
| SIMPLEX TRADING, LLC 0.00% of their portfolio | 165.3k $146.3k | Added +74.8k |
| Verdence Capital Advisors LLC 0.01% of their portfolio | 158.3k $140.1k | Reduced -45.5k |
| Mariner, LLC 0.00% of their portfolio | 157.7k $139.6k | Reduced -42.0k |
| Shay Capital LLC 0.01% of their portfolio | 150.9k $133.6k | Unchanged |
| FMR LLC 0.00% of their portfolio | 123.8k $109.5k | Added +91.8k |
| GROUP ONE TRADING LLC 0.00% of their portfolio | 107.5k $95.1k | Reduced -176.5k |
| JONES FINANCIAL COMPANIES LLLP 0.00% of their portfolio | 100.5k $85.8k | Reduced -9.4k |
| HRT FINANCIAL LP 0.00% of their portfolio | 93.6k $82.0k | New |
| AlphaCore Capital LLC 0.00% of their portfolio | 89.4k $79.1k | Reduced -39.1k |
| Cerity Partners LLC 0.00% of their portfolio | 85.3k $75.5k | Added +4.7k |
| Vanguard Global Advisers, LLC 0.00% of their portfolio | 84.8k $75.0k | Unchanged |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC 0.00% of their portfolio | 84.6k $74.9k | Reduced -373.0k |
| Y-Intercept (Hong Kong) Ltd 0.00% of their portfolio | 79.1k $70.0k | New |
| JTC Employer Solutions Trustee Ltd 0.01% of their portfolio | 77.8k $69.0k | Added +43.2k |
| MERCER GLOBAL ADVISORS INC /ADV 0.00% of their portfolio | 77.3k $68.4k | Added +22.1k |
| RHUMBLINE ADVISERS 0.00% of their portfolio | 76.0k $67.2k | Reduced -117.1k |
| WINTON GROUP Ltd 0.00% of their portfolio | 75.8k $67.1k | New |
| Cambridge Investment Research Advisors, Inc. 0.00% of their portfolio | 75.6k $66.0k | Added +33.8k |
| CAPTRUST FINANCIAL ADVISORS 0.00% of their portfolio | 73.1k $64.7k | Added +4.1k |
| HOLLENCREST CAPITAL MANAGEMENT 0.00% of their portfolio | 65.0k $57.5k | Added +24.9k |
| WEALTH ENHANCEMENT ADVISORY SERVICES, LLC 0.00% of their portfolio | 63.4k $45.2k | Reduced -26.1k |
| GSA CAPITAL PARTNERS LLP 0.00% of their portfolio | 60.0k $53.0k | New |
| BANK OF AMERICA CORP /DE/ 0.00% of their portfolio | 59.6k $52.7k | Reduced -102.4k |
| Creative Planning 0.00% of their portfolio | 55.9k $49.5k | Added +3.3k |
| Atom Investors LP 0.00% of their portfolio | 51.6k $45.6k | New |
| Green Alpha Advisors, LLC 0.03% of their portfolio | 45.9k $40.6k | Added +2.7k |
| CITADEL ADVISORS LLC 0.00% of their portfolio | 44.3k $39.2k | Added +28.8k |
| Sanctuary Advisors, LLC 0.00% of their portfolio | 41.4k $36.6k | Reduced -1.4k |
| Stratos Wealth Advisors, LLC 0.00% of their portfolio | 40.0k $35.4k | Added +25.0k |
| Point72 Asset Management, L.P. 0.00% of their portfolio | 39.1k $34.6k | New |
| BRIGHTON JONES LLC 0.00% of their portfolio | 38.6k $34.1k | Added +11.0k |
| Corient Private Wealth LP 0.00% of their portfolio | 38.3k $33.9k | New |
| Red Wave Investments LLC 0.01% of their portfolio | 37.0k $32.7k | Unchanged |
| Arax Advisory Partners 0.00% of their portfolio | 36.8k $32.6k | Added +35.4k |
| SBI Securities Co., Ltd. 0.00% of their portfolio | 33.0k $29.2k | Added +876 |
| China Universal Asset Management Co., Ltd. 0.00% of their portfolio | 31.5k $27.9k | Reduced -3.2k |
| Kovack Advisors, Inc. 0.00% of their portfolio | 31.0k $27.4k | Added +1.0k |
| IPG Investment Advisors LLC 0.00% of their portfolio | 30.9k $27.3k | New |
| Nuveen, LLC 0.00% of their portfolio | 30.1k $26.6k | Reduced -421.3k |
| Northern Lights Advisors, Inc. 0.01% of their portfolio | 30.0k $26.5k | Unchanged |
| COMMONWEALTH EQUITY SERVICES, LLC 0.00% of their portfolio | 27.1k $24.0k | Reduced -2.7k |
| Wealth Management Associates, Inc. 0.01% of their portfolio | 26.4k $23.3k | Reduced -600 |
| Tower Research Capital LLC (TRC) 0.00% of their portfolio | 23.8k $21.0k | Reduced -1.2k |
| Merit Financial Group, LLC 0.00% of their portfolio | 23.6k $20.9k | Reduced -12.7k |
| Pallas Capital Advisors LLC 0.00% of their portfolio | 23.3k $20.6k | Reduced -2.4k |
| Leonteq Securities AG 0.00% of their portfolio | 22.5k $19.9k | Reduced -2.5k |
| HBW ADVISORY SERVICES LLC 0.00% of their portfolio | 22.3k $19.7k | Reduced -405 |
| NEUBERGER BERMAN GROUP LLC 0.00% of their portfolio | 21.8k $19.3k | New |
| LPL Financial LLC 0.00% of their portfolio | 21.0k $18.6k | Reduced -1.5k |
| Vanguard Personalized Indexing Management, LLC 0.00% of their portfolio | 20.4k $18.0k | Reduced -3.6k |
| Capital Investment Advisory Services, LLC 0.00% of their portfolio | 20.0k $17.7k | Unchanged |
| VICTORY CAPITAL MANAGEMENT INC 0.00% of their portfolio | 19.6k $17.4k | Reduced -178 |
| DLK Investment Management, LLC 0.01% of their portfolio | 19.0k $19.9k | Added +2.2k |
| ANCHYRA PARTNERS LLC 0.00% of their portfolio | 19.0k $16.8k | New |
| Bank of New York Mellon Corp 0.00% of their portfolio | 18.8k $16.6k | Reduced -364.3k |
| SG Americas Securities, LLC 0.00% of their portfolio | 17.5k $15.0k | Reduced -16.2k |
| Focus Partners Wealth 0.00% of their portfolio | 17.2k $15.2k | Reduced -6.3k |
| JPMORGAN CHASE & CO 0.00% of their portfolio | 17.1k $15.2k | Reduced -66.4k |
| Flagship Private Wealth, LLC 0.00% of their portfolio | 14.2k $12.5k | Unchanged |
| Procyon Advisors, LLC 0.00% of their portfolio | 13.7k $12.1k | Unchanged |
| Balyasny Asset Management L.P. 0.00% of their portfolio | 13.6k $12.1k | New |
| RAYMOND JAMES FINANCIAL INC 0.00% of their portfolio | 13.0k $11.5k | New |
| Laurion Capital Management LP 0.00% of their portfolio | 12.7k $11.3k | New |
| Callan Family Office, LLC 0.00% of their portfolio | 12.1k $10.7k | New |
| Jefferies Financial Group Inc. 0.00% of their portfolio | 11.3k $10.0k | New |
| Integrated Wealth Concepts LLC 0.00% of their portfolio | 11.3k $10.0k | Reduced -3.2k |
| NorthCrest Asset Manangement, LLC 0.00% of their portfolio | 11.2k $10.8k | Reduced -926 |
| NewEdge Advisors, LLC 0.00% of their portfolio | 11.2k $9.9k | Reduced -4.7k |
| Abel Hall, LLC 0.00% of their portfolio | 11.1k $9.8k | New |
| Krilogy Financial LLC 0.00% of their portfolio | 10.6k $9.4k | Reduced -6.1k |
| Schonfeld Strategic Advisors LLC 0.00% of their portfolio | 10.4k $9.2k | New |