Sec Form 3 Filing - CQ Invest I LLC @ Quantinuum Inc. - 2026-06-04

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person CQ Invest I LLC 2. Issuer Name and Ticker or Trading Symbol Quantinuum Inc. [ QNT] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O CAMBRIDGE QUANTUM NORTH AMERICA, 1300 N 17TH STREET, SUITE 530 3. Date of Earliest Transaction (MM/DD/YY) 06/04/2026 (Street) ARLINGTON, VA22209 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class B Common Stock 82,884,823 I See Footnotes ( 1 ) ( 2 ) ( 3 ) Class A Common Stock 480,511 D ( 4 ) Class A Common Stock 27,001 D ( 5 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Common Units ( 3 ) ( 3 ) ( 3 ) Class A Common Stock 82,884,823 I See Footnotes ( 1 ) ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other CQ Invest I LLC C/O CAMBRIDGE QUANTUM NORTH AMERICA 1300 N 17TH STREET, SUITE 530 ARLINGTON, VA22209 X Cambridge Quantum Holdings Ltd C/O CAMBRIDGE QUANTUM NORTH AMERICA 1300 N 17TH STREET, SUITE 530 ARLINGTON, VA22209 X Khan Ilyas C/O CAMBRIDGE QUANTUM NORTH AMERICA 1300 N 17TH STREET, SUITE 530 ARLINGTON, VA22209 X Shiraz Waseem C/O CAMBRIDGE QUANTUM NORTH AMERICA 1300 N 17TH STREET, SUITE 530 ARLINGTON, VA22209 X Signatures /s/ Waseem Shiraz, as Director of CQ Invest I LLC 06/04/2026 Signature of Reporting Person Date /s/ Waseem Shiraz, as Director of Cambridge Quantum Holdings Limited 06/04/2026 Signature of Reporting Person Date Ilyas Khan, /s/ Waseem Shiraz, Waseem Shiraz, Attorney-in-Fact 06/04/2026 Signature of Reporting Person Date Waseem Shiraz, /s/ Waseem Shiraz 06/04/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Includes (i) 531,720 Common Units and a corresponding number of shares of Class B common stock held directly by CQ Invest I LLC and (ii) 82,353,103 Common Units and a corresponding number of shares of Class B common stock held directly by Cambridge Quantum Holdings Limited. Cambridge Quantum Holdings Limited is the administrative manager of CQ Invest I LLC, and has the right to manage, control and conduct the affairs and operations of CQ Invest I LLC. Cambridge Quantum Holdings Limited is managed by a board of directors, which is composed of Ilyas Khan and Waseem Shiraz, who have the power to vote or direct the vote of, and power to dispose or to direct the disposition of, the shares and units held by CQ Invest I LLC. Mr. Khan, including entities controlled by him, is the controlling shareholder of Cambridge Quantum Holdings Limited. ( 2 )Each of the Reporting Persons (other than to the extent it directly holds securities reported herein) disclaims beneficial ownership of the securities held by the other Reporting Persons, except to the extent of such Reporting Person's pecuniary interest therein, and, pursuant to Rule 16a-1(a)(4) under the Securities Exchange Act of 1934, each of the Reporting Persons (other than to the extent it directly holds securities reported herein) states that the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of all of the reported securities for purposes of Section 16 or for any other purpose. ( 3 )Each common unit of Quantinuum Holdings, LLC ("Common Unit") may be redeemed or exchanged for one share of Class A common stock of the Issuer (or, at the Issuer's election, cash). Common Units have no expiration date. Upon the redemption or exchange of Common Units, a number of shares of Class B common stock equal to the number of Common Units that are redeemed or exchanged will automatically be cancelled for no consideration. ( 4 )The reported securities are directly owned by Ilyas Khan in his personal capacity and the other Reporting Persons have no pecuniary interest in these securities. Includes 179,028 restricted shares units ("RSUs"), which will vest according to the terms of the award agreement. Each RSU represents a contingent right to receive one share of Class A common stock. ( 5 )The reported securities are directly owned by Waseem Shiraz in his personal capacity and the other Reporting Persons have no pecuniary interest in these securities. Includes 10,426 RSUs, which will vest according to the terms of the award agreement. Each RSU represents a contingent right to receive one share of Class A common stock.

Remarks: Exhibit 24 - Power of Attorney

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.