X0202 SCHEDULE 13G 0000773840 XXXXXXXX LIVE Class A Common Stock, par value $0.0001 per share 06/30/2026 0002110105 Quantinuum Inc. 74768A104 303 S Technology Court Broomfield CO 80021 Rule 13d-1(d) Honeywell International Inc. DE 95998655.00 28630074.00 95998655.00 28630074.00 124628729.00 N 79.1 CO Honeywell Holdings International Inc. DE 0.00 28630074.00 0.00 28630074.00 28630074.00 N 46.6 CO Quantinuum Inc. 303 S Technology Court, Broomfield, CO, 80021 Each of the following is hereinafter individually referred to as a "Reporting Person" and collectively as the "Reporting Persons." This statement is filed on behalf of: Honeywell International Inc. ("Honeywell Technologies") Honeywell Holdings International Inc. The principal business address of each of the Reporting Persons is c/o Honeywell International Inc., 855 S. Mint Street, Charlotte, NC 28202. Each of the Reporting Persons is organized under the laws of the State of Delaware. Y The ownership information presented below represents beneficial ownership of the shares of Class A Common Stock as of June 30, 2026, based upon 32,862,895 shares of Class A Common Stock outstanding at the completion of the Issuer's initial public offering on June 5, 2026, as disclosed in the Issuer's Prospectus on Form 424B4 filed with the Securities and Exchange Commission on June 5, 2026. The ownership information also assumes the redemption of the common unit of Quantinuum Holdings, LLC ("Common Units") into shares of Class A Common Stock of the Issuer on a one-to-one basis, as applicable. The amounts reported as beneficially owned consist of (i) 28,630,074 shares of Class A Common Stock underlying Common Units held directly by Honeywell Holdings International Inc. and (ii) 95,998,655 shares of Class A Common Stock underlying Common Units held directly by Honeywell Technologies. Honeywell Holdings International Inc. is a wholly owned subsidiary of Honeywell Technologies, which is a publicly traded company with securities listed on The Nasdaq Stock Market LLC. Honeywell Technologies: 79.1% Honeywell Holdings International Inc.: 46.6% Honeywell Technologies: 95,998,655 Honeywell Holdings International Inc.: 0 Honeywell Technologies: 28,630,074 Honeywell Holdings International Inc.: 28,630,074 Honeywell Technologies: 95,998,655 Honeywell Holdings International Inc.: 0 Honeywell Technologies: 28,630,074 Honeywell Holdings International Inc.: 28,630,074 Y Y Y Y Y Y Exhibit 99.1: Joint Filing Agreement. Honeywell International Inc. /s/ Su Ping Lu 08/13/2026 Honeywell Holdings International Inc. /s/ Jake Wasserman 08/13/2026