Document

Exhibit 5.1


			811 Main Street, Suite 3700 Houston, TX 77002 Tel: +1.713.546.5400 Fax: +1.713.546.5401 www.lw.com FIRM / AFFILIATE OFFICES
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We have acted as special counsel to Quantinuum Inc., a Delaware corporation (the “Company”), in connection with the preparation and filing by the Company on the date hereof with the Securities and Exchange Commission (the “Commission”) of a registration statement (the “Registration Statement”) on Form S-8 under the Securities Act of 1933, as amended (the “Act”), relating to the issuance of up to 44,556,275 shares (the “Shares”) of the Company’s Class A common stock, par value $0.0001 per share (the “Common Stock”), which may be issued pursuant to the Company’s 2026 Incentive Award Plan (the “2026 Plan”) and the Company’s Amended and Restated 2023 Equity Incentive Plan (the “2023 Plan”). This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or related prospectus, other than as expressly stated herein with respect to the issue of the Shares.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein as to General Corporation Law of the State of Delaware (the “DGCL”) and we express no opinion with respect to any other laws.

Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof, when the Shares shall have been duly registered on the books of the transfer agent and registrar therefor in the name or on behalf of the purchasers, and have been issued by

the Company for legal consideration of not less than par value in the circumstances contemplated by the 2026 Plan or the 2023 Plan, as applicable, assuming that the individual issuances, grants or awards under the 2026 Plan and the 2023 Plan, as applicable, are duly authorized by all necessary corporate action and duly issued, granted or awarded and exercised in accordance with the requirements of law and the applicable provisions of the 2026 Plan and the 2023 Plan, as applicable (and the agreements duly adopted thereunder and in accordance therewith), the issue and sale of the Shares will have been duly authorized by all necessary corporate action of the Company, and such Shares will be validly issued, fully paid and nonassessable. In rendering the foregoing opinion, we have assumed that the Company will comply with all applicable notice requirements regarding uncertificated shares provided in the DGCL.

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act. We consent to your filing this opinion as an exhibit to the Registration Statement. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.


Re:			Registration Statement on Form S-8
			44,556,275 shares of Class A common stock, par value $0.0001 per share.