UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(D)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): January 10, 2022

Supernova Partners Acquisition Company II, Ltd.

(Exact name of registrant as specified in its charter)

(202) 918-7050

(Registrant’s telephone number, including area code)

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Securities Exchange Act of 1934:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company  ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☐

On January 10, 2022, Supernova Partners Acquisition Company II, Ltd. (“Supernova”) issued a press release announcing a record date of January 18, 2022 for the determination of stockholders eligible to receive the proxy and vote at the extraordinary general meeting to be held to consider and approve the previously announced business combination (the “Business Combination”) with Rigetti Holdings, Inc. (“Rigetti”). The press release is attached hereto as Exhibit 99.1 and incorporated by reference herein.

The information in this Item 7.01, including Exhibit 99.1, is furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to liabilities under that section, and shall not be deemed to be incorporated by reference into the filings of Supernova under the Securities Act or the Exchange Act, regardless of any general incorporation language in such filings. This Current Report on Form 8-K will not be deemed an admission as to the materiality of any information in this Item 7.01, including Exhibit 99.1.

(d) Exhibits. The following exhibits are filed with this Form 8-K:

Additional Information and Where to Find It

Supernova has filed with the SEC a registration statement on Form S-4 (as amended, the “Form S-4”), which includes a preliminary proxy statement/prospectus in connection with the proposed Business Combination and will mail a definitive proxy statement/prospectus and other relevant documents to its shareholders. Supernova’s shareholders and other interested persons are advised to read the preliminary proxy statement/prospectus, and amendments thereto, and the definitive proxy statement/prospectus in connection with Supernova’s solicitation of proxies for its shareholders’ meeting to be held to approve the proposed Business Combination because the proxy statement/prospectus will contain important information about Supernova, Rigetti and the proposed Business Combination. The definitive proxy statement/prospectus will be mailed to shareholders of Supernova as of a record date to be established for voting on the proposed Business Combination. Shareholders are also be able to obtain copies of the Form S-4 and the proxy statement/prospectus, without charge at the SEC’s website at www.sec.gov or by directing a request to Supernova Partners Acquisition Company II, Ltd., 4301 50th Street NW, Suite 300, PMB 1044, Washington, DC 20016.

Participants in the Solicitation

Supernova, Rigetti and certain of their respective directors and officers may be deemed participants in the solicitation of proxies of Supernova’s shareholders with respect to the approval of the proposed Business Combination. Supernova and Rigetti urge investors, shareholders and other interested persons to read the Form S-4, including the preliminary proxy statement/prospectus and amendments thereto and the definitive proxy statement/prospectus, as well as other documents filed with the SEC in connection with the proposed Business Combination, as these materials contain important information about Rigetti, Supernova and the proposed Business Combination. Information regarding Supernova’s directors and officers and a description of their interests in Supernova is contained in Supernova’s prospectus dated March 3, 2021 relating to its initial public offering. Additional information regarding the participants in the proxy solicitation, including Rigetti’s directors and officers, and a description of their direct and indirect interests, by security holdings or otherwise, is included in the Form S-4 and the definitive proxy statement/prospectus for the Business Combination when available. Each of these documents is, or will be, available at the SEC’s website or by directing a request to Supernova as described above under “Additional Information and Where to Find It.”

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Forward-Looking Statements

Certain statements in this report and the exhibits to this report may be considered forward-looking statements. Forward-looking statements generally relate to future events and can be identified by terminology such as “pro forma”, “may”, “should”, “could”, “might”, “plan”, “possible”, “project”, “strive”, “budget”, “forecast”, “expect”, “intend”, “will”, “estimate”, “anticipate”, “believe”, “predict”, “potential” or “continue”, or the negatives of these terms or variations of them or similar terminology. Such forward-looking statements are subject to risks, uncertainties, and other factors which could cause actual results to differ materially from those expressed or implied by such forward looking statements. These forward-looking statements are based upon estimates and assumptions that, while considered reasonable by Supernova and its management, and Rigetti and its management, as the case may be, are inherently uncertain. Factors that may cause actual results to differ materially from current expectations include, but are not limited to: the outcome of any legal proceedings that may be instituted against Supernova, Rigetti, the combined company or others following the announcement of the Business Combination and any definitive agreements with respect thereto; the inability to complete the proposed Business Combination due to the failure to obtain approval of the shareholders of Supernova or to satisfy other conditions to the closing of the Business Combination; changes to the proposed structure of the Business Combination that may be required or appropriate as a result of applicable laws or regulations or as a condition to obtaining regulatory approval of the Business Combination; the ability to meet stock exchange listing standards following the consummation of the Business Combination; the risk that the proposed Business Combination disrupts current plans and operations of Rigetti as a result of the announcement and consummation of the Business Combination; the ability to recognize the anticipated benefits of the Business Combination, which may be affected by, among other things, competition, the ability of the combined company to grow and manage growth profitably, maintain relationships with customers and suppliers and retain its management and key employees; costs related to the Business Combination; changes in applicable laws or regulations; the possibility that Rigetti or the combined company may be adversely affected by other economic, business, or competitive factors; Rigetti’s estimates of expenses and profitability; the evolution of the markets in which Rigetti competes; the ability of Rigetti to execute on its technology roadmap; the ability of Rigetti to implement its strategic initiatives, expansion plans and continue to innovate its existing services; the impact of the COVID-19 pandemic on Rigetti’s business; and other risks and uncertainties set forth in the section entitled “Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements” in the registration on Form S-4 and proxy statement/prospectus discussed above and other documents filed with Supernova from time to time with the SEC.

Nothing in this report or the exhibits to this report should be regarded as a representation by any person that the forward-looking statements set forth herein will be achieved or that any of the contemplated results of such forward-looking statements will be achieved. You should not place undue reliance on forward-looking statements, which speak only as of the date they are made. Neither Supernova nor Rigetti undertakes any duty to update these forward-looking statements.

No Offer or Solicitation

This communication is not a proxy statement or solicitation of a proxy, consent, or authorization with respect to any securities or in respect of the proposed Business Combination and shall neither constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which the offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such jurisdiction.

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SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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Exhibit 99.1

SUPERNOVA PARTNERS ACQUISITION COMPANY II, LTD. ANNOUNCES RECORD DATE FOR SHAREHOLDERS ELIGIBLE TO VOTE ON MERGER

WASHINGTON, DC, January 10, 2022 — Supernova Partners Acquisition Company II, Ltd. (“Supernova”) announced that the close of business on Tuesday, January 18, 2022, has been set as the record date for the determination of shareholders eligible to receive the proxy and vote at the extraordinary general meeting to be held to consider and approve the previously announced merger with Rigetti Holdings, Inc., a Delaware corporation (“Rigetti”).

On October 6, 2021, Rigetti and Supernova announced a definitive agreement for a business combination that would result in Rigetti becoming a publicly listed company.

A proxy statement, once final, will be mailed together with a proxy card to Supernova’s shareholders. The final proxy statement will include the date, time and location of the extraordinary general meeting.

About Rigetti Computing

Rigetti Computing is a pioneer in full-stack quantum computing. Rigetti has operated quantum computers over the cloud since 2017 and serves global enterprise, government and research clients through its Rigetti Quantum Cloud Services platform. Rigetti’s proprietary quantum-classical infrastructure provides ultra-low latency integration with public and private clouds for high-performance practical quantum computing. Rigetti has developed the industry’s first multi-chip quantum processor for scalable quantum computing systems. Rigetti designs and manufactures its chips in-house at Fab-1, the industry’s first dedicated and integrated quantum device manufacturing facility. Rigetti was founded in 2013 by Chad Rigetti and today employs more than 140 people with offices in the United States, U.K. and Australia. Learn more at www.rigetti.com.

About Supernova

Supernova is led by Michael Clifton, who was most recently a technology investor at The Carlyle Group; Robert Reid, a long-time senior partner at Blackstone; Spencer Rascoff, a serial entrepreneur who co-founded Hotwire, Zillow, dot.LA and Pacaso and who led Zillow as CEO for nearly a decade; and Alexander Klabin, founder and CEO of Ancient and former managing partner, co-CIO and co-founder of Senator Investment Group.

Additional Information and Where to Find It

Supernova has filed a registration statement on Form S-4 (as amended, the “Form S-4”) with the Securities Exchange Commission (the “SEC”), which includes a proxy statement/prospectus, that will be both the proxy statement to be distributed to holders of Supernova’s common shares in connection with its solicitation of proxies for the vote by Supernova’s shareholders with respect to the proposed business combination and other matters as may be described in the registration statement, as well as the prospectus relating to the offer and sale of the securities to be issued in the business combination. After the registration statement is declared effective, Supernova will

mail a definitive proxy statement/prospectus and other relevant documents to its shareholders. This communication does not contain all the information that should be considered concerning the proposed business combination and is not intended to form the basis of any investment decision or any other decision in respect of the business combination. Supernova’s shareholders and other interested persons are advised to read, when available, the preliminary proxy statement/prospectus included in the registration statement and the amendments thereto and the definitive proxy statement/prospectus and other documents filed in connection with the proposed business combination, as these materials will contain important information about Rigetti, Supernova and the business combination. When available, the definitive proxy statement/prospectus and other relevant materials for the proposed business combination will be mailed to shareholders of Supernova as of a record date to be established for voting on the proposed business combination. Shareholders will also be able to obtain copies of the preliminary proxy statement, the definitive proxy statement and other documents filed with the SEC, without charge, once available, at the SEC’s website at www.sec.gov, or by directing a request to Supernova’s secretary at 4301 50th Street NW, Suite 300 PMB 1044, Washington, D.C. 20016, (202) 918-7050.

Participants in the Solicitation

Supernova and its directors and executive officers may be deemed participants in the solicitation of proxies from Supernova’s shareholders with respect to the proposed business combination. A list of the names of those directors and executive officers and a description of their interests in Supernova is contained in Supernova’s prospectus dated March 3, 2021 relating to its initial public offering, which was filed with the SEC and is available free of charge at the SEC’s website at www.sec.gov. To the extent such holdings of Supernova’s securities may have changed since that time, such changes have been or will be reflected on Statements of Change in Ownership on Form 4 filed with the SEC. Additional information regarding the interests of such participants will be contained in the proxy statement/prospectus for the proposed business combination when available.

Rigetti and its directors and executive officers may also be deemed to be participants in the solicitation of proxies from the shareholders of Supernova in connection with the proposed business combination. A list of the names of such directors and executive officers and information regarding their interests in the proposed business combination will be included in the proxy statement/prospectus for the proposed

business combination when available.

No Offer or Solicitation

This communication does not constitute (i) a solicitation of a proxy, consent or authorization with respect to any securities or in respect of the proposed business combination or (ii) an offer to sell, a solicitation of an offer to buy, or a recommendation to purchase any security of Supernova, Rigetti, or any of their respective affiliates.

Forward-Looking Statements

Certain statements in this communication may be considered forward-looking statements. Forward-looking statements generally relate to future events and can be identified by terminology such as “pro forma”, “may”, “should”, “could”, “might”, “plan”, “possible”, “project”, “strive”, “budget”, “forecast”, “expect”, “intend”, “will”, “estimate”, “anticipate”, “believe”, “predict”, “potential” or “continue”, or the negatives of these terms or variations of them or similar terminology. Such forward-looking statements are subject to risks, uncertainties, and other factors which could cause actual results to differ materially from those expressed or implied by such forward looking statements. These forward-looking statements are based upon estimates and assumptions that, while considered reasonable by Supernova and its management, and Rigetti and its management, as the case may be, are inherently uncertain. Factors that may cause actual results to differ materially from current expectations include, but are not limited to: the outcome of any legal proceedings that may be instituted against Supernova, Rigetti, the combined company or others following the announcement of the business combination and any definitive agreements with respect thereto; the inability to complete the proposed business combination due to the failure to obtain approval of the shareholders of Supernova or to satisfy other conditions to closing; changes to the proposed structure of the business combination that may be required or appropriate as a result of applicable laws or regulations or as a condition to obtaining regulatory approval of the business combination; the ability to meet stock exchange listing standards following the consummation of the business combination; the risk that the proposed business combination disrupts current plans and operations of Rigetti as a result of the announcement and consummation of the proposed business combination; the ability to recognize the anticipated benefits of the business combination, which may be affected by, among other things, competition, the ability of the combined company to grow and manage growth profitably, maintain relationships with customers and suppliers and retain its management and key employees; costs related to the business combination; changes in applicable laws or regulations; the possibility that Rigetti or the combined company may be adversely affected by other economic, business, or competitive factors; Rigetti’s estimates of expenses and profitability; the evolution of the markets in which Rigetti competes; the ability of Rigetti to execute on its technology roadmap; the ability of Rigetti to implement its strategic initiatives, expansion plans and continue to innovate its existing services; the impact of the COVID-19 pandemic on Rigetti’s business; and other risks and uncertainties set forth in the section entitled “Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements” in the registration on Form S-4 and proxy statement/prospectus discussed above and other documents filed with Supernova from time to time with the SEC.

Nothing in this communication should be regarded as a representation by any person that the forward-looking statements set forth herein will be achieved or that any of the contemplated results of such forward-looking statements will be achieved. You should not place undue reliance on forward-looking statements, which speak only as of the date they are made. Neither Supernova nor Rigetti undertakes any duty to update these forward-looking statements.