Exhibit 99.1

Arqit Quantum Inc.
Announces Financial Results for First Half of Fiscal Year 2026

London, UK – 21 May 2026

Arqit Quantum Inc. (Nasdaq: ARQQ) (“Arqit” or the “Company”), a global leader in quantum-safe encryption, announces financial results for the first half of fiscal year 2026.

Recent Developments

CEO’s statement

Andy Leaver, Chief Executive Officer, noted, “Broad recognition for the need to address the cryptographic cybersecurity risk posed by quantum computers now exists. While the U.S. National Security Memorandum 10 has been mandating government migration to a post-quantum security posture since 2022, other countries including the U.K. and Canada have more recently been mandating post-quantum migration as well. The commercial market is now on board with leading players like Google, IBM and Cloudflare recently accelerating timetables for post-quantum migration to 2029. Even that time horizon may be too distant as IonQ recently announced it has accelerated its roadmap for a quantum computer with a logical qubit count sufficient to challenge RSA 2048 to the 2028 to 2029 window. The threat to cybersecurity is real and the time to begin addressing it is now.

With the commercial launch in the period of Arqit’s Encryption Intelligence cryptographic risk-analysis tools and advisory service, Arqit is well positioned to help governments and enterprises take the initial steps in migrating to a post-quantum cryptographic security posture. Organizations need to understand their current architectures and embedded risks before they can implement post-quantum solutions. Arqit this week signed its first Encryption Intelligence related contract and, also, executed an Encryption Intelligence partnership agreement with a European specialist cybersecurity provider focused on PQC migration for financial services organizations. We see multiple near-term opportunities for Encryption Intelligence either directly with customers or through channel partners. We believe Encryption Intelligence is an important addition to Arqit’s ability to provide an end-to-end PQC migration offering.

Our post-quantum cryptographic solutions, led by our NetworkSecureTM product, offer clients software based cryptographically agile post-quantum solutions. Current applications include securing data in transit (e.g. secure VPNs) and data in process (e.g. quantum secure data computation on Intel Netsec accelerator cards). The applicability of Arqit’s post-quantum cryptographic solutions is broad. Current implementations include an international bank securing its data traffic via a Tier 1 telecom partner, a defence contractor securing communications of a major government’s research network and a defence contractor securing tactical control of unmanned platforms for a major European Ministry of Defence. We see increasing engagement and demand for our quantum secure cryptographic solutions in our key target markets of telecommunications, government and defence as evidenced by our increased contract activity during the period in these markets.

With heightened urgency in the marketplace and a complete end-to-end PQC migration product offering, we believe Arqit is well positioned for success. The sell-through of our solutions by current partners, the renewal and upsizing of certain existing contracts and our increasing contract base give us confidence in the direction of the business.”

Focus for the second half of Fiscal Year 2026

Conference Call

Arqit will host a conference call at 11:00 a.m. ET / 8:00 a.m. PT on 21 May, 2026 with the Company’s CEO, Andy Leaver, and CFO, Nick Pointon. A live webcast of the call will be available on the “IR Calendar” page of the Company’s website at ir.arqit.uk. To access the call by phone, please go to this link (registration link) and you will be provided with dial in details. To avoid delays, we encourage participants to dial into the conference call fifteen minutes ahead of the scheduled start time. A replay of the webcast will also be available for a limited time at ir.arqit.uk.

About Arqit

Arqit Quantum Inc. (Nasdaq: ARQQ, ARQQW) secures the world’s most critical data with quantum-safe encryption software. Simple, scalable, and compliant, its products integrate with existing infrastructure, requiring no hardware changes. Arqit provides a complete “Detect, Protect, Comply” solution for governments and enterprises that protects data, ensures compliance, and safeguards their transition to the post-quantum era.

Arqit’s primary product offerings are Encryption Intelligence and NetworkSecure™. Encryption Intelligence detects cryptographic exposure, identifies vulnerabilities, and maps dependencies. NetworkSecure™ protects data in transit with provably secure post-quantum cryptography and contributes to establishment of confidential compute environments for complete data sovereignty.

Arqit is an IDC Innovator for Post-Quantum Cryptography (2024) and a multi-award-winner in quantum-safe security. For more information, visit www.arqitgroup.com

Media relations enquiries:

Arqit: pr@arqit.uk

Investor relations enquiries:

Arqit: investorrelations@arqit.uk

Caution About Forward-Looking Statements

This communication includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements, other than statements of historical facts, may be forward-looking statements. These forward-looking statements are based on Arqit’s expectations and beliefs concerning future events and involve risks and uncertainties that may cause actual results to differ materially from current expectations. These factors are difficult to predict accurately and may be beyond Arqit’s control. Forward-looking statements in this communication or elsewhere speak only as of the date made. New uncertainties and risks arise from time to time, and it is impossible for Arqit to predict these events or how they may affect it. Except as required by law, Arqit does not have any duty to, and does not intend to, update or revise the forward-looking statements in this communication or elsewhere after the date this communication is issued. In light of these risks and uncertainties, investors should keep in mind that results, events or developments discussed in any forward-looking statement made in this communication may not occur. Uncertainties and risk factors that could affect Arqit’s future performance and cause results to differ from the forward-looking statements in this release include, but are not limited to: (i) the outcome of any legal proceedings that may be instituted against Arqit, (ii) the ability to maintain the listing of Arqit’s securities on a national securities exchange, (iii) changes in the competitive and regulated industries in which Arqit operates, variations in operating performance across competitors and changes in laws and regulations affecting Arqit’s business, (iv) the ability to implement business plans, forecasts, and other expectations, and identify and realise additional opportunities, (v) the potential inability of Arqit to successfully deliver its operational technology, (vi) the risk of interruption or failure of Arqit’s information technology and communications system, (vii) the enforceability of Arqit’s intellectual property, (viii) market and other conditions, and (ix) other risks and uncertainties set forth in the sections entitled “Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements” in Arqit’s annual report on Form 20-F (the “Form 20-F”), filed with the U.S. Securities and Exchange Commission (the “SEC”) on 9 December 2025 and in subsequent filings with the SEC. While the list of factors discussed above and in the Form 20-F and other SEC filings are considered representative, no such list should be considered to be a complete statement of all potential risks and uncertainties. Unlisted factors may present significant additional obstacles to the realisation of forward-looking statements.

Exhibit 99.3

Results of Operations of Arqit Quantum Inc., (“Arqit” or the “Company”)

Comparison of the Six Months Ended March 31, 2026 and 2025

Revenue

Revenue increased by $556 thousand from $67 thousand for the six months ended March 31, 2025 to $623 thousand for the six months ended March 31, 2026. The increase was due to an increase in the number of customer contracts and the commencement of services being provided under contracts for which revenue is recognized over time as services are provided under the contract.

Other Income

Other income was $187 thousand for the six months ended March 31, 2026 representing grants received during the period, compared to $101 thousand for the six months ended March 31, 2025.

Administrative Expenses

Total administrative expenses increased by $13.7 million from $20.2 million for the six months ended March 31, 2025 to $33.9 million for the six months ended March 31, 2026. An increase in employee related costs and share based compensation as a result of more employees during the six months ended March 31, 2026 were partially offset by a decrease in property costs as a result of the termination of Arqit’s previous office lease arrangement and a decrease in foreign exchange expenses during the period.

Change in Fair Value of Warrants

The change in fair value of warrants represents the difference in valuation of Arqit’s warrants as of March 31, 2026, compared with the valuation as of September 30, 2025, which was non-cash profit of $261 thousand for the six months ended March 31, 2026, compared with a non-cash loss of $2 thousand for the six months ended March 31, 2025.

Finance Costs

Finance costs increased by $21 thousand from $26 thousand for the six months ended March 31, 2025 to $47 thousand for the six months ended March 31, 2026. The increase was primarily due to an increase in the amount of office floor space leased during the six months ended March 31, 2026.

Finance Income

Finance income decreased by $156 thousand from $566 thousand for the six months ended March 31, 2025 to $410 thousand for the six months ended March 31, 2026.  The decrease was primarily due to a decrease in interest earned during the period.

Discontinued Operations

Profit from discontinued operations, net of tax, was $24 thousand for the six months ended March 31, 2026, compared with $91 thousand for the six months ended March 31, 2025. In both periods, the profit from discontinued operations related to residual grant income from satellite operations and proceeds from the disposal of certain satellite assets.

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Liquidity and Capital Resources

Arqit began to generate revenue from its principal business operations which is the provision of cybersecurity services, in the fiscal year ended September 30, 2021. Arqit will continue to incur net losses in accordance with its operating plan as it further develops the commercialization of its products.

In the period under review, Arqit has funded its operations, capital expenditure and working capital requirements through public offerings of its securities including proceeds from (1) sales of ordinary shares under its ATM Program (as defined below) and (2) sales of ordinary shares and warrants in registered direct offerings in 2023 and 2024. Historically, Arqit also funded its operations from proceeds from the completion of the business combination in 2021, capital contributions, loans and borrowings from certain venture investors and grants from the UK government’s Future Fund, including convertible loan notes that were converted into ordinary shares in connection with the completion of the business combination in 2021. Arqit’s primary uses of liquidity in the period under review have been working capital requirements as it continues to increase commercialization of its products.

In January 2026, Arqit filed a registration statement on Form F-3 in order to establish an at-the-market equity offering program, which replaced a prior at-the-market equity offering program (the current and prior at-the-market equity offering program, together the “ATM Program”) pursuant to which it may issue and sell ordinary shares with an aggregate offering price of up to $125.0 million.  Arqit has no obligation to sell any such shares under its ATM Program. Actual sales will depend on a variety of factors to be determined by the Group from time to time, including, among others, whether additional capital is required, market conditions, the trading price of Arqit’s ordinary shares, determination of the appropriate sources of funding for the Group, and potential uses of available funding. Arqit intends to use the net proceeds from the offering of such shares, if any, for general corporate purposes. During the six months ended March 31, 2026, Arqit issued 846,911 shares under the ATM Program, generating proceeds to the Company before fees and expenses of approximately $18 million.

Cash Flows Summary

Cash Flows Used in Operating Activities

Cash flows used in operating activities to date have primarily resulted from personnel related costs, fluctuations in trade payables and other current assets and liabilities. During the six months ended March 31, 2025 cash used in operating activities was $12.5 million. During the six months ended March 31, 2026 cash used in operating activities was $25.7 million.

Arqit’s non-cash items primarily consist of fair value movement on warrant valuation, share-based charges, impairment charges and depreciation, while movements in working capital are primarily driven by changes in trade and other payables.

Cash Flows Used in Investing Activities

Net cash generated in investing activities was $0.4 million for the six months ended March 31, 2026, compared with net cash used $0.3 million for the six months ended March 31, 2025. This increase was primarily attributed to a reduction in capital expenditure on intangible assets.

Cash Flows Generated from Financing Activities

Net cash generated from financing activities was $17.4 million for the six months ended March 31, 2026, compared with $18.2 million for the six months ended March 31, 2025. Net cash provided by financing activities for the six months ended March 31, 2026 and March 31, 2025 was primarily related to proceeds from shares issued in connection with a registered direct offering and sales under the ATM Program during the period offset by lease costs.