Terms of Service

Last updated: 29 September 2026

These Terms of Service (“Terms”) constitute a binding agreement between you and ZKSF, the Zero Kelvin Simulation Foundry (“ZKSF”, “we”, “us” or “our”), governing your access to and use of the ZKSF website, web console, mobile application, application programming interface, software development kits and related services (together, the “Service”). Please read Sections 3, 4, 8, 9 and 17 to 20 with particular care: they set out what the Service may not be used for, allocate risk to you, limit our liability and require you to indemnify us in defined circumstances.

1. Acceptance and Eligibility

By creating an account, submitting a job, calling the API or otherwise accessing the Service, you accept these Terms and the Privacy Policy in full. If you do not accept them, you must not use the Service.
Where you use the Service on behalf of an organisation, you warrant that you have authority to bind that organisation, and references to “you” include it.
You must be at least sixteen years of age, have the legal capacity to enter into a binding contract, and not be barred from using the Service under the laws of any applicable jurisdiction.
Where a separate written agreement signed by both parties covers your use of the Service, that agreement prevails over these Terms to the extent of any conflict.

2. The Service

ZKSF provides classical simulation of quantum circuits and related quantum programs on high performance compute, together with access to real quantum processing units (“QPUs”) operated by third party QPU providers, through a single service and API.
Simulation methods include exact statevector, stabilizer, tensor network, Pauli propagation and neural network techniques. Approximate methods carry method dependent accuracy limits, which are reported with each result.
The Service may decline to execute a program it cannot run reliably. Rejection diagnostics are provided on a best efforts basis. A rejected job is charged for any compute it used before it was rejected.
We may modify, suspend or discontinue features at any time.

3. Experimental Technology

You expressly acknowledge that quantum computing and quantum simulation are emerging and experimental fields. QPUs are inherently subject to noise, decoherence, calibration drift and readout error, and approximate simulation methods are subject to truncation and sampling error. Methods, error models and QPU behaviour are the subject of active research and may produce results that are incorrect, unexpected, unstable, irreproducible or unsuitable for a given purpose, without any indication that this has occurred. These are inherent characteristics of the field and are not defects in the Service.

4. Accuracy and Reliance

Exact simulations are exact only up to floating point precision and sampling noise.
Approximate simulations return estimates. Accompanying error indicators, such as convergence deviation, are evidence based estimates and not mathematical guarantees, unless expressly labelled as certified bounds, and then only to the extent that the bound itself states.
Results obtained from third party QPUs reflect that QPU’s physical noise and calibration at the time of execution. We neither control nor warrant QPU fidelity, availability or behaviour.
Cost estimates, runtime predictions, resource estimates, projections and extrapolations produced by the Service are predictions, not guarantees.
The Service must not be used as the sole basis for any decision where an incorrect result could cause death, personal injury, environmental damage, or material financial or property loss, including in medical, safety critical, aviation, nuclear, weapons, or critical infrastructure applications.
You are responsible for validating every result before relying on it in research, publication, engineering, security assessment or commercial decision making.
You are solely responsible for any decision, publication, product, experiment or commercial action taken in reliance on a result, estimate or certificate, and we accept no responsibility for any outcome, loss or consequence arising from that reliance.

5. Certification Protocols

ZCC-v0.1, the ZKSF Convergence Certificate for simulated results, ZHF-v0.1, the ZKSF Hardware Fidelity certificate for QPU results, and ZQEC-v0.1 for error correction results, are in house protocols developed, versioned and maintained by us.
The specification and methodology of the protocols are published openly under the licence stated in Section 14. Citing them, independently reproducing them, or referencing certificate methodology in your own work is expressly permitted.
A certificate records the method, parameters and accuracy, fidelity or error rate statement applicable to the specific job from which it was generated. It is not a warranty of correctness beyond what that statement itself asserts, and it does not constitute validation of your research.
You must not present a certificate as an endorsement, accreditation or guarantee by us of any result, product or claim, and you must not alter a certificate or present an altered certificate as genuine.

6. Your Data

Circuits, programs, parameters and account information are collected and stored because you have instructed us to execute them and because the Service cannot run, price or return a job otherwise. Submission is inherent to using the Service, and it is not possible to use the Service while withholding that authorisation.
We do not sell or share your information, save for transmitting a program to a QPU provider you have expressly selected and as otherwise described in the Privacy Policy.
You warrant that you are entitled to submit everything you submit, that doing so does not infringe the rights of any third party or breach any obligation of confidence, and that it contains no personal data of others unless you have a lawful basis to process it.
You are responsible for keeping your own copies of your programs, results and certificates. The Service is not a backup or archival service. Records are retained as described in the Privacy Policy, and may be lost, corrupted or become unavailable through technical failure, provider failure, account closure or deletion.

7. Accounts and Credentials

You must provide accurate account information and keep it current.
You are responsible for safeguarding your password and API keys. All activity carried out under your account or keys is attributed to you, and charges incurred by it are yours, whether or not you authorised them.
You must notify us promptly at legal@zksf.org of any unauthorised use of your account or keys, and revoke any key you believe has been exposed.
One individual or organisation may not operate multiple accounts to circumvent limits, pricing or enforcement.

8. Acceptable Use

You must use the Service lawfully, in good faith and only for legitimate research, educational, development or commercial purposes. Without limitation, you must not use the Service, or permit it to be used, to:

Attack cryptographic systems you are not authorised to test. This includes attempting to recover, derive or brute force private keys, passwords, seeds or other secrets belonging to any person, wallet, account, network or system, or to decrypt, forge or tamper with communications, signatures or transactions, other than keys and systems that you own or are expressly authorised in writing to assess. Published research on keys generated for the purpose is permitted.
Engage in or facilitate unlawful activity, including fraud, theft, money laundering, sanctions evasion, the financing of terrorism, unauthorised access to computer systems, or the infringement of intellectual property or privacy rights.
Abuse, manipulate or exploit the Service or its commercial terms, including by circumventing or interfering with billing, metering, credit, quotas, rate limits, pricing or free usage; exploiting a defect or error in the Service for gain rather than reporting it; obtaining credit or services by deception, chargeback abuse or the use of stolen payment instruments; or opening accounts to avoid suspension or limits.
Compromise the Service, including by probing, scanning or testing its vulnerabilities beyond the scope published in our security policy, breaching or circumventing authentication or access controls, introducing malicious code, submitting programs designed to exhaust resources or degrade the Service for others, or conducting load, stress or denial of service testing.
Access what is not yours, including other users’ accounts, data, programs or results, or any non public part of the Service.
Extract or reproduce the Service, including by scraping, harvesting or systematically collecting its outputs, routing decisions or pricing to build, train or benchmark a competing service in breach of Section 13, or by reselling, sublicensing or providing access to the Service to third parties without our written agreement.
Develop weapons or cause harm, including the design, development or production of nuclear, chemical, biological or radiological weapons or their delivery systems, or any other use prohibited by applicable export control law.

Security research conducted within the scope and rules of our published security policy, and reported privately to info@zksf.org, is welcome and is not a breach of this Section. Benchmarking the Service and publishing the results is expressly permitted.

9. Enforcement, Suspension and Cooperation with Authorities

We may monitor use of the Service, including job metadata, request patterns and billing activity, to detect and prevent breaches of these Terms, and may investigate any suspected breach.
Where we reasonably believe that an account has been used in breach of Section 8, or in a way that exposes the Service, its users, its providers or any third party to harm or legal liability, we may immediately and without prior notice suspend or terminate the account, revoke its API keys, cancel or decline its jobs, and withhold results.
Credit, services or results obtained through a breach of Section 8 may be reversed, voided or forfeited, and we may recover from you any charges, costs or losses we incur as a result of the breach, including third party provider charges and reasonable investigation and legal costs.
We will cooperate fully with law enforcement, regulatory and other competent authorities investigating suspected unlawful use of the Service. Where we believe the Service has been used for unlawful purposes, we may preserve records and disclose account information, job records, request logs and payment references to those authorities, and may report the activity to them on our own initiative, to the extent permitted by applicable law.
Suspension or termination under this Section does not limit any other right or remedy available to us.

10. Fees, Credit and Billing

Usage is charged at the rates published on the pricing page, by reference to the compute time and resources consumed or, for QPUs, the QPU provider’s charges. A pre run estimate is available for every job.
Pre run estimates are good faith predictions and not quotations. Actual charges may differ. Estimates are deliberately conservative.
Estimates disclaimer. A simulation is billed by the seconds it actually runs, so the charge can differ. Simulation estimates vary with the width, depth and structure of each circuit and are a reference point only. Your final charge is set by your job’s actual runtime, as described in our pricing. Estimates are often higher than the runtime charged, but can also be lower. QPU estimates stay close to the final charge, because each provider sets its price per shot
QPU charges are passed through at the QPU provider’s cost. QPU provider price changes take effect when the provider applies them. We may change our published rates at any time; the rate in force when a job is submitted applies to it.
Mobile app. We aim to update the mobile app as the Service changes, but every release must first pass Google Play’s review, which usually takes three to seven business days and can take longer. The mobile app may therefore show rates, engines or other information that is out of date for a week or more. Where the mobile app differs from the API or from the documentation on our website, the API and the website documentation prevail, and charges are made at the rates in force under this Section.
The Service operates on prepaid credit. Credit is personal to the account, is not transferable, carries no interest and has no cash value except as provided in Section 11 and in the Privacy Policy on account closure.
Payments are processed by an external provider certified to PCI DSS. Card data is handled entirely by that provider and never reaches our systems.
Disputed charges must be raised within thirty days of the relevant charge, by writing to legal@zksf.org.
Fees are exclusive of taxes, for which you are responsible.

11. Refunds

Charges for executed jobs are final and non refundable. Every job consumes real compute, and for QPU jobs incurs a real third party charge, at the moment it executes, so the cost is incurred whether or not the result is the one you hoped for.
In exchange we keep pricing deliberately low so that laboratories, students and independent researchers can afford the Service, and every job displays a conservative cost estimate before you commit to running it.

12. Third Party QPUs and Services

QPUs made available through the Service are owned and operated by third party providers. Access to them, their availability windows, queue times, calibration and results are controlled by those providers and are outside our control.
When you route a job to a provider’s QPU, you instruct us to transmit the program to that provider, and the provider’s own terms and policies may apply to its execution.
We are not responsible for the acts, omissions, outages, price changes or withdrawal of any third party provider, and a provider may withdraw a device from the Service at any time.

13. Intellectual Property and Copyright

Your content

You retain all rights in the programs you submit and the results you receive. We claim no ownership of your science and assert no publication or authorship rights over it.
You grant us a limited, non exclusive licence to host, store, process and transmit your programs and results solely as necessary to provide the Service to you.
We retain job metadata, being sizes, timings, methods and resource use, in order to operate, secure, debug and improve routing and estimation. Program contents are not used to train models made available to others and are not shared with third parties, save as required to execute a job on a QPU you have selected.

Our proprietary technology and content

The Service and everything comprised in it, other than your content and the open source material listed in Section 14, is owned by us or our licensors and is protected by copyright, trade secret, trade mark and other intellectual property laws. This includes, without limitation, our engine routing and selection technology, cost and runtime estimation models, execution and certification implementations, software, algorithms, interfaces, application programming interfaces, databases, documentation, benchmark data and results, articles, graphics, videos and the design and arrangement of the website and applications.
Except as expressly permitted by these Terms or by the licence of an item listed in Section 14, you must not, without our express prior written approval, copy, reproduce, clone, replicate, imitate, modify, translate, adapt, create derivative works from, distribute, publicly display, sell, license or otherwise exploit any part of the Service or our proprietary technology or content, or attempt to reverse engineer, decompile, disassemble or otherwise derive its source code, underlying models or logic.
You must not use the Service, its outputs, its routing decisions or its pricing to build, train, calibrate or reproduce a product or service that replicates or substitutes for the Service, save that publishing independent benchmarks of the Service is permitted.
Short quotations from our published articles and documentation, with attribution and a link to the source, are permitted for commentary, research, criticism and review.

Our brand

ZKSF, Zero Kelvin Simulation Foundry, our logos, product names, certificate names and the look and feel of the Service are our trade marks and trade dress, whether or not registered. You must not use them, or any confusingly similar name, mark or domain, without our express prior written approval, except to refer accurately to the Service, for example when citing it or describing results obtained on it, in a way that does not suggest sponsorship, endorsement or affiliation.

Third party marks

Third party names, marks and logos shown on this site, including those of QPU manufacturers, processor and accelerator makers and open source projects, are the property of their respective owners. They are used only to identify the hardware, software and services the Service integrates with. Their use does not imply any affiliation with, sponsorship by or endorsement from those owners, and we claim no ownership of them and assert no rights in them. An owner who objects to our use of their mark may write to legal@zksf.org.

Permissions and infringement notices

Requests for permission to use our intellectual property, and notices alleging that material on the Service infringes your rights, should be sent to legal@zksf.org. A notice should identify the work concerned, the material alleged to infringe it and where it appears, your contact details, and a statement that you believe in good faith that the use is not authorised and that the information in the notice is accurate.

14. Open Source Software and Published Material

The following are published under open licences and may be used, copied, modified and distributed in accordance with those licences:

qsim-sdk, the Python SDK, with its documentation and example scripts, under the MIT License.
qiskit-zksf, the Qiskit provider, under the MIT License.
pennylane-zksf, the PennyLane device plugin, under the MIT License.
Reporting the Accuracy of Approximate Quantum Circuit Simulation, the paper specifying the certification protocols, under the Creative Commons Attribution 4.0 International (CC BY 4.0).

Each item is governed by its own licence, whose full text is published with it. Where that licence conflicts with these Terms in respect of that item, the licence prevails.
An open licence covers the item it is attached to and nothing else. It grants no right in the hosted Service, our proprietary technology or content, or our trade marks, and use of the Service through open source software remains subject to these Terms.
Open source software is provided as is, as stated in its licence.

15. Feedback

If you send us suggestions, ideas or other feedback about the Service, you grant us a perpetual, irrevocable, worldwide, royalty free licence to use it for any purpose without obligation to you. You remain free to use your own ideas as you wish.

16. Availability

The Service is provided without any uptime guarantee unless covered by a separate written service level agreement.
Cold start latency, queue times and QPU availability windows vary and are not warranted.
We may carry out maintenance at any time, which may interrupt the Service.
We do not warrant that the Service will be uninterrupted, timely, secure or error free, or that defects will be corrected.

17. Disclaimer of Warranties

To the maximum extent permitted by applicable law, the Service, its results, estimates and certificates are provided on an “as is” and “as available” basis, without warranty, condition or representation of any kind, whether express, implied or statutory, including any implied warranty of merchantability, satisfactory quality, fitness for a particular purpose, accuracy, completeness, availability, security or non infringement.

18. Data and Results: Allocation of Risk

Because quantum computing is an error prone and experimental field, and because the Service is not a storage service, you agree that, to the maximum extent permitted by applicable law, we are not liable for, and you release us from any claim in respect of:

any loss, corruption, deletion, unavailability or delayed delivery of data, programs, results or certificates, however caused, including through technical failure, the failure of a third party provider, or the closure or deletion of an account;
any error, inaccuracy, noise, instability or irreproducibility in a result, estimate, projection or certificate, whether produced by simulation or on a QPU;
any use or misuse of data, programs or results by you, by anyone using your account or keys, by any person to whom you disclose them, or by any third party who obtains them through a cause outside our reasonable control; and
any decision, action, publication or omission taken in reliance on the Service or its outputs.

19. Limitation of Liability

To the maximum extent permitted by law, we shall not be liable for any indirect, incidental, special, consequential, exemplary or punitive damages, nor for any loss of profit, revenue, business, opportunity, goodwill, data, research time or research outcome, however caused and under any theory of liability, even if advised of the possibility of such loss.
To the maximum extent permitted by law, our aggregate liability arising out of or in connection with the Service and these Terms shall not exceed the total amount paid by you to us in the three months immediately preceding the event giving rise to the claim.
These limitations apply regardless of the legal theory on which a claim is brought, survive termination, and reflect a reasonable allocation of risk that forms an essential basis of the agreement between us.

20. Indemnification

You agree to indemnify, defend and hold harmless ZKSF and its affiliates, owners, officers, employees, contractors and licensors from and against any claims, demands, proceedings, liabilities, damages, losses, penalties, fines, costs and expenses, including reasonable legal fees, arising out of or relating to: the programs, data or content you submit; your use of, publication of, or reliance on any result, estimate or certificate; any loss or misuse of data for which you are responsible under these Terms; any use of your account or keys; your breach of these Terms, including Section 8, or of any applicable law; your infringement of the rights of any third party; and any claim connected with your research, product or commercial activity. We may, at our own expense, assume exclusive defence and control of any matter subject to indemnification by you, in which case you agree to cooperate. This indemnity survives termination.

21. Export Control and Sanctions

You agree to comply with all applicable export control and sanctions laws, including restrictions on access from embargoed jurisdictions, and you warrant that you are not a person with whom dealings are prohibited under any such law, nor owned or controlled by one.
You must not use the Service for any end use, or make it available to any end user, prohibited by those laws.
QPU access may be subject to further provider level restrictions beyond our control.

22. Suspension and Termination

You may close your account at any time from the application, as described in the Privacy Policy. Closure does not entitle you to a refund of charges already incurred.
We may suspend or terminate an account for breach of these Terms, for non payment, for suspected fraud or misuse under Section 9, where required by law, or for activity that endangers the Service or other users, with notice where practicable and lawful.
On termination, your right to use the Service ends. Sections 3, 4, 6, 9, 10 in respect of amounts owed, 13, 14 and 17 to 25 survive termination.

23. Governing Law and Disputes

These Terms and any dispute or claim arising out of or in connection with them or the Service, including non contractual disputes, are governed by the laws of the State of Delaware, United States of America, without regard to its conflict of laws rules.
The state and federal courts located in the State of Delaware have exclusive jurisdiction over any such dispute, and each party submits to their jurisdiction, save that we may seek injunctive or other equitable relief in any court of competent jurisdiction to protect our intellectual property or the security of the Service.
Before starting proceedings, a party must first notify the other in writing of the dispute, by email to legal@zksf.org in our case, and the parties will attempt in good faith to resolve it within thirty days.

24. Changes to These Terms

We may amend these Terms from time to time. The date at the head of this page records the current version. Material changes are notified by email to the address held on your account before taking effect. Continued use of the Service after that date constitutes acceptance. If you do not accept an amendment, you must stop using the Service.

25. General Provisions

Entire agreement. These Terms and the Privacy Policy constitute the entire agreement between the parties concerning the Service, subject to Section 1 in respect of a separate signed agreement.
Severability. If any provision is held invalid or unenforceable it shall be modified to the minimum extent necessary, or severed, and the remainder continues in force.
No waiver. Failure or delay in enforcing a provision is not a waiver of it.
Assignment. You may not assign or transfer these Terms or your account without our written consent. We may assign them in connection with a merger, acquisition, reorganisation or sale of assets.
Force majeure. We are not liable for failure or delay caused by events beyond our reasonable control, including the failure of third party providers, networks or utilities.
Relationship. Nothing in these Terms creates a partnership, joint venture, agency or employment relationship between the parties.
Notices. We may give notices by email to the address held on your account or by posting them in the Service. You agree that such electronic communications satisfy any requirement that a notice be in writing. Notices to us must be sent to legal@zksf.org.
Claims period. Any claim must be brought within one year after the cause of action arises, or within such longer period as applicable law requires.
Language. These Terms are written in English, and the English version prevails over any translation.

26. Contact

For anything concerning these Terms, including permissions, intellectual property notices and disputes, write to legal@zksf.org. Security vulnerabilities should be reported privately to info@zksf.org, as our security policy describes.