PTAB’s Reversal Sheds Light on Quantum Computing Patents

Despite its potential to transform the global economy and impact national security, quantum computing has advanced largely outside public scrutiny. Artificial intelligence has dominated public discourse, while quantum computing remains a field marked by a mix of skepticism and optimism. Yet, with the sunset of Moore's law and the race to lead the quantum future, the need for a clear intellectual property (IP) protection framework, which will play a pivotal role in shaping the industry’s trajectory, has become increasingly critical. A recent decision of the PTAB in favor of patentability provides an indication as to which way the law in this field may unfold.

Like the early days of software patents, quantum computing patents face a range of challenges. Given the scarcity of decisions in this field, tracking the evolving positions of courts and the U.S. Patent and Trademark Office (USPTO) is essential for clients in considering appropriate IP protection strategies in the coming years. 

The recent Patent Trial and Appeal Board (PTAB) decision in Ex parte Yudong Cao, Appeal 2024-002159, Application No. 16/591,239, offers valuable guidance for those interested in quantum computing patents. The Board reversed the Examiner’s rejections under 35 U.S.C. § 101 (patent eligibility) and 35 U.S.C. § 112(a) (written description). This ruling not only informs patent drafting strategies but also signals a potentially favorable precedent for future litigation that would reinforce patents as a viable IP protection mechanism in the quantum computing sector.

The Patent at Issue

The patent application at issue concerns a hybrid quantum-classical (HQC) computer system for solving linear systems. Specifically, the claimed system splits the linear system into subsystems solvable by a quantum computer, controlled by a classical computer, which then synthesizes the outputs. 

For example, the independent claim 1 recites a method for preparing a quantum state that approximates a solution x to a linear system of equations Ax = b. A key element in the claim is:

"(a) on a classical computer, generating an objective function that depends on: (1) at least one expectation-value term derivable from the matrix A, and (2) at least one overlap term derivable from the vector b and the matrix A." 

The Written Description Rejection

The Examiner had rejected Claim 1 and others (Claims 2-15 and 17-31), on the grounds that the specification disclosed only two "species" of objective functions (paragraphs 49 and 57) and failed to provide written description support for the broader "genus" of objective functions claimed.

On appeal, the PTAB disagreed, finding that the specification, viewed from the perspective of a person of ordinary skill in the art, adequately conveyed possession of the claimed invention. The Board emphasized that:

• The original claim 1, as part of the specification, served as strong initial evidence of possession.
• Paragraphs 22, 49, and 57 provided sufficient description and implementation examples to demonstrate possession of the invention.

Significantly, the Board noted that the Examiner’s arguments resembled an enablement rejection rather than a written description rejection. Enablement-based rejections are common in quantum computing patents due to uncertainties about the technology’s feasibility, as evidenced by multiple appeals before the PTAB (e.g., Appeal Nos. 2023-000069, 2023-002850, and 2023-003447). 

The Patent Eligibility Rejection under § 101

More notably, regarding 35 U.S.C. § 101, the PTAB ruled that the claims integrated the abstract idea—mathematical relationships—into a practical application, thus satisfying the Alice/Mayo test (Step 2A, Prong 2). The Board found that:

• The claims provided a technological improvement by enabling quantum computers to solve linear systems practically—something that other quantum computers could not achieve.
• The specification described the limitations of quantum computers, reinforcing the technological improvement argument.

This decision is particularly significant for innovators in hybrid computing, where quantum and classical methods are combined to enhance computational efficiency. The PTAB recognized that hybrid quantum-classical systems, even when performing tasks that classical computers can already routinely execute, may still qualify as technological improvements under § 101. In a way, the patent eligibility decision acknowledges the infancy of quantum computing technology and the need for significant advancements to bridge the gap between classical and quantum computers. This point will likely influence future patent applications and litigation strategies, especially for those developing quantum and AI in a hybrid models to make classical computing more efficient in certain matrix math use cases while also lowering power utilization. 

Practical Implications for Patent Drafting and Litigation

The PTAB’s decision underscores several best practices for quantum computing patent prosecution and litigation:

• Strategic Claim Drafting: The Board’s reliance on the original claim language as evidence of possession highlights the importance of carefully drafting claims for initial filings. Patent applicants should ensure that their claims align with the specification to preempt § 112 challenges.
• Multiple Concrete Embodiments: The PTAB placed weight on specific examples of objective functions in the specification. For quantum algorithm patents, providing detailed examples of quantum circuits, error correction schemes, and computational methodologies will help withstand scrutiny.
• Clear Differentiation Between Written Description and Enablement: Litigators must be prepared to counter opposing arguments that conflate these two distinct legal requirements. Establishing that an invention was “possessed” at the time of filing is different from proving that it is fully enabled. In this instance, the Board astutely noted that the Examiner’s determination about “genus” of objective functions disclosure not meeting the written description requirement is conflated with the enablement requirement. The Examiner’s assertion that the Specification “does not indicate how the inventors intended for the objective function to be generated” is unpersuasive, as the Specification provides specific examples. To the extent relevant regarding the enablement requirement, Appellant argued that the “infinite number of objective functions” the Examiner found implicit in the disputed claim is not dispositive in establishing that practicing the limitation requires undue experimentation. 

Looking Ahead

While this decision sets a positive precedent under § 112 and § 101, patentability challenges under § 101 remain. As quantum computing evolves, patent claims may become less rooted in hardware and directed more closely toward quantum algorithms. Widespread energy savings from hybrid quantum-classical computing will depend on overcoming current technical barriers and achieving scalability in real-world applications. But the energy demands of AI and quantum computing suggest that energy-efficient hybrid quantum-classical approaches may be poised to gain traction and that their patentability will likely continue to be a key topic. Quantum computing's importance to U.S. technology and security may point to easing of the challenges this emerging technology has faced in patent prosecution, as this recent decision seems to indicate.

 

This informational piece, which may be considered advertising under the ethical rules of certain jurisdictions, is provided on the understanding that it does not constitute the rendering of legal advice or other professional advice by Goodwin or its lawyers. Prior results do not guarantee similar outcomes.