Quantum Computing Patents: Early 101 Guidance from PTAB Decisions

By Victoria Carrington and Michael Mauriel

Quantum computing progress from theory to commercial reality is accelerating – and, in parallel, so is quantum computing patenting. In 2016, only 71 new U.S. patent publications referenced quantum computing in their abstracts. However, for each of the past four years (2021-2024), over 500 new U.S. patent publication abstracts have referenced quantum computing, a 700% increase relative to 2016.

The growth in patent filings mirrors the broader momentum of the quantum computing industry. In the first ten months of 2024, venture capital investments into early stage quantum computing companies nearly doubled the total investments in quantum computing seen in all of 2023. The Sutor Group recently reported that there are 80 companies worldwide offering quantum processors. Given accelerating growth in the field, companies and patent practitioners naturally seek to position themselves strategically in the quantum computing intellectual property landscape. Understanding how patent law is being applied to quantum computing-related inventions is therefore a timely endeavor.

One expects prior art principles regarding novelty and non-obviousness to be relatively consistent across technology areas, including in newly emerging areas such as quantum computing. However, it is often less clear how the principles of subject matter eligibility under 35 U.S.C. § 101 and those of enablement, written description, and definiteness under 35 U.S.C. § 112 will be applied to new technology areas until a sufficient body of case law is established.

The upsurge in quantum computing patenting is still relatively new and, therefore, very few, if any, cases have reached the U.S. Court of Appeals for the Federal Circuit. However, the Patent Trial and Appeal Board (PTAB) has addressed several quantum computing cases on appeals from examiner decisions rejecting claims. For now, these PTAB decisions are presumably shaping the U.S. Patent and Trademark Office’s approach to quantum computing patent prosecution. Here is a look at a few of them in the context of the subject matter eligibility doctrine under §101.

Subject Matter Eligibility and Qubit Computations

As patent practitioners in the computer arts well know, a patent claim covering mathematical operations, without more, is typically considered an “abstract idea” and, therefore, not patent-eligible subject matter. And merely adding language to the claim invoking use of a computer to perform the operations does not, by itself, render the claim eligible subject matter. But we also know that many patents covering software rather than hardware have issued and been found by courts to cover patentable subject matter. At the same time, the courts, and therefore the USPTO, have had difficulty defining what types of computer processing algorithms are patentable subject matter and what other types are ineligible “abstract ideas.” If a claim recites processing that, on its own, would be considered an abstract idea (one of the judicial exceptions to statutory categories of eligible subject matter), then the USPTO asks whether the claim as a whole “integrates the exception into a practical application.” If so, then the claim is considered to be subject matter eligible. One way of showing that the claim integrated an abstract idea into a practical application is showing that the claimed invention “improves the functioning of a computer or improves another technology or technical field.”

These principles would seem applicable to the claimed invention considered in a 2017 PTAB decision, Ex Parte Alexei Ashikhmin. The PTAB’s decision contained little reasoning, but the case’s subject matter, quantum error correction, gives the result significance. The patent application in question dates to 2013, well before quantum computing patents were being filed in significant volumes. The application covered an apparatus for improved quantum error identification and correction. The improvement related to a technique of checking whether an error measurement (known in the art as a “syndrome”) itself contained error. The claim considered on appeal included a quantum circuit that transformed preset states of one or more qubits based on the physical state of a set of qubits for whom error is being tested. The circuit was “configured” such that the transformed preset states can be measured to obtain both “bits of a syndrome” and at least one “parity check bit” for checking the syndrome bits.

The Examiner had found the claimed invention to be “directed to the abstract idea of generating abstract mathematical quantities call syndromes.” The PTAB reversed, noting: “Quantum processing using quantum bits or ‘qubits’ and measuring physical states and syndromes associated therewith, may be esoteric technology, but this does not make the claimed invention abstract . . ..”

Unfortunately, the PTAB did not elaborate on its reasoning. However, in the art of data error correction generally, “syndromes” by definition have practical application for identifying errors in stored and/or transmitted data. In its broadest respects, a “syndrome” simply refers to one or more values that identify / measure whether error is present in a data signal. It is borrowed from the medical term “syndrome,” meaning a collection of symptoms suggesting presence of an illness.

Techniques for such things as data compression, virus detection, and data integrity checking have well-established practical applications in telecommunications, data processing, and data storage generally. Therefore, it is not surprising that the subject matter eligibility of inventions that improve upon such techniques is not generally questioned. And one would naturally expect that an invention for improving quantum error correction, like the one addressed in Ex Parte Ashikhmin, would be found acceptable under 35 U.S.C. § 101.

Perhaps less clear is whether inventions directed to solving a general class of math equations using quantum processing are eligible subject matter for patenting. One such case was recently addressed by the PTAB earlier this year in Ex Parte Yudong Cao.

The patent application at issue in Ex Parte Yudong Cao involved using a hybrid quantum-classical computer system for estimating an objective function to solve a linear system of equations. In its decision, the PTAB provided a full 101 analysis and ultimately found the subject matter to be patent eligible based on the claims integrating the abstract idea into a practical application, specifically, “enabling noisy quantum computers, which have limited circuit depths, to practically solve linear systems—a technology improvement.”

While not dispositive, it seemed significant to the PTAB that the invention involved a mix of quantum and classical hardware and that this interaction allowed discovery of a set of quantum circuit parameters that enabled a practical use of the quantum computer in solving linear systems. Whether reciting steps that combine use of a classical computer and a quantum computer will prove important to finding a claim to be subject-matter eligible remains to be seen. However, many current and proposed applications of quantum computing involve performing some computations on a classical computer before and/or after performing operations on a quantum computer. The result in Ex Parte Yudong Cao suggests that a wide variety of algorithms used with quantum computers will be treated as eligible by the USPTO, as long as those algorithms are clearly articulated in the patent application and help improve a quantum computer’s ability to solve a particular class of problems having practical applications.

However, in Ex Parte Yili Zhang, the mere presence of quantum processing in the claims was insufficient, in the PTAB’s view, to transform an otherwise “abstract idea” regarding financial analysis into patent eligible subject matter. The independent claim in question involved calculating credit risk factors by calculating, at a first time step (and then at a second time step), “a discrete probabilistic wave function representing a superposition state of scores.” .

Notably, the independent method claim implied the use of quantum hardware for at least some of the steps because it referenced both “a superposition state” and “measuring . . . the discrete probabilistic wave function.” However, the claim did not recite such hardware expressly. In evaluating the claim, the PTAB noted that “claim 1 only requires ‘a number of processors.’ These components are described in the Specification at a high level of generality.” Dependent claim 9 did reference qubits, but this failed to impact the PTAB’s decision.

The claims in question in Ex Parte Yili Zhang are perhaps an imperfect test of whether use of a quantum computer to solve a non-technological problem (e.g., risk analysis) can transform an invention that the USPTO would normally consider too abstract for patent protection into a patent-eligible one. Those familiar with the USPTO’s 101 guidance, the jurisprudence underlying that guidance, and the USPTO’s application of it in prosecution would find it unsurprising that the PTAB readily dismissed the generic reference to “a number of processors” as insufficient. A claim directed to use of a quantum computing system (or a hybrid classical quantum computing system) for processing financial (or other non-technological data) that more fully detailed the utilized quantum processing (e.g., by reciting details of an applicable quantum circuit) might or might not pass muster with the PTAB and/or the Federal Circuit. That remains to be seen.

Michael Mauriel

Michael is a Partner in Maschoff Brennan’s New York Office. He prepares and prosecutes patent applications dealing with a wide variety of cutting-edge technologies. He counsels clients regarding managing and monetizing large patent portfolios. He also represents clients in high-stakes patent negotiations and litigations. Michael currently serves as co-chair of the firm’s patent prosecution department.

Victoria Tomoko Carrington

Victoria helps clients protect and promote innovation from the firm’s Salt Lake City office. Her practice focuses on patent and trademark prosecution for clients in tech-heavy industries. She is an active member of many legal, tech, and medical organizations and is also a published researcher.

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Maschoff Brennan provides legal counsel and representation to some of the world’s most innovative companies. With almost 50 attorneys and offices in the technology-focused regions of Utah, California, and New York, our attorneys are known for having the breadth of experience and the forward-thinking insight needed to handle complex technological and business issues across all industries and geographic boundaries. In addition, we have extensive experience representing clients before the ITC, PTAB, TTAB, and other administrative agencies in Washington D.C.