Abstract on Article 069 EPC for the decision T2651/22 of 19.03.2025

In T 2651/22 the patent related to impedance matched microwave quantum circuit systems, in particular to a system comprising a parametric amplifier for amplifying a qubit readout. The interpretation of the feature "impedance matching circuit" in claim 1 was relevant to assess inventive step. The respondent (patent proprietor) submitted that the claim could not be interpreted as covering a single integrated circuit. Feature 1.3 defined a quantum circuit device. Feature 1.4 defined an impedance matching circuit coupled to the quantum device. For the person skilled in the art it was clear that these were two different circuits. The scope of protection did not extend to one integrated circuit with double functionality as that of D8. Had the patentee desired to cover such a circuit it would have worded the claim differently, for instance to define an impedance matched circuit, not an impedance matching circuit. The specification was also consistent in describing two different circuits (figures 5, 6, 8A and 8B), one of which being placed in front of the amplifier and providing only impedance matching functionality and no amplification. The appellant (opponent) argued that the patentee's intention when drafting the claim was irrelevant. If the claimed technical features could be mapped to the prior art then that was sufficient for the features to be disclosed. In order to establish a difference vis-à-vis D8 the claim should have been limited by inserting features from the specification into the claim, instead of relying on the specification for interpretation. The board found the position of both parties to be reasoned and reasonable. The problem lay in the inherent difficulty of defining whether and when circuitry which is part of a larger circuitry can be identified as one circuit separate from the rest, or as fulfilling only one function. In the present case for instance, the presence of an impedance matching circuit as described in the specification also influenced the amplifying function; it improved it by reducing losses. Considering this context, the board was of the opinion that the claim had to be interpreted in the light of the description. On that basis the board concluded that the claimed impedance matching circuit was to be interpreted as a circuit designed specifically for the (sole) purpose of impedance matching of a preexisting quantum device circuit to external circuitry. It was undisputed that D8 did not disclose such a circuit. Further, the appellant did not argue that under this interpretation the claimed matter was obvious. Accordingly, the board came to the conclusion that claim 1 of the patent as maintained was inventive over D8.