# How to Connect Quantum Computer Bits with a Superconducting Circuit > This patent describes a superconducting circuit called an rf-SQUID that can precisely turn on, turn off, or change the way two quantum computer bits (qubits) interact with each other. - **Patent:** US 20080238531 - **Original title:** Systems, devices, and methods for controllably coupling qubits - **Owner:** Individual - **Status:** Active - **Times cited:** 57 - **Field:** quantum_computing, semiconductors, telecommunications, software ## What it does This system provides a way to controllably link two quantum bits, or qubits, using a special superconducting loop called an rf-SQUID (Claim 1). This rf-SQUID has a 'compound Josephson junction' and is connected to both a first qubit and a second qubit through magnetic fields (mutual inductance). A separate 'magnetic flux inductor' is also connected to the Josephson junction (Claim 1). By adjusting the magnetic field produced by this inductor, the system can control how the two qubits interact, allowing for different 'coupling states' such as anti-ferromagnetic coupling, ferromagnetic coupling, or even no coupling at all (Claim 3, Claim 5). For example, if you want two qubits in a quantum computer to perform a calculation together, this system could turn on their interaction, and then turn it off when they need to operate independently. ## What it does NOT cover - Does not cover qubit coupling systems that do not use an rf-SQUID as the intermediate coupling device. - Does not cover coupling mechanisms that do not rely on mutual inductance between the rf-SQUID and the qubits. - Does not cover control methods for qubit coupling that do not involve a magnetic flux inductor adjusting flux through a compound Josephson junction. - Does not cover qubits that are not superconducting, as the claims specifically mention 'superconducting flux qubit' (Claim 2) and 'superconducting material' (Claim 1). - Does not cover direct coupling between qubits without an intermediate tunable coupler. ## The clever bit The cleverness lies in using an rf-SQUID with a compound Josephson junction as a tunable intermediary, allowing a magnetic flux inductor to precisely switch and adjust the quantum mechanical coupling between two qubits from zero to ferromagnetic or anti-ferromagnetic states. ## Real-world examples 1. Superconducting quantum processors 2. Tunable couplers in quantum computing architectures 3. IBM Quantum computers 4. Google's Sycamore processor 5. Rigetti Computing quantum systems ## Why it matters Controlling how qubits interact is fundamental to building functional quantum computers. This patent offers a precise method to switch and tune these interactions, which is essential for executing quantum algorithms and building scalable quantum processors. Without such control, qubits would either always interact or never interact, severely limiting the types of computations possible. ## Frequently asked questions ### What does How to Connect Quantum Computer Bits with a Superconducting Circuit cover? This patent describes a superconducting circuit called an rf-SQUID that can precisely turn on, turn off, or change the way two quantum computer bits (qubits) interact with each other. ### Who owns patent US 20080238531? This patent is owned by Individual. ### When does this patent expire? This patent is expected to expire on January 22, 2028, when the invention enters the public domain. ### What is patent US 20080238531 cited by? This patent has been cited by 57 later patents that build on its ideas. ### What problem does this patent solve? Controlling how qubits interact is fundamental to building functional quantum computers. This patent offers a precise method to switch and tune these interactions, which is essential for executing quantum algorithms and building scalable quantum processors. Without such control, qubits would either always interact or never interact, severely limiting the types of computations possible. ### What does this patent NOT cover? Does not cover qubit coupling systems that do not use an rf-SQUID as the intermediate coupling device. **Full plain-English explainer:** https://patentbrief.org/patent/us/20080238531/systems-devices-and-methods-for-controllably-coupling-qubits **Original patent:** https://patents.google.com/patent/US20080238531 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How D-Wave Clears Magnetic Noise in Quantum Computers](https://patentbrief.org/patent/us/11295225/superconducting-quantum-processor-and-method-of-operating-same) — A method for improving quantum computer accuracy by actively clearing out magnetic interference that builds up during calculations. - [How Quantum Computers Use Special Devices to Control Qubits](https://patentbrief.org/patent/us/9256834/quantum-computers-having-partial-interferometric-quantum-gates) — This patent describes a way for quantum computers to control special quantum bits, called topological qubits, using a "partial interferometric device" to perform specific operations. - [How to Build a Room-Temperature Quantum-Like Computer with Regular Electronics](https://patentbrief.org/patent/us/20230229951/quantum-analog-computing-at-room-temperature-using-conventional-electronic-circu) — This patent describes an integrated circuit and method for performing 'quantum analog computing' at room temperature using conventional electronic components like resistors, inductors, capacitors, and switches, arranged in a specific network. - [Solving Big Math Problems with Small Quantum Computers](https://patentbrief.org/patent/us/12008436/machine-learning-mapping-for-quantum-processing-units) — This patent describes how a classical computer can break down large mathematical problems into smaller pieces that even limited quantum computers can solve, then combine the results. - [How Quantum Computers Learn to Sort Data](https://patentbrief.org/patent/us/20240296359/classification-using-quantum-neural-networks) — This patent describes a method for training a data classifier using a quantum computer, where classical AI helps prepare the data and interpret the quantum results to improve the quantum system's ability to sort information.