The D-Wave Advantage and IBM's quantum computers are based on different approaches to quantum computing, which accounts for the difference in the number of qubits and the way they are characterized. It's important to understand that the number of qubits alone doesn't provide a complete picture of the capabilities or performance of a quantum computer.
D-Wave Advantage is a quantum annealing computer developed by D-Wave Systems. It is designed specifically for solving optimization problems using a method called quantum annealing. Quantum annealing is a specialized approach to quantum computing that leverages quantum effects to explore and find optimal solutions for certain types of problems. D-Wave systems refer to their qubits as "usable qubits," which implies that not all qubits are fully connected or actively participating in computations. The D-Wave Advantage system has more than 5000 such usable qubits.
On the other hand, IBM's quantum computers, such as the IBM Quantum System One, are based on a different approach known as gate-based or circuit-based quantum computing. These systems use qubits that are typically more connected and can perform a wider range of quantum operations. IBM's characterization of "high-quality qubits" refers to the reliability, coherence, and error rates of their qubits, which are crucial factors in the performance of quantum algorithms. IBM has focused on improving the quality and reliability of their qubits rather than maximizing the sheer number.
Comparing the two systems, D-Wave Advantage emphasizes a large number of usable qubits for optimization problems using quantum annealing, while IBM focuses on improving the quality and reliability of fewer qubits for general-purpose gate-based quantum computing. The choice of approach and the intended applications differ between these systems, leading to variations in the number of qubits and their performance characteristics.
It's also worth noting that the field of quantum computing is evolving rapidly, and both D-Wave and IBM, along with other companies and research institutions, continue to make advancements in their respective technologies. The number and quality of qubits, as well as the overall capabilities of quantum computers, are expected to improve over time.