The possibility of quantum computing breaking encryption algorithms
The possibility of breaking encryption algorithms is a powerful motivating factor for many countries of the world. Thus, knowledge of the enemy's encryption systems could give a huge advantage in intelligence, while at the same time contributing to the conduct of new fundamental research in the field of physics, since modern experimental systems have at their disposal only less than 100 qubits.
To achieve the useful computing performance of a supercomputer, we probably need machines with hundreds of thousands of qubits. In order for the devices to function correctly, they must correct all minor random errors in the software. In a quantum computer, such errors arise due to imperfect elements of the circuit and the interaction of qubits with their environment. For these reasons, qubits can lose coherence in literally a split second.
A quantum computer with 100 qubits can simultaneously represent 2100 solutions. For some tasks, this exponential parallelism can be used to create a huge advantage in computational speed. At the same time, there is another, narrower approach to quantum computing, in which qubits are used to accelerate optimization problems.
For example, D-Wave Systems, a company based in Canada, has built optimization systems that use qubits for this purpose, although some critics claim that the resulting systems work no better than classic computers.