The concept of "quantum computational supremacy" refers to the point at which a quantum computer can solve a specific computational problem that is believed to be intractable for classical computers. The exact number of qubits required for quantum computational supremacy depends on several factors, including the problem being solved, the quantum algorithm used, the level of error correction implemented, and the specific criteria for achieving supremacy.
In 2019, Google's research team claimed to have achieved quantum computational supremacy with a 53-qubit quantum processor called Sycamore. They designed a quantum circuit to perform a random sampling task known as a "random quantum circuit sampling" problem. According to their study, this task was expected to be infeasible for classical computers to solve within a reasonable timeframe.
It's worth noting that achieving quantum computational supremacy does not necessarily mean that quantum computers will be superior in all computational tasks. Rather, it demonstrates that there are specific problems for which quantum computers can provide an advantage over classical computers. The field of quantum computing is still in its early stages, and researchers are actively exploring ways to scale up quantum systems and improve their capabilities.
As quantum computing technology progresses and researchers continue to develop more advanced algorithms and error correction techniques, the number of qubits required for quantum computational supremacy may change. However, it is difficult to predict a specific threshold or number of qubits required as it depends on various factors and the specific problem being targeted.