Quantum processors do not need error correction in certain calculations, and their related capabilities surpass classical computing

On the 14th, Nature magazine reported a quantum processor that can surpass classical computing without error correction. This IBM 127-qubit processor surpasses the current best classical computing methods in terms of manufacturing and measuring highly entangled quantum states. This achievement shows that quantum computers may be used for some specific calculations in the near future without the need for fault tolerance (avoiding or quickly correcting errors when running quantum computers to keep them under control), which is a big step towards practicality.

IBM's 127-qubit processor surpasses the current best classical computing methods in terms of manufacturing and measuring highly entangled quantum states.
Image source: Nature website

A key goal of quantum computing is to outperform classical computing and perform specific tasks efficiently. To achieve this goal, many practical challenges need to be addressed, such as keeping error rates low, penetrating quantum "noise" (interference from the underlying system or environment), and scaling up quantum computers. Errors and noise can reduce or eliminate the benefits of quantum computing over classical computing. With current technology, fault tolerance is still out of reach. Although existing quantum processors are already able to outperform classical computers on some specific but artificial problems, it is still controversial whether current or near-future noisy quantum computers can perform useful quantum calculations (such as for research purposes).

The IBM Thomas J. Watson Research Center research team has provided evidence that their quantum chip can reliably generate, manipulate and measure quantum states that are so complex that classical methods cannot reliably estimate their properties. The results show that quantum machines, even without error correction, can already help solve certain problems that classical computers are helpless to solve (such as studying physical models).

The experiment was based on a 127-qubit processor running 60 layers deep, with about 2,800 two-qubit gates (the quantum version of classical computer logic gates). This quantum circuit produces huge, highly entangled quantum states that are too demanding to be reliably reproduced by numerical approximations on classical computers. But the quantum computer can accurately estimate the properties of these states by measuring expectation values, creating and measuring these huge states without incurring too many errors that would weaken the calculation.

Glenn Wentin and Jonas Brandl of Chalmers University of Technology in Sweden commented: "The fundamental quantum advantage lies in scale rather than speed - 127 qubits encode a huge state space, and classical computers do not have such a large memory."