According to experts, i quantum computers they will not be able to surpass the traditional ones for at least the next 5-10 years. And this in the elaborations that have to do with specific calculations, completely impracticable using classical information technology. In fact, we have seen what problems quantum computers can solve.
Il noise they errors are among the main problems that experts encounter when they have to perform calculations using modern quantum computers. The unwanted phenomena that can influence the “goodness” of the calculations are often attributed to the very nature of the qubits and are the direct consequence of quantum effects widely known.
Factors that negatively affect the behavior of quantum computers
Environmental factors such as temperature fluctuations and electromagnetic interference can disturb the quantum system and lead to measurement errors or loss of coherence. Some errors can also arise from defects or imperfections in the construction of the qubits or in the control operations. Furthermore, the phenomenon ofentanglement, essential for exploiting the potential of quantum computers, can be both desired and unwanted. L’entanglement unwanted between qubits can lead to processing errors making it difficult to control and manipulate quantum data.
The problem of noise and errors represents a challenge significant in the realization of scalable and reliable quantum computers. The scientific community and companies in the sector are actively working to address this challenge and improve the quality and reliability of quantum computers, in order to reach ever higher levels of performance.
The researchers of theIBM Quantum of New York, jointly with collaborators from the University of California (Berkeley) and the Lawrence Berkeley National Laboratorythey just explained in the magazine Nature to have made significant progress. A IBM’s 127 qubit quantum computer he was able to develop a process of great interest to physicists without errors when a supercomputer, called to carry out the same computation, failed to do so.
An inside view of the cryostat that cools the IBM Eagle, an industrial-scale quantum system containing 127 qubits (source: IBM Research).
Mitigation of quantum errors
In the concrete case described by IBM and the team of academic experts, the brilliantly solved problem with the quantum computer is not so important. Much more important is the goal achieved inquantum error attenuation.
Big Blue has in fact successfully put into practice a new technique for reduce noise that accompanies quantum computing. IBM researchers have controllably increased the noise in the quantum circuit to paradoxically get even louder and less accurate answers. They then extrapolated the data and estimated the response the computer would have gotten if there had been no noise. In this way it was possible to understand more accurately how noise negatively affects quantum circuits and to carry out output predictions. The technique has been baptized zero noise extrapolation (ZNE).
The concept and approach used by IBM is illustrated very clearly in this video posted on YouTube by the IBM Research team.
The more the qubits are “intertwined” with each other (the state of some depends on the state of others…), the greater the negative effect that noise introduces on the elaborations. Furthermore, calculations involving a set of qubits can introduce random errors in other qubits not directly affected.
Do you know the ECC memories that integrate the error correction? Here, IBM scientists count on being able to use a similar concept by introducing qubit extra to track errors so they can be corrected. Get to get one fault-tolerant error correction scalable however, it represents an enormous engineering challenge which still remains to be demonstrated in practice.
However, researchers prefer to move using the proverbial feet of lead. It will take some time to see if IBM’s proposed ZNE approach will be successful with a wide range of practical applications.
The opening image is made by IBM Research.