Zero noise extrapolation (ZNE) is a technique used in quantum computing to mitigate errors caused by noise and imperfections in quantum systems. It is a method that leverages multiple runs of a quantum circuit with different noise levels to estimate and correct for errors, ultimately improving the accuracy of the computation.
Quantum computers are susceptible to various sources of noise, including decoherence, gate errors, and environmental interactions, which can introduce errors and reduce the reliability of computation. ZNE addresses these challenges by utilizing the concept of noise scaling.
The basic idea behind ZNE is to perform computations on a quantum circuit at different noise levels, including a noise-free or "zero noise" scenario. By executing the circuit multiple times with varying noise levels, it becomes possible to observe how the circuit's output changes as noise is introduced.
Typically, ZNE involves running the circuit on a noisy quantum computer several times, gradually increasing the noise level for each run. The output results of these runs are then used to extrapolate the expected result in the absence of noise. This extrapolation is achieved by fitting a mathematical model to the observed data points and extrapolating it to the limit of zero noise.
Once the noise-free or near-zero noise result is estimated through extrapolation, it can be compared to the noisy results obtained from actual quantum computers. The discrepancies between the noisy results and the extrapolated noise-free result indicate the presence of errors caused by noise. By analyzing these discrepancies, researchers can gain insights into the noise characteristics of the quantum system and develop error mitigation techniques.
ZNE provides a way to estimate the true outcome of a quantum computation by extrapolating from noisy data. This estimation can be used to correct for errors, improving the fidelity and reliability of quantum computations. It enables researchers to better understand the noise sources and develop strategies to mitigate their impact, such as error correction codes or noise-adaptive algorithms.
It's worth noting that ZNE is not a complete solution to the challenges of noise and errors in quantum computing. It is an active area of research, and techniques like error correction codes and noise-adaptive algorithms are also being explored to further enhance the robustness and scalability of quantum computations. Nonetheless, ZNE offers a valuable tool in the arsenal of error mitigation techniques for quantum computing.