不同光学网络结构玻色采样发生随机光子损失的模拟研究

Simulation of random photon loss in boson sampling of different optical networks

玻色采样机是最有可能真正意义上实现量子优势的专用量子计算机之一,其在量子化学等领域也有着很好的应用前景.然而,光子损失相关的噪声会引起玻色采样样本的误差.为了研究光子损失对玻色采样的影响,基于等效分束器原理,对玻色采样展开经典的模拟研究.对于对应任意幺正矩阵的两种光学网络,当在每一个光学单元中有一定概率发生光子损失时,发现具有Clements结构光学网络的玻色采样相比于Reck结构的样本误差更小.进一步地,当光子损失的概率符合正态分布时,发现若光子损失概率平均值不变,标准差越大,玻色采样的样本误差越大.最后,考虑输出光子数的实验结果表明,随着光子损失概率的提高,无光子损失的输出组合比例急剧下降,说明光子损失会明显影响玻色采样的量子优势.随机光子损失的玻色采样模拟研究有助于玻色采样实验的开展,为含噪声量子计算研究提供思路.

Boson sampling is a candidate for quantum protocols to truly realize the quantum computation advantage and to be used in advanced fields where complex computations are needed,such as quantum chemistry.However,this proposal is hard to achieve due to the existence of noise sources such as photon losses.In order to quant ificationally analyze the influences of photon losses in optical networks,boson sampling is classically simulated based on the equivalent beam splitter mechanism,where the photon loss happening in optical units is equivalent to the photon transmission into the environmental paths through a virtual beam splitter.In our simulation,networks corresponding to random unitary matrices are made up,considering both the Reck structure and the Clements structure.The photon loss probability in an optical unit is well controlled by adjusting the parameters of the virtual beam splitter.Therefore,to simulate boson sampling with photon losses in optical networks is actually to simulate ideal boson sampling with more modes.It is found that when the photon loss probability is constant,boson sampling with Clements structures distinctly performs much better than that with Reck structures.Furthermore,the photon loss probability is also set to follow the normal distribution,which is thought to be closer to the situation in reality.It is found that when the mean value of photon loss probability is constant,for both network structures,errors of outputs become more obvious with the increase of standard deviation.It can be inferred that the increase of error rate can be explained by the network depth and the conclusion is suitable for larger-scale boson sampling.Finally,the number of output photons is taken into consideration,which is directly related to the classical computation complexity.It is found that with the photon loss probability,the ratio of output combinations without photon losses decreases sharply,implying that photon losses can obviously affect the quantum computation advantage of boson sampling.Our results indicate that photon losses can result in serious errors for boson sampling,even with a stable network structure such as that of Clements.This work is helpful for boson sampling experiments in reality and it is desired to develop a better protocol,for example,a well-designed network or excellent optical units,to well suppress photon losses.