Contemporary quantum computers have relatively high levels of noise, making it difficult to use them to perform useful calculations, even with a large number of qubits. Quantum error correction is expected to eventually enable fault-tolerant quantum computation at large scales, but until then it will be necessary to use alternative strategies to mitigate the impact of errors. We propose a near-term friendly strategy to mitigate errors by entangling and measuring $M$ copies of a noisy state $ρ$. This enables us to estimate expectation values with respect to a state with dramatically reduced error, $ρ^M/ \mathrm{Tr}(ρ^M)$, without explicitly preparing it, hence the name "virtual distillation". As $M$ increases, this state approaches the closest pure state to $ρ$, exponentially quickly. We analyze the effectiveness of virtual distillation and find that it is governed in many regimes by the behavior of this pure state (corresponding to the dominant eigenvector of $ρ$). We numerically demonstrate that virtual distillation is capable of suppressing errors by multiple orders of magnitude and explain how this effect is enhanced as the system size grows. Finally, we show that this technique can improve the convergence of randomized quantum algorithms, even in the absence of device noise.
Error Mitigation in Bosonic Systems via Virtual Distillation
Chalmers University of Technology（查尔姆斯理工大学）；École polytechnique, Institut Polytechnique de Paris（巴黎综合理工学院，巴黎理工学院）；Université libre de Bruxelles（布鲁塞尔自由大学）；International Iberian Nanotechnology Laboratory (INL)（国际伊比利亚纳米技术实验室）；University of Minho（米尼奥大学）
All about quantum error correction: distillation, mitigation, self-correction and beyond
Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）
Below-threshold error reduction in single photons through photon distillation
MESA+ Institute for Nanotechnology, University of Twente（特温特大学纳米技术研究所）；NASA Ames Research Center（美国宇航局艾姆斯研究中心）；QuiX Quantum B.V.（QuiX量子有限公司）；USRA Research Institute for Advanced Computer Science（美国大学空间研究协会先进计算机科学研究院）；Dahlem Center for Complex Quantum Systems, Freie Universitat Berlin（柏林自由大学达勒姆复杂量子系统中心）；Fraunhofer Heinrich Hertz Institute（弗劳恩霍夫海因里希赫兹研究所）
Robust design under uncertainty in quantum error mitigation
Institute of Theoretical Physics, Jagiellonian University（雅盖隆大学理论物理研究所）；Szkoła Doktorska Nauk Ścisłych i Przyrodniczych, Uniwersytet Jagielloński（雅盖隆大学自然科学博士学院）；Mark Kac Center for Complex Systems Research, Jagiellonian University（雅盖隆大学马克·卡克复杂系统研究中心）；Information Sciences, Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室信息科学部）；The Uncertainty Quantification Foundation（不确定性量化基金会）；Quantum Science Center（量子科学中心）；Theoretical Division, Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室理论部）
Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China（中国科学技术大学物理科学学院和微观尺度物理国家研究中心）；Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China（中国科学技术大学上海量子科学研究与创新中心和中国科学院量子信息与量子物理学前沿卓越创新中心）；Hefei National Laboratory, University of Science and Technology of China（中国科学技术大学合肥国家实验室）；State Key Lab of Millimeter Waves, Southeast University（东南大学毫米波国家重点实验室）；College of Computer Science and Technology, National University of Defense Technology（国防科技大学计算机学院）
Can Error Mitigation Improve Trainability of Noisy Variational Quantum Algorithms?
Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；Imperial College London（帝国理工学院）；Jagiellonian University（雅盖隆大学）；Quantum Science Center（量子科学中心）；Center for Nonlinear Studies（非线性研究中心）
Multipartite quantum resource distillation through local measurement programs
School of Physics, Hangzhou Normal University（杭州师范大学物理学院）；CAS Key Laboratory of Quantum Information, University of Science and Technology of China（中国科学院量子信息重点实验室，中国科学技术大学）；Anhui Province Key Laboratory of Quantum Network, University of Science and Technology of China（安徽省量子通信与量子计算重点实验室，中国科学技术大学）；CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China（中国科学院量子信息与量子物理学前沿卓越创新中心，中国科学技术大学）；Hefei National Laboratory, University of Science and Technology of China（合肥国家实验室，中国科学技术大学）
