We propose a method to estimate the average fidelity using the unitary 2t-design of a twirled noisy channel, which is suitable for large-scale quantum circuits. Compared with the unitary 2-design in randomized benchma...We propose a method to estimate the average fidelity using the unitary 2t-design of a twirled noisy channel, which is suitable for large-scale quantum circuits. Compared with the unitary 2-design in randomized benchmarking, the unitary2t-design for the twirling of noisy channels is more flexible in construction and can provide more information. In addition,we prove that the proposed method provides an efficient and reliable estimation of the average fidelity in benchmarking multistage quantum gates and estimating the weakly gate-and time-dependent noise. For time-dependent noise, we provide a scheme of moment superoperator to analyze the noise in different experiments. In particular, we give a lower bound on the average fidelity of a channel with imperfect implementation of benchmarking and state preparation and measurement errors(SPAM).展开更多
Entanglement in quantum theory is a peculiar concept to scientists. With this concept we are forced to re-consider the cluster property which means that one event is irrelevant to another event when they are fully far...Entanglement in quantum theory is a peculiar concept to scientists. With this concept we are forced to re-consider the cluster property which means that one event is irrelevant to another event when they are fully far away. In the recent works we showed that the quasi-degenerate states induce the violation of cluster property in antiferromagnets when the continuous symmetry breaks spontaneously. We expect that the violation of cluster property will be observed in other materials too, because the spontaneous symmetry breaking is found in many systems such as the high temperature superconductors and the superfluidity. In order to examine the cluster property for these materials, we studied a quantum nonlinear sigma model with U(1) symmetry in the previous work. There we showed that the model does have quasi-degenerate states. In this paper we study the quantum nonlinear sigma model with SU(2) symmetry. In our approach we first define the quantum system on the lattice and then adopt the representation where the kinetic term is diagonalized. Since we have no definition on the conjugate variable to the angle variable, we use the angular momentum operators instead for the kinetic term. In this representation we introduce the states with the fixed quantum numbers and carry out numerical calculations using quantum Monte Carlo methods and other methods. Through analytical and numerical studies, we conclude that the energy of the quasi-degenerate state is proportional to the squared total angular momentum as well as to the inverse of the lattice size.展开更多
提出了一种采用酉ESPRIT(Unitary-Estimation ofSignal Parameters via Rotational Invariant Technique,Unitary-ESPRIT)算法对目标的二维波达方向(Direction-of-Arrival,DOA)进行估计,接收信号模型为中心对称的平面阵。与二维MUSIC(Mu...提出了一种采用酉ESPRIT(Unitary-Estimation ofSignal Parameters via Rotational Invariant Technique,Unitary-ESPRIT)算法对目标的二维波达方向(Direction-of-Arrival,DOA)进行估计,接收信号模型为中心对称的平面阵。与二维MUSIC(Multiple Signal Classification)算法、二维求根MUSIC算法、二维ESPRIT算法不同的是,该算法将复矩阵运算转化为实矩阵计算,简化了运算复杂程度,并且目标的DOA估计精度也相应的得到提高,是一种比较高效的DOA估计算法。展开更多
The Dyson form of the q-deformed boson realization of the quantum group SU(2)_(q) is constructed.The unitary Holstein-Primakoff representation of SU(2)_(q) is obtained from non-unitary Dyson representation by means of...The Dyson form of the q-deformed boson realization of the quantum group SU(2)_(q) is constructed.The unitary Holstein-Primakoff representation of SU(2)_(q) is obtained from non-unitary Dyson representation by means of K-matrix technique.展开更多
二维波达方向(Direction of Arrival,DOA)估计是智能天线技术中的一个关键问题.在低信噪比、低快拍数条件下,常规DOA估计算法的性能会严重下降.针对此问题,提出了一种基于均匀面阵的酉ESPRIT算法.算法将复矩阵转化为实矩阵计算,使运算...二维波达方向(Direction of Arrival,DOA)估计是智能天线技术中的一个关键问题.在低信噪比、低快拍数条件下,常规DOA估计算法的性能会严重下降.针对此问题,提出了一种基于均匀面阵的酉ESPRIT算法.算法将复矩阵转化为实矩阵计算,使运算复杂程度简化,估计精度提高,且可实现参数自动配对,是一种比较高效的DOA估计算法.计算机仿真结果表明了所提算法在测向性能方面比常规DOA估计算法有更好的估计性能,且在低信噪比和低快拍数条件下估计性能不受影响,同时具有更小的运算量.展开更多
In this paper, we construct some 1（1/2）-designs, which are also known as partial geometric designs, using totally isotropic subspaces of the unitary space. Phrthermore, these 1（1/2）-designs yield six infinite fami...In this paper, we construct some 1（1/2）-designs, which are also known as partial geometric designs, using totally isotropic subspaces of the unitary space. Phrthermore, these 1（1/2）-designs yield six infinite families of directed strongly regular graphs.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61372076 and 61701375)the 111 Project,China(Grant No.B08038)+1 种基金the Key Research and Development Plan of Shannxi Province,China(Grant No.BBD24017290001)the Foundation of Science and Technology on Communication Networks Laboratory,China(Grant No.KX172600031)
文摘We propose a method to estimate the average fidelity using the unitary 2t-design of a twirled noisy channel, which is suitable for large-scale quantum circuits. Compared with the unitary 2-design in randomized benchmarking, the unitary2t-design for the twirling of noisy channels is more flexible in construction and can provide more information. In addition,we prove that the proposed method provides an efficient and reliable estimation of the average fidelity in benchmarking multistage quantum gates and estimating the weakly gate-and time-dependent noise. For time-dependent noise, we provide a scheme of moment superoperator to analyze the noise in different experiments. In particular, we give a lower bound on the average fidelity of a channel with imperfect implementation of benchmarking and state preparation and measurement errors(SPAM).
文摘Entanglement in quantum theory is a peculiar concept to scientists. With this concept we are forced to re-consider the cluster property which means that one event is irrelevant to another event when they are fully far away. In the recent works we showed that the quasi-degenerate states induce the violation of cluster property in antiferromagnets when the continuous symmetry breaks spontaneously. We expect that the violation of cluster property will be observed in other materials too, because the spontaneous symmetry breaking is found in many systems such as the high temperature superconductors and the superfluidity. In order to examine the cluster property for these materials, we studied a quantum nonlinear sigma model with U(1) symmetry in the previous work. There we showed that the model does have quasi-degenerate states. In this paper we study the quantum nonlinear sigma model with SU(2) symmetry. In our approach we first define the quantum system on the lattice and then adopt the representation where the kinetic term is diagonalized. Since we have no definition on the conjugate variable to the angle variable, we use the angular momentum operators instead for the kinetic term. In this representation we introduce the states with the fixed quantum numbers and carry out numerical calculations using quantum Monte Carlo methods and other methods. Through analytical and numerical studies, we conclude that the energy of the quasi-degenerate state is proportional to the squared total angular momentum as well as to the inverse of the lattice size.
文摘提出了一种采用酉ESPRIT(Unitary-Estimation ofSignal Parameters via Rotational Invariant Technique,Unitary-ESPRIT)算法对目标的二维波达方向(Direction-of-Arrival,DOA)进行估计,接收信号模型为中心对称的平面阵。与二维MUSIC(Multiple Signal Classification)算法、二维求根MUSIC算法、二维ESPRIT算法不同的是,该算法将复矩阵运算转化为实矩阵计算,简化了运算复杂程度,并且目标的DOA估计精度也相应的得到提高,是一种比较高效的DOA估计算法。
文摘The Dyson form of the q-deformed boson realization of the quantum group SU(2)_(q) is constructed.The unitary Holstein-Primakoff representation of SU(2)_(q) is obtained from non-unitary Dyson representation by means of K-matrix technique.
文摘二维波达方向(Direction of Arrival,DOA)估计是智能天线技术中的一个关键问题.在低信噪比、低快拍数条件下,常规DOA估计算法的性能会严重下降.针对此问题,提出了一种基于均匀面阵的酉ESPRIT算法.算法将复矩阵转化为实矩阵计算,使运算复杂程度简化,估计精度提高,且可实现参数自动配对,是一种比较高效的DOA估计算法.计算机仿真结果表明了所提算法在测向性能方面比常规DOA估计算法有更好的估计性能,且在低信噪比和低快拍数条件下估计性能不受影响,同时具有更小的运算量.
文摘In this paper, we construct some 1（1/2）-designs, which are also known as partial geometric designs, using totally isotropic subspaces of the unitary space. Phrthermore, these 1（1/2）-designs yield six infinite families of directed strongly regular graphs.
