Measuring Loschmidt echo via Floquet engineering in superconducting circuits

The Loschmidt echo is a useful diagnostic for the perfection of quantum time-reversal process and the sensitivity of quantum evolution to small perturbations. The main challenge for measuring the Loschmidt echo is the time reversal of a quantum evolution. In this work, we demonstrate the measurement of the Loschmidt echo in a superconducting 10-qubit system using Floquet engineering and discuss the imperfection of an initial Bell-state recovery arising from the next-nearest-neighbor (NNN) coupling present in the qubit device. Our results show that the Loschmidt echo is very sensitive to small perturbations during quantum-state evolution, in contrast to the quantities like qubit population that is often considered in the time-reversal experiment. These properties may be employed for the investigation of multiqubit system concerning many-body decoherence and entanglement, etc., especially when devices with reduced or vanishing NNN coupling are used.     

由因式化L算子所构成的经典可积动力学体系

用因式化的L算子构造了一类在非周期边界条件下的可积模型.对体系的transfer矩阵取三角和标度极限情况下,得到了n维体系(n为奇数)的经典哈密顿量的具体形式.结果表明,这类可积体系与Calogero等人所发现的一系列可积体系是相类似的.     

动力学椭圆代数Aq,p,(^π)(∧gln)的Drinfeld流

从推广的Yang-Baxter关系"RLL=LLR*"出发,利用高秩高斯分解,得到了动力学椭圆代数Aq,p,^π(∧gln)及其对应的Drinfeld流.其中R,R*是A(1)n-1面模型对应的谱参数有一关于代数中心平移的动力学R矩阵.     

动力学椭圆代数A_(q,p,)()的Drinfeld流

从推广的Yang -Baxter关系“RLL =LLR ”出发 ,利用高秩高斯分解 ,得到了动力学椭圆代数Aq,p ,^π(gln〈)及其对应的Drinfeld流 .其中R ,R 是A(1)n -1面模型对应的谱参数有一关于代数中心平移的动力学R矩阵     

Zn Belavin模型反射方程的多参数解

利用A_(n－1)⁽¹⁾面模型反射方程的对角解,得到了ZnBelavin模型反射方程的含有n+1个参数的解.当n=2时,其结果与侯伯宇等人给出的8项角反射方程的解是一致的.     

Nonlocal advantage of quantum coherence in a dephasing channel with memory

We investigate nonlocal advantage of quantum coherence(NAQC)in a correlated dephasing channel modeled by themultimode bosonic reservoir.We obtain analytically the dephasing and memory factors of this channel for the reservoirhaving a Lorentzian spectral density,and analyze how they affect the NAQC defined by the l1 norm and relative entropy.It is shown that the memory effects of this channel on NAQC are state-dependent,and they suppress noticeably the rapiddecay of NAQC for the family of input Bell-like states with one excitation.For the given transmission time of each qubit,we also obtain the regions of the dephasing and memory factors during which there is NAQC in the output states.     

Construction of Complete Orthogonal Genuine Multipartite Entanglement State

With the development of quantum information processing, multipartite entanglement measures are needed in many cases. However, there are still no complete orthogonal genuine multipartite entanglement(GME) bases available as Bell states to bipartite systems. To achieve this goal, we find a method to construct complete orthogonal GME states, and we exclude many equivalent states by leveraging the group theory. We also provide the case of a 3-order 3-dimensional Hilbert space as an example and study the application of general results in the dense coding scheme as an application. Moreover, we discuss some open questions and believe that this work will enlighten extensive studies in this field.     

量子计算纠错取得突破性进展

谷歌团队利用超导量子芯片,实现了两种规模的量子纠错表面码,利用辅助比特进行多次测量和初始化操作进行纠错,表明使用更多量子比特表面码的逻辑比特,其性能表现更好,达到了量子纠错规模化的盈亏平衡点,本文简要回顾量子纠错的机制,讨论谷歌量子纠错结果的意义,以及系列量子纠错进展,最后将展望量子计算的发展方向.     

用玻色化顶点算子实现与Z_n对称的BelavinR矩阵相关的Z-F代数

根据Ａｓａｉ，Ｊｉｍｂｏ，Ｍｉｗａ和Ｐｕｇａｉ给出的玻色化的Ａ￣（１）＿（ｎ－１）面模型的顶点算子，用面顶点对应关系，得到了与Ｚ＿ｎ对称的ＢｅｌａｖｉｎＲ矩阵相关的玻色化顶点算，它们实现了与这种Ｒ矩阵对应的Ｚａｍｏｌｏｄｃｈｉｋｏｖ－Ｆａｄｅｅｖ代数。     

Beating standard quantum limit via two-axis magnetic susceptibility measurement

We report a metrology scheme which measures the magnetic susceptibility of an atomic spin ensemble along the $x$ and $z$ directions and produces parameter estimation with precision beating the standard quantum limit. The atomic ensemble is initialized via one-axis spin squeezing with optimized squeezing time and parameter $\phi$ (to be estimated) assumed as uniformly distributed between 0 and $2\pi$ while fixed in each estimation. One estimation of $\phi$ can be produced with every two magnetic susceptibility data measured along the two axes respectively, which has an imprecision scaling $({1.43\pm0.02})/N^{0.687\pm0.003}$ with respect to the number $N$ of the atomic spins. The measurement scheme is easy to implement and is robust against the measurement fluctuation caused by environment noise and measurement defects.