From a quite general form of the Lindblad-like master equation of open two-level systems(qubits), we study the effect of Lamb shift on the non-Markovian dynamics. We find that the Lamb shift can induce a non-uniform r...From a quite general form of the Lindblad-like master equation of open two-level systems(qubits), we study the effect of Lamb shift on the non-Markovian dynamics. We find that the Lamb shift can induce a non-uniform rotation of the Bloch sphere, but that it does not affect the non-Markovianity of the open system dynamics. We determine the optimal initial-state pairs that maximize the backflow of information for the considered master equation and find an interesting phenomenon–the sudden change of the non-Markovianity. We relate the dynamics to the evolution of the Bloch sphere to help us comprehend the obtained results.展开更多
As technological innovations in computers begin to advance past their limit (Moore’s law), a new problem arises: What computational device would emerge after the classical supercomputers reach their physical limitati...As technological innovations in computers begin to advance past their limit (Moore’s law), a new problem arises: What computational device would emerge after the classical supercomputers reach their physical limitations? At this moment in time, quantum computers are at their starting stage and there are already some strengths and advantages when compared with modern, classical computers. In its testing period, there are a variety of ways to create a quantum computer by processes such as the trapped-ion and the spin-dot methods. Nowadays, there are many drawbacks with quantum computers such as issues with decoherence and scalability, but many of these issues are easily emended. Nevertheless, the benefits of quantum computers at the moment outweigh the potential drawbacks. These benefits include its use of many properties of quantum mechanics such as quantum superposition, entanglement, and parallelism. Using these basic properties of quantum mechanics, quantum computers are capable of achieving faster computational times for certain problems such as finding prime factors of an integer by using Shor’s algorithm. From the advantages such as faster computing times in certain situations and higher computing powers than classical computers, quantum computers have a high probability to be the future of computing after classical computers hit their peak.展开更多
By describing the evolution of a quantum state with the trajectories of the Majorana stars on a Bloch sphere,Majorana’s stellar representation provides an intuitive geometric perspective to comprehend the quantum sys...By describing the evolution of a quantum state with the trajectories of the Majorana stars on a Bloch sphere,Majorana’s stellar representation provides an intuitive geometric perspective to comprehend the quantum system with highdimensional Hilbert space.However,the representation of a two-spin coupling system on a Bloch sphere has not been solved satisfactorily yet.Here,a practical method is presented to resolve the problem for the mixed-spin(s,1/2)system and describe the entanglement of the system.The system can be decomposed into two spins:spin-(s+1/2)and spin-(s−1/2)at the coupling bases,which can be regarded as independent spins.Besides,any pure state may be written as a superposition of two orthonormal states with one spin-(s+1/2)state and the other spin-(s−1/2)state.Thus,the whole initial state can be regarded as a state of a pseudo spin-1/2.In this way,the mixed spin decomposes into three spins.Therefore,the state can be represented by(2s+1)+(2s−1)+1=4s+1 sets of stars on a Bloch sphere.Finally,some examples are given to show symmetric patterns on the Bloch sphere and unveil the properties of the high-spin system by analyzing the trajectories of the Majorana stars on the Bloch sphere.展开更多
In this paper, we propose a scheme for photon echo chirped detection process composed of additional modulation pulses to obtain controllable geometric phase. The geometric phases are observed and measured by a beat si...In this paper, we propose a scheme for photon echo chirped detection process composed of additional modulation pulses to obtain controllable geometric phase. The geometric phases are observed and measured by a beat signal between the photon echo field and the chirped field. The chirped detection model reveals that the period of the beat signal increases as the chirped rate and delay time increase. Additionally, a two-fold relationship between the modulation phase and the echo shift phase is obtained. The numerical simulations accord with the theoretical results obtained by the finite difference time domain(FDTD) method.展开更多
To enhance the performance of the artificial bee colony optimization by integrating the quantum computing model into bee colony optimization, we present a quantum-inspired bee colony optimization algorithm. In our met...To enhance the performance of the artificial bee colony optimization by integrating the quantum computing model into bee colony optimization, we present a quantum-inspired bee colony optimization algorithm. In our method, the bees are encoded with the qubits described on the Bloch sphere. The classical bee colony algorithm is used to compute the rotation axes and rotation angles. The Pauli matrices are used to construct the rotation matrices. The evolutionary search is achieved by rotating the qubit about the rotation axis to the target qubit on the Bloch sphere. By measuring with the Pauli matrices, the Bloch coordinates of qubit can be obtained, and the optimization solutions can be presented through the solution space transformation. The proposed method can simultaneously adjust two parameters of a qubit and automatically achieve the best match between two adjustment quantities, which may accelerate the optimization process. The experimental results show that the proposed method is obviously superior to the classical one for some benchmark functions.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11275064 and 11075050)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20124306110003)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT0964)the Construct Program of the National Key Discipline,China
文摘From a quite general form of the Lindblad-like master equation of open two-level systems(qubits), we study the effect of Lamb shift on the non-Markovian dynamics. We find that the Lamb shift can induce a non-uniform rotation of the Bloch sphere, but that it does not affect the non-Markovianity of the open system dynamics. We determine the optimal initial-state pairs that maximize the backflow of information for the considered master equation and find an interesting phenomenon–the sudden change of the non-Markovianity. We relate the dynamics to the evolution of the Bloch sphere to help us comprehend the obtained results.
基金supported in part by the National Science Foundation of China under Grant No.61074050the National Key Basic Research Program under Grant No.2009CB929601
文摘在控制领域下面的州的转移基于单个 qubit 的 Bloch 范围表示被分析。为了从一个任意的起始的状态完成目标到一个目标，说，参数应该满足的条件在二个不同要求独立被推出：一个人在在被修理的 X 轴附近的旋转角度的情况中，另外一个处于有一给定的进化时间的状况。几条典型状态轨道被数字模拟在 Bloch 范围上表明。在参数和轨道之间的关系被分析。
文摘As technological innovations in computers begin to advance past their limit (Moore’s law), a new problem arises: What computational device would emerge after the classical supercomputers reach their physical limitations? At this moment in time, quantum computers are at their starting stage and there are already some strengths and advantages when compared with modern, classical computers. In its testing period, there are a variety of ways to create a quantum computer by processes such as the trapped-ion and the spin-dot methods. Nowadays, there are many drawbacks with quantum computers such as issues with decoherence and scalability, but many of these issues are easily emended. Nevertheless, the benefits of quantum computers at the moment outweigh the potential drawbacks. These benefits include its use of many properties of quantum mechanics such as quantum superposition, entanglement, and parallelism. Using these basic properties of quantum mechanics, quantum computers are capable of achieving faster computational times for certain problems such as finding prime factors of an integer by using Shor’s algorithm. From the advantages such as faster computing times in certain situations and higher computing powers than classical computers, quantum computers have a high probability to be the future of computing after classical computers hit their peak.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0304202 and 2017YFA0205700)the National Natural Science Foundation of China(Grant No.11875231)the Fundamental Research Funds for the Central Universities,China(Grant No.2018FZA3005).
文摘By describing the evolution of a quantum state with the trajectories of the Majorana stars on a Bloch sphere,Majorana’s stellar representation provides an intuitive geometric perspective to comprehend the quantum system with highdimensional Hilbert space.However,the representation of a two-spin coupling system on a Bloch sphere has not been solved satisfactorily yet.Here,a practical method is presented to resolve the problem for the mixed-spin(s,1/2)system and describe the entanglement of the system.The system can be decomposed into two spins:spin-(s+1/2)and spin-(s−1/2)at the coupling bases,which can be regarded as independent spins.Besides,any pure state may be written as a superposition of two orthonormal states with one spin-(s+1/2)state and the other spin-(s−1/2)state.Thus,the whole initial state can be regarded as a state of a pseudo spin-1/2.In this way,the mixed spin decomposes into three spins.Therefore,the state can be represented by(2s+1)+(2s−1)+1=4s+1 sets of stars on a Bloch sphere.Finally,some examples are given to show symmetric patterns on the Bloch sphere and unveil the properties of the high-spin system by analyzing the trajectories of the Majorana stars on the Bloch sphere.
基金The project supported by Special Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20050285002It is a pleasure to thank Profs. Yin-Sheng Ling and Jian-Xing Fang for their enlightening discussions on this topic.
基金Project supported by the Tianjin Research Program of Application Foundation and Advanced Technology,China(Grant No.15JCQNJC01100)
文摘In this paper, we propose a scheme for photon echo chirped detection process composed of additional modulation pulses to obtain controllable geometric phase. The geometric phases are observed and measured by a beat signal between the photon echo field and the chirped field. The chirped detection model reveals that the period of the beat signal increases as the chirped rate and delay time increase. Additionally, a two-fold relationship between the modulation phase and the echo shift phase is obtained. The numerical simulations accord with the theoretical results obtained by the finite difference time domain(FDTD) method.
文摘To enhance the performance of the artificial bee colony optimization by integrating the quantum computing model into bee colony optimization, we present a quantum-inspired bee colony optimization algorithm. In our method, the bees are encoded with the qubits described on the Bloch sphere. The classical bee colony algorithm is used to compute the rotation axes and rotation angles. The Pauli matrices are used to construct the rotation matrices. The evolutionary search is achieved by rotating the qubit about the rotation axis to the target qubit on the Bloch sphere. By measuring with the Pauli matrices, the Bloch coordinates of qubit can be obtained, and the optimization solutions can be presented through the solution space transformation. The proposed method can simultaneously adjust two parameters of a qubit and automatically achieve the best match between two adjustment quantities, which may accelerate the optimization process. The experimental results show that the proposed method is obviously superior to the classical one for some benchmark functions.
