We study the phenomenon of decoherence during the operation of one qubit transformation, controlled-not (CNOT) and controlled-controlled-not (C2NOT) quantum gates in a quantum computer model formed by a linear chain o...We study the phenomenon of decoherence during the operation of one qubit transformation, controlled-not (CNOT) and controlled-controlled-not (C2NOT) quantum gates in a quantum computer model formed by a linear chain of three nuclear spins system. We make this study with different type of environments, and we determine the associated decoherence time as a function of the dissipative parameter. We found that the dissipation parameter to get a well defined quantum gates (without significant decoherence) must be within the range of . We also study the behavior of the purity parameter for these gates and different environments and found linear or quadratic decays of this parameter depending on the type of environments.展开更多
We propose a scheme to engineer a non-local two-qubit phase gate between two remote quantum-dot spins. Along with one-qubit local operations, one can in principal perform various types of distributed quantum informati...We propose a scheme to engineer a non-local two-qubit phase gate between two remote quantum-dot spins. Along with one-qubit local operations, one can in principal perform various types of distributed quantum information processing. The scheme employs a photon with linearly polarisation interacting one after the other with two remote quantum-dot spins in cavities. Due to the optical spin selection rule, the photon obtains a Faraday rotation after the interaction process. By measuring the polarisation of the final output photon, a non-local two-qubit phase gate between the two remote quantum-dot spins is constituted. Our scheme may has very important applications in the distributed quantum information processing.展开更多
We study the electron transmission tuned by quantum gate in an Aharonov Casher (AC) ring. Transmission probability is obtained as a function of the normalized textured electric fields and Fermi energy. We find that ...We study the electron transmission tuned by quantum gate in an Aharonov Casher (AC) ring. Transmission probability is obtained as a function of the normalized textured electric fields and Fermi energy. We find that modulating electron wavefunction in the stub can drastically affects electron transmission through the ring system. As Fermi energy crosses every eigenenergy of the isolated stub, the phases of both anomalous and periodic oscillations of the AC conductance generally have abrupt change by π. On two sides of several special Fermi energies, both anomalous and periodic oscillations have no abrupt phase change and are in phase. The detailed characteristics of the anomalous oscillations are dependent on the difference between the tilt angle of the spin and that of textured electric field. By modulating external magnetic field applied to the stub, we present AC oscillations of spin polarized conductance within adiabatic limit.展开更多
The carrier-density-dependent spin relaxation dynamics for modulation-doped GaAs/Al0.3 Gao,TAs quantum wells is studied using the time-resolved magneto-Kerr rotation measurements. The electron spin relaxation time and...The carrier-density-dependent spin relaxation dynamics for modulation-doped GaAs/Al0.3 Gao,TAs quantum wells is studied using the time-resolved magneto-Kerr rotation measurements. The electron spin relaxation time and its in-plane anisotropy are studied as a function of the optically injected electron density, Moreover, the relative strength of the Rashba and the Dresselhaus spin-rbit coupling fields, and thus the observed spin relaxation time anisotropy, is further tuned by the additional excitation of a 532nm continuous wave laser, demonstrating an effective spin relaxation manipulation via an optical gating method.展开更多
Nitrogen-vacancy （NV） center in diamond is one of the most promising candidates to implement room temperature quantum computing. In this review, we briefly discuss the working principles and recent experimental prog...Nitrogen-vacancy （NV） center in diamond is one of the most promising candidates to implement room temperature quantum computing. In this review, we briefly discuss the working principles and recent experimental progresses of this spin qubit. These results focus on understanding and prolonging center spin coherence, steering and probing spin states with dedicated quantum control techniques, and exploiting the quantum nature of these multi-spin systems, such as superposition and entanglement, to demonstrate the superiority of quantum information processing. Those techniques also stimulate the fast development of NV-based quantum sensing, which is an interdisciplinary field with great potential applications.展开更多
提出了一种在金刚石中两个临近氮-空位色心(nitrogen-vacancy color center,简称NV色心)之间施加受控非门(C-NOT gate)的新方案.在该方案中,临近NV色心间的强电偶极耦合将导致态依赖的能级移动,从而施加可控的激光共振激发可以实现快速...提出了一种在金刚石中两个临近氮-空位色心(nitrogen-vacancy color center,简称NV色心)之间施加受控非门(C-NOT gate)的新方案.在该方案中,临近NV色心间的强电偶极耦合将导致态依赖的能级移动,从而施加可控的激光共振激发可以实现快速受控相位门(C-phase gate),结合单比特操作,可以快速实现C-NOT门.在两个相邻10 nm的NV色心之间,C-NOT门操作时间最快可达120 ns,比传统磁偶极方式快了2个量级.为了降低激发态自发辐射的影响,提出利用非共振腔抑制自发辐射.模拟结果显示C-phase门操控保真度可以达到98.88%.最后,将该方案扩展到一维NV色心自旋链.展开更多
We show that a local unitary(LU) equivalent Fredkin gate can be obtained from the free evolution of three mixed-spin qubits by virtue of numerical simulation with only one step.The spin-1 qubit acts as the control qub...We show that a local unitary(LU) equivalent Fredkin gate can be obtained from the free evolution of three mixed-spin qubits by virtue of numerical simulation with only one step.The spin-1 qubit acts as the control qubit,and two spin-1/2 qubits,which interact with the spin-1 qubit via the first neighbor spin interaction,respectively,play the role of target qubits.We also examine the imperfect Fredkin gate operation by considering the effects of nonidentical coupling constants,uniform and inhomogeneous magnetic fields.展开更多
文摘We study the phenomenon of decoherence during the operation of one qubit transformation, controlled-not (CNOT) and controlled-controlled-not (C2NOT) quantum gates in a quantum computer model formed by a linear chain of three nuclear spins system. We make this study with different type of environments, and we determine the associated decoherence time as a function of the dissipative parameter. We found that the dissipation parameter to get a well defined quantum gates (without significant decoherence) must be within the range of . We also study the behavior of the purity parameter for these gates and different environments and found linear or quadratic decays of this parameter depending on the type of environments.
基金Project supported by the National Fundamental Research Program of China (Grant No. 2007CB925204)the National Natural Science Foundation of China (Grant No. 10775048)+1 种基金the Key Project of Chinese Ministry of Education (Grant No. 206103)the Construct Program of the National Key Discipline
文摘We propose a scheme to engineer a non-local two-qubit phase gate between two remote quantum-dot spins. Along with one-qubit local operations, one can in principal perform various types of distributed quantum information processing. The scheme employs a photon with linearly polarisation interacting one after the other with two remote quantum-dot spins in cavities. Due to the optical spin selection rule, the photon obtains a Faraday rotation after the interaction process. By measuring the polarisation of the final output photon, a non-local two-qubit phase gate between the two remote quantum-dot spins is constituted. Our scheme may has very important applications in the distributed quantum information processing.
文摘We study the electron transmission tuned by quantum gate in an Aharonov Casher (AC) ring. Transmission probability is obtained as a function of the normalized textured electric fields and Fermi energy. We find that modulating electron wavefunction in the stub can drastically affects electron transmission through the ring system. As Fermi energy crosses every eigenenergy of the isolated stub, the phases of both anomalous and periodic oscillations of the AC conductance generally have abrupt change by π. On two sides of several special Fermi energies, both anomalous and periodic oscillations have no abrupt phase change and are in phase. The detailed characteristics of the anomalous oscillations are dependent on the difference between the tilt angle of the spin and that of textured electric field. By modulating external magnetic field applied to the stub, we present AC oscillations of spin polarized conductance within adiabatic limit.
基金Supported by the National Natural Science Foundation Program of China under Grant Nos 11274302,11474276 and 61290303
文摘The carrier-density-dependent spin relaxation dynamics for modulation-doped GaAs/Al0.3 Gao,TAs quantum wells is studied using the time-resolved magneto-Kerr rotation measurements. The electron spin relaxation time and its in-plane anisotropy are studied as a function of the optically injected electron density, Moreover, the relative strength of the Rashba and the Dresselhaus spin-rbit coupling fields, and thus the observed spin relaxation time anisotropy, is further tuned by the additional excitation of a 532nm continuous wave laser, demonstrating an effective spin relaxation manipulation via an optical gating method.
基金Project supported by the National Basic Research Program of China(Grant Nos.2014CB921402 and 2015CB921103)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB07010300)+1 种基金the National Natural Science Foundation of China(Grant No.11574386)the Key Research Program of the Chinese Academy of Sciences(Grant No.XDPB0803)
文摘Nitrogen-vacancy （NV） center in diamond is one of the most promising candidates to implement room temperature quantum computing. In this review, we briefly discuss the working principles and recent experimental progresses of this spin qubit. These results focus on understanding and prolonging center spin coherence, steering and probing spin states with dedicated quantum control techniques, and exploiting the quantum nature of these multi-spin systems, such as superposition and entanglement, to demonstrate the superiority of quantum information processing. Those techniques also stimulate the fast development of NV-based quantum sensing, which is an interdisciplinary field with great potential applications.
基金National Key Research and Development Program of China(Nos.2018YFA0306600,2017YFA0305000)National Natural Science Foundation of China(Item Numbers:11775209,81788101,11761131011)+2 种基金Anhui Quantum Information Technology Leading Project(Item Number:AHY050000)Fundamental Research Funds for the Central UniversitiesUSTC Research Funds of the Double First-Class Initiative.
文摘提出了一种在金刚石中两个临近氮-空位色心(nitrogen-vacancy color center,简称NV色心)之间施加受控非门(C-NOT gate)的新方案.在该方案中,临近NV色心间的强电偶极耦合将导致态依赖的能级移动,从而施加可控的激光共振激发可以实现快速受控相位门(C-phase gate),结合单比特操作,可以快速实现C-NOT门.在两个相邻10 nm的NV色心之间,C-NOT门操作时间最快可达120 ns,比传统磁偶极方式快了2个量级.为了降低激发态自发辐射的影响,提出利用非共振腔抑制自发辐射.模拟结果显示C-phase门操控保真度可以达到98.88%.最后,将该方案扩展到一维NV色心自旋链.
文摘We show that a local unitary(LU) equivalent Fredkin gate can be obtained from the free evolution of three mixed-spin qubits by virtue of numerical simulation with only one step.The spin-1 qubit acts as the control qubit,and two spin-1/2 qubits,which interact with the spin-1 qubit via the first neighbor spin interaction,respectively,play the role of target qubits.We also examine the imperfect Fredkin gate operation by considering the effects of nonidentical coupling constants,uniform and inhomogeneous magnetic fields.
