2018 24th Asia-Pacific Conference on Communications (APCC), 2018
Interference-aware coordinated multi-point can mitigate inter-cell interference and improve total... more Interference-aware coordinated multi-point can mitigate inter-cell interference and improve total throughput. However, it is crucial to select the scheduled users, cluster the cooperative base stations, and determine the transmit power of each base station over all physical resource blocks. Select the scheduled users and the cooperative BSs which served the users respectively based on affinity propagation at first. Then, we develop a power allocation scheme which considers the fairness among users. The scheme is a generalized proportional fairness based on Nash bargaining solutions. Simulation results demonstrate the superiority of the user-centric approach of scheduling and power control in CoMP.
2018 24th Asia-Pacific Conference on Communications (APCC), 2018
Interference-aware coordinated multi-point can mitigate inter-cell interference and improve total... more Interference-aware coordinated multi-point can mitigate inter-cell interference and improve total throughput. However, it is crucial to select the scheduled users, cluster the cooperative base stations, and determine the transmit power of each base station over all physical resource blocks. Select the scheduled users and the cooperative BSs which served the users respectively based on affinity propagation at first. Then, we develop a power allocation scheme which considers the fairness among users. The scheme is a generalized proportional fairness based on Nash bargaining solutions. Simulation results demonstrate the superiority of the user-centric approach of scheduling and power control in CoMP.
Wireless communication systems assisted by unmanned aerial vehicles (UAVs) can well extend the co... more Wireless communication systems assisted by unmanned aerial vehicles (UAVs) can well extend the coverage of conventional communication networks and quickly provide service wherein the communication infrastructures are destroyed. However, radio resources are always limited and coupled with complex interference in the orthogonal multiple access framework. Thus, non-orthogonal multiple access (NOMA), which can enhance spectrum efficiency and inherently has capability to mitigate interference, is integrated with UAV communication networks in this article. We first propose a cooperative UAV NOMA network (CUNN) architecture and analyze its technical challenges. In addition, with the goal of cooperatively or competitively utilizing the limited resources effectively in a distributed manner, game theory shows its potential in addressing various technical challenges in wireless networks. Thus, we further survey game theoretical approaches for NOMA networks and UAV-based relay networks, and provide insights on how these game theoretical approaches can be adopted to solve technical challenges in CUNNs. Finally, aiming to achieve high spectrum efficiency and ensure fairness among user equipments, we propose a UAV-iUE (isolated user equipment) association, UAVs' position optimization, and power allocation algorithm in a dynamic cooperative game-theoretic framework. In the numerical results and discussions Section, the effectiveness of the proposed dynamic cooperative game-theoretic framework is shown through multiple simulations.
Wireless communication systems assisted by unmanned aerial vehicles (UAVs) can well extend the co... more Wireless communication systems assisted by unmanned aerial vehicles (UAVs) can well extend the coverage of conventional communication networks and quickly provide service wherein the communication infrastructures are destroyed. However, radio resources are always limited and coupled with complex interference in the orthogonal multiple access framework. Thus, non-orthogonal multiple access (NOMA), which can enhance spectrum efficiency and inherently has capability to mitigate interference, is integrated with UAV communication networks in this article. We first propose a cooperative UAV NOMA network (CUNN) architecture and analyze its technical challenges. In addition, with the goal of cooperatively or competitively utilizing the limited resources effectively in a distributed manner, game theory shows its potential in addressing various technical challenges in wireless networks. Thus, we further survey game theoretical approaches for NOMA networks and UAV-based relay networks, and provide insights on how these game theoretical approaches can be adopted to solve technical challenges in CUNNs. Finally, aiming to achieve high spectrum efficiency and ensure fairness among user equipments, we propose a UAV-iUE (isolated user equipment) association, UAVs' position optimization, and power allocation algorithm in a dynamic cooperative game-theoretic framework. In the numerical results and discussions Section, the effectiveness of the proposed dynamic cooperative game-theoretic framework is shown through multiple simulations.
Fog computing, as a promising technique, is with huge advantages in dealing with large amounts of... more Fog computing, as a promising technique, is with huge advantages in dealing with large amounts of data and information with low latency and high security. We introduce a promising multiple access technique entitled Non-orthogonal multiple access (NOMA) to provide communication service between the fog layer and the IoT device layer in fog computing, and propose a dynamic cooperative framework containing two stages. At the first stage, dynamic IoT device clustering is solved to reduce the system complexity and the delay for the IoT devices with better channel conditions. At the second stage, power allocation based energy management is solved using Nash bargaining solution (NBS) in each cluster to ensure fairness among IoT devices. The simulation results reveal that our proposed scheme can simultaneously achieve higher spectrum efficiency and ensure fairness among IoT devices compared to the other schemes.
Fog computing, as a promising technique, is with huge advantages in dealing with large amounts of... more Fog computing, as a promising technique, is with huge advantages in dealing with large amounts of data and information with low latency and high security. We introduce a promising multiple access technique entitled Non-orthogonal multiple access (NOMA) to provide communication service between the fog layer and the IoT device layer in fog computing, and propose a dynamic cooperative framework containing two stages. At the first stage, dynamic IoT device clustering is solved to reduce the system complexity and the delay for the IoT devices with better channel conditions. At the second stage, power allocation based energy management is solved using Nash bargaining solution (NBS) in each cluster to ensure fairness among IoT devices. The simulation results reveal that our proposed scheme can simultaneously achieve higher spectrum efficiency and ensure fairness among IoT devices compared to the other schemes.
Interference and traffic imbalance hinder the improved system performance in heterogeneous ultra-... more Interference and traffic imbalance hinder the improved system performance in heterogeneous ultra-dense networks. Network cooperation becomes a promising paradigm with sophisticated techniques which can significantly enhance the performance. In this article, a coalition game-theoretic framework is introduced to characterize the cooperative behaviors, and thus exploring these cooperative benefits and diversity gains. First, we introduce the basis of the coalition games, and then we survey its latest applications, in particular, the interference mitigation and traffic offloading. Different from most of the current applications, we concentrate on the cooperative incentive mechanism design since the node cooperation always means resource consumption and other costs. Moreover, for the incentive mechanism, a cooperative spectrum leasing is introduced. To mitigate the interference and balance traffic, we propose two schemes under the presented framework: interference alignment with spectrum leasing (IASL) and traffic offloading with spectrum leasing (TOSL). Simulation results show the improved performance of the cooperative gains using the proposed IASL and TOSL schemes.
We present a new approach for implementing a √ swap gate between two spatially far apart sites co... more We present a new approach for implementing a √ swap gate between two spatially far apart sites connected by a large-size coupled cavity array as quantum bus. The duration is only related to the parity of cavity number but independent of a specific number of cavity, thus it is possible to process quantum information in an arbitrary long distance in principle without time varied. Referring to the recent experimental progresses on coupled-cavity array, we also make an assessment of the scalability and take the cavity number N = 5 as an example to illustrate the robustness of our proposal via quantum process tomography.
Based on the quantum Zeno dynamics, we present an approach for deterministic preparation of arbit... more Based on the quantum Zeno dynamics, we present an approach for deterministic preparation of arbitrary four-qubit decoherence-free state of superconducting quantum interference devices with respective to collective amplitude damping in a decoherence-free way, namely, not only the form of the target state is free of decoherence, but also the whole process for preparation. The operation is fast and convenient since we only need to manipulate three weak laser pulses sequentially. Other decoherence effects such as cavity decay and the spontaneous emission of qubits are also taken into account in virtue of master equation, and the strictly numerical simulation signifies the final fidelity is high corresponding to the current experimental technology. Keywords DFS • Quantum Zeno dynamics • SQUID The most prominent advantage of a quantum computer over the classical counterpart is that it can make direct use of quantum mechanical phenomena, such as superposition and entanglement to perform operations on data [1,2]. Thus much attention has been paid to the preparation of various entanglement quantum states recently [3-6]. Nevertheless, every coin has two sides. The quantum superposition and entanglement may also play a negative role while becoming the basic principle of quantum computing. Once the quantum operation is carried out in a realistic situation, the entanglement will arise between the relevant system and environment. This effect, leading to the loss
A scalable way for implementation of ancilla-free optimal 1→ M phase-covariant quantum cloning (P... more A scalable way for implementation of ancilla-free optimal 1→ M phase-covariant quantum cloning (PCC) is proposed by combining quantum Zeno dynamics and adiabatic passage. An optimal 1→ M PCC can be achieved directly from the existed optimal 1→(M− 1) PCC ...
A scheme for implementing a three-qubit Toffoli gate with atoms sent through a microwave cavity i... more A scheme for implementing a three-qubit Toffoli gate with atoms sent through a microwave cavity is proposed by choosing nonidentical coupling constants between the atoms and cavity. The scheme can be generalized to implement an N-qubit Toffoli gate and the gating time does not change with an increase of the number of qubits.
We investigate the effect of the Dzyaloshinskii-Moriya (DM) interaction on the fidelity of the 1 ... more We investigate the effect of the Dzyaloshinskii-Moriya (DM) interaction on the fidelity of the 1 → M phasecovariant cloning machine (PCCM) in a spin star network. The results of numerical calculation show that the DM interaction can further improve the cloning fidelity to reach the optimal value. Furthermore, the physical mechanism is investigated by analyzing the effect of the DM interaction on the populations of the qubits. It is shown that the DM interaction leads to the populations of states |1 |S(M,k + 1) and |1 |S(M,k) [or |0 |S(M,k) and |0 |S(M,k − 1) ] simultaneously reaching the maximum or minimum value periodically, where the first ket |i (i ∈ 0,1) in |i |S(M,k) denotes the state of central spin with |0 and |1 representing the spin-up and spin-down states, respectively, while the second ket |S(M,k) denotes the state of outer spins with M being the total number of outer spins and k the number of up spins. At these extreme overlapping points of two states, the fidelity of quantum cloning can reach optimal value. Finally the forms of these two different 1 → M optimal cloning transformations are presented.
We propose a scheme to realize a quantum cloning machine via coupled electron spins in quantum do... more We propose a scheme to realize a quantum cloning machine via coupled electron spins in quantum dots. By properly designing the position of the quantum dots and controlling the coupling between them, a multi-purpose quantum cloning machine (MPCM) including an optimal symmetric (asymmetric) 1-->2 universal quantum cloning machine (UQCM) and optimal symmetric (asymmetric) 1-->2 phase-covariant quantum cloning machine (PCCM) can
We propose a simple linear optical scheme for directly implementing an ancilla-free two-qubit qua... more We propose a simple linear optical scheme for directly implementing an ancilla-free two-qubit quantum SWAP gate with high success probability. The proposed setup consists of only simple linear optical elements and photon detectors without introducing additionally ancillary single photons or entangled photons sources. The scheme is feasible and within the reach of current experimental technology.
We present a scheme to implement the three-qubit Fredkin gate. The scheme uses an atomic ensemble... more We present a scheme to implement the three-qubit Fredkin gate. The scheme uses an atomic ensemble consisting of four-level atoms interacting resonantly with a two-mode eld. Both the situations with and without cavity decay are considered. We discuss the advantages and the experimental feasibility of our scheme.
ABSTRACT The Casimir force between a perfectly conducting wall and a dielectric wall in a cavity ... more ABSTRACT The Casimir force between a perfectly conducting wall and a dielectric wall in a cavity comprising a transparent dielectric with output coupling is investigated. By using full quantum theory, we obtain the analysis expression of the force, which shows that the interaction of the two walls in this system is always repulsive. And the value of the Casimir force varies with the field amplitude reflectivity and the cavity size.
A scheme is presented for generating steady three-atom singlet states via three V-type atoms inte... more A scheme is presented for generating steady three-atom singlet states via three V-type atoms interacting with a strongly dissipative two-mode cavity. The local quantum feedback control is applied based on quantum-jump detection to make the target state fidelity as high as possible. This scheme is insensitive to detection inefficiencies since it only delays the time at which stationarity is achieved. Nevertheless, the spontaneous emission plays a negative role in the current system.
In 2005, Palla & Baraffe proposed that brown dwarfs (BDs) and very-low-mass stars (VLMSs; < 0.1 s... more In 2005, Palla & Baraffe proposed that brown dwarfs (BDs) and very-low-mass stars (VLMSs; < 0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated periods of one to four hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of low-mass objects in the 1-15 million year age range. Following up on reports of short-period variability in young clusters, we designed a high-cadence photometric monitoring campaign to search for deuterium-burning pulsation among a sample of 348 BDs and VLMSs in the four young clusters σ Orionis, Chamaeleon I, IC 348, and Upper Scorpius. In the resulting light curves we achieved sensitivity to periodic signals of amplitude several millimagnitudes, on timescales from 15 minutes to two weeks. Despite the exquisite data quality, we failed to detect any periodicities below seven hours. We conclude that D-burning pulsations are not able to grow to observable amplitudes in the early pre-main sequence. In spite of the nondetection, we did uncover a rich set of variability behavior-both periodic and aperiodic-on day to week timescales. We present new compilations of variable sources from our sample, as well as three new candidate cluster members in Chamaeleon I.
A scheme for implementing a two-qubit phase gate with atoms sent through a high-Q optical cavity ... more A scheme for implementing a two-qubit phase gate with atoms sent through a high-Q optical cavity is proposed by choosing nonidentical coupling constants between the atoms and cavity. The atomic spontaneous emission can be suppressed due to the large atom-field detuning. Moreover, the scheme can be generalized to implement an N-qubit phase gate and the gating time does not change
2018 24th Asia-Pacific Conference on Communications (APCC), 2018
Interference-aware coordinated multi-point can mitigate inter-cell interference and improve total... more Interference-aware coordinated multi-point can mitigate inter-cell interference and improve total throughput. However, it is crucial to select the scheduled users, cluster the cooperative base stations, and determine the transmit power of each base station over all physical resource blocks. Select the scheduled users and the cooperative BSs which served the users respectively based on affinity propagation at first. Then, we develop a power allocation scheme which considers the fairness among users. The scheme is a generalized proportional fairness based on Nash bargaining solutions. Simulation results demonstrate the superiority of the user-centric approach of scheduling and power control in CoMP.
2018 24th Asia-Pacific Conference on Communications (APCC), 2018
Interference-aware coordinated multi-point can mitigate inter-cell interference and improve total... more Interference-aware coordinated multi-point can mitigate inter-cell interference and improve total throughput. However, it is crucial to select the scheduled users, cluster the cooperative base stations, and determine the transmit power of each base station over all physical resource blocks. Select the scheduled users and the cooperative BSs which served the users respectively based on affinity propagation at first. Then, we develop a power allocation scheme which considers the fairness among users. The scheme is a generalized proportional fairness based on Nash bargaining solutions. Simulation results demonstrate the superiority of the user-centric approach of scheduling and power control in CoMP.
Wireless communication systems assisted by unmanned aerial vehicles (UAVs) can well extend the co... more Wireless communication systems assisted by unmanned aerial vehicles (UAVs) can well extend the coverage of conventional communication networks and quickly provide service wherein the communication infrastructures are destroyed. However, radio resources are always limited and coupled with complex interference in the orthogonal multiple access framework. Thus, non-orthogonal multiple access (NOMA), which can enhance spectrum efficiency and inherently has capability to mitigate interference, is integrated with UAV communication networks in this article. We first propose a cooperative UAV NOMA network (CUNN) architecture and analyze its technical challenges. In addition, with the goal of cooperatively or competitively utilizing the limited resources effectively in a distributed manner, game theory shows its potential in addressing various technical challenges in wireless networks. Thus, we further survey game theoretical approaches for NOMA networks and UAV-based relay networks, and provide insights on how these game theoretical approaches can be adopted to solve technical challenges in CUNNs. Finally, aiming to achieve high spectrum efficiency and ensure fairness among user equipments, we propose a UAV-iUE (isolated user equipment) association, UAVs' position optimization, and power allocation algorithm in a dynamic cooperative game-theoretic framework. In the numerical results and discussions Section, the effectiveness of the proposed dynamic cooperative game-theoretic framework is shown through multiple simulations.
Wireless communication systems assisted by unmanned aerial vehicles (UAVs) can well extend the co... more Wireless communication systems assisted by unmanned aerial vehicles (UAVs) can well extend the coverage of conventional communication networks and quickly provide service wherein the communication infrastructures are destroyed. However, radio resources are always limited and coupled with complex interference in the orthogonal multiple access framework. Thus, non-orthogonal multiple access (NOMA), which can enhance spectrum efficiency and inherently has capability to mitigate interference, is integrated with UAV communication networks in this article. We first propose a cooperative UAV NOMA network (CUNN) architecture and analyze its technical challenges. In addition, with the goal of cooperatively or competitively utilizing the limited resources effectively in a distributed manner, game theory shows its potential in addressing various technical challenges in wireless networks. Thus, we further survey game theoretical approaches for NOMA networks and UAV-based relay networks, and provide insights on how these game theoretical approaches can be adopted to solve technical challenges in CUNNs. Finally, aiming to achieve high spectrum efficiency and ensure fairness among user equipments, we propose a UAV-iUE (isolated user equipment) association, UAVs' position optimization, and power allocation algorithm in a dynamic cooperative game-theoretic framework. In the numerical results and discussions Section, the effectiveness of the proposed dynamic cooperative game-theoretic framework is shown through multiple simulations.
Fog computing, as a promising technique, is with huge advantages in dealing with large amounts of... more Fog computing, as a promising technique, is with huge advantages in dealing with large amounts of data and information with low latency and high security. We introduce a promising multiple access technique entitled Non-orthogonal multiple access (NOMA) to provide communication service between the fog layer and the IoT device layer in fog computing, and propose a dynamic cooperative framework containing two stages. At the first stage, dynamic IoT device clustering is solved to reduce the system complexity and the delay for the IoT devices with better channel conditions. At the second stage, power allocation based energy management is solved using Nash bargaining solution (NBS) in each cluster to ensure fairness among IoT devices. The simulation results reveal that our proposed scheme can simultaneously achieve higher spectrum efficiency and ensure fairness among IoT devices compared to the other schemes.
Fog computing, as a promising technique, is with huge advantages in dealing with large amounts of... more Fog computing, as a promising technique, is with huge advantages in dealing with large amounts of data and information with low latency and high security. We introduce a promising multiple access technique entitled Non-orthogonal multiple access (NOMA) to provide communication service between the fog layer and the IoT device layer in fog computing, and propose a dynamic cooperative framework containing two stages. At the first stage, dynamic IoT device clustering is solved to reduce the system complexity and the delay for the IoT devices with better channel conditions. At the second stage, power allocation based energy management is solved using Nash bargaining solution (NBS) in each cluster to ensure fairness among IoT devices. The simulation results reveal that our proposed scheme can simultaneously achieve higher spectrum efficiency and ensure fairness among IoT devices compared to the other schemes.
Interference and traffic imbalance hinder the improved system performance in heterogeneous ultra-... more Interference and traffic imbalance hinder the improved system performance in heterogeneous ultra-dense networks. Network cooperation becomes a promising paradigm with sophisticated techniques which can significantly enhance the performance. In this article, a coalition game-theoretic framework is introduced to characterize the cooperative behaviors, and thus exploring these cooperative benefits and diversity gains. First, we introduce the basis of the coalition games, and then we survey its latest applications, in particular, the interference mitigation and traffic offloading. Different from most of the current applications, we concentrate on the cooperative incentive mechanism design since the node cooperation always means resource consumption and other costs. Moreover, for the incentive mechanism, a cooperative spectrum leasing is introduced. To mitigate the interference and balance traffic, we propose two schemes under the presented framework: interference alignment with spectrum leasing (IASL) and traffic offloading with spectrum leasing (TOSL). Simulation results show the improved performance of the cooperative gains using the proposed IASL and TOSL schemes.
We present a new approach for implementing a √ swap gate between two spatially far apart sites co... more We present a new approach for implementing a √ swap gate between two spatially far apart sites connected by a large-size coupled cavity array as quantum bus. The duration is only related to the parity of cavity number but independent of a specific number of cavity, thus it is possible to process quantum information in an arbitrary long distance in principle without time varied. Referring to the recent experimental progresses on coupled-cavity array, we also make an assessment of the scalability and take the cavity number N = 5 as an example to illustrate the robustness of our proposal via quantum process tomography.
Based on the quantum Zeno dynamics, we present an approach for deterministic preparation of arbit... more Based on the quantum Zeno dynamics, we present an approach for deterministic preparation of arbitrary four-qubit decoherence-free state of superconducting quantum interference devices with respective to collective amplitude damping in a decoherence-free way, namely, not only the form of the target state is free of decoherence, but also the whole process for preparation. The operation is fast and convenient since we only need to manipulate three weak laser pulses sequentially. Other decoherence effects such as cavity decay and the spontaneous emission of qubits are also taken into account in virtue of master equation, and the strictly numerical simulation signifies the final fidelity is high corresponding to the current experimental technology. Keywords DFS • Quantum Zeno dynamics • SQUID The most prominent advantage of a quantum computer over the classical counterpart is that it can make direct use of quantum mechanical phenomena, such as superposition and entanglement to perform operations on data [1,2]. Thus much attention has been paid to the preparation of various entanglement quantum states recently [3-6]. Nevertheless, every coin has two sides. The quantum superposition and entanglement may also play a negative role while becoming the basic principle of quantum computing. Once the quantum operation is carried out in a realistic situation, the entanglement will arise between the relevant system and environment. This effect, leading to the loss
A scalable way for implementation of ancilla-free optimal 1→ M phase-covariant quantum cloning (P... more A scalable way for implementation of ancilla-free optimal 1→ M phase-covariant quantum cloning (PCC) is proposed by combining quantum Zeno dynamics and adiabatic passage. An optimal 1→ M PCC can be achieved directly from the existed optimal 1→(M− 1) PCC ...
A scheme for implementing a three-qubit Toffoli gate with atoms sent through a microwave cavity i... more A scheme for implementing a three-qubit Toffoli gate with atoms sent through a microwave cavity is proposed by choosing nonidentical coupling constants between the atoms and cavity. The scheme can be generalized to implement an N-qubit Toffoli gate and the gating time does not change with an increase of the number of qubits.
We investigate the effect of the Dzyaloshinskii-Moriya (DM) interaction on the fidelity of the 1 ... more We investigate the effect of the Dzyaloshinskii-Moriya (DM) interaction on the fidelity of the 1 → M phasecovariant cloning machine (PCCM) in a spin star network. The results of numerical calculation show that the DM interaction can further improve the cloning fidelity to reach the optimal value. Furthermore, the physical mechanism is investigated by analyzing the effect of the DM interaction on the populations of the qubits. It is shown that the DM interaction leads to the populations of states |1 |S(M,k + 1) and |1 |S(M,k) [or |0 |S(M,k) and |0 |S(M,k − 1) ] simultaneously reaching the maximum or minimum value periodically, where the first ket |i (i ∈ 0,1) in |i |S(M,k) denotes the state of central spin with |0 and |1 representing the spin-up and spin-down states, respectively, while the second ket |S(M,k) denotes the state of outer spins with M being the total number of outer spins and k the number of up spins. At these extreme overlapping points of two states, the fidelity of quantum cloning can reach optimal value. Finally the forms of these two different 1 → M optimal cloning transformations are presented.
We propose a scheme to realize a quantum cloning machine via coupled electron spins in quantum do... more We propose a scheme to realize a quantum cloning machine via coupled electron spins in quantum dots. By properly designing the position of the quantum dots and controlling the coupling between them, a multi-purpose quantum cloning machine (MPCM) including an optimal symmetric (asymmetric) 1--&gt;2 universal quantum cloning machine (UQCM) and optimal symmetric (asymmetric) 1--&gt;2 phase-covariant quantum cloning machine (PCCM) can
We propose a simple linear optical scheme for directly implementing an ancilla-free two-qubit qua... more We propose a simple linear optical scheme for directly implementing an ancilla-free two-qubit quantum SWAP gate with high success probability. The proposed setup consists of only simple linear optical elements and photon detectors without introducing additionally ancillary single photons or entangled photons sources. The scheme is feasible and within the reach of current experimental technology.
We present a scheme to implement the three-qubit Fredkin gate. The scheme uses an atomic ensemble... more We present a scheme to implement the three-qubit Fredkin gate. The scheme uses an atomic ensemble consisting of four-level atoms interacting resonantly with a two-mode eld. Both the situations with and without cavity decay are considered. We discuss the advantages and the experimental feasibility of our scheme.
ABSTRACT The Casimir force between a perfectly conducting wall and a dielectric wall in a cavity ... more ABSTRACT The Casimir force between a perfectly conducting wall and a dielectric wall in a cavity comprising a transparent dielectric with output coupling is investigated. By using full quantum theory, we obtain the analysis expression of the force, which shows that the interaction of the two walls in this system is always repulsive. And the value of the Casimir force varies with the field amplitude reflectivity and the cavity size.
A scheme is presented for generating steady three-atom singlet states via three V-type atoms inte... more A scheme is presented for generating steady three-atom singlet states via three V-type atoms interacting with a strongly dissipative two-mode cavity. The local quantum feedback control is applied based on quantum-jump detection to make the target state fidelity as high as possible. This scheme is insensitive to detection inefficiencies since it only delays the time at which stationarity is achieved. Nevertheless, the spontaneous emission plays a negative role in the current system.
In 2005, Palla & Baraffe proposed that brown dwarfs (BDs) and very-low-mass stars (VLMSs; < 0.1 s... more In 2005, Palla & Baraffe proposed that brown dwarfs (BDs) and very-low-mass stars (VLMSs; < 0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated periods of one to four hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of low-mass objects in the 1-15 million year age range. Following up on reports of short-period variability in young clusters, we designed a high-cadence photometric monitoring campaign to search for deuterium-burning pulsation among a sample of 348 BDs and VLMSs in the four young clusters σ Orionis, Chamaeleon I, IC 348, and Upper Scorpius. In the resulting light curves we achieved sensitivity to periodic signals of amplitude several millimagnitudes, on timescales from 15 minutes to two weeks. Despite the exquisite data quality, we failed to detect any periodicities below seven hours. We conclude that D-burning pulsations are not able to grow to observable amplitudes in the early pre-main sequence. In spite of the nondetection, we did uncover a rich set of variability behavior-both periodic and aperiodic-on day to week timescales. We present new compilations of variable sources from our sample, as well as three new candidate cluster members in Chamaeleon I.
A scheme for implementing a two-qubit phase gate with atoms sent through a high-Q optical cavity ... more A scheme for implementing a two-qubit phase gate with atoms sent through a high-Q optical cavity is proposed by choosing nonidentical coupling constants between the atoms and cavity. The atomic spontaneous emission can be suppressed due to the large atom-field detuning. Moreover, the scheme can be generalized to implement an N-qubit phase gate and the gating time does not change
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