Based on Bures distance, a Lyapunov function that represents the distance between a desired state and the actual state of a quantum system is selected. Considering the cases that an initial state is and is not orthogo...Based on Bures distance, a Lyapunov function that represents the distance between a desired state and the actual state of a quantum system is selected. Considering the cases that an initial state is and is not orthogonal to the desired state respectively, we propose a class of control strategies with state feedback that ensures the stability of the closed-loop control system. Especially, the asymptotic stability of the control system is analyzed, deduced and proved in detail. Finally, a simulation experiment on a spin-1/2 particle system is done and the relation between the system state evolution time and control value is analyzed with diffierent parameters . Research results have general theoretical meaning for control of quantum systems.展开更多
By introducing the von Neumann entropy as a measure of the extent of noise, this paper discusses the entropy evolution in a two-level quantum feedback controlled system. The results show that the feedback control can ...By introducing the von Neumann entropy as a measure of the extent of noise, this paper discusses the entropy evolution in a two-level quantum feedback controlled system. The results show that the feedback control can induce the reduction of the degree of noise, and different control schemes exhibit different noise controlling ability, the extent of the reduction also related with the position of the target state on the Bloch sphere. It is shown that the evolution of entropy can provide a real time noise observation and a systematic guideline to make reasonable choice of control strategy.展开更多
We present a novel feedback control method for quantum systems.Feedback does not affect the controlled system itself.Instead,it controls the unravelling of the quantum channel of interaction between the system and its...We present a novel feedback control method for quantum systems.Feedback does not affect the controlled system itself.Instead,it controls the unravelling of the quantum channel of interaction between the system and its environment.This interaction can be represented as a history of events.If their informational content is changed,their back-action on the system is also modified.Feedback action is trigged by the events,thus granting the system the degree of control over its own state.The efficiency of the proposed scheme is demonstrated on the example of two-mode atomic Bose-Einstein condensate,with one of its modes subject to phase-contrast imaging in a Mach–Zehnder interferometer.The histories of photocounts in the output channels of the interferometer are used for feedback.Its capabilities of state engineering are studied for different settings of the feedback loop and different numbers of events in the recorded histories.展开更多
A quantum teleportation network involving multiple users is essential for future quantum internet.So far,controlled quantum teleportation has been demonstrated in a three-user network.However,versatile and controlled ...A quantum teleportation network involving multiple users is essential for future quantum internet.So far,controlled quantum teleportation has been demonstrated in a three-user network.However,versatile and controlled quantum teleportation network involving more users is in demand,which satisfies different combinations of users for practical requirements.Here we propose a highly versatile and controlled teleportation network that can switch among various combinations of different users.We use a single continuous-variable six-partite Greenberger-Horne-Zeilinger(GHZ)state to realize such a task by choosing the different measurement and feedback operations.The controlled teleportation network,which includes one sub-network,two sub-networks and three sub-networks,can be realized for different application of user combinations.Furthermore,the coherent feedback control(CFC)can manipulate and improve the teleportation performance.Our approach is flexible and scalable,and would provide a versatile platform for demonstrations of complex quantum communication and quantum computing protocols.展开更多
Bosonic modes have wide applications in various quantum technologies,such as optical photons for quantum communication,magnons in spin ensembles for quantum information storage and mechanical modes for reversible micr...Bosonic modes have wide applications in various quantum technologies,such as optical photons for quantum communication,magnons in spin ensembles for quantum information storage and mechanical modes for reversible microwave-to-optical quantum transduction.There is emerging interest in utilizing bosonic modes for quantum information processing,with circuit quantum electrodynamics(circuit QED)as one of the leading architectures.Quantum information can be encoded into subspaces of a bosonic superconducting cavity mode with long coherence time.However,standard Gaussian operations(e.g.,beam splitting and two-mode squeezing)are insufficient for universal quantum computing.The major challenge is to introduce additional nonlinear control beyond Gaussian operations without adding significant bosonic loss or decoherence.Here we review recent advances in universal control of a single bosonic code with superconducting circuits,including unitary control,quantum feedback control,drivendissipative control and holonomic dissipative control.Various approaches to entangling different bosonic modes are also discussed.展开更多
The development of the theory on quantum systems control in the last 20 years is reviewed in detail.The research on the controllability of quantum systems is first introduced,then the study on the quantum open-loop co...The development of the theory on quantum systems control in the last 20 years is reviewed in detail.The research on the controllability of quantum systems is first introduced,then the study on the quantum open-loop control methods often used for controlling simple quantum systems is analyzed briefly.The learning control method and the feedback control method are mainly discussed for they are two important methods in quantum systems control and their advantages and disadvantages are presented.According to the trends in quantum systems control development,the paper predicts the future trends of its development and applications.A complete design procedure necessary for the quantum control system is presented.Finally,several vital problems hindering the advancement of quantum control are pointed out.展开更多
A robust and scalable scheme to generate a steady three-dimensional entangled state for a V-type atom and a A- type atom trapped in a strongly dissipative bimodal cavity is proposed by direct feedback control based on...A robust and scalable scheme to generate a steady three-dimensional entangled state for a V-type atom and a A- type atom trapped in a strongly dissipative bimodal cavity is proposed by direct feedback control based on quantum-jump detection. The robustness of this scheme reflects in the insensitivity to detection inefficiencies and the strong ability against the parameter fluctuations in the feedback, driving, and coupling strengths. The influence of atomic spontaneous emission can be suppressed by using the local feedback control. The scalability is ensured that N-dimensional entangled states of two atoms can be deterministically generated.展开更多
For an N-dimensional quantum system under the influence of continuous measurement, this paper presents a switching control scheme where the control law is of bang-bang type and achieves asymptotic preparation of an ar...For an N-dimensional quantum system under the influence of continuous measurement, this paper presents a switching control scheme where the control law is of bang-bang type and achieves asymptotic preparation of an arbitrarily given eigenstate of a non-degenerate and degenerate measurement operator, respectively. In the switching control strategy, we divide the state space into two parts： a set containing a target state, and its complementary set. By analyzing the stability of the stochastic system model under consideration, we design a constant control law and give some conditions that the control Hamiltonian satisfies so that the system trajectories in the complementary set converge to the set which contains the target state. Further, for the case of a non-degenerate measurement operator, we show that the system trajectories in the set containing the target state will automatically converge to the target state via quantum continuous measurement theory; while for the case of a degenerate measurement operator, the corresponding system trajectories will also converge to the target state via the construction of the control Hamiltonians. The convergence of the whole closed-loop systems under the cases of a non-degenerate and a degenerate measurement operator is strictly proved. The effectiveness of the proposed switching control scheme is verified by the simulation experiments on a finite-dimensional angular momentum system and a two-qubit system.展开更多
Monolithic electro absorption modulated distributed feedback(DFB) lasers are proposed and fabricated by using a modified double stack active layer.The 38mA threshold,9dB extinction ratio (from 0 5V to 3 0V),and ab...Monolithic electro absorption modulated distributed feedback(DFB) lasers are proposed and fabricated by using a modified double stack active layer.The 38mA threshold,9dB extinction ratio (from 0 5V to 3 0V),and about 5mW output power at the 100mA operation current are achieved.Compared with other reported results (only 1 5mW at the same operation current) of the traditional stack active structure,the proposed structure improves the output power of devices.展开更多
Quantum metrology provides a fundamental limit on the precision of multi-parameter estimation,called the Heisenberg limit,which has been achieved in noiseless quantum systems.However,for systems subject to noises,it i...Quantum metrology provides a fundamental limit on the precision of multi-parameter estimation,called the Heisenberg limit,which has been achieved in noiseless quantum systems.However,for systems subject to noises,it is hard to achieve this limit since noises are inclined to destroy quantum coherence and entanglement.In this paper,a combined control scheme with feedback and quantum error correction(QEC)is proposed to achieve the Heisenberg limit in the presence of spontaneous emission,where the feedback control is used to protect a stabilizer code space containing an optimal probe state and an additional control is applied to eliminate the measurement incompatibility among three parameters.Although an ancilla system is necessary for the preparation of the optimal probe state,our scheme does not require the ancilla system to be noiseless.In addition,the control scheme in this paper has a low-dimensional code space.For the three components of a magnetic field,it can achieve the highest estimation precision with only a 2-dimensional code space,while at least a4-dimensional code space is required in the common optimal error correction protocols.展开更多
This paper studies the real-time optimal state estimation-based feedback control for twolevel stochastic quantum systems in the non-Markovian case.The system model is established by combining the time-convolutionless ...This paper studies the real-time optimal state estimation-based feedback control for twolevel stochastic quantum systems in the non-Markovian case.The system model is established by combining the time-convolutionless non-Markovian master equation and the stochastic master equation.A nonlinear filter based on the state-dependent Riccati equation is designed in order to achieve the realtime optimal estimation of quantum states.A quadratic function multiplied with an exponential term is selected as the Lyapunov function,and a continuous-time control law is deduced via the stochastic Lyapunov stability theorem to realize eigenstate feedback control based on real-time optimal state estimation.Numerical simulation results illustrate that the proposed control scheme is capable of steering the two-level quantum system from an arbitrary initial state to the desired eigenstate with a fidelity higher than 99%within a time of 3 a.u.展开更多
In quantum information technologies,quantum weak measurement is beneficial for protecting coherence of systems.In order to further improve the protection effect of quantum weak measurement on coherence,we propose an o...In quantum information technologies,quantum weak measurement is beneficial for protecting coherence of systems.In order to further improve the protection effect of quantum weak measurement on coherence,we propose an optimization scheme of quantum Fisher information(QFI)protection in an open quantum system by combing no-knowledge quantum feedback control with quantum weak measurement.On the basis of solving the dynamic equations of a stochastic two-level quantum system under feedback control,we compare the effects of different feedback Hamiltonians on QFI and find that via no-knowledge quantum feedback,the observation operatorσx(orσx andσz)can protect QFI for a long time.Namely,no-knowledge quantum feedback can improve the estimation precision of feedback coefficient as well as that of detection coefficient.展开更多
We report the InAs/GaAs quantum dot laterally coupled distributed feedback(LC-DFB)lasers operating at room temperature in the wavelength range of 1.31μm.First-order chromium Bragg gratings were fabricated alongside t...We report the InAs/GaAs quantum dot laterally coupled distributed feedback(LC-DFB)lasers operating at room temperature in the wavelength range of 1.31μm.First-order chromium Bragg gratings were fabricated alongside the ridge waveguide to obtain the maximum coupling coefficient with the optical field.Stable continuous-wave single-frequency operation has been achieved with output power above 5 mW/facet and side mode suppression ratio exceeding 52 dB.Moreover,a single chip integrating three LC-DFB lasers was tentatively explored.The three LC-DFB lasers on the chip can operate in single mode at room temperature,covering the wavelength span of 35.6 nm.展开更多
基金Supported by National Natural Science Foundation of P.R.China(No. 50375148)
文摘Based on Bures distance, a Lyapunov function that represents the distance between a desired state and the actual state of a quantum system is selected. Considering the cases that an initial state is and is not orthogonal to the desired state respectively, we propose a class of control strategies with state feedback that ensures the stability of the closed-loop control system. Especially, the asymptotic stability of the control system is analyzed, deduced and proved in detail. Finally, a simulation experiment on a spin-1/2 particle system is done and the relation between the system state evolution time and control value is analyzed with diffierent parameters . Research results have general theoretical meaning for control of quantum systems.
基金Project supported by the National Natural Science Foundation of China （Grant No 10374025）.
文摘By introducing the von Neumann entropy as a measure of the extent of noise, this paper discusses the entropy evolution in a two-level quantum feedback controlled system. The results show that the feedback control can induce the reduction of the degree of noise, and different control schemes exhibit different noise controlling ability, the extent of the reduction also related with the position of the target state on the Bloch sphere. It is shown that the evolution of entropy can provide a real time noise observation and a systematic guideline to make reasonable choice of control strategy.
基金This work was supported by the State order(Project AAAA-A21-121021800168-4)at the Institute of Automation and Electrometry SB RAS.
文摘We present a novel feedback control method for quantum systems.Feedback does not affect the controlled system itself.Instead,it controls the unravelling of the quantum channel of interaction between the system and its environment.This interaction can be represented as a history of events.If their informational content is changed,their back-action on the system is also modified.Feedback action is trigged by the events,thus granting the system the degree of control over its own state.The efficiency of the proposed scheme is demonstrated on the example of two-mode atomic Bose-Einstein condensate,with one of its modes subject to phase-contrast imaging in a Mach–Zehnder interferometer.The histories of photocounts in the output channels of the interferometer are used for feedback.Its capabilities of state engineering are studied for different settings of the feedback loop and different numbers of events in the recorded histories.
基金Project supported by the Natural Science Foundation of Shanxi Province of China (Grant No. 202203021221214)the National Natural Science Foundation of China (Grant Nos. 62122044, 62135008, 61925503, 11904218, 12004276, 12147215, and 11834010)+4 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province of China (Grant Nos. 2019L0092 and 2020L0029)the Key Project of the National Key Research and Development Program of China (Grant No. 2022YFA1404500)the Program for the Innovative Talents of Higher Education Institutions of Shanxi Province of Chinathe Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxithe Fund for Shanxi “1331 Project” Key Subjects Construction
文摘A quantum teleportation network involving multiple users is essential for future quantum internet.So far,controlled quantum teleportation has been demonstrated in a three-user network.However,versatile and controlled quantum teleportation network involving more users is in demand,which satisfies different combinations of users for practical requirements.Here we propose a highly versatile and controlled teleportation network that can switch among various combinations of different users.We use a single continuous-variable six-partite Greenberger-Horne-Zeilinger(GHZ)state to realize such a task by choosing the different measurement and feedback operations.The controlled teleportation network,which includes one sub-network,two sub-networks and three sub-networks,can be realized for different application of user combinations.Furthermore,the coherent feedback control(CFC)can manipulate and improve the teleportation performance.Our approach is flexible and scalable,and would provide a versatile platform for demonstrations of complex quantum communication and quantum computing protocols.
基金support from the ARO (W911NF-18-1-0020 and W911NF-18-1-0212)ARO MURI (W911NF-16-1-0349)+3 种基金AFOSR MURI (FA9550-19-1-0399)NSF (EFMA-1640959, OMA-1936118, EEC-1941583)NTT Research, the Packard Foundation (201339273)the Startup Foundation of Institute of Semiconductors, Chinese Academy of Sciences (E0SEBB11)。
文摘Bosonic modes have wide applications in various quantum technologies,such as optical photons for quantum communication,magnons in spin ensembles for quantum information storage and mechanical modes for reversible microwave-to-optical quantum transduction.There is emerging interest in utilizing bosonic modes for quantum information processing,with circuit quantum electrodynamics(circuit QED)as one of the leading architectures.Quantum information can be encoded into subspaces of a bosonic superconducting cavity mode with long coherence time.However,standard Gaussian operations(e.g.,beam splitting and two-mode squeezing)are insufficient for universal quantum computing.The major challenge is to introduce additional nonlinear control beyond Gaussian operations without adding significant bosonic loss or decoherence.Here we review recent advances in universal control of a single bosonic code with superconducting circuits,including unitary control,quantum feedback control,drivendissipative control and holonomic dissipative control.Various approaches to entangling different bosonic modes are also discussed.
文摘The development of the theory on quantum systems control in the last 20 years is reviewed in detail.The research on the controllability of quantum systems is first introduced,then the study on the quantum open-loop control methods often used for controlling simple quantum systems is analyzed briefly.The learning control method and the feedback control method are mainly discussed for they are two important methods in quantum systems control and their advantages and disadvantages are presented.According to the trends in quantum systems control development,the paper predicts the future trends of its development and applications.A complete design procedure necessary for the quantum control system is presented.Finally,several vital problems hindering the advancement of quantum control are pointed out.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61068001 and 11264042)the Postdoctoral Science Foundation of China(Grant No.2012M520612)the Talent Program of Yanbian University of China(Grant No.950010001)
文摘A robust and scalable scheme to generate a steady three-dimensional entangled state for a V-type atom and a A- type atom trapped in a strongly dissipative bimodal cavity is proposed by direct feedback control based on quantum-jump detection. The robustness of this scheme reflects in the insensitivity to detection inefficiencies and the strong ability against the parameter fluctuations in the feedback, driving, and coupling strengths. The influence of atomic spontaneous emission can be suppressed by using the local feedback control. The scalability is ensured that N-dimensional entangled states of two atoms can be deterministically generated.
基金This paper is dedicated to Professor lan R. Petersen on the occasion of his 60th birthday. This work was supported by the Anhui Provincial Natural Science Foundation （No. 1708085MF144） and the National Natural Science Foundation of China （No. 61573330）.Acknowledgements We thank Dr. Daoyi Dong for helpful discussion.
文摘For an N-dimensional quantum system under the influence of continuous measurement, this paper presents a switching control scheme where the control law is of bang-bang type and achieves asymptotic preparation of an arbitrarily given eigenstate of a non-degenerate and degenerate measurement operator, respectively. In the switching control strategy, we divide the state space into two parts： a set containing a target state, and its complementary set. By analyzing the stability of the stochastic system model under consideration, we design a constant control law and give some conditions that the control Hamiltonian satisfies so that the system trajectories in the complementary set converge to the set which contains the target state. Further, for the case of a non-degenerate measurement operator, we show that the system trajectories in the set containing the target state will automatically converge to the target state via quantum continuous measurement theory; while for the case of a degenerate measurement operator, the corresponding system trajectories will also converge to the target state via the construction of the control Hamiltonians. The convergence of the whole closed-loop systems under the cases of a non-degenerate and a degenerate measurement operator is strictly proved. The effectiveness of the proposed switching control scheme is verified by the simulation experiments on a finite-dimensional angular momentum system and a two-qubit system.
文摘Monolithic electro absorption modulated distributed feedback(DFB) lasers are proposed and fabricated by using a modified double stack active layer.The 38mA threshold,9dB extinction ratio (from 0 5V to 3 0V),and about 5mW output power at the 100mA operation current are achieved.Compared with other reported results (only 1 5mW at the same operation current) of the traditional stack active structure,the proposed structure improves the output power of devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.61873251)。
文摘Quantum metrology provides a fundamental limit on the precision of multi-parameter estimation,called the Heisenberg limit,which has been achieved in noiseless quantum systems.However,for systems subject to noises,it is hard to achieve this limit since noises are inclined to destroy quantum coherence and entanglement.In this paper,a combined control scheme with feedback and quantum error correction(QEC)is proposed to achieve the Heisenberg limit in the presence of spontaneous emission,where the feedback control is used to protect a stabilizer code space containing an optimal probe state and an additional control is applied to eliminate the measurement incompatibility among three parameters.Although an ancilla system is necessary for the preparation of the optimal probe state,our scheme does not require the ancilla system to be noiseless.In addition,the control scheme in this paper has a low-dimensional code space.For the three components of a magnetic field,it can achieve the highest estimation precision with only a 2-dimensional code space,while at least a4-dimensional code space is required in the common optimal error correction protocols.
基金supported by the National Natural Science Foundation of China under Grant No.61973290。
文摘This paper studies the real-time optimal state estimation-based feedback control for twolevel stochastic quantum systems in the non-Markovian case.The system model is established by combining the time-convolutionless non-Markovian master equation and the stochastic master equation.A nonlinear filter based on the state-dependent Riccati equation is designed in order to achieve the realtime optimal estimation of quantum states.A quadratic function multiplied with an exponential term is selected as the Lyapunov function,and a continuous-time control law is deduced via the stochastic Lyapunov stability theorem to realize eigenstate feedback control based on real-time optimal state estimation.Numerical simulation results illustrate that the proposed control scheme is capable of steering the two-level quantum system from an arbitrary initial state to the desired eigenstate with a fidelity higher than 99%within a time of 3 a.u.
基金supported by the National Key Research and Development Program of China(2020YFA0309000)the National Natural Science Foundation of China(12174251)+1 种基金the Natural Science Foundation of Shanghai(22ZR142830)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61663016 and 11264015)。
文摘In quantum information technologies,quantum weak measurement is beneficial for protecting coherence of systems.In order to further improve the protection effect of quantum weak measurement on coherence,we propose an optimization scheme of quantum Fisher information(QFI)protection in an open quantum system by combing no-knowledge quantum feedback control with quantum weak measurement.On the basis of solving the dynamic equations of a stochastic two-level quantum system under feedback control,we compare the effects of different feedback Hamiltonians on QFI and find that via no-knowledge quantum feedback,the observation operatorσx(orσx andσz)can protect QFI for a long time.Namely,no-knowledge quantum feedback can improve the estimation precision of feedback coefficient as well as that of detection coefficient.
基金supported by the National Key Research and Development Program of China(No.2021YFB2800500).
文摘We report the InAs/GaAs quantum dot laterally coupled distributed feedback(LC-DFB)lasers operating at room temperature in the wavelength range of 1.31μm.First-order chromium Bragg gratings were fabricated alongside the ridge waveguide to obtain the maximum coupling coefficient with the optical field.Stable continuous-wave single-frequency operation has been achieved with output power above 5 mW/facet and side mode suppression ratio exceeding 52 dB.Moreover,a single chip integrating three LC-DFB lasers was tentatively explored.The three LC-DFB lasers on the chip can operate in single mode at room temperature,covering the wavelength span of 35.6 nm.
