For the quantum error correction and noisy intermediate-scale quantum algorithms to function with high efficiency,the raw fidelity of quantum logic gates on physical qubits needs to satisfy strict requirements.The neu...For the quantum error correction and noisy intermediate-scale quantum algorithms to function with high efficiency,the raw fidelity of quantum logic gates on physical qubits needs to satisfy strict requirements.The neutral atom quantum computing equipped with Rydberg blockade gates has made impressive progress recently,which makes it worthwhile to explore its potential in the two-qubit entangling gates,including the controlledphase gate,and in particular,the CZ gate.Provided the quantum coherence is well preserved,improving the fidelity of Rydberg blockade gates calls for special mechanisms to deal with adverse effects caused by realistic experimental conditions.Here,the heralded very-high-fidelity Rydberg blockade controlled-phase gate is designed to address these issues,which contains self-correction and projection as the key steps.This trailblazing method builds upon the previously established buffer-atom-mediated gate framework,with a special form of symmetry under parity–time transformation playing a crucial role in the process.We further analyze the performance with respect to a few typical sources of imperfections.This procedure can also be regarded as quantum hardware error correction or mitigation.While this paper by itself does not cover every single subtle issue and still contains many oversimplifications,we find it reasonable to anticipate a very-high-fidelity two-qubit quantum logic gate operated in the sense of heralded but probabilistic,whose gate error can be reduced to the level of 10^(-4)–10^(-6)or even lower with reasonably high possibilities.展开更多
Spin qubits and superconducting qubits are promising candidates for realizing solid-state quantum information processors.Designing a hybrid architecture that combines the advantages of different qubits on the same chi...Spin qubits and superconducting qubits are promising candidates for realizing solid-state quantum information processors.Designing a hybrid architecture that combines the advantages of different qubits on the same chip is a highly desirable but challenging goal.Here we propose a hybrid architecture that utilizes a high-impedance SQUID array resonator as a quantum bus,thereby coherently coupling different solid-state qubits.We employ a resonant exchange spin qubit hosted in a triple quantum dot and a superconducting transmon qubit.Since this hybrid system is highly tunable,it can operate in a dispersive regime,where the interaction between the different qubits is mediated by virtual photons.By utilizing such interactions,entangling gate operations between different qubits can be realized in a short time of 30 ns with a fidelity of up to 96.5%under realistic parameter conditions.Further utilizing this interaction,remote entangled state between different qubits can be prepared and is robust to perturbations of various parameters.These results pave the way for exploring efficient fault-tolerant quantum computation on hybrid quantum architecture platforms.展开更多
Limited by the thermal environment, the entanglement of a massive object is extremely difficult to generate. Based on a coherent scattering mechanism, we propose a scheme to generate the entanglement of two optically ...Limited by the thermal environment, the entanglement of a massive object is extremely difficult to generate. Based on a coherent scattering mechanism, we propose a scheme to generate the entanglement of two optically levitated nanospheres through the Coulomb interaction. Two nanospheres are charged and coupled to each other through the Coulomb interaction.In this manner, the entanglement of two nanospheres is induced either under a weak/strong optomechanical coupling regime or under an ultra-strong optomechanical coupling regime. The charges, radius and distance of the two nanospheres are taken into consideration to enhance the Coulomb interaction, thereby achieving a higher degree of entanglement in the absence of ground-state cooling. The corresponding maximum entanglement can be attained as the dynamics of the system approaches the boundary between the steady and the unsteady regimes. This provides a useful resource for both quantum-enhanced sensing and quantum information processing, as well as a new platform for studying many-body physics.展开更多
In this work, we propose a high-fidelity phonon-mediated entangling gate in a hybrid mechanical system based on two silicon-vacancy color centers in diamond. In order to suppress the influence of the spin decoherence ...In this work, we propose a high-fidelity phonon-mediated entangling gate in a hybrid mechanical system based on two silicon-vacancy color centers in diamond. In order to suppress the influence of the spin decoherence on the entangling gate, we use a continuous dynamical decoupling approach to create new dressed spin states, which are less sensitive to environmental fluctuations and exhibit an extended T_(2)^(*) spin dephasing time. The effective spin-spin Hamiltonian modified by the mechanical driving field and the corresponding master equation are derived in the dispersive regime. We show that in the presence of the mechanical driving field, the effective spin-spin coupling can be highly controlled. By calculating the entangling gate fidelity in the dressed basis, we find that once the mechanical field is turned on, the gate fidelity can be significantly improved. In particular, under an optimized spin-phonon detuning and a stronger Rabi frequency of the mechanical driving field, the two-qubit gate is capable of reaching fidelity exceeding 0.99. Moreover, by employing appropriate driving modulation, we show that a highfidelity full quantum gate can be also realized, in which the initial and final spin states are on a bare basis. Our work provides a promising scheme for realizing high-fidelity quantum information processing.展开更多
We propose a novel scheme for generating the entanglement of two oscillating mirrors in an optomechanical system via a flying atom. In this scheme, a two-level atom, in an arbitrary superposition state, passes through...We propose a novel scheme for generating the entanglement of two oscillating mirrors in an optomechanical system via a flying atom. In this scheme, a two-level atom, in an arbitrary superposition state, passes through an optomechanical system with two oscillating cavity-mirrors, and then its states are detected. In this way, we can generate the entangled states of the two oscillating mirrors. We derive the analytical expressions of the entangled states and make numerical calculations. We find that the entanglement of the two oscillating mirrors can be controlled by the initial state of the atom, the optomechanical coupling strength, and the coupling strength between the atom and the cavity field. We investigate the dynamics of the system with dissipations and discuss the experimental feasibility.展开更多
A scheme is presented for the generation of entangled states for two cavity mirrors. In the scheme each mirror initially in a vacuum state interacts with a weak coherent field, resulting in a photon-number dependent k...A scheme is presented for the generation of entangled states for two cavity mirrors. In the scheme each mirror initially in a vacuum state interacts with a weak coherent field, resulting in a photon-number dependent kick. The detection of a photon leaking from the cavities collapses the two mirrors to an entangled state.展开更多
Considering two light beams which are in general single-mode Gaussian states and incident on input ports of an ideal beam splitter, respectively, this paper investigates how separability and entanglement of the output...Considering two light beams which are in general single-mode Gaussian states and incident on input ports of an ideal beam splitter, respectively, this paper investigates how separability and entanglement of the output lights depend on degrees of nonclassicality and purities of the input states. The minimum and maximum amounts of attainable entanglement in the output state are found展开更多
A new scheme for quantum teleportation of single quantum bit state with using continuous variables entangling channel is presented. In our scheme two entangled light fields are employed. An outstanding characteristic ...A new scheme for quantum teleportation of single quantum bit state with using continuous variables entangling channel is presented. In our scheme two entangled light fields are employed. An outstanding characteristic of this scheme is that one atomic state is transmitted directly to another atom without using the third atom as the mediate.展开更多
A scheme is presented for the generation of entangled states for two atoms trapped in two distant cavities. In the scheme each atom is resonantly coupled with the respective cavity mode and driven by a strong classica...A scheme is presented for the generation of entangled states for two atoms trapped in two distant cavities. In the scheme each atom is resonantly coupled with the respective cavity mode and driven by a strong classical field. The detection of a photon decaying from the cavities and passing through a beam-splitter collapses the atoms to an entangled state. The required atom-field interaction time is very short and thus the decoherence effect is suppressed. Our scheme is within the reach of presently available cavity QED techniques.展开更多
We propose a scheme for the generation of two collections of atoms trapped in distant cavities connected by an optical fiber.The virtual photon exchange leads to the entanglement between these two atomic ensembles.Dur...We propose a scheme for the generation of two collections of atoms trapped in distant cavities connected by an optical fiber.The virtual photon exchange leads to the entanglement between these two atomic ensembles.During the operation the atomic system,cavity modes,and fiber are not excited,which is important in view of decoherence.展开更多
A scheme has been proposed for generating the macroscopic entanglement between the mesoscopic squeezed vacuum states and mesoscopic coherent states by considering both the two-photon interaction and the single photon ...A scheme has been proposed for generating the macroscopic entanglement between the mesoscopic squeezed vacuum states and mesoscopic coherent states by considering both the two-photon interaction and the single photon interaction of N two-level atoms in cavities with high quality factor assisted by a strong driving field. Moreover, we derive the dissipative interaction models for single photon interaction and two-photon interaction, respectively. The corresponding analytical expressions of the fidelities can be given. Our scheme can be realized in the current techniques on the cavity QED.展开更多
Solid-state rare-earth ions are promising candidates for implementing repeater nodes for quantum networks.However,the state-of-the-art quantum nodes use only a single qubit per node,which greatly limits the functional...Solid-state rare-earth ions are promising candidates for implementing repeater nodes for quantum networks.However,the state-of-the-art quantum nodes use only a single qubit per node,which greatly limits the functionality of the node and the scalability of the network.Here,we propose a scheme that utilizes a hybrid system of two ion qubits coupled to a nanophotonic cavity as a quantum node.Simultaneously applying a fast adiabatic pulse to the two ions can lead to an effective interaction between the two ion spin qubits by exchanging virtual photons in the cavity.Using this interaction,a controlled phase gate between the two ion qubits can be realized with a fidelity of 99.6%.Further utilizing this interaction,entangled states within the node can be generated deterministically with high fidelity,and are robust to a variety of noises and fluctuations.These results pave a way for fully functional quantum repeater nodes based on solid-state rare-earth ions.展开更多
We present a robust quantum optimal control framework for implementing fast entangling gates on ion-trap quantum processors.The framework leverages tailored laser pulses to drive the multiple vibrational sidebands of ...We present a robust quantum optimal control framework for implementing fast entangling gates on ion-trap quantum processors.The framework leverages tailored laser pulses to drive the multiple vibrational sidebands of the ions to create phonon-mediated entangling gates and,unlike the state of the art,requires neither weakcoupling Lamb-Dicke approximation nor perturbation treatment.With the application of gradient-based optimal control,it enables finding amplitude-and phase-modulated laser control protocols that work without the Lamb-Dicke approximation,promising gate speeds on the order of microseconds comparable to the characteristic trap frequencies.Also,robustness requirements on the temperature of the ions and initial optical phase can be conveniently included to pursue high-quality fast gates against experimental imperfections.Our approach represents a step in speeding up quantum gates to achieve larger quantum circuits for quantum computation and simulation,and thus can find applications in near-future experiments.展开更多
Implementing quantum wireless multi-hop network communication is essential to improve the global quantum network system. In this paper, we employ eight-level GHZ states as quantum channels to realize multi-hop quantum...Implementing quantum wireless multi-hop network communication is essential to improve the global quantum network system. In this paper, we employ eight-level GHZ states as quantum channels to realize multi-hop quantum communication, and utilize the logical relationship between the measurements of each node to derive the unitary operation performed by the end node. The hierarchical simultaneous entanglement switching(HSES) method is adopted, resulting in a significant reduction in the consumption of classical information compared to multi-hop quantum teleportation(QT)based on general simultaneous entanglement switching(SES). In addition, the proposed protocol is simulated on the IBM Quantum Experiment platform(IBM QE). Then, the data obtained from the experiment are analyzed using quantum state tomography, which verifies the protocol's good fidelity and accuracy. Finally, by calculating fidelity, we analyze the impact of four different types of noise(phase-damping, amplitude-damping, phase-flip and bit-flip) in this protocol.展开更多
The no-cloning theorem has sparked considerable interest in achieving high-fidelity approximate quantum cloning.Most of the previous studies mainly focused on the cloning of single particle states,and cloning schemes ...The no-cloning theorem has sparked considerable interest in achieving high-fidelity approximate quantum cloning.Most of the previous studies mainly focused on the cloning of single particle states,and cloning schemes used there are incapable of cloning quantum entangled states in multipartite systems.Few schemes were proposed for cloning multiparticle states,which consume more entanglement resources with loss of qubits,and the fidelity of the cloned state is relatively low.In this paper,cloning schemes for bipartite and tripartite entangled states based on photonic quantum walk and entanglement swapping are proposed.The results show that according to the proposed schemes,two high-fidelity(up to 0.75)cloned states can be obtained with less quantum resource consumption.Because of the simple cloning steps,few quantum resources and high fidelity,these schemes are both efficient and feasible.Moreover,this cloning machine eliminates the need for tracing out cloning machine,thereby minimizing resource waste.展开更多
Hybrid entangled states are crucial in quantum physics,offering significant benefits for hybrid quantum communication and quantum computation,and then the conversion of hybrid entangled states is equally critical.This...Hybrid entangled states are crucial in quantum physics,offering significant benefits for hybrid quantum communication and quantum computation,and then the conversion of hybrid entangled states is equally critical.This paper presents two novel schemes,that is,one converts the two-qubit hybrid Knill–Laflamme–Milburn(KLM)entangled state into Bell states and the other one transforms the three-qubit hybrid KLM state into Greenberger–Horne–Zeilinger(GHZ)states assisted by error-predicted and parity-discriminated devices.Importantly,the integration of single photon detectors into the parity-discriminated device enhances predictive capabilities,mitigates potential failures,and facilitates seamless interaction between the nitrogen-vacancy center and photons,so the two protocols operate in an error-predicted way,improving the experimental feasibility.Additionally,our schemes demonstrate robust fidelities(close to 1)and efficiencies,indicating their feasibility with existing technology.展开更多
In this second part of a study about quantum field oscillators with sub-oscillators and semi-quanta (IQuO), it is possible to show that in the initial phase of an interaction between two particles a no-dynamic process...In this second part of a study about quantum field oscillators with sub-oscillators and semi-quanta (IQuO), it is possible to show that in the initial phase of an interaction between two particles a no-dynamic process of reduction from a non-local to a local state takes place which cannot be described by Hamiltonian. We then describe the coupling of two IQuO of different particle-fields either at one point in space or at two distant points via an intermediary chain of coupled IQuO. The first aspect provides an understanding of the basic processes of creating and annihilating a pair. The second aspect describes the behaviour of two electrically charged particles through a process of phase shifts between the respective IQuO chains (CF1, CF2) implemented in a quantum entanglement via an intermediary chain (CB) of IQuO that originates changes in the direction of the two (CF1, CF2) distance-correlated ones. Thus, the semi-quanta structure of an IQuO and quantum entanglement identify the origin of the empirical law of attraction and repulsion between two electric charges.展开更多
A classification of multipartite entanglement is introduced for pure and mixed states.The classification is based on the distribution of entanglement between the qubits of a given system,with a mathematical framework ...A classification of multipartite entanglement is introduced for pure and mixed states.The classification is based on the distribution of entanglement between the qubits of a given system,with a mathematical framework used to characterize fully entangled states.Then we use current machine learning and deep learning techniques to automatically classify a random state of two,three,and four qubits without the need to compute the amount of the different types of entanglement in each run;rather this is done only in the learning process.The technique shows high,near-perfect,accuracy in the case of pure states.As expected,this accuracy drops,more or less,when dealing with mixed states and when increasing the number of parties involved.展开更多
Hybrid entangled states(HESs),which involve different particles with various degrees of freedom,have garnered significant attention and been applied in a wide range of quantum technologies.However,similar to other cat...Hybrid entangled states(HESs),which involve different particles with various degrees of freedom,have garnered significant attention and been applied in a wide range of quantum technologies.However,similar to other categories of entanglement,maximally HESs inevitably degrade to mixed states due to the environmental noise and operational imperfections.To address the degradation problem,measurement-based entanglement purification offers a feasible and robust solution alternative to conventional gate-based purification methods.In this paper,we propose a measurement-based hybrid entanglement purification protocol(MB-HEPP)for a certain kind of HES which consists of polarization photons and coherent states.We extend our methodology to several conditions,such as the multi-copy and multi-party scenarios,and the photon-loss condition.Compared with previous HEPPs,this protocol has several advantages.First,it does not depend on post-selection and the purified HESs can be retained for further application.Second,it does not require the Bell state measurement,but only uses the parity check with conventional linear optical elements,which makes it have the higher success probability and more feasible.Our MB-HEPP has potential applications in future heterogeneous quantum networks.展开更多
We present a quantum ranging protocol that overcomes photon-loss limitations using optimized partially frequencyentangled states.By establishing the fundamental relationship between the degree of entanglement,channel ...We present a quantum ranging protocol that overcomes photon-loss limitations using optimized partially frequencyentangled states.By establishing the fundamental relationship between the degree of entanglement,channel transmission efficiency and measurement precision,we demonstrate superclassical timing resolution in both lossless and lossy regimes.Theoretical analysis and numerical simulations reveal that,under a lossless channel,the precision gain increases with the degree of entanglement,approaching the Heisenberg limit.Importantly,in lossy channels,the precision gain is significantly influenced by both the channel transmission efficiency and the degree of entanglement.For transmission efficiencies above50%,the proposed method provides up to 1.5 times the precision gain of classical methods when entanglement parameters are optimized.Moreover,by optimizing intra-group and inter-group covariances in the multi-structured entangled state,we achieve substantial precision gains even at low transmission efficiencies(~30%),demonstrating its robustness against loss.This study resolves the critical trade-off between entanglement-enhanced precision and loss-induced information degradation.Future implementation could extend to satellite-based quantum positioning,remote sensing,quantum illumination,and other fields that require high-precision ranging in lossy environments.The protocol establishes a universal framework for loss-tolerant quantum metrology,advancing the practical deployment of quantum-enhanced sensing in real-world applications.展开更多
基金supported by the Science and Technology Commission of Shanghai Municipality(Grant No.24DP2600202)the National Key R&D Program of China(Grant No.2024YFB4504002)the National Natural Science Foundation of China(Grant No.92165107)。
文摘For the quantum error correction and noisy intermediate-scale quantum algorithms to function with high efficiency,the raw fidelity of quantum logic gates on physical qubits needs to satisfy strict requirements.The neutral atom quantum computing equipped with Rydberg blockade gates has made impressive progress recently,which makes it worthwhile to explore its potential in the two-qubit entangling gates,including the controlledphase gate,and in particular,the CZ gate.Provided the quantum coherence is well preserved,improving the fidelity of Rydberg blockade gates calls for special mechanisms to deal with adverse effects caused by realistic experimental conditions.Here,the heralded very-high-fidelity Rydberg blockade controlled-phase gate is designed to address these issues,which contains self-correction and projection as the key steps.This trailblazing method builds upon the previously established buffer-atom-mediated gate framework,with a special form of symmetry under parity–time transformation playing a crucial role in the process.We further analyze the performance with respect to a few typical sources of imperfections.This procedure can also be regarded as quantum hardware error correction or mitigation.While this paper by itself does not cover every single subtle issue and still contains many oversimplifications,we find it reasonable to anticipate a very-high-fidelity two-qubit quantum logic gate operated in the sense of heralded but probabilistic,whose gate error can be reduced to the level of 10^(-4)–10^(-6)or even lower with reasonably high possibilities.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974336 and 12304401)the National Key R&D Program of China(Grant No.2017YFA0304100)+1 种基金the Key Project of Natural Science Research in Universities of Anhui Province(Grant No.KJ2021A1107)the Scientific Research Foundation of Suzhou University(Grant Nos.2020BS006 and 2021XJPT18).
文摘Spin qubits and superconducting qubits are promising candidates for realizing solid-state quantum information processors.Designing a hybrid architecture that combines the advantages of different qubits on the same chip is a highly desirable but challenging goal.Here we propose a hybrid architecture that utilizes a high-impedance SQUID array resonator as a quantum bus,thereby coherently coupling different solid-state qubits.We employ a resonant exchange spin qubit hosted in a triple quantum dot and a superconducting transmon qubit.Since this hybrid system is highly tunable,it can operate in a dispersive regime,where the interaction between the different qubits is mediated by virtual photons.By utilizing such interactions,entangling gate operations between different qubits can be realized in a short time of 30 ns with a fidelity of up to 96.5%under realistic parameter conditions.Further utilizing this interaction,remote entangled state between different qubits can be prepared and is robust to perturbations of various parameters.These results pave the way for exploring efficient fault-tolerant quantum computation on hybrid quantum architecture platforms.
基金supported by the National Natural Science Foundation of China(Grant No.61771278)the Beijing Institute of Technology Research Fund Program for Young Scholars。
文摘Limited by the thermal environment, the entanglement of a massive object is extremely difficult to generate. Based on a coherent scattering mechanism, we propose a scheme to generate the entanglement of two optically levitated nanospheres through the Coulomb interaction. Two nanospheres are charged and coupled to each other through the Coulomb interaction.In this manner, the entanglement of two nanospheres is induced either under a weak/strong optomechanical coupling regime or under an ultra-strong optomechanical coupling regime. The charges, radius and distance of the two nanospheres are taken into consideration to enhance the Coulomb interaction, thereby achieving a higher degree of entanglement in the absence of ground-state cooling. The corresponding maximum entanglement can be attained as the dynamics of the system approaches the boundary between the steady and the unsteady regimes. This provides a useful resource for both quantum-enhanced sensing and quantum information processing, as well as a new platform for studying many-body physics.
基金supported by the Natural Science Foundation of Henan Province (No. 222300420233)。
文摘In this work, we propose a high-fidelity phonon-mediated entangling gate in a hybrid mechanical system based on two silicon-vacancy color centers in diamond. In order to suppress the influence of the spin decoherence on the entangling gate, we use a continuous dynamical decoupling approach to create new dressed spin states, which are less sensitive to environmental fluctuations and exhibit an extended T_(2)^(*) spin dephasing time. The effective spin-spin Hamiltonian modified by the mechanical driving field and the corresponding master equation are derived in the dispersive regime. We show that in the presence of the mechanical driving field, the effective spin-spin coupling can be highly controlled. By calculating the entangling gate fidelity in the dressed basis, we find that once the mechanical field is turned on, the gate fidelity can be significantly improved. In particular, under an optimized spin-phonon detuning and a stronger Rabi frequency of the mechanical driving field, the two-qubit gate is capable of reaching fidelity exceeding 0.99. Moreover, by employing appropriate driving modulation, we show that a highfidelity full quantum gate can be also realized, in which the initial and final spin states are on a bare basis. Our work provides a promising scheme for realizing high-fidelity quantum information processing.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574092,61775062,61378012,91121023,and 60978009)the National Basic Research Program of China(Grant No.2013CB921804)
文摘We propose a novel scheme for generating the entanglement of two oscillating mirrors in an optomechanical system via a flying atom. In this scheme, a two-level atom, in an arbitrary superposition state, passes through an optomechanical system with two oscillating cavity-mirrors, and then its states are detected. In this way, we can generate the entangled states of the two oscillating mirrors. We derive the analytical expressions of the entangled states and make numerical calculations. We find that the entanglement of the two oscillating mirrors can be controlled by the initial state of the atom, the optomechanical coupling strength, and the coupling strength between the atom and the cavity field. We investigate the dynamics of the system with dissipations and discuss the experimental feasibility.
基金The project supported by National Natural Science Foundation of China under Grant No.10674025Funds from Fuzhou University
文摘A scheme is presented for the generation of entangled states for two cavity mirrors. In the scheme each mirror initially in a vacuum state interacts with a weak coherent field, resulting in a photon-number dependent kick. The detection of a photon leaking from the cavities collapses the two mirrors to an entangled state.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574103）.
文摘Considering two light beams which are in general single-mode Gaussian states and incident on input ports of an ideal beam splitter, respectively, this paper investigates how separability and entanglement of the output lights depend on degrees of nonclassicality and purities of the input states. The minimum and maximum amounts of attainable entanglement in the output state are found
基金Project supported by the Natural Science Foundation of Anhui Province,China (Grant No. 090412060)the Natural Science Foundation of the Education Committee of Anhui Province,China (Grant No. KJ2008A029)
文摘A new scheme for quantum teleportation of single quantum bit state with using continuous variables entangling channel is presented. In our scheme two entangled light fields are employed. An outstanding characteristic of this scheme is that one atomic state is transmitted directly to another atom without using the third atom as the mediate.
基金National Natural Science Foundation of China under Grant No.10674025the Funds from Fuzhou University
文摘A scheme is presented for the generation of entangled states for two atoms trapped in two distant cavities. In the scheme each atom is resonantly coupled with the respective cavity mode and driven by a strong classical field. The detection of a photon decaying from the cavities and passing through a beam-splitter collapses the atoms to an entangled state. The required atom-field interaction time is very short and thus the decoherence effect is suppressed. Our scheme is within the reach of presently available cavity QED techniques.
基金Supported by the Doctoral Foundation of the Ministry of Education of China under Grant No.20093514110009
文摘We propose a scheme for the generation of two collections of atoms trapped in distant cavities connected by an optical fiber.The virtual photon exchange leads to the entanglement between these two atomic ensembles.During the operation the atomic system,cavity modes,and fiber are not excited,which is important in view of decoherence.
基金supported by National Natural Science Foundation of China under Grant Nos.10774042,10474118,and 1047200the National Fundamental Research Program of China under Grant No.2005CB724502
文摘A scheme has been proposed for generating the macroscopic entanglement between the mesoscopic squeezed vacuum states and mesoscopic coherent states by considering both the two-photon interaction and the single photon interaction of N two-level atoms in cavities with high quality factor assisted by a strong driving field. Moreover, we derive the dissipative interaction models for single photon interaction and two-photon interaction, respectively. The corresponding analytical expressions of the fidelities can be given. Our scheme can be realized in the current techniques on the cavity QED.
基金supported by the National Natural Science Foundation of China(Grant Nos.12304401 and 12350006)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301200)USTC Research Funds of the Double First-Class Initiative(Grant No.YD2030002026)。
文摘Solid-state rare-earth ions are promising candidates for implementing repeater nodes for quantum networks.However,the state-of-the-art quantum nodes use only a single qubit per node,which greatly limits the functionality of the node and the scalability of the network.Here,we propose a scheme that utilizes a hybrid system of two ion qubits coupled to a nanophotonic cavity as a quantum node.Simultaneously applying a fast adiabatic pulse to the two ions can lead to an effective interaction between the two ion spin qubits by exchanging virtual photons in the cavity.Using this interaction,a controlled phase gate between the two ion qubits can be realized with a fidelity of 99.6%.Further utilizing this interaction,entangled states within the node can be generated deterministically with high fidelity,and are robust to a variety of noises and fluctuations.These results pave a way for fully functional quantum repeater nodes based on solid-state rare-earth ions.
基金supported by the National Natural Science Foundation of China(Grant Nos.12441502,12122506,12204230,and 12404554)the National Science and Technology Major Project of the Ministry of Science and Technology of China(2024ZD0300404)+6 种基金Guangdong Basic and Applied Basic Research Foundation(Grant No.2021B1515020070)Shenzhen Science and Technology Program(Grant No.RCYX20200714114522109)China Postdoctoral Science Foundation(CPSF)(2024M762114)Postdoctoral Fellowship Program of CPSF(GZC20231727)supported by the National Natural Science Foundation of China(Grant Nos.92165206 and 11974330)Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301603)the Fundamental Research Funds for the Central Universities。
文摘We present a robust quantum optimal control framework for implementing fast entangling gates on ion-trap quantum processors.The framework leverages tailored laser pulses to drive the multiple vibrational sidebands of the ions to create phonon-mediated entangling gates and,unlike the state of the art,requires neither weakcoupling Lamb-Dicke approximation nor perturbation treatment.With the application of gradient-based optimal control,it enables finding amplitude-and phase-modulated laser control protocols that work without the Lamb-Dicke approximation,promising gate speeds on the order of microseconds comparable to the characteristic trap frequencies.Also,robustness requirements on the temperature of the ions and initial optical phase can be conveniently included to pursue high-quality fast gates against experimental imperfections.Our approach represents a step in speeding up quantum gates to achieve larger quantum circuits for quantum computation and simulation,and thus can find applications in near-future experiments.
基金Project supported by the Open Fund of Anhui Key Laboratory of Mine Intelligent Equipment and Technology (Grant No. ZKSYS202204)the Talent Introduction Fund of Anhui University of Science and Technology (Grant No. 2021yjrc34)the Scientific Research Fund of Anhui Provincial Education Department (Grant No. KJ2020A0301)。
文摘Implementing quantum wireless multi-hop network communication is essential to improve the global quantum network system. In this paper, we employ eight-level GHZ states as quantum channels to realize multi-hop quantum communication, and utilize the logical relationship between the measurements of each node to derive the unitary operation performed by the end node. The hierarchical simultaneous entanglement switching(HSES) method is adopted, resulting in a significant reduction in the consumption of classical information compared to multi-hop quantum teleportation(QT)based on general simultaneous entanglement switching(SES). In addition, the proposed protocol is simulated on the IBM Quantum Experiment platform(IBM QE). Then, the data obtained from the experiment are analyzed using quantum state tomography, which verifies the protocol's good fidelity and accuracy. Finally, by calculating fidelity, we analyze the impact of four different types of noise(phase-damping, amplitude-damping, phase-flip and bit-flip) in this protocol.
文摘The no-cloning theorem has sparked considerable interest in achieving high-fidelity approximate quantum cloning.Most of the previous studies mainly focused on the cloning of single particle states,and cloning schemes used there are incapable of cloning quantum entangled states in multipartite systems.Few schemes were proposed for cloning multiparticle states,which consume more entanglement resources with loss of qubits,and the fidelity of the cloned state is relatively low.In this paper,cloning schemes for bipartite and tripartite entangled states based on photonic quantum walk and entanglement swapping are proposed.The results show that according to the proposed schemes,two high-fidelity(up to 0.75)cloned states can be obtained with less quantum resource consumption.Because of the simple cloning steps,few quantum resources and high fidelity,these schemes are both efficient and feasible.Moreover,this cloning machine eliminates the need for tracing out cloning machine,thereby minimizing resource waste.
基金supported by the National Key R&D Program of China(Grant No.2022YFB3203400)the National Natural Science Foundation of China(Grant No.61901420)Fundamental Research Program of Shanxi Province(Grant No.20230302121116)。
文摘Hybrid entangled states are crucial in quantum physics,offering significant benefits for hybrid quantum communication and quantum computation,and then the conversion of hybrid entangled states is equally critical.This paper presents two novel schemes,that is,one converts the two-qubit hybrid Knill–Laflamme–Milburn(KLM)entangled state into Bell states and the other one transforms the three-qubit hybrid KLM state into Greenberger–Horne–Zeilinger(GHZ)states assisted by error-predicted and parity-discriminated devices.Importantly,the integration of single photon detectors into the parity-discriminated device enhances predictive capabilities,mitigates potential failures,and facilitates seamless interaction between the nitrogen-vacancy center and photons,so the two protocols operate in an error-predicted way,improving the experimental feasibility.Additionally,our schemes demonstrate robust fidelities(close to 1)and efficiencies,indicating their feasibility with existing technology.
文摘In this second part of a study about quantum field oscillators with sub-oscillators and semi-quanta (IQuO), it is possible to show that in the initial phase of an interaction between two particles a no-dynamic process of reduction from a non-local to a local state takes place which cannot be described by Hamiltonian. We then describe the coupling of two IQuO of different particle-fields either at one point in space or at two distant points via an intermediary chain of coupled IQuO. The first aspect provides an understanding of the basic processes of creating and annihilating a pair. The second aspect describes the behaviour of two electrically charged particles through a process of phase shifts between the respective IQuO chains (CF1, CF2) implemented in a quantum entanglement via an intermediary chain (CB) of IQuO that originates changes in the direction of the two (CF1, CF2) distance-correlated ones. Thus, the semi-quanta structure of an IQuO and quantum entanglement identify the origin of the empirical law of attraction and repulsion between two electric charges.
基金supported through computational resources of HPC-MARWAN(www.marwan.ma/hpc)provided by CNRST,Rabat,Morocco。
文摘A classification of multipartite entanglement is introduced for pure and mixed states.The classification is based on the distribution of entanglement between the qubits of a given system,with a mathematical framework used to characterize fully entangled states.Then we use current machine learning and deep learning techniques to automatically classify a random state of two,three,and four qubits without the need to compute the amount of the different types of entanglement in each run;rather this is done only in the learning process.The technique shows high,near-perfect,accuracy in the case of pure states.As expected,this accuracy drops,more or less,when dealing with mixed states and when increasing the number of parties involved.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12175106 and 92365110)the Postgraduate Research and Practice Innovation Program of Jiangsu Province(Grant No.KYCX23-1028)。
文摘Hybrid entangled states(HESs),which involve different particles with various degrees of freedom,have garnered significant attention and been applied in a wide range of quantum technologies.However,similar to other categories of entanglement,maximally HESs inevitably degrade to mixed states due to the environmental noise and operational imperfections.To address the degradation problem,measurement-based entanglement purification offers a feasible and robust solution alternative to conventional gate-based purification methods.In this paper,we propose a measurement-based hybrid entanglement purification protocol(MB-HEPP)for a certain kind of HES which consists of polarization photons and coherent states.We extend our methodology to several conditions,such as the multi-copy and multi-party scenarios,and the photon-loss condition.Compared with previous HEPPs,this protocol has several advantages.First,it does not depend on post-selection and the purified HESs can be retained for further application.Second,it does not require the Bell state measurement,but only uses the parity check with conventional linear optical elements,which makes it have the higher success probability and more feasible.Our MB-HEPP has potential applications in future heterogeneous quantum networks.
基金Project supported by the National Natural Science Foundation of China(Grant No.62071363)the Key Research and Development Projects of Shaanxi Province,China(Grant No.2021LLRH-06)。
文摘We present a quantum ranging protocol that overcomes photon-loss limitations using optimized partially frequencyentangled states.By establishing the fundamental relationship between the degree of entanglement,channel transmission efficiency and measurement precision,we demonstrate superclassical timing resolution in both lossless and lossy regimes.Theoretical analysis and numerical simulations reveal that,under a lossless channel,the precision gain increases with the degree of entanglement,approaching the Heisenberg limit.Importantly,in lossy channels,the precision gain is significantly influenced by both the channel transmission efficiency and the degree of entanglement.For transmission efficiencies above50%,the proposed method provides up to 1.5 times the precision gain of classical methods when entanglement parameters are optimized.Moreover,by optimizing intra-group and inter-group covariances in the multi-structured entangled state,we achieve substantial precision gains even at low transmission efficiencies(~30%),demonstrating its robustness against loss.This study resolves the critical trade-off between entanglement-enhanced precision and loss-induced information degradation.Future implementation could extend to satellite-based quantum positioning,remote sensing,quantum illumination,and other fields that require high-precision ranging in lossy environments.The protocol establishes a universal framework for loss-tolerant quantum metrology,advancing the practical deployment of quantum-enhanced sensing in real-world applications.
