Trapped ion hardware has made significant progress recently and is now one of the leading platforms for quantum computing.To construct two-qubit gates in trapped ions,experimentalmanipulation approaches for ion chains...Trapped ion hardware has made significant progress recently and is now one of the leading platforms for quantum computing.To construct two-qubit gates in trapped ions,experimentalmanipulation approaches for ion chains are becoming increasingly prevalent.Given the restricted control technology,how implementing high-fidelity quantum gate operations is crucial.Many works in current pulse design optimization focus on ion–phonon and effective ion–ion couplings while ignoring the first-order derivative terms expansion impacts of these two terms brought on by experiment defects.This paper proposes a novel robust quantum control optimization method in trapped ions.By introducing the first-order derivative terms caused by the error into the optimization cost function,we generate an extremely robust Mølmer–Sørensen gate with infidelity below 10^(−3) under a drift noise range of±10 kHz,the relative robustness achieves a tolerance of±5%,compared to the 200-kHz frequency spacing between phonon modes,and for time noise drift,the tolerance reached to 2%.Our work reveals the vital role of the first-order derivative terms of coupling in trapped ion pulse control optimization,especially the first-order derivative terms of ion–ion coupling.It provides a robust optimization scheme for realizing more efficient entangled states in trapped ion platforms.展开更多
Quantum teleportation as the key strategy for quantum communication requires pure maximally shared entangled states among quantum nodes.In practice,quantum decoherence drastically degrades the shared entanglement duri...Quantum teleportation as the key strategy for quantum communication requires pure maximally shared entangled states among quantum nodes.In practice,quantum decoherence drastically degrades the shared entanglement during entanglement distribution,which is a serious challenge for the development of quantum networks.However,most of the decoherence control strategies proposed thus far are either resource-intensive or time-consuming.To overcome this obstacle,we enable noise-resistant teleportation through a noisy channel with a limited number of qubits and without applying time-consuming weak measurements.We apply a quantum gate control unit consisting of a controlled NOT gate and a rotation gate after the original teleportation protocol is accomplished.Furthermore,we demonstrate that a teleportation fidelity of unity is attainable when environment-assisted measurement is added to the proposed teleportation protocol via quantum gates.Moreover,we present an entanglement distribution process by employing the designed quantum gate control unit followed by the deterministic standard teleportation protocol to improve teleportation fidelity by establishing improved shared entanglement.Our performance analysis indicates that the proposed teleportation schemes offer a competitive fidelity and success probability compared with the conventional schemes and a recent weak measurement-based teleportation protocol.展开更多
A quantum BP neural networks model with learning algorithm is proposed. First, based on the universality of single qubit rotation gate and two-qubit controlled-NOT gate, a quantum neuron model is constructed, which is...A quantum BP neural networks model with learning algorithm is proposed. First, based on the universality of single qubit rotation gate and two-qubit controlled-NOT gate, a quantum neuron model is constructed, which is composed of input, phase rotation, aggregation, reversal rotation and output. In this model, the input is described by qubits, and the output is given by the probability of the state in which （1） is observed. The phase rotation and the reversal rotation are performed by the universal quantum gates. Secondly, the quantum BP neural networks model is constructed, in which the output layer and the hide layer are quantum neurons. With the application of the gradient descent algorithm, a learning algorithm of the model is proposed, and the continuity of the model is proved. It is shown that this model and algorithm are superior to the conventional BP networks in three aspects： convergence speed, convergence rate and robustness, by two application examples of pattern recognition and function approximation.展开更多
A scheme to perfectly preserve an initial qubit state in geometric quantum computation is proposed for a single- qubit geometric quantum gate in a nuclear magnetic resonance system. At first, by adjusting some magneti...A scheme to perfectly preserve an initial qubit state in geometric quantum computation is proposed for a single- qubit geometric quantum gate in a nuclear magnetic resonance system. At first, by adjusting some magnetic field parameters, one can let the dynamic phase be proportional to the geometric phase. Then, by controlling the azimuthal angle in the initial state, we may realize a geometric quantum gate whose fidelity is equal to one under cyclic evolution. This means that the quantum information is no distortion in the process of geometric quantum computation.展开更多
A kind of new operators, the generalized pseudo-spin operators are introduced and a universad intrinsic Hamiltonian of two-qubit interaction is studied in terms of the generalized pseudo-spin operators. A fundamental ...A kind of new operators, the generalized pseudo-spin operators are introduced and a universad intrinsic Hamiltonian of two-qubit interaction is studied in terms of the generalized pseudo-spin operators. A fundamental quantum gate U（θ） is constructed based on the universal Hamiltonian and shown that the roles of the new quantum gate U （θ） is equivalent, functionally, to the joint operation of Hadamard and C-Not gates.展开更多
Based on a one dimensional quantum wave guide theory, we investigate the ballistic conductance through an Aharonov Bohm ring with a quantum gate. The analytical expression of the conductance is exactly obtained as t...Based on a one dimensional quantum wave guide theory, we investigate the ballistic conductance through an Aharonov Bohm ring with a quantum gate. The analytical expression of the conductance is exactly obtained as the function of magnetic flux penetrating the ring and Fermi energy of indcident electrons. When Fermi energy equals that of bound states in the isolated stub, the conductance is fixed at a constant value which is only determined by the geometric structure of the ring system. We have found that there are a new kind of conductance oscillations for some special mesoscopic ring systems. As Fermi energy of incident electrons crosses that of bound state in the isolated stub, the conductance oscillations have no abrupt change of phase by π and are in phase. This striking feature is not in ageement with that of previous experiments and theories. The mechanism causing this new feature is discussed.展开更多
Construction of optimal gate operations is significant for quantum computation.Here an efficient scheme is proposed for performing shortcut-based quantum gates on superconducting qubits in circuit quantum electrodynam...Construction of optimal gate operations is significant for quantum computation.Here an efficient scheme is proposed for performing shortcut-based quantum gates on superconducting qubits in circuit quantum electrodynamics(QED).Two four-level artificial atoms of Cooper-pair box circuits,having sufficient level anharmonicity,are placed in a common quantized field of circuit QED and are driven by individual classical microwaves.Without the effect of cross resonance,one-qubit NOT gate and phase gate in a decoupled atom can be implemented using the invariant-based shortcuts to adiabaticity.With the assistance of cavity bus,a one-step SWAP gate can be obtained within a composite qubit-photon-qubit system by inversely engineering the classical drivings.We further consider the gate realizations by adjusting the microwave fields.With the accessible decoherence rates,the shortcut-based gates have high fidelities.The present strategy could offer a promising route towards fast and robust quantum computation with superconducting circuits experimentally.展开更多
Anyons can be used to realize quantum computation, because they are two-level systems in two dimensions. In this paper, we propose a scheme to simulate single-qubit gates and CNOT gate using Abelian anyons in the Kita...Anyons can be used to realize quantum computation, because they are two-level systems in two dimensions. In this paper, we propose a scheme to simulate single-qubit gates and CNOT gate using Abelian anyons in the Kitaev model. Two pairs of anyons （six spins） are used to realize single-qubit gates, while ten spins are needed for the CNOT gate. Based on these quantum gates, we show how to realize the Grover algorithm in a two-qubit system.展开更多
We derive normally ordered quantum gate operators for continuum variables by mapping classical transforms onto Fock space. Successive gate operations can be treated in a unified way that is using the technique of inte...We derive normally ordered quantum gate operators for continuum variables by mapping classical transforms onto Fock space. Successive gate operations can be treated in a unified way that is using the technique of integration within an ordered product of operators.展开更多
In this paper,focus has been given to design and implement signed binary subtraction in quantum logic.Since the type of operand may be positive or negative,therefore a novel algorithm has been developed to detect the ...In this paper,focus has been given to design and implement signed binary subtraction in quantum logic.Since the type of operand may be positive or negative,therefore a novel algorithm has been developed to detect the type of operand and as per the selection of the type of operands,separate design techniques have been developed to make the circuit compact and work very efficiently.Two separate methods have been shown in the paper to perform the signed subtraction.The results show promising for the second method in respect of ancillary input count and garbage output count but at the cost of quantum cost.展开更多
In this paper, we give an efficient physical realization of a double-slit duality quantum gate. Weak cross- Kerr nonlinearity is exploited here. The probability of success can reach 1/2. Asymmetrical slit duality cont...In this paper, we give an efficient physical realization of a double-slit duality quantum gate. Weak cross- Kerr nonlinearity is exploited here. The probability of success can reach 1/2. Asymmetrical slit duality control gate also can be constructed conveniently. The special quantum control gate could be realized easily in optical system by our current experimental technology.展开更多
Harnessing the frequency dimension in integrated photonics offers key advantages in terms of scalability,noise resilience,parallelization,and compatibility with telecom multiplexing techniques.Integrated ring resonato...Harnessing the frequency dimension in integrated photonics offers key advantages in terms of scalability,noise resilience,parallelization,and compatibility with telecom multiplexing techniques.Integrated ring resonators have been used to generate frequency-entangled states through spontaneous four-wave mixing.However,state-of-the-art integrated resonators are limited by trade-offs among size,spectral separation,and efficient photon pair generation.We have developed silicon ring resonators with a footprint below 0.05 mm^(2)providing more than 70 frequency channels separated by 21 GHz.We exploit the narrow frequency separation to parallelize and independently control 34 single qubit-gates with a single set of three off-the-shelf electro-optic devices.We fully characterize 17 frequency-bin maximally entangled qubit pairs by performing quantum state tomography.We demonstrate for the first time,we believe,a fully connected five-user quantum network in the frequency domain.These results are a step towards a generation of quantum circuits implemented with scalable silicon photonics technology,for applications in quantum computing and secure communications.展开更多
The most general duality gates were introduced by Long,Liu and Wang and named allowable generalized quantum gates (AGQGs,for short).By definition,an allowable generalized quantum gate has the form of U=YfkjsckUK,where...The most general duality gates were introduced by Long,Liu and Wang and named allowable generalized quantum gates (AGQGs,for short).By definition,an allowable generalized quantum gate has the form of U=YfkjsckUK,where Uk’s are unitary operators on a Hilbert space H and the coefficients ck’s are complex numbers with |Yfijo ck\ ∧ 1 an d 1ck| 【1 for all k=0,1,...,d-1.In this paper,we prove that an AGQG U=YfkZo ck∧k is realizable,i.e.there are two d by d unitary matrices W and V such that ck=W0kVk0 (0【k【d-1) if and only if YfkJt 1c*|【m that case,the matrices W and V are constructed.展开更多
High-fidelity quantum gates are essential for large-scale quantum computation.However,any quantum manipulation will inevitably affected by noises,systematic errors and decoherence effects,which lead to infidelity of a...High-fidelity quantum gates are essential for large-scale quantum computation.However,any quantum manipulation will inevitably affected by noises,systematic errors and decoherence effects,which lead to infidelity of a target quantum task.Therefore,implementing high-fidelity,robust and fast quantum gates is highly desired.Here,we propose a fast and robust scheme to construct high-fidelity holonomic quantum gates for universal quantum computation based on resonant interaction of three-level quantum systems via shortcuts to adiabaticity.In our proposal,the target Hamiltonian to induce noncyclic non-Abelian geometric phases can be inversely engineered with less evolution time and demanding experimentally,leading to high-fidelity quantum gates in a simple setup.Besides,our scheme is readily realizable in physical system currently pursued for implementation of quantum computation.Therefore,our proposal represents a promising way towards fault-tolerant geometric quantum computation.展开更多
We propose a method of realizing a three-qubit quantum gate with a superconducting quantum interference device（SQUID） in a cavity.In this proposal,the gate operation involves the SQUID ground-states and the Fock sta...We propose a method of realizing a three-qubit quantum gate with a superconducting quantum interference device（SQUID） in a cavity.In this proposal,the gate operation involves the SQUID ground-states and the Fock states of cavity modes b and c.The two field-modes act as the controlling qubits,and the two SQUID states form the target qubit.Since only the metastable lower levels are involved in the gate operation,the gate is not affected by the SQUID decay rates.展开更多
We study the electron transmission tuned by quantum gate in an Aharonov Casher (AC) ring. Transmission probability is obtained as a function of the normalized textured electric fields and Fermi energy. We find that ...We study the electron transmission tuned by quantum gate in an Aharonov Casher (AC) ring. Transmission probability is obtained as a function of the normalized textured electric fields and Fermi energy. We find that modulating electron wavefunction in the stub can drastically affects electron transmission through the ring system. As Fermi energy crosses every eigenenergy of the isolated stub, the phases of both anomalous and periodic oscillations of the AC conductance generally have abrupt change by π. On two sides of several special Fermi energies, both anomalous and periodic oscillations have no abrupt phase change and are in phase. The detailed characteristics of the anomalous oscillations are dependent on the difference between the tilt angle of the spin and that of textured electric field. By modulating external magnetic field applied to the stub, we present AC oscillations of spin polarized conductance within adiabatic limit.展开更多
In the system with superconducting quantum interference devices （SQUID） in cavity, a scheme for constructing two-qubit quantum phase gate via a conventional geometric phase-shift is proposed by using a quantized cav...In the system with superconducting quantum interference devices （SQUID） in cavity, a scheme for constructing two-qubit quantum phase gate via a conventional geometric phase-shift is proposed by using a quantized cavity field and classical microwave pulses. In this scheme, the gate operation is realized in the subspace spanned by the two lower flux states of the SQUID system mud the population operator of the excited state has no effect on it. Thus the effect of decoherence caused from the levels of the SQUID system is possible to minimize. Under cavity decay, our strictly numerical simulation shows that it is also possible to realize the unconventional geometric phase gate. The experimental feasibility is discussed in detail.展开更多
One-way quantum computation focuses on initially generating an entangled cluster state followed by a sequence of measurements with classical communication of their individual outcomes.Recently,a delayed-measurement ap...One-way quantum computation focuses on initially generating an entangled cluster state followed by a sequence of measurements with classical communication of their individual outcomes.Recently,a delayed-measurement approach has been applied to replace classical communication of individual measurement outcomes.In this work,by considering the delayed-measurement approach,we demonstrate a modified one-way CNOT gate using the on-cloud superconducting quantum computing platform:Quafu.The modified protocol for one-way quantum computing requires only three qubits rather than the four used in the standard protocol.Since this modified cluster state decreases the number of physical qubits required to implement one-way computation,both the scalability and complexity of the computing process are improved.Compared to previous work,this modified one-way CNOT gate is superior to the standard one in both fidelity and resource requirements.We have also numerically compared the behavior of standard and modified methods in large-scale one-way quantum computing.Our results suggest that in a noisy intermediate-scale quantum(NISQ)era,the modified method shows a significant advantage for one-way quantum computation.展开更多
An allowable generalized quantum gate(introduced by Long,Liu and Wang)has the form of U1 0 d kk k c U -=∑,where Uk's are unitary operators on a Hilbert space H and 1 0 1 d kkc -= |∑|≤and 1 k |c|≤(0≤k≤d-1).I...An allowable generalized quantum gate(introduced by Long,Liu and Wang)has the form of U1 0 d kk k c U -=∑,where Uk's are unitary operators on a Hilbert space H and 1 0 1 d kkc -= |∑|≤and 1 k |c|≤(0≤k≤d-1).In this work we consider a kind of AGQGs,called restricted allowable generalized quantum gates(RAGQGs),satisfying 1 0 0 1 d kk c -= <∑||≤.Some properties of the set RAGQG(H)of all RAGQGs on H are established.Especially,we prove that the extreme points of RAGQG(H)are exactly unitary operators on H and that B(H)=R+RAGQG(H).展开更多
We present a scheme to realize the basic two-qubit logic gates such as the quantum phase gate and SWAP gate using a detuned microwave cavity interacting with three-level superconducting-quantum-interference-device （S...We present a scheme to realize the basic two-qubit logic gates such as the quantum phase gate and SWAP gate using a detuned microwave cavity interacting with three-level superconducting-quantum-interference-device （SQUID） qubit（s）, by placing SQUID（s） in a two-mode microwave cavity and using adiabatic passage methods. In this scheme, the two logical states of the qubit are represented by the two lowest levels of the SQUID, and the cavity fields are treated as quantized. Compared with the previous method, the complex procedures of adjusting tile level spacing of the SQUID and applying the resonant microwave pulse to the SQUID to create transformation are not required. Based on superconducting device with relatively long decoherence time and simplified operation procedure, the gates operate at a high speed, which is important in view of decoherence.展开更多
文摘Trapped ion hardware has made significant progress recently and is now one of the leading platforms for quantum computing.To construct two-qubit gates in trapped ions,experimentalmanipulation approaches for ion chains are becoming increasingly prevalent.Given the restricted control technology,how implementing high-fidelity quantum gate operations is crucial.Many works in current pulse design optimization focus on ion–phonon and effective ion–ion couplings while ignoring the first-order derivative terms expansion impacts of these two terms brought on by experiment defects.This paper proposes a novel robust quantum control optimization method in trapped ions.By introducing the first-order derivative terms caused by the error into the optimization cost function,we generate an extremely robust Mølmer–Sørensen gate with infidelity below 10^(−3) under a drift noise range of±10 kHz,the relative robustness achieves a tolerance of±5%,compared to the 200-kHz frequency spacing between phonon modes,and for time noise drift,the tolerance reached to 2%.Our work reveals the vital role of the first-order derivative terms of coupling in trapped ion pulse control optimization,especially the first-order derivative terms of ion–ion coupling.It provides a robust optimization scheme for realizing more efficient entangled states in trapped ion platforms.
基金supported by the National Natural Science Foundation of China under grant no.61973290Ministry of Science and Technology of P.R.China Program under the grant no.QN2022200007L。
文摘Quantum teleportation as the key strategy for quantum communication requires pure maximally shared entangled states among quantum nodes.In practice,quantum decoherence drastically degrades the shared entanglement during entanglement distribution,which is a serious challenge for the development of quantum networks.However,most of the decoherence control strategies proposed thus far are either resource-intensive or time-consuming.To overcome this obstacle,we enable noise-resistant teleportation through a noisy channel with a limited number of qubits and without applying time-consuming weak measurements.We apply a quantum gate control unit consisting of a controlled NOT gate and a rotation gate after the original teleportation protocol is accomplished.Furthermore,we demonstrate that a teleportation fidelity of unity is attainable when environment-assisted measurement is added to the proposed teleportation protocol via quantum gates.Moreover,we present an entanglement distribution process by employing the designed quantum gate control unit followed by the deterministic standard teleportation protocol to improve teleportation fidelity by establishing improved shared entanglement.Our performance analysis indicates that the proposed teleportation schemes offer a competitive fidelity and success probability compared with the conventional schemes and a recent weak measurement-based teleportation protocol.
基金the National Natural Science Foundation of China (50138010)
文摘A quantum BP neural networks model with learning algorithm is proposed. First, based on the universality of single qubit rotation gate and two-qubit controlled-NOT gate, a quantum neuron model is constructed, which is composed of input, phase rotation, aggregation, reversal rotation and output. In this model, the input is described by qubits, and the output is given by the probability of the state in which （1） is observed. The phase rotation and the reversal rotation are performed by the universal quantum gates. Secondly, the quantum BP neural networks model is constructed, in which the output layer and the hide layer are quantum neurons. With the application of the gradient descent algorithm, a learning algorithm of the model is proposed, and the continuity of the model is proved. It is shown that this model and algorithm are superior to the conventional BP networks in three aspects： convergence speed, convergence rate and robustness, by two application examples of pattern recognition and function approximation.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10864002)
文摘A scheme to perfectly preserve an initial qubit state in geometric quantum computation is proposed for a single- qubit geometric quantum gate in a nuclear magnetic resonance system. At first, by adjusting some magnetic field parameters, one can let the dynamic phase be proportional to the geometric phase. Then, by controlling the azimuthal angle in the initial state, we may realize a geometric quantum gate whose fidelity is equal to one under cyclic evolution. This means that the quantum information is no distortion in the process of geometric quantum computation.
基金The project supported by National Natural Science Foundation of China under Grant No. 60472017
文摘A kind of new operators, the generalized pseudo-spin operators are introduced and a universad intrinsic Hamiltonian of two-qubit interaction is studied in terms of the generalized pseudo-spin operators. A fundamental quantum gate U（θ） is constructed based on the universal Hamiltonian and shown that the roles of the new quantum gate U （θ） is equivalent, functionally, to the joint operation of Hadamard and C-Not gates.
文摘Based on a one dimensional quantum wave guide theory, we investigate the ballistic conductance through an Aharonov Bohm ring with a quantum gate. The analytical expression of the conductance is exactly obtained as the function of magnetic flux penetrating the ring and Fermi energy of indcident electrons. When Fermi energy equals that of bound states in the isolated stub, the conductance is fixed at a constant value which is only determined by the geometric structure of the ring system. We have found that there are a new kind of conductance oscillations for some special mesoscopic ring systems. As Fermi energy of incident electrons crosses that of bound state in the isolated stub, the conductance oscillations have no abrupt change of phase by π and are in phase. This striking feature is not in ageement with that of previous experiments and theories. The mechanism causing this new feature is discussed.
基金Project supported by the Natural Science Foundation of Henan Province,China (Grant No. 212300410388)the “316” Project Plan of Xuchang University
文摘Construction of optimal gate operations is significant for quantum computation.Here an efficient scheme is proposed for performing shortcut-based quantum gates on superconducting qubits in circuit quantum electrodynamics(QED).Two four-level artificial atoms of Cooper-pair box circuits,having sufficient level anharmonicity,are placed in a common quantized field of circuit QED and are driven by individual classical microwaves.Without the effect of cross resonance,one-qubit NOT gate and phase gate in a decoupled atom can be implemented using the invariant-based shortcuts to adiabaticity.With the assistance of cavity bus,a one-step SWAP gate can be obtained within a composite qubit-photon-qubit system by inversely engineering the classical drivings.We further consider the gate realizations by adjusting the microwave fields.With the accessible decoherence rates,the shortcut-based gates have high fidelities.The present strategy could offer a promising route towards fast and robust quantum computation with superconducting circuits experimentally.
基金Supported by the National Natural Science Foundation of China under Grant No. 10874098the National Basic Research Program of China under Grant Nos. 2009CB929402, 2011CB9216002the Specialized Research Fund for the Doctoral Program of Education Ministry of China under Grant No. 20060003048
文摘Anyons can be used to realize quantum computation, because they are two-level systems in two dimensions. In this paper, we propose a scheme to simulate single-qubit gates and CNOT gate using Abelian anyons in the Kitaev model. Two pairs of anyons （six spins） are used to realize single-qubit gates, while ten spins are needed for the CNOT gate. Based on these quantum gates, we show how to realize the Grover algorithm in a two-qubit system.
文摘We derive normally ordered quantum gate operators for continuum variables by mapping classical transforms onto Fock space. Successive gate operations can be treated in a unified way that is using the technique of integration within an ordered product of operators.
文摘In this paper,focus has been given to design and implement signed binary subtraction in quantum logic.Since the type of operand may be positive or negative,therefore a novel algorithm has been developed to detect the type of operand and as per the selection of the type of operands,separate design techniques have been developed to make the circuit compact and work very efficiently.Two separate methods have been shown in the paper to perform the signed subtraction.The results show promising for the second method in respect of ancillary input count and garbage output count but at the cost of quantum cost.
基金Supported by National Natural Science Foundation of China under Grant Nos.10775076 and 10874098the National Basic Research Program of China under Grant No.2009CB929402the Specialized Research Fund for the Doctoral Program of Education Ministry of China under Grant No.20060003048
文摘In this paper, we give an efficient physical realization of a double-slit duality quantum gate. Weak cross- Kerr nonlinearity is exploited here. The probability of success can reach 1/2. Asymmetrical slit duality control gate also can be constructed conveniently. The special quantum control gate could be realized easily in optical system by our current experimental technology.
基金supported by Region Ile-de-France in the framework of DIM SIRTEQthe European Union’s Horizon 2020 research under the Marie Skłodowska-Curie(Grant No.800306)
文摘Harnessing the frequency dimension in integrated photonics offers key advantages in terms of scalability,noise resilience,parallelization,and compatibility with telecom multiplexing techniques.Integrated ring resonators have been used to generate frequency-entangled states through spontaneous four-wave mixing.However,state-of-the-art integrated resonators are limited by trade-offs among size,spectral separation,and efficient photon pair generation.We have developed silicon ring resonators with a footprint below 0.05 mm^(2)providing more than 70 frequency channels separated by 21 GHz.We exploit the narrow frequency separation to parallelize and independently control 34 single qubit-gates with a single set of three off-the-shelf electro-optic devices.We fully characterize 17 frequency-bin maximally entangled qubit pairs by performing quantum state tomography.We demonstrate for the first time,we believe,a fully connected five-user quantum network in the frequency domain.These results are a step towards a generation of quantum circuits implemented with scalable silicon photonics technology,for applications in quantum computing and secure communications.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10571113 and 10871224)the Natural Science Research Program of Shaanxi Province (Grant No. 2009JM1011)
文摘The most general duality gates were introduced by Long,Liu and Wang and named allowable generalized quantum gates (AGQGs,for short).By definition,an allowable generalized quantum gate has the form of U=YfkjsckUK,where Uk’s are unitary operators on a Hilbert space H and the coefficients ck’s are complex numbers with |Yfijo ck\ ∧ 1 an d 1ck| 【1 for all k=0,1,...,d-1.In this paper,we prove that an AGQG U=YfkZo ck∧k is realizable,i.e.there are two d by d unitary matrices W and V such that ck=W0kVk0 (0【k【d-1) if and only if YfkJt 1c*|【m that case,the matrices W and V are constructed.
基金This work was supported by the Key R&D Program of Guangdong Province(Grant No.2018B030326001)the National Natural Science Foundation of China(Grant No.11874156)Science and Technology Program of Guangzhou(Grant No.2019050001).
文摘High-fidelity quantum gates are essential for large-scale quantum computation.However,any quantum manipulation will inevitably affected by noises,systematic errors and decoherence effects,which lead to infidelity of a target quantum task.Therefore,implementing high-fidelity,robust and fast quantum gates is highly desired.Here,we propose a fast and robust scheme to construct high-fidelity holonomic quantum gates for universal quantum computation based on resonant interaction of three-level quantum systems via shortcuts to adiabaticity.In our proposal,the target Hamiltonian to induce noncyclic non-Abelian geometric phases can be inversely engineered with less evolution time and demanding experimentally,leading to high-fidelity quantum gates in a simple setup.Besides,our scheme is readily realizable in physical system currently pursued for implementation of quantum computation.Therefore,our proposal represents a promising way towards fault-tolerant geometric quantum computation.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60978009)the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91121023)the National Basic Research Program of China (Grant No. 2011CBA00200)
文摘We propose a method of realizing a three-qubit quantum gate with a superconducting quantum interference device（SQUID） in a cavity.In this proposal,the gate operation involves the SQUID ground-states and the Fock states of cavity modes b and c.The two field-modes act as the controlling qubits,and the two SQUID states form the target qubit.Since only the metastable lower levels are involved in the gate operation,the gate is not affected by the SQUID decay rates.
文摘We study the electron transmission tuned by quantum gate in an Aharonov Casher (AC) ring. Transmission probability is obtained as a function of the normalized textured electric fields and Fermi energy. We find that modulating electron wavefunction in the stub can drastically affects electron transmission through the ring system. As Fermi energy crosses every eigenenergy of the isolated stub, the phases of both anomalous and periodic oscillations of the AC conductance generally have abrupt change by π. On two sides of several special Fermi energies, both anomalous and periodic oscillations have no abrupt phase change and are in phase. The detailed characteristics of the anomalous oscillations are dependent on the difference between the tilt angle of the spin and that of textured electric field. By modulating external magnetic field applied to the stub, we present AC oscillations of spin polarized conductance within adiabatic limit.
基金The project supported by National Fundamental Research Program of China under Grant No.2005CB724508National Natural Science Foundation of China under Grant Nos.60478029,90503010,10634060,and 10575040
文摘In the system with superconducting quantum interference devices （SQUID） in cavity, a scheme for constructing two-qubit quantum phase gate via a conventional geometric phase-shift is proposed by using a quantized cavity field and classical microwave pulses. In this scheme, the gate operation is realized in the subspace spanned by the two lower flux states of the SQUID system mud the population operator of the excited state has no effect on it. Thus the effect of decoherence caused from the levels of the SQUID system is possible to minimize. Under cavity decay, our strictly numerical simulation shows that it is also possible to realize the unconventional geometric phase gate. The experimental feasibility is discussed in detail.
基金the valuable discussions.Project supported by the National Natural Science Foundation of China(Grant Nos.92265207 and T2121001)Beijing Natural Science Foundation(Grant No.Z200009).
文摘One-way quantum computation focuses on initially generating an entangled cluster state followed by a sequence of measurements with classical communication of their individual outcomes.Recently,a delayed-measurement approach has been applied to replace classical communication of individual measurement outcomes.In this work,by considering the delayed-measurement approach,we demonstrate a modified one-way CNOT gate using the on-cloud superconducting quantum computing platform:Quafu.The modified protocol for one-way quantum computing requires only three qubits rather than the four used in the standard protocol.Since this modified cluster state decreases the number of physical qubits required to implement one-way computation,both the scalability and complexity of the computing process are improved.Compared to previous work,this modified one-way CNOT gate is superior to the standard one in both fidelity and resource requirements.We have also numerically compared the behavior of standard and modified methods in large-scale one-way quantum computing.Our results suggest that in a noisy intermediate-scale quantum(NISQ)era,the modified method shows a significant advantage for one-way quantum computation.
基金supported by the National Natural Science Foundation of China(10571113 and 10871224)the Natural Science Research Program of Shaanxi Province (2009JM1011)
文摘An allowable generalized quantum gate(introduced by Long,Liu and Wang)has the form of U1 0 d kk k c U -=∑,where Uk's are unitary operators on a Hilbert space H and 1 0 1 d kkc -= |∑|≤and 1 k |c|≤(0≤k≤d-1).In this work we consider a kind of AGQGs,called restricted allowable generalized quantum gates(RAGQGs),satisfying 1 0 0 1 d kk c -= <∑||≤.Some properties of the set RAGQG(H)of all RAGQGs on H are established.Especially,we prove that the extreme points of RAGQG(H)are exactly unitary operators on H and that B(H)=R+RAGQG(H).
文摘We present a scheme to realize the basic two-qubit logic gates such as the quantum phase gate and SWAP gate using a detuned microwave cavity interacting with three-level superconducting-quantum-interference-device （SQUID） qubit（s）, by placing SQUID（s） in a two-mode microwave cavity and using adiabatic passage methods. In this scheme, the two logical states of the qubit are represented by the two lowest levels of the SQUID, and the cavity fields are treated as quantized. Compared with the previous method, the complex procedures of adjusting tile level spacing of the SQUID and applying the resonant microwave pulse to the SQUID to create transformation are not required. Based on superconducting device with relatively long decoherence time and simplified operation procedure, the gates operate at a high speed, which is important in view of decoherence.
