We investigate the controlled implementation of a non-local CNOT operation using a three-qubit entangled state. Firstly, we show how the non-local CNOT operation can be implemented with unit fidelity and unit probabil...We investigate the controlled implementation of a non-local CNOT operation using a three-qubit entangled state. Firstly, we show how the non-local CNOT operation can be implemented with unit fidelity and unit probability by using a maximally entangled GHZ state as controlled quantum channel. Then, we put forward two schemes for conclusively implementing the non-local operation with unit fidelity by employing a partially entangled pure GHZ state as quantum channel. The feature of these schemes is that a third side is included, who may participate the process of quantum non-local implementation as a supervisor. Furthermore, when the quantum channel is partially entangled,the third one can rectify the state distorted by imperfect quantum channel. In addition to the GHZ class state, the W class state can also be used to implement the same non-local operation probabilistically. The probability of successful implementation using the W class state is always less than that using the GHZ class state.展开更多
Compact controlled-NOT(CNOT)gates are essential for achieving large-scale quantum information processing.Recently,metasurfaces have been emerging as a promising miniaturized platform for quantum optics thanks to their...Compact controlled-NOT(CNOT)gates are essential for achieving large-scale quantum information processing.Recently,metasurfaces have been emerging as a promising miniaturized platform for quantum optics thanks to their advanced light field manipulation capability and subwavelength thickness.Here we report,for the first time,to our knowledge,the experimental demonstration of a quantum CNOT gate realized with a single-layer Pancharatnam–Berry phase-based dielectric metasurface.The metasurface completes the functions of three beam splitters,reducing the thickness of the logic gate to the subwavelength scale.The truth table fidelity reaches as high as 94.7%and state fidelities of the generated maximally entangled Bell states exceed 80%.This provides an ultrathin device for quantum information processing and holds promise for advancing quantum technology.展开更多
Nuclear magnetic resonance (NMR) is one of the experimental schemes for quantum computation. Most initial state of quantum algorithm in NMR computation is the pseudopure state. Until now, there are several methods to ...Nuclear magnetic resonance (NMR) is one of the experimental schemes for quantum computation. Most initial state of quantum algorithm in NMR computation is the pseudopure state. Until now, there are several methods to prepare pseudopure state. This note, based on the idea of controlled-not (CNOT) gates combination, has analyzed the characteristics of this method in the odd- and even-qubit system. Also, we have designed the pulse sequence for a 4-qubit sample to obtain pseudopure state, and realized it in the experiment. This method reduces the complexity of experiment and gives a high signal-to-noise (S/N) ratio.展开更多
This paper is based on previous quantum encryption proposed by researchers developing a scheme for cryptography using symmetric keys.This study has pointed out that the scheme consists of a pitfall that could lead to ...This paper is based on previous quantum encryption proposed by researchers developing a scheme for cryptography using symmetric keys.This study has pointed out that the scheme consists of a pitfall that could lead to a controlled-NOT(CNOT)extraction attack.A malicious user can obtain the secret message of a sender without being detected by using a sequence of single photons and a controlled-NOT gate.展开更多
Recently, Li et al. presented a two-party quantum private comparison scheme using Greenberger-- Horne-Zeitinger （GHZ） states and error-correcting code （ECC） lint. J. Theor. Phys. 52, 2818 （2013）], claiming it is...Recently, Li et al. presented a two-party quantum private comparison scheme using Greenberger-- Horne-Zeitinger （GHZ） states and error-correcting code （ECC） lint. J. Theor. Phys. 52, 2818 （2013）], claiming it is fault-tolerant and could be performed in a non-ideal scenario. However, there ex- ists a fatal loophole in their private comparison scheme under a special attack, namely the twice- Hadamard-CNOT attack. Specifically, a malicious party may intercept the other party＇s particles and execute Hadamard operations on the intercepted particles as well as on his or her own particles. Then, the malicious party could sequentially perform a controlled-NOT （CNOT） operation between intercepted particles and the auxiliary particles, as well as between his or her own particles and the auxiliary particles prepared in advance. By measuring the auxiliary particles, the secret input will be revealed to the malicious party without being detected. For resisting this special attack, a feasible improved scheme is proposed by introducing a permutation operator before the third party （TP） sends the particle sequences to each participant.展开更多
Arbitrated quantum signature(AQS) is an important branch in quantum cryptography to authenticate quantum information, and cryptanalysis on AQS protocols helps to evaluate and improve security of AQS. Recently, it is d...Arbitrated quantum signature(AQS) is an important branch in quantum cryptography to authenticate quantum information, and cryptanalysis on AQS protocols helps to evaluate and improve security of AQS. Recently, it is discovered that an AQS protocol based on chained controlled-NOT(CNOT) algorithm is vulnerable to a novel attack because a transformation from binary keys into permutations and the chained CNOT algorithm have special properties, which enables a malicious receiver to forge signatures with probability 1/2. Moreover, a malicious signer can also deny his signatures with probability 1/4. Then, two possible improved methods are presented to resist these attacks: one is padding constants to reduce probability of the successful attacks, and the other is a circular chained CNOT algorithm to make the attack strategy invalid. And the security analysis shows that both the two improve methods could well resist these attacks.展开更多
文摘We investigate the controlled implementation of a non-local CNOT operation using a three-qubit entangled state. Firstly, we show how the non-local CNOT operation can be implemented with unit fidelity and unit probability by using a maximally entangled GHZ state as controlled quantum channel. Then, we put forward two schemes for conclusively implementing the non-local operation with unit fidelity by employing a partially entangled pure GHZ state as quantum channel. The feature of these schemes is that a third side is included, who may participate the process of quantum non-local implementation as a supervisor. Furthermore, when the quantum channel is partially entangled,the third one can rectify the state distorted by imperfect quantum channel. In addition to the GHZ class state, the W class state can also be used to implement the same non-local operation probabilistically. The probability of successful implementation using the W class state is always less than that using the GHZ class state.
基金National Natural Science Foundation of China(12134001,11527901,61590933)National Key Research and Development Program of China(2018YFB1107205)Innovation Program for Quantum Science and Technology(2021ZD0301500)。
文摘Compact controlled-NOT(CNOT)gates are essential for achieving large-scale quantum information processing.Recently,metasurfaces have been emerging as a promising miniaturized platform for quantum optics thanks to their advanced light field manipulation capability and subwavelength thickness.Here we report,for the first time,to our knowledge,the experimental demonstration of a quantum CNOT gate realized with a single-layer Pancharatnam–Berry phase-based dielectric metasurface.The metasurface completes the functions of three beam splitters,reducing the thickness of the logic gate to the subwavelength scale.The truth table fidelity reaches as high as 94.7%and state fidelities of the generated maximally entangled Bell states exceed 80%.This provides an ultrathin device for quantum information processing and holds promise for advancing quantum technology.
基金This work was supported by the National Natural Science Foundation of China(Grant No.19974064).
文摘Nuclear magnetic resonance (NMR) is one of the experimental schemes for quantum computation. Most initial state of quantum algorithm in NMR computation is the pseudopure state. Until now, there are several methods to prepare pseudopure state. This note, based on the idea of controlled-not (CNOT) gates combination, has analyzed the characteristics of this method in the odd- and even-qubit system. Also, we have designed the pulse sequence for a 4-qubit sample to obtain pseudopure state, and realized it in the experiment. This method reduces the complexity of experiment and gives a high signal-to-noise (S/N) ratio.
基金supported by the Research Center of Quantum Communication and Security,National Cheng Kung University,Taiwan,China (Grant No. D100-36002)
文摘This paper is based on previous quantum encryption proposed by researchers developing a scheme for cryptography using symmetric keys.This study has pointed out that the scheme consists of a pitfall that could lead to a controlled-NOT(CNOT)extraction attack.A malicious user can obtain the secret message of a sender without being detected by using a sequence of single photons and a controlled-NOT gate.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant Nos. 61103235, 61373131, and 61373016）, the Priority Academic Program Development of Jiangsu Higher Education Institutions （PAPD）, the Natural Science Foundation of Jiangsu Province under Grant No. BK20140651, and the Scientific Research Innovation Project for College Graduates of Jiangsu Province （Grant No. KYLX_0855）.
文摘Recently, Li et al. presented a two-party quantum private comparison scheme using Greenberger-- Horne-Zeitinger （GHZ） states and error-correcting code （ECC） lint. J. Theor. Phys. 52, 2818 （2013）], claiming it is fault-tolerant and could be performed in a non-ideal scenario. However, there ex- ists a fatal loophole in their private comparison scheme under a special attack, namely the twice- Hadamard-CNOT attack. Specifically, a malicious party may intercept the other party＇s particles and execute Hadamard operations on the intercepted particles as well as on his or her own particles. Then, the malicious party could sequentially perform a controlled-NOT （CNOT） operation between intercepted particles and the auxiliary particles, as well as between his or her own particles and the auxiliary particles prepared in advance. By measuring the auxiliary particles, the secret input will be revealed to the malicious party without being detected. For resisting this special attack, a feasible improved scheme is proposed by introducing a permutation operator before the third party （TP） sends the particle sequences to each participant.
基金supported by the National Natural Science Foundation of China (61502048)the National Science and Technology Major Project (2017YFB0803001)
文摘Arbitrated quantum signature(AQS) is an important branch in quantum cryptography to authenticate quantum information, and cryptanalysis on AQS protocols helps to evaluate and improve security of AQS. Recently, it is discovered that an AQS protocol based on chained controlled-NOT(CNOT) algorithm is vulnerable to a novel attack because a transformation from binary keys into permutations and the chained CNOT algorithm have special properties, which enables a malicious receiver to forge signatures with probability 1/2. Moreover, a malicious signer can also deny his signatures with probability 1/4. Then, two possible improved methods are presented to resist these attacks: one is padding constants to reduce probability of the successful attacks, and the other is a circular chained CNOT algorithm to make the attack strategy invalid. And the security analysis shows that both the two improve methods could well resist these attacks.
